1965 Fender Blackface Deluxe Reverb needing Tremolo and Reverb Repair

well greetings out there on youtube land and welcome to today's video extravaganza which features the magnificent amplifier chassis that you see before you this was sent to us by a viewer named lewis in ohio and i think uh this will really be an interesting video in that it is featuring one of the i guess all-time great amps that was ever made by the fender company the blackface deluxe reverb that's right you heard me it's the blackface deluxe reverb if you've been keeping up with prices on ebay and reverb lately you know that these jewels are escalating in value as we speak okay they're up around the 2500 or 3 000 range uh so if you want one of these you better get it uh if you wait it's just going to cost you more let's see what you get if you buy one let's take a look at the cosmetic aspects of this joule as is our standard procedure and then we will proceed to repair it tune it up and make it work at least as well as it did when it was new okay if this interests you then stay tuned because we're just about to begin first off the parts that came with it of course the full-sized aquatronics a reverb tank an after-market uh two-button uh foot switch made in mexico as most of the fender equipment is nowadays and also the tubes in a separate box okay let's move over now to uh checking out the uh chassis itself the deluxe reverb is a perfect amp for those who don't need the power of the super reverb or the weight and can get by with about 24 25 watts of output power in a lighter more compact package but it still has the reverb and tremolo effects we'll start here on the chassis uh we see that it's a 125 p23c power transformer whereas on the schematic they say 23b what i found uh from experience is that these numbers are rather arbitrary okay they uh would use up whatever transformers they had on hand order more and if they came in with a c they'd use them i'm sure there's little or no difference okay the filter choke output transformer and reverb driver transformers all check out exactly with the schematic let's look at the uh overall finish here on the chassis surface we see it does have some corrosion some discoloration we look over here on the output transformer and it looks to me like some wax or something has leaked down here i'm not sure if that means anything or not but it is unusual let's lift the dog house and see if we have the original filter caps or if it has been redone yes it has been redone i'm not sure when um apparently at some time in the past you know i'm very tempted to go ahead and just replace these with f and t uh caps which i've had really good luck with uh there's something also that we need to look at here after looking at super reverbs and twins and other circuits like that notice how small these two caps are normally they're giant what are they 70 microfarad at 350 in series so that adds up to 35 microfarads at 700 volts okay but these are nothing like that was this done in error or does the deluxe reverb vary from its larger brothers in the reservoir cap category right here let's take a look at the schematic and sure enough we see that the deluxe reverb uses two 16 microfarads in parallel at 450 volts instead of the 70s at 350s in series so this then is going to add up to 32 microfarads at 450 volts for our reservoir capacitance okay and we see that they used 222's at 500 which is perfectly fine we're going to have 44 microfarads and at 500 volts which may actually be even better the other three filter caps are the standard 22 microfarads at 500 volts now let's look at the control panel and it is immaculate i see really no serious dance scratches anything of that sort uh it's got the proper knobs pots all turned smoothly this is i would say as good as it gets right here beautiful let's take a look at the rear control panel and we can see that there's a little bit of corrosion on the bare metal portion of the chassis but that the rear control panel is essentially perfect okay i'm going to do my standard conversion the ground switch since it's no longer needed once i install the three wire power cord we're going to make this a switchable negative feedback uh loop here that uh we find that at low to moderate volumes is a really great modification for uh this style of fender amplifier looking here at the serial number it's ao 8118 is right in the middle of 1965. okay which is pretty much what you'd expect okay that was definitely the blackface era also uh we see here a two-wire cord has been installed uh that of course will have to be replaced and we'll have to wire the primary circuit properly because they never are okay let's take a look then at the circuit itself we'll start down here in the preamp end and we'll see that the blue molded caps have been left intact they're almost always fully functional and trustworthy we see that the cathode bypass caps the electrolytics have been replaced at some time in the past overall everything really looks nice it's had work but the work was well done from what i can see okay also you notice the cloth covered wire that is so typical of the blackface era as we go back uh come to the more modern ants up in the silver face area we'll see they start to use a lot more vinyl wire everything looks great here and until i get to the power transformer now notice that we have vinyl covered wire remember this had the c suffix instead of the b also i'm looking i mean you really have to look close but look at underneath where that lock washer has scratched the surface now that could have just been from tightening the um transformer bolts or it could be that this is a replacement power transformer if so it was done a long time ago and i don't think would have any negative bearing since it is essentially the right part number for this circuit we see that they have overhauled the negative dc bias supply you can see where the power cord attaches to the ac output receptacle as usual but that the rest of the primary wiring is all incorrect and that the appears that the death cap and the ground or polarity switch is still wired into the circuit that will have to be changed now i'm going to be honest with you i see nothing wrong with this uh it has been recapped and done well uh yes it needs a three wire power cord but what i'm gonna have to do because no letter came with this although i haven't opened the tube box yet but i'm wondering what exactly was wrong with this that inspired the owner to send it to us so what i'll do is i'm going to go in and write him an email real quick and uh the next time that you hear from me i will have input from him on what he wants he may just want like an oil change okay we're we're just going to go through and uh say replace the filter caps with uh f and t's install a three wire power cord bias the output tubes properly and just sort of a general tune up okay but we'll know more in just a few minutes so stay tuned an email has been sent and while we're waiting for a response from the owner let's go ahead and take care of those repairs uh that are uh necessary uh number one let's replace the to our power cord with the three wire and let's remove that pesky old death capacitor now before we start on the replacement of the power cord let's resolve a quick question here about which circuit we have here in this particular blackface deluxe reverb there's two possibilities the double a763 and the ab763 now i'm going to go into this in much greater detail on the part two video in which i discuss the evolution of the deluxe reverb circuit but for now the easiest way to tell the difference is that on the double a which have been the first circuit the plate resistors for the 1287 long-tail pair phase inverter are both 100k ohms whereas in the a b circuit they're the more familiar 100k and 82k okay so let's look over here at our circuit and see which one we have and here we see that we have an 82k and 100k the plate resistors to our two uh six v6 output tubes so there is no doubt then that we are working on an ab-763 circuit okay let's proceed now with that power cord first i unsoldered the two leads of the original 2r power cord from the ac receptacle on the back of the chassis and then extracted it and then i reused the strain relief with the new three wire power cord and next we're going to remove all of these yellow wires from the receptacle from the ground switch from the fuse holder and from the on off switch all right now all the yellow wires have been removed so our ground switch has been isolated and we will use it for our negative feedback uh switch modification we have the two primary wires from our power transformer one is going to the on off switch one is going to the fuse and we're going to change that we're going to separate the primary wire from the on off switch terminal and while you're at it remove the lead from the depth capacitor up here to the bottom terminal on the ground switch okay i usually tuck the wire down underneath the capacitor and leave it in place for originality's sake next we'll take that primary wire that we unsoldered from the on off toggle and bring it over here and solder it to the silver screw on the ac receptacle then you solder the white wire from your three wire power cord to that same silver screwed receptacle so now the return wire is continuous with one of the two primary wires of the power transformer next i will solder a six inch black wire to the end of the black wire from the three wire power cord and at their junction i will solder that to the gold screw terminal of the uh ac receptacle once that junction has been soldered to the gold terminal then we'll bring that six inch wire over here and solder it to the left hand or distal terminal of the on off toggle now all that's left is to connect the proximal or right hand terminal of the toggle switch to the end terminal of the fuse holder like so from here to that and bayonet on the fuse holder now you have your hot wire come in here it communicates with the gold terminal of the ac receptacle travels down here to the on off toggle when it's turned on then the power will come in through the fuse and into the primary of the power transformer the white wire the return wire is connected directly to the other primary wire of the power transformer okay now i prefer this method because then when the toggle switch is off everything is off in the circuit some people like to have it where they run the hot wire through the fuse first and then over to the on off toggle switch in which case while the amp is plugged in even if it's turned off the fuse is energized which can really give you a heck of a shock if you check the fuse without first unplugging the amp now while we're working in this area here of the chassis why don't we wire up the negative feedback loop switch okay and we're going to start over here now here are your two speaker output jacks if you look they communicate from here to here but also there will be another wire a long wire that comes out from this terminal and comes over here and communicates with our eyelet board it goes down inside a hole in the eyelet board step one is let's go ahead and remove that long wire from this terminal step two once it's removed from the terminal then i run it underneath some of the existing wires here to hold it down and bring it over and i'm going to solder it to the left hand single terminal of our original ground switch like so right there now we're going to run a wire from the lower of the two uh terminals on this end of the switch the bottom one we're going to run it back over here to where we liberated the yellow wire originally like so from the bottom terminal over here to that terminal that the yellow wire was originally connected to then we're going to tuck this back under the edge of the chassis so that it's hit like so completely hidden now when we flip the switch we can connect or disconnect our negative feedback loop and for low to medium volume when you switch the nfb loop off you're going to get a whole lot better gain you know what it reminds me of is remember there used to be a loudness switch on uh car stereos and when you pushed it it kind of boosted the base and gave you just a really great sounding tone even though you're at low volume that's what this will do for you now at high volume you probably need to switch it on because that will help keep the distortion from just getting all completely out of control okay so uh it's up to you depending on the volume that you operate at whether you want your negative feedback loop or not i have an email here from the owner giving us our instructions it says replace the killer cap i think remove the death cap but probably the best bet set it up for grounded outlet that would be with a three wire power cord that's uh with the properly wired primary circuit i'm not sure if the new reverb cables if new reverb cables are needed we'll check them out works but makes noise now and is unusable so apparently we got some hum or background noise we need to check switchable feedback loop like on the youtube cir super reverb video which has already been done and pedal for the reverb trim works i guess we'll double check to make sure it does okay so that's it uh other than the noise that makes the amp unusable everything's pretty straightforward so why don't we plug the tubes into it hook it up and see what we think of that noise and if maybe we can figure out the source of it i'm looking here at the reverb cables while i'm getting the amp all hooked up they look fine to me there's some corrosion down on this one uh so i think i'll clean the contact surfaces before i plug it in okay we've got everything hooked up here um the reverb tank foot switch the two uh eurotubes bias probes got a 12 inch 8 ohm shop speaker and i've got the amp on but on standby set everything down here to minimum and we'll let it warm up a bit then we'll switch it on and see what happens bear in mind since these 6v6s are fixed bias which means that the cathodes are grounded that we will buy us at about 70 percent of maximum and so that'd be around 8.4 uh plate dissipation watts and i'm right at that level now i crank down the bias a little bit so this would be more appropriate it's always good when you're doing checks like this that you first determine that the output tubes are not way over biased because while you're sitting here fussing around with this thing for 20 minutes you might be burning up your output tubes so double check to make sure that the bias is appropriate and then proceed okay so wiggle some tubes no problem no microphonics and i'm not hearing any more crackling or popping and what i'm going to do is turn it off let it cool down and then start it up again and see if we do hear it i'm going to input a 500 cycle per second tone into the normal channel input we'll switch the amp off of standby tubes are warmed up let's see if we can hear it oh yeah [Music] wow noisy trouble [Music] bass is okay [Music] all right now i'm going to unplug it plug it into channel 2 make sure it works okay channel 2. sounds great [Music] okay now we're in the vibrato channel of course improperly named should be the tremolo channel [Music] sounds great let's see about our tremolo [Music] well i'm not overwhelmed be honest i don't hear any tremolo let's try reverb [Music] none well we're off to a great start let's take a little break from amp repair and have jack and casey help us open a couple presents uh both of which came from a viewer in canada and much to my delight i see that one of my gifts was examined by u.s customs and border protection okay so since it's here apparently it does not contain either anthrax spores or any high-grade weed we can always hope though okay so let's open one of them and see what it contains jack says that one no jack which which is it gonna be boy okay this okay i've got the flaps open so to speak and i can see why they opened it i bet the x-ray machine had fits with this it's some foil backed foam okay let's continue on i'm not through on packing but jack is finding all of this very fascinating casey on the other hand is just sort of kicking back here and taking it all in well first i notice a pack of canadian treats for canadian kitties and since jack is of french ancestry i know he will enjoy these right jack he's still enjoying the package here look at these treats jackie yep now here's what's in the box you won't believe this it's uncle doug's esr meter and apparently this gentleman has actually hand built a an esr meter for us just beautiful i can't wait to try it out i'll include a test in a future video but he also provided some nice clips that will connect to the probe and to the capacitors being tested i can't imagine what will be in the second box let's see if jack likes the treats oh yeah how about casey casey looks like the treats are a hit vincent jack's begging for more here before we continue i just found this letter from the viewer who so generously built and sent the esr meter he says that he knows i have a digital meter that i might appreciate a backup analog meter and um i guess the circuit was created by w2aew now i am a subscriber to his channel and i recommend him to any of you who really want to hear someone with tremendous knowledge of electronics speak flawlessly about them he's really good okay so if this design came from him i bet it's a dandy instruction is oh i like the warranty a lifetime warranty against defects just return to the great white north po box one i bet that'll be a one-way tree uh trip okay let's open the second box well i got the second box open it looks like we have the shroud of turin or something in here let's get this wrapping material off and see what lurks within well a second box contained a bunch of tubes some are nos some are good used another pack of fantastic cat treats and here's a nice note some treats for the cats and some tubes for the stash it's kind of poetic well thanks so much vincent i know that i'm just going to leave the packing material here for jack he's really enjoying it and uh i'm going to take the esr meter and go start playing with it right away but i really appreciate it this is very generous of you very thoughtful and i'm going to make uh i promise y'all make good use of it so thanks so much well after further discussion with the owner of the amp he has verified that he wants these electrolytic caps replaced uh because he wants uh the uh optimum reliability for the amp uh and i i guess he plans on using it frequently so let's do that i'm starting off by uh removing uh the 322 microfarad at 500 volt ic caps and then i will install the same value but in a f and t cap which i think is of higher quality all right the first three electrolytics have been replaced and i've tested the internodal resistors and they are right on the money these appear to be fresh uh replacements so i'm going to leave them now we'll move on here to the reservoir cap parallel pair and there you have it all five electrolytics replaced with brand new f and t's and a new touch here that i think is a good idea i've added the date that these five caps were installed to help the next person so they'll know the age of these capacitors and whether or not they need to be replaced again get the doghouse cover reinstalled to prevent any shock hazard because the b plus is present all along uh in all of the wires between these caps now it's time to address the two other problems that we recognized earlier and that is that the reverb does not work and the tremolo does not work now since these are very common issues with amps of this sort let's go into some detailed analysis of how we can troubleshoot both of those circuits let's start off with the reverb and think for a second about all the different places where the problem could arise number one perhaps the reverb driver 1287 is faulty the uh transformer that drives the tank may be faulty the recovery uh triode of the 12ax7 uh may be bad tank itself may be bad could have our cables reversed or uh perhaps the foot switch has problems so let's go through all those different possibilities and eliminate any flaws in them so that we can get this pesky old reverb to start working again number one we don't need the foot switch for the reverb so uh let's just disconnect it okay we will need it for the tremolo you have to have the foot switch for the tremolo uh but for now get that out of the way so there's one variable okay the next one is let's find out if this tube and this transformer are working and we can do that quite simply and to do so we're going to need to make a cable take any old rca cable that you have okay i've got about 900 of them from all the electronic gear that i've bought over the years and just remove the insulation from one end of it and install a little alligator clip on the signal lead that connects to the central prong and then another alligator clip to the shield which connects to the shield of the rca plug okay i'm going to give you a few minutes to do that and then we will proceed now looking at our schematic we see that the 1287 and the tr4 reverb driver transformer connect to the input of the reverb unit so you'll plug your rca plug into the reverb input now this seems counter intuitive because you'd think there's the output from our amp but for reasons uh unfathomable to us mere mortals we have to plug into the reverb input then uh the other ends you connect to any uh 8 ohm speaker you might have laying around now how is this going to work well the reverb driver the 1287 and the little transformer it's really an output transformer and as far as it's concerned it's driving an 8 ohm speaker but we're sneaky so we substitute an 8 ohm reverb tank instead and it drives it now we're going to let it drive a speaker and if it can we will hear it now to avoid having our reverb driven speaker be drowned out by our shop speaker or cabinet speaker let's just pull the uh long tail pair up 1287 a phase inverter tube so that we'll have silence okay turn up your volume to about five and your reverb knob to a 10. okay then let's turn on the amp i'm going to inject a 500 cycle signal you can plug in a guitar if you want strum a few notes and let's see if we can hear anything from our reverb driven speaker we might have turned on the amp taking it off of standby and as you can hear the signal comes through strong there is nothing wrong then with this portion of the reverb circuit the problem must exist in either in the tank the cables or the recovery triode next step let's evaluate our cables and our tank to do that we have to take it out of that vinyl protective tank bag um move it around see if we you know i'm hearing something loose in there um let's remove these four screws and take a look at what that is that's rattling around in our tank also we notice this is not an acutronics tank but a gibbs tank okay i removed that cardboard uh floor from it and i believe the noise i heard was just the spring bouncing around but lo and behold look at this a broken wire one of the wires to our transducer here is broken uh let's hope that's all that's wrong with it uh it may be okay we might get off uh easy let's strip the tip of that re-solder it and see if our tank has proper impedance at both ends and if so we might be back in business all right i re-soldered that green wire to the signal lug and i also tightened this strain relief copper band here so that as the tank a spring carrier vibrates around it prevents that vibration from reaching this solder joint and breaking again now i'm going to check the resistance of the transducer coil we know that this should be around 8 ohms and instead it's only 1.4 which is troublesome gibbs tanks i'm used to seeing in gibson amplifiers i'm not sure if this is the right tank it may well be but we'll see if it works okay maybe the 8 ohm impedance is not correct on this particular model next i'm looking at these rca uh plugs here on the cables and they are a corroded mess you can see where the shield most of it is not even soldered to the exterior shell um i just i can't see using these if i had a valve of acid i might dip them in there and it might pep them up that i don't i'm thinking i'm going to replace these cables at least for testing purposes right now i went back to my stash of rca cables and found a nice pair here that are color coded they're also gold plated now i have communicated with the owner and he said he would prefer reliability and performance over uh strict originality so i'm going to go ahead and install these and uh we'll see if this helps so now let's wiggle the tank and see if we hear reverb noises oh yeah very nice okay it appears then that our reverb is repaired and now let's focus on the tremolo now because the tremolo on these larger fender amps requires a foot switch in the grounded position to allow the tremolo loop to oscillate we have our foot switch here but what if it isn't functioning properly let's eliminate it as a variable and make a very simple rca plug here in which our shield and signal wires are connected together this then will fool the tremolo into thinking it does have a a proper functioning uh foot switch in the grounded position now let's uh inject a 500 cycle per second uh tone into the vibrato channel we'll turn the volume up to five and let's turn our speed and intensity up to five okay and let's see if the tremolo works with the addition of our shorted plug if it does then it's the foot switch if it doesn't then we're going to have to start checking oscillation tube and oscillation loop in the circuit all right the amp is on i turn the volume down to a tolerable level and as you can see intensity control does not start any sort of tremolo effect so let's take a look at the schematic and see where we need to look next well we're looking here at the schematic of the tremolo circuit and the normal trouble spots are that the 12ax7 tube is not a good oscillator there might be a value that is drifted in the oscillation loop which no longer allows it to oscillate or there might be problems in the neon bulb or photoresistor for the opto coupler circuit so there are three main places we need to look okay and first off let's see if that opto coupler is even flashing now here is the little opto uh coupler unit we have a photo resistor in the bottom that makes that round bulge and a neon bulb up on top and if the oscillation circuit works we will see light flashing here in the little bedroll that the unit lives in took the app off of standby and as you can see there's all sorts of flashing going on in there okay it's like a jimi hendrix concert so we know darn well that this whole system here works otherwise we wouldn't see flashing now the bulb flashing does not mean that the photoresistor works so next we're going to check to see if the bulb is having any effect on the photoresistor now there's two ends to the little optocoupler burrito here one end feeds the high voltage end to the neon bulb uh you can tell that end because it'll be a 100k uh resistor here and a 10 meg resistor here now we know this works because the bulbs flashing let's go to the other side though this is going to be the varying resistance that our uh photo resistor uh creates in response to the flashing light now i've hooked on my two little alligator leads i'm over here on my mighty simpson 260 and you can see we're getting a really nice modulation in our photoresistor in response to the flashing neon light you're better off with an analog meter if you're trying to look at rapid response like this if i hook this up to a digital multimeter uh will the values will jump all over the place but you can see it is being modulated in a consistent range okay so it appears that there is no problem with the oscillation loop or with the photoresistor unit and yet as you can see and here we still have no tremolo effect so now we've eliminated a bunch of variables in a very short period of time we've eliminated the foot switch the oscillation loop the 12ax7 oscillator tube the optocoupler unit and now the problem must reside from this point into the circuit let's check the pot here the intensity part and make sure that it's functional i've hooked my probes onto the wiper and one side of the intensity pot and it's supposed to be a 50k pot there is 55.3 k and we can dial it down close to zero so the part seems fine i'll tell you this is an elusive tremolo problem usually by now you found what's going on let's check the wiring of that pump when i disconnected my jumpers look what i found the wire is broken away completely from the wiper okay so you know you can be as scientific as you want but sometimes just luck helps you'll see something happen in this case this wire moved and it shouldn't let's strip away the end here the insulation solder it on there and see if that isn't the break in our tremolo signal okay i've soldered that wiper wire back in place and let's see if the tremolo works okay here goes speed at five intensity at five ten works perfectly [Music] you know you couldn't ask for two better teaching opportunities for troubleshooting reverb and tremolo circuits in these rather complex amps now as you could see we went through and eliminated all the possibilities not a bunch of yanking tubes and pulling wires and tearing out your hair you approach it in a systematic manner and eliminate all possibilities and then when all else fails you pull out your hair and curse and look for broken wires so amp repair is not the glamorous uh hobby or or job that you might assume yes you spend hours chatting with rock gods about their amplifier needs but from time to time you just got to roll up the sleeves and get to work and it's a gritty dirty dirty job but heck somebody has to do it now unfortunately despite finding that broken wire on the input transducer and fixing it and the tank seeming to work because we could hear a reverb noises when we bounced it it turns out that the output transducer has an open winding as you can see there is no continuity through it so despite the heroic repair over here i don't happen to have an output transducer to transplant into this jewel so let's stop production here for a moment and order a replacement a proper tank and boom as if by magic here's our replacement i prefer the mod tanks they sound like the old acutronics tanks whereas the new acutronics tanks don't okay it's odd but these are vastly superior in my opinion and you see we they go by the same number the 4ab 3 c1b so this is the proper tank for the deluxe reverb let's check what the dc resistance is on the two transducers this will help you measure the dc resistance of tanks that you may have that are of the same model number as this and you can judge whether or not the transducers are in good shape this is the input we know it's supposed to have 8 ohms of impedance that does not translate to 8 ohms of dc resistance though and as you can see uh it's only like around 1.2 ohms 1.3 ohms of dc resistance okay so this transducer then the input transducer has that dc resistance now let's check the dc resistance of the output transducer which is i recall is supposed to be around what 2250 ohms okay and we see that it is 212.4 so kind of a i guess a general overview of this would be that the uh impedance is about 10 times the dc resistance that would put this at around 10 ohms and this at about 21.24 okay which is about uh the correct impedance for them so don't be worried if your dc resistance measurements come in low if they're about one-tenth what the impedance should be then both of your transducers are probably in good shape now for the uh correct polarity on our cables the output is the inner jack plug the red into it and the red into the output of the tank okay um i know that seems counterintuitive you'd think that it would be input from the output and output to the input but it's it's i guess they try to keep it as simple as possible so it's out to out end to end okay so now it's properly wired let's see if the reverb will work with the new tab before we continue there's one more indignity which must be resolved and that is that these uh fender dual button uh foot switches from mexico uh are almost always wired backwards okay i don't know no quality control i guess but if you notice the uh cable to the reverb pedal is shielded that's because the signal itself comes out to the reverb pedal so you have to shield so you don't pick up any noise now notice on this the reverb is on the right and the tremolo is on the left well as you can see the tremolo has the shielded cable and the reverb does not so you have to reverse the switches or some people have said oh just peel up the sticker and put it on uh backwards 180 degrees rotate well it doesn't peel up okay not easily and this isn't mine so i don't feel like destroying it so i'm going to have to rewire this switch before the shielded cable will go to the reverb and it will operate properly if you have one of these switches you might want to check it because i think it's probably a 50 50 chance that you've got one that's wired backwards also all i'm going to do is unsolder the white wire from this switch and the white wire from this switch and reverse them as you can see now the shielded cable that's on the left here goes over to the reverb switch and the unshielded white wire goes to the tremolo switch okay now we'll put the back cover on and proceed all right all of the pots have been cleaned as well as the tube sockets knobs have been adjusted so that the one aligns with the indicator mark let's go ahead and plug a guitar in and check all of the controls as well as the tremolo and the reverb okay let's start off with the normal channel input number one and the volume at three now both the treble and bass are turned all the way down let's turn the treble up [Music] we'll leave it at five and turn the bass all the way up leave them both at five now just to be sure let's go to input number two make sure it sounds okay [Music] all right i'd say our normal input is just fine now let's shift up to the vibrato channel now we're in the vibrato channel input 1 volume is at three everything else is turned off okay let's turn the treble all the way up that works leave it at five and now let's turn the base all the way up well that certainly works we'll leave them both at five [Music] okay now let's see uh how the reverb works and the foot switch turn the reverb up to five foot switch is off now let's turn on the reverb [Music] well that sure works now we'll try the vibrato let's go five and five speed and intensity the foot switch is off now the foot switch is on [Music] speed works great intensity works well reverb works great foot switch works now just for fun let's try the reverb and the tremolo at the same time foot switch both of the switches are off vibrato reverb [Music] i'd say everything works on this amp very very well so now let's go get ollie and jack and get them all tuned up and let's have our audio demonstration okay we're all set up here in the workshop for our audio demonstration we have our sm57 pointed at our jensen 12 inch ceramic speaker and the mighty uh deluxe reverb ready to go with its new reverb tank okay jack and ollie are all tuned up and ready to go so let's get started [Music] do [Music] [Applause] [Music] [Music] [Music] [Applause] [Music] [Applause] [Music] so [Applause] [Laughter] [Applause] [Music] [Music] [Music] [Applause] [Music] do [Music] [Music] so [Music] so [Music] [Applause] [Music] [Applause] [Music] [Applause] [Music] [Music] [Applause] [Music] [Applause] [Music] [Music] [Applause] [Laughter] [Applause] [Music] [Laughter] [Music] [Applause] [Music] [Laughter] so [Laughter] [Applause] [Music] [Applause] [Music] [Music] do [Music] [Applause] [Music] [Applause] [Music] do [Music] [Applause] [Music] [Music] [Applause] well i guess that's about it for this video extravaganza on the really nice 1965 blackface fender deluxe reverb i hope you enjoyed it and that you will subscribe to our channel if you have not already i wanted to send out a major thanks to all my patreon patrons and paypal contributors for keeping us on the air advertising free for another month if you would like to join them and supporting our channel please see the links that i put in the video description to assist you to do so and now without further ado it's time to announce our part two video uh in it i will discuss the evolution of the fender tweed deluxe amp from the very first version of the 583 all the way up to the crowning glory of deluxe tweeds the 5e3 if that sounds interesting then please stay tuned well greetings and welcome to our part two video in which we will trace the evolution of the fender tweed deluxe amp i thought it might be helpful before we start to have a brief discussion here on the fender tweed numbering system i'm not sure how many of you realize there is a very strict and helpful numbering system for fender tweed amps first number uh is the year now this is a little general five is fifties six is sixties but the second letter is more specific and it has to do with the cabinet type now all the cabinets are covered with tweed but if the five is pre uh followed by an a then it's a tv front cabinet bcd is going to be a wide panel and e is the narrow panel tweed cabinet there is a little bit of overlap on the b's in which some of them may have tv fronts the third number is very helpful also and that tells us what model the amp is if it's uh the third number is a one it's a champ two princeton three deluxe four super five pro six basement 7 band master and 8 twin now you can throw all your friends with your vast knowledge of fender tweed apps if a friend calls you and says hey i hear there's a 5d6 fender tweed amp for sale you can say oh that's a 1950s wide panel basement amp okay so you see how it works now the ones we're going to be discussing here shortly will all be 1950s we're going to talk about a b c d and e uh iterations of the 3 or deluxe amp circuit now in a previous video i already discussed the evolution of the fender woody amps they were the very first of the fender amps actually in the late 40s and that included the princeton the deluxe and the pro so if you're interested then in the amps that come before the series will just we're going to discuss right now then you'll have to go check out that previous video series so now let's start off with our first circuit which is appropriately uh designated as a 1950s um tv front deluxe okay and uh there is a little overlap on the five designation in that some of these were actually created in the late 40s we say that the 583 amp then was produced from 1948 up to 1953 and all had the tv front cabinet okay we're looking over here we see that we have two separate input uh channels number one has two input jacks each with a 75k grid blocker passing through a 0.05 microfarad capacitor to the grid of the upper triode of a 6s c7 the bottom input does not have any grid blocker but it does have the 0.05 microfarad input capacitor it will feed the bottom triode of the 6sc 7 preamp tube now the first thing of note here is the very primitive way that the 6 sc7 is biased it uses a method called grid leak bias in which the cathode is grounded but the grids are separated from ground by a high resistance okay this creates a weak negative charge on the grid which helps it suppress just the runaway plate current okay now this was inherited from radio technology remember that leo fender started out repairing radios and he then when he started designing amp circuits continued with this grid leak biasing technique which is like i said very primitive it works well in radios where you have a very consistent input from your radio receiver into the radio amplifier but with guitar input signals they can vary greatly in strength you can hook up some humbuckers and crank the guitar wide open and really overpower the grid biasing of this 6sc 7. so it was a cheap simple sort of time-proven method of grid biasing but it could not cope well with the transition to guitar use because of the uh potential for very high voltage input from the guitar and lap steel pickups so i think we can consider that a weakness in other words you uh plug into a 5a3 uh with a guitar with humbuckers crank it up and start flailing away at the strings and you're going to get all sorts of blocking distortion from your preamp tube let's move on now then to the rather unusual and interactive volume and tone controls to get there we pass through 0.05 microfarad coupling caps i mention that because these values will change in our subsequent circuits we see here something a little bit unusual and that is we have a volume control for the upper channel here we have a separate volume control for the bottom channel but what's rather unusual about this type of design is that both volume controls interact with each other and they interact with the tone control so uh if you change the setting on any one of these you will be affecting the overall tone on really on all of them one other detail of note is that the circuit provides for a bypass this is a 500 picofarad capacitor high frequencies coming through here can bypass that one meg volume control and go straight through to our phase inverter okay so you have on the upper channel a high frequency bypass on the lower channel you don't okay so um if you plug in then to this channel you will notice probably uh more mellow or base frequencies than if you plug into the upper channel but once again uh to emphasize the interaction between all these controls the amount of bypass varies depending on the volume control or the tone control so as you can see these are very fluid adjustments here uh which can require all sorts of uh kind of finagling around to get everything balanced to get the tone you want once you've done that then we pass through a single wire to the six sc7 paraphase inverter we see that this paraphase inverter is a 6sc7 the same as the preamp tube we also see that it is cathode biased and cathode by past okay to maximize gain it should also be noted that a paraphase inverter like this one and i'll discuss in a second what that means has full triode gain so this is a relatively high gain stage even though it's a phase inverter the paraphase type of phase inversion has greater gain than the cathodine or the long-tail pair okay so keep that in mind when we talk about future circuits now i've already discussed in detail how the paraphase phase inverter works in a previous video series but i'll go over it again here a little briefly just for clarity's sake we see that only the top triad of the 6sc 7 is driven by the preamp stage however if we follow the output from that plate we go through the coupling cap which blocks the high voltage dc and only allows our guitar signal to proceed and it can go on here to the grid of the upper 6v6 output tube or some of it after passing through a resistor can be fed back in down here to the lower grid uh of the lower triode so we don't want to send the full blast output signal down here because it would greatly overpower the lower triad and also result in completely imbalanced out of phase outputs from it so instead we send just a small amount of it down here to the grid just enough so that once we amplify it through this lower triode we have equal but opposite phase outputs from our six sc7 phase inverter they then pass through these coupling caps to the grids of the 6v6 output tubes the rest is fairly straightforward the cathodes of the 6v6s are both cathode biased and bypassed as were the uh cathodes of the six sc7 output from the plates goes to the push pull output transformer and then out to our speaker the only other uh thing to notice down here is our power supply uses a 5y3 very standard but look at our filter caps 16 16 16. keep those in mind as well as the 10k and 10k internodal resistors because we'll see variations in the uh subsequent circuits that we're going to discuss now when we move to the 5b3 if the circuit is the same but because of the letter b we know that we will see that enclosed in a wide panel cabinet so um from what i understand that's the only difference a 5b3 is a 583 circuit in a wide panel instead of a tv panel cabinet so let's move on now to the 5 c3 and here we have the 5c3 circuit now this one has the signal pathway marked in gray by rob robinette who i highly recommend if you want to do further research or do more study on the evolution of the deluxe amps he has an excellent site that covers it in great detail i've designated the changes in red okay right off the bat here uh the input capacitors uh have been doubled in value remember that on the 5a and 5 b3 circuits they were 0.05 microfarads now this will allow more base frequency to enter the amplifier circuit and be amplified so this will warm things up a bit let's stop for a second here and discuss why we even have these input capacitors here on the pathway to the grids of our six sc7 preamp tube i've heard three different explanations one of them is that they're like input filters imagine if you put a 0.001 microfarad cap here and here then you're only going to get high frequencies into the amplifier by doubling the values on the input caps we in increase the base frequencies that are allowed to enter so we end up then with more base frequencies amplified and a sort of a warmer bassier output the number two explanation is some [Music] sources of music signal might have their own power supplies and there might be dc present in the input signal this then will block it to keep it from making it to the grid and altering the bias of our six sc7 preamp tube the third explanation uh makes the best sense i think in this context and that is when you use grid leak bias you're creating a weak negative dc charge on your grid to moderate your plate current now that dc charge could leak to ground if it were not blocked by uh this capacitor in this position in this position so the cap then can also serve to preserve and stabilize the negative dc bias voltage that is uh created on the grid of our preamp tube the next change is over here in which they are fine tuning that voltage divider that sends some of the signal from the upper trial to the six sc7 back down to the lower grid uh for phase inversion this is to achieve a better balance in the two out of phase output signals from the phase inverter now the third change is by far the most significant and it is the provision of an nfb loop in which some of the signal being output to the speaker is sent back into the circuit out of phase to neutralize some of the amplified signal okay it's sort of like a governor the harder you drive the amp the more signal will be returned and will neutralize more of the signal to calm things down now i have a feeling this was done because of the remember i said primitive method of grid leak biasing the 6sc7 preamp tube i'm thinking people were plugging guitars into this thing and if it was single coils or low output pickups they probably did okay but some people would get all sorts of distortion at very low volume levels so leo added the nfb loop to sort of calm things down to tame the amp to reduce the distortion and to increase the headroom the fourth change is just more for convenience in that there is a auxiliary speaker output jack also you notice that they made the cabinet speaker detachable from the circuit to me i don't see why you need this if you can just detach the cabinet speaker and plug in a external cabinet you could do so here instead of up here the problem arises when you leave this connected and then connect in another uh speaker or cabinet and you cut your output impedance in half okay apparently the output transformer could cope with it but we know that's really not the best way to do things now that we're through with the model 5 c3 which we know was a 1950s wide panel deluxe just like the 5b3 let's move on to the 5d3 and now it's time for the 5d3 version of the fender deluxe we see that the input section has been reconfigured and that the preamp tube is no longer a 6s c7 but a more customary 12 a y7 no more primitive grid leak bias we see that the tube is cathode biased so we don't need those capacitors and the input lines to maintain the charge on the grid we see that the blocking resistors now have been reduced to 68k down from 75k the interactive tone and volume controls have been kept the same except it's upside down as you remember uh this bypass loop was on the upper triad now it's on the lower uh signal still is fed into a new uh type of phase inverter which is a 12ax7 instead of the 6sc7 unlike the 6sc7 that had a shared cathode we have two separate cathodes now for a 12ax7 phase inverter one of them is cathode biased and bypassed and the other is simply cathode biased they still used the paraphase phase inversion method uh which the output from the upper plate goes through the coupling cap and then through a 220k ohm resistor into the grid of the lower triode of the 12ax7 because of the change of tubes they had to change the voltage divider resistors to send a different amount of signal back here to the lower triode they also strapped the plates with a .0001 microfarad cap that is supposed to prevent oscillation apparently after they assemble this oscillation was a problem maybe with some 12ax7s so they put this in as sort of a safety feature and the final uh change is really a deletion and that is that they eliminated the nfb loop and i think the reason for that is once they did away with the grid leak biasing then the distortion problem was pretty well eliminated here in the preamp you could drive the tube now uh with humbuckers and not get the type of distortion you did with the old primitive grid leak bias therefore you did not need the nfb loop to reduce a distortion and increase headroom which brings us to the 5e3 circuit for the fender deluxe and this is the one that most people feel is the absolute best of all the tweed deluxe circuits because of the letter e here we know that this is the first of the tweet amps in a narrow panel tweed cabinet now looking at the input circuit we see that instead of three input jacks we now have four and the each one is different this will be the bright high gain input bright low gain input normal high gain input normal low gain input now the bright and normal are differentiated because of the bypass to the volume control that we discussed way back in the beginning of this series okay and that bypass only works for the upper two inputs hence they are the bright inputs the bottom triode here does not have that so it will be called normal the high and low part has to do with the way that the inputs are grounded and the configuration of the grid blocker resistors now i cover this in great detail and a a video titled the offender input circuit and if you want to find out exactly why this occurs you'll need to go check that video now we see that they retained the same preamp tube the 12a y7 but they doubled the value of the coupling capacitors from 0.05 up to 0.1 this then will greatly increase the base frequencies that will proceed on into the amplification circuit we see here that instead of the 12ax7 being used as a paraphase phase inverter that it is divided and we use one triode as an extra amplification stage and the second triode as a cathodine faisenberger now the cathodine phase inversion is simple and it only uses one triad instead of two but it has almost no gain whatsoever whereas the paraphase used two triodes and had a great deal of gain so this extra amplification stage will help to compensate for the loss of gain by using the cathodine phase inversion method then just to ensure that the base frequencies that we let in back here go on undiminished we uh increase the coupling caps between the phase inverter and output tubes we double them from 0.05 up to 0.1 so once again this enhances the base output of our amplifier uh in a first here we see that grid blocker resistors are included for 6v6s these act to reduce the blocking distortion that can happen when you overdrive the amplifier so this is a new addition and we'll see it on almost all subsequent fender amps there is still uh no negative feedback loop we'll see it in some later models uh but uh it's still been left off apparently it wasn't felt that it was necessary to suppress distortion and increase headroom with this circuit let's look down here at the internodal resistors and this one has been uh cut in half it was 10 000 ohms now it is 5000 ohms that will increase the screen voltage when you increase the voltage on the screens you increase the gain within the tube it makes the tube more efficient and you'll get a greater output from it so this then boosts the output from the 6v6s then we increase the second nodal resistor from 10k all the way up to 22k and that is going to rain in the tendency for the preamp to uh distort okay so we're going to reduce the preamp gain a little bit and increase the output gain that's what this alteration accomplishes well that's about it then for this review of the fender deluxe tweed amplifier circuits i hope you enjoyed it and uh that you will stay tuned and join us for future videos thanks so much for watching bye for now

Channel: Uncle Doug

Views: 59,774

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Id: T-sAgh41vUQ

Length: 88min 8sec (5288 seconds)

Published: Thu Mar 25 2021