1950 Fender Super Amp: Naked and Thrashed but still SUPER !!

[Music] so [Music] well greetings out there on youtube land and welcome to today's big video which features the contents of this gigantic box i think it's at least two feet squared by probably 15 or 16 inches deep so let's get it open and see what our challenge will be for the next week or two well i've got the flaps open and we see that the dreaded styrofoam jingle berries have been used to pack this and a great big roll of the green bubble wrap okay so you know these are probably the bee's knees for sending a a little teapot to aunt gertrude but as far as sending amps man it's not the hot setup okay notice that they've all shifted from that side so that there's absolutely nothing protecting the amp from injury on one of its four sides and one other little tidbit is as i carried this into the workshop i could hear some ominous rattling going on it sounded kind of like a loose glass tube or something but let's go ahead and get it out of here and see what we're up against well here's something you don't see every day it looks like at one time it was about a 1950 tweed fender super amp okay this was what was rattling around in the box okay it gave a rather strange sounds that really made me apprehensive but apparently it caused no problem now as you can see the grill here has been filled in with some kind of fretwork that somebody made the original center chrome steel piece is in place thank heavens but really if it weren't for that you might have a little trouble telling exactly what this is okay now um strange looking grill cloth it looks like uh the placemat from some chinese restaurant um and i don't know what that is from the smell it's uh either rat or cat urine uh the stanch here is just overpowering and rats apparently have good taste in amps um okay so we see there's that's just stuck on the side it's not a patch or anything uh let's turn it around and see what's awaiting us uh in the rear of this amp that's a new handle has been installed it's structurally sound but it's like a mile and a half from the way it came from the factory i'd have to say the rear view is every bit as strange as the front um we've got the three wire power cord here from probably a table saw that was recently sold at home depot got a roll of paper towels probably to soak up the rat urine i think these are the tubes down here and i'm seeing something that just sent shivers up my spine which is a old output transformer tacked onto one of the speakers now the control panel however is probably the nicest thing about it it's actually you know how these tweed amp the control panels don't hold up well the silk screening is very flimsy on them but this one held up pretty well god i'm having to hold my breath here this is pretty fierce this makes this that silver tone what a 14 84 that i did a year or two ago smell like chanel number five okay uh let's go ahead and remove this upper cover here and take a look at what's going on inside this chassis and also just because i didn't mention it don't think i didn't notice it uh the elephant in the room is of course that all the tweed has been carefully peeled off of this jewel which is indeed sad there's just two original tweet panels and we're going to remove this well the upper panel is off and as you can see every single capacitor in the circuit has been replaced with a very obviously new replacement cap um the power transformer apparently is still in place uh we'll have to see if it's the original one and i'm not sure why this i've never worked on a super amp before this vintage and somehow i can't believe fender uh left the output transformer hanging like this and little things like you know loose wires uh oh man this is and look down here a nice big glob of solder grounded against the body of the output transformer oh boy looks like the work's cut out for us on this jewel i'm having to shield the amp so we don't get any glare well anyway that's what we got let's take a look at the letter and see what the owner uh instructs us to do okay the fender super removing the tubes a small piece of plastic broke off you know that's probably the indexing uh peg there in the middle of the 6l6 base tubes are wrapped in paper towels okay my complaints about the amp i had a dual professional from a year or two earlier wow and it was louder had more headroom more highs it was more marshall-like when cranked i can see why billy gibbons uh has dozens of them this one is bassier and somewhat gutless so it's weak flubby and no trouble output to speak of okay so uh and he says it may be the speakers but odds are uh it's more than that from what we've just seen looking at it okay it's been worked on by other people uh and i'm gonna refrain from making any comments about the work but uh we'll uh proceed here okay uh i'm scared to just he suggested i just plug it in and see what i think of how it sounds but when i see stuff like this and this i just can't do that okay uh i don't know how anyone who works on amps could return this to a customer i just can't okay so that said uh let's get started on the chassis well one happy discovery here is the uh tube chart is still glued in the cabinet and is still in really good shape see that serial number is 905. is that low enough for you three digits and notice what an unusual circuit this is and we're going to discuss it the circuit in just a minute but it uses six sc7s three of them these two will be preamp this one will be a phase inverter i have a feeling and then two 6l6 g's now these are not gcs just g's and a 5u4 rectifier tube okay all in all other than [Applause] the obvious staining here from i'll let you guess what the cabinet interior is in real nice shape well i'm in here disconnecting the speakers from the old wiring and i can see that that glob of solder formerly was a speaker log here to connect uh the output transformer to the speaker so that's broken loose mainly because there was no bolt or nut here holding this end of the output transformer to the basket i'm going to have to do some research on these to see if this basket mounted output transformer is legit uh i've never seen that before in a fender amp but one never knows on these early ones okay let me continue i've got to get that strain relief off of the wiring so that i can get the speaker out apparently the speakers are in are very questionable so i need to get them out and take a look at the cones okay this first speaker's out and other than a couple holes the suspension is solid the cone is fairly thick and still seems completely intact i have no idea about the strength of that alnico magnet alnicos lose their strength over time okay so they can get weak and that might be part of the issue i'm not sure but cone wise this jewel looks pretty good let's now try to remove the second well here's the second speaker other than all the urine stains on it the cones in perfect shape good solid surround good suspension filthy but i don't think the speakers are what are wrong with this amp um okay let me set this aside well let's look at the speaker code here while we're at it all right we see 220 for jensen uh 1950 the 16th week this one is from the 21st week of 1950 that goes along pretty well with the dating of the amplifier chassis and here's all the part numbers uh p10 arts and alneco speaker of course 10 inch in diameter and the part numbers are exactly the same c 4898-3 c-4898-3 so to me there's no doubt at all that these are the original speakers and they're in surprisingly good shape you know now that i set them down and i look at the cone and the contrast between the dust cap and the um speaker cone and the fact that this dust caps off center uh i also look at the gasketing material this doesn't look like the old-fashioned type of gasketing material but i just have a feeling these have been re-coned at some time in the past um somebody i think had these recalled which is fine that's that's just peachy okay it'll save money and time that they don't have to be reconed again hopefully i have the chassis out of the cabinet the power transformer is monstrous it's a triad number 6516 and it's massive and since it matches the holes in the cabinet i've got a feeling probably original and also since there are no empty mounting holes anywhere for the output transformer apparently they were basket mounted on the super amps and this poor wretched thing here i'm going to figure out where the broken wires go and all but i guess that's uh really supposed to to be mounted the way it was so i'll have to put it back and let's turn over this chassis and take a close-up look at the circuit i'm looking all over on the inner surfaces of the chassis for that telltale piece of tape with the name of the probably lady who soldered this amp as you can see though the kind of corrosion and other unknown organic substances have pretty well wiped out the area where you'd expect that to be found so i don't know if loopy soldered this one or not it's going to remain a mystery i guess also there's something else i noticed here if you look let me get it where there's no glare at 47 microfarads which seems real high and 222's let's look at the layout for this circuit and see how that agreed well the layout shows a 16 16 instead of 20 to 22 and they'll notice there's two 16's in parallel which should give you 32 microfarads and they installed a single 47 microfarad now i don't see room here for the two parallel caps so i i'm wondering if maybe the layout might not be incorrect i've seen other pictures of the um chassis circuitry and in each case there are only three electrolytic caps the whoever recapped this went kind of uh over like about 50 percent on the values on the electrolytics but uh judging from the massive size of this uh power transformer though it should have no trouble coping with that uh initial current flow on startup one other thing i noticed uh when looking over the circuit and comparing it to the layout drawing are these uh 250k resistors going to the wipers of the two volume controls whereas down here on the layout you see there are no resistors going to those wipers so maybe that has something to do with the reduced output volume of this amp i'm going to try it then with and without these and see if it makes a difference we can see here that the tone pot has been replaced as has the on off switch the toggle and the fuse holder you can see that the three wire power cord has been wired a fuse first then switch then primary of the power transformer which is not the way i wire them but a lot of people wire them that way resistors [Music] well i think what we got to do is make sure there's no loose wires maybe plug in some tubes into this jewel hook it up to a good speaker and see if it does sound okay or if it destroys the entire neighborhood in a fiery ball of smoldering rat nectar look at the light just right here and i can see that the serial number is stamped into the steel chassis it's zero nine zero five a three digit serial number um and since that matches the tube chart that was glued into the cabinet we can then assume that both the chassis and cabinet came together as a unit from fender back in 1950 now i'm trying to decipher these wires here on this output transformer i'm drawing a little simple diagram here to help me and it appears that that broken wire that was flapping in the breeze there in the cabinet uh connects the chassis to the body of the transformer this ground wire here then grounds the secondary to the body of the transformer to the chassis of the amp and to one of the lugs of the speaker which then travels through this wire to the corresponding log on the other speaker okay so uh i know now how this can be wired so that we can test our circuit well i open the tube setup i'm installing them and you can see that the three uh six sc7s are in real nice shape um unfortunately these are not 6l6 g's but gcs which are not appropriate and as predicted that piece of plastic that was broken uh when the tubes were removed is indeed the indexing peg for the bottom of one of the six l sixes i think i'm going to convert this back to regular 6l6 gs these just aren't right they operate at a different plate voltage and at different plate dissipation than the tubes for which this amp was intended let's take a little break from that smoldering hot workshop to open a very interesting looking package that arrived here from umea sweden it was sent by a fine chap named max wieberg and already jack is doing his traditional cat scan sniffing away and judging by his reaction i think we're in for a really pleasant surprise okay he seems quite excited about this casey's playing it cool over here on the footstool waiting to see if there's any cat treats so let's get it open and see well we got a really nice letter here uh telling us about the contents addressed to uh uncle doe jack and casey and sure enough the gang's all here hey casey how are you doing so without further ado let's get the box open and see what max has said well packed inside is if to resist a nuclear holocaust there's a group of el86 tubes and 7199s which are always welcome and a couple others here that were tacked on with uh duct tape and i'm going to have to get scissors to get these open you know it's it's kind of ironic but sometimes the extremes of packing actually jeopardize the contents of when you try to open it okay in this case i'm going to have to be very careful with a pair of scissors do surgery on this packet to get the tube out safely well the box and packing material do look like they've withstood a nuclear holocaust and look at the packets that it contained el86s 7199s ecc 84s it looks like so let's get these packets open and take a look at the tubes well i'll tell you the contents were indeed a treasure trove first there are 10 el-86s still in the sealed telefunken boxes it's my understanding i believe this is an output pinto similar to the el-84 but it operates at a higher current and lower voltage three of the ultra hard to get 7199s all nos and sylvania boxes and a pair of ecc 81s which i believe are 12 at7s which are always come in handy with fender amplifiers so thanks so much max i'll tell you it's a phenomenal assortment of tubes i know you went to great effort and expense to send them to us and i assure you they'll be put to really good use thanks again i was doing some research on the internet on the fender pro amp and i saw this view of one that's for sale and you can see the outline of the intricately carved speaker baffles on either side which are identical to the ones on the amp that i'm working on so those baffles are correct and original and now i need to get this a plain brown cloth to cover over the outside of the baffles instead of that sort of high density cloth that's between the baffle and the speaker and probably largely responsible for the absence of high frequency and the muffled tone let's pause for just a second here for a brief discussion on grill cloth physics okay now there's two ways that the grill cloth can be mounted the way that it is on the amp at the moment is that the speaker is connected to the baffle this is the hole in the baffle for the speaker and the grille cloth is right up against tightly against the face of the speaker the way it should be is that the grill cloth should be outside here spaced away from the speaker by at least the thickness of the valve now think for a moment uh about the comparison between this setup and the compression ratio in a car imagine that this is the piston and this is the compression space now when the grill cloth is directly against the face of the speaker the compression ratio if you will is maximum it's quite high when the speaker tries to push forward the cloth is right there to prevent it from doing so or slow it down now the further away that we space the grill cloth from the speaker the lower the compression ratio just like the roof of a combustion chamber so now our speaker has freedom to move and an air space here in which it can compress and move forward and backward with some breathing room okay now what you want in an engine is a relatively high compression rate ratio but in speakers and grill costs the lower the better zero it would be ideal so as you can see putting the grill cloth where it is now is the worst possible arrangement and moving it further away from the speaker will behoove the free motion of the speaker cone also i discovered this photograph that shows the output transformer mounted on the speaker basket as it is in the amp that i'm working on um so this is original and it looks very much like the output transformer i received so i'll have to remount it back on the basket and rewire it like the one you see the presence of the power transformer drooping down toward the speaker magnets is a deceptive because the chassis has been removed from the cabinet and rotated normally this is pointing uh directly toward the speaker baffle now for an example of how this amp uh looked when it was first made uh this is an add-on reverb it's for a 1950 super uh identical to the one that we're working on except in way better condition in fact um this uh tweed looks to me almost like it's been retweeted it's too good these amps hard really didn't hold up all that well the tweed's normally in shreds this looks like it's been replated and also this one has the little fender name tag which ours is lacking i don't even see any holes in the cabinet of the one we're working on where that tag was but i have a feeling that the tag was on it and was probably lost when all the tweed was torn off of the cabinet now here's a inside rear view of that reverb fender super amp and we don't see the piggyback output transformer here now maybe they've rotated the speaker so that it is it would have to be atop this one maybe it's up here kind of hidden but that's different than the one we have but i do think that the output transformer should be in the piggyback configuration the ad for the reverb super is very informative says here that it evolved from the dual professional which is often cited as the world's first twin speaker amplifier that what that was uh introduced in 1947 it has the two angled 10 inch jensen speakers and two 6l sixes producing 18 watts of output power it was renamed the super in the fall of 1947. amps are rare due to low production totals well since the originality train left the station a long time ago on this jewel i'm going to take a little bit of latitude and the grill cloth that i'm going to cover these baffles with i've got a dark brown material it's pretty darn close to what was used originally but it has some gold sparkles in it okay and i know that's not original but it'll pep things up i think just a little bit okay so let's get these baffles out of here and uh get this off and then we can start covering them now that those two speaker baffles have been removed as well as that nickel plated metal strip i'm going to take advantage of the situation to clean sterilize and hopefully deodorize the floor of the cabinet well i think you'll agree it does look a little better now there's a pencil number 20 in a circle here which usually has something to do with the different parts of the cabinet all getting back together in a matched set okay so we'll let this dry out while i'm addressing the speaker baffles now before i start covering i'm going to show you a little trick here probably your material has been folded up or rolled and there's going to be wrinkles like this in when you try to stretch them out it's not going to work very well odds are let me show you a little secret just take a squirt bottle like this and kind of mist the material along that crease and let the material relax you can iron it i guess if you wanted to but there's really no need because once the material gets damp [Applause] it completely relaxes it accepts a new kind of a flat shape and now when i stretch it and staple it when it dries it's going to draw up a little bit to make it even tighter okay so as you can see just very quickly there that fold that almost made this piece of material unusable now is essentially gone step one of course would be to remove this old material that's been tacked onto the rear of each baffle after pulling all sorts of staples out i've got the pieces of material removed it's kind of ironic the material does look sort of like the oxblood grill cloth that you'll see in later tweed amps but they installed it backwards with the unpatterned uncolored side outward and the oxblood portion to the inside okay which which seems strange but anyway this stuff is headed for the dumpster and we'll install our new grill cloth now that i've got the grill cloth off it's kind of interesting the number 20 remember that was in the cabinet is here on each of these with an arrow pointing toward the bottom center then so that the two arrows would come together apparently that's the way they were cut and that's the way they fit so the assembler want to make sure that these things are put back in right and there we have it all the edges are securely stapled down and glued in certain areas and uh it's just taught as a drum head and now it's time to do the other speaker baffle then using a in this case sharpened screwdriver and your acetylene torch heat up the short point and melt or burn holes for the screws that we'll use to reassemble the baffle if you don't do this it's going to ravel what you're doing really is mounting it into a ring right here so that no threads will pull out it's just a whole lot better way to do it okay after washing and sterilizing the floor of the cabinet the odor is essentially gone and just to make sure it stays gone i sprayed a coat of matte clear coat lacquer over the floors you can see it doesn't look like it's been coated with anything but that does seal it and it keeps whatever odors in it from coming out and any new spills or nasty substances from soaking in all right i've got the grill cloth the two panels connected together uh with that nickel plated centerpiece and now it's time to install this back in the cabinet well the two uh speaker baffles are now screwed in place and you can see just how transparent that grille cloth is and it will be that transparent to the sound waves coming through it also so uh i think the suppression of high frequencies and all and perhaps volume will probably be very noticeably reduced with this new grill cloth installed properly and here's the full frontal view if you will you know that front works kind of neat and all once the speakers are in you won't be able to see it even if the lights behind the cabinet but this is the way uh this cabinet's supposed to look with a fairly plain brown cloth in place all right now i'm going to set the cabinet down here out of the way and we'll get started on the speakers and on the uh amp chassis insert now that i've got the cabinet all cleaned up with new grill cloth i've got the speakers checked out and one of the cones repaired i'm going to reinstall the output transformer here on this speaker basket okay i have to partially reassemble this if i'm going to continue the repairs and testing you just can't do it with everything strung out all over the top of the workbench so first step will be to reunite the output transformer with this speaker basket and figure out some sort of a simplified wiring system where we can test the circuit using the original speakers now to facilitate matters i'm going to separate the output transformer from the chassis and circuit uh there'll be three wires one is the b plus and one is from each of the six l6 plates okay so i need to trace them in and mark them depending on what position they connect to now everything's separated from the different pins and labeled and now i've gotta untie this rotten knot here uh which is just a short circuit in about to happen and uh get these old rotted wires out of here now that i've untied that knot i think you can see just how wretched these wires are all kinds of bare exposed wire three of these now carry b plus and one is a ground which is a not a very good combination and they're right near the chassis so i'm going to replace these uh four wires uh first i'm going to uh install the output transformer on the basket of the left speaker install the speakers in the amp wire the output transformer to the speakers and then i will use fresh wire to connect the output transformer to the amp circuit now the chassis speakers and output transformer are all separated which will make uh handling them a whole lot easier with the output transformer separated from the circuit uh i measured the resistance of the uh two half windings of the primary and found them to be a 128 144 and then when i measured from t1 to t2 it was 272 ohms so it appears that the primary is in good shape i compressed the sides of the output transformer back together and screwed it down to the basket and then uh reconstructed that missing a lug on the speaker and i've wired the secondary connections to the first speaker and since they are in parallel there will be two other wires and that come out to the right hand speaker so now i can install this in the cabinet both of them connect them together and then reunite them with the circuit and it should be a functional unit well the two uh 10 inch jensen speakers are reinstalled in the cabinet with the output transformer these are the wires uh for the primary that are going up here that it will connect to the circuit and the secondary wires are all connected the speakers are in siri let's take a few seconds here to discuss speaker polarity polarity in a speaker means that when the positive waveform of the music signal uh reaches the speaker the cone will move forward outward and when the negative waveform uh encounters the speaker the cone will move backward or back in toward the basket now this is only an issue if you have two or more speakers they have to both be moving in the same coordinated way okay both cones out for the uh positive music signal both cones back in for the negative now the polarity of many times is marked on the speaker it might be a red a little dab of paint or something on both of the positive terminals if it's not marked you can take a nine volt battery and apply the positive pole to one of the speaker logs the negative to the other and if the speaker moves out when the positive pole is attached to this log then that's the positive log okay if the speaker moves back in when you apply positive to this lug it's the negative log so when we're wiring our speakers in parallel we will bring the wire in here to this positive lug and then over here to this one the other speaker wire will go to the two negative logs now in the case of the speakers in this particular amp it's a little confusing because they're not uh positionally so we have to keep it straight that this speaker in effect is rotated 180 degrees compared to this speaker so the plus is at the top here bottom here so my wire will come in like so and then the negative lugs will be at the bottom of this one and at the top of this one in effect in this case the wires will cross and the speakers are connected in phase when you have two or more speakers you have to be sure that they're properly phased if you notice the white wire from the top terminal here goes to the this is 180 degrees rotated to the bottom here black wire to black wire so the wires cross uh and the speakers are now in phase if they're not then you'll get sort of a flat tone very dead flat tone and uh you'll be lacking a lot of bottom end okay so that much is done now it's time to hook the uh primary up to the chassis plug in some tubes and see how our amp functions and what else needs to be done to well the chassis is now installed in the cabinet and i have strung the four uh wires that uh interact between the output transformer and the circuit threw a grommet uh in a hole in the back there in the chassis and now i'll reconnect them to the 606 plates the b plus and to ground all right the uh output transformer primary has been rewired into the circuit uh now it's time to plug in some tubes and let's test the circuit see how it sounds check voltages and current and uh just sort of get a idea of how well it's functioning well the tube set is all installed and i have my euro tubes bias probes in place beneath the 6l6s so that we can monitor the plate current and plate voltage let's uh switch it on we're plugged into the current limiter so uh no harm can be fall of the components hopefully and let's see what happens does it hum or does it know the words [Applause] okay the amp is turned on no flashing of the current limiter bulb and we see that the plate current is flowing quite nicely we have a 48 there's 35 about 17 to 18 watts of plate dissipation now bear in mind these 606 gcs are cathode biased so they could theoretically go up to 30 watts okay i don't know if the power supply in this amp can handle it but right now it looks like we have an acceptable plate dissipation so why don't i plug in a guitar and strum a few chords let's see if we have volume and clarity remember those were the two things that the owner complained about okay an absence of volume and clarity okay i'm plugged into the instrument channel the volume is at 4 out of 12 which should be a conservative volume setting tone control is straight up at 6 out of 12. well the volume is not too bad but it is really lacking in high frequency definition let's uh turn the tone all the way to treble [Music] a little bit better but really not the kind of clarity that you would hope for let's change channels now and go into the microphone channel turn it up to 4 out of 12. sounds just the same so the issue is probably nothing to do with either of the inputs it has to do with the common shared components like the volume control tone control coupling caps things like that so let's take a look at the schematic and see if we can see where we're losing or blocking the high frequency let's take a look here at the fender super model 5 c4 schematic we see that each of the inputs is virtually identical and in each case there is a 0.1 microfarad at 200 volt capacitor that will block any sort of dc from getting in here and changing the bias of the grid we also see that the biasing of the six sc7 preamp tubes is grid leak bias which is rather primitive it's something i think leo fender learned from working on radios and it's really not ideal for guitar amps but that's the way it is configured all right we're going to come in then to either of the six sc7 preamp tubes the plates will feed out here through 0.1 microfarad at 600 volt coupling caps well those are rather high values for coupling caps they're certainly not filtering out the high frequencies but let's look right here at the tone control this is the standard fender tone control for all of these early amps and most of them did not have a sound like this where it was real muffled and had low treble also we have a one meg ohm volume control here for both channels and really it's not any way for the high frequencies to leak out at one meg this is about the same value as most amplifier volume controls have okay let's start off here with the 0.0005 microfarad uh sort of entrance a tone cap that goes to the tone pot we see that it is right here and that its value is really 0.001153 so it's more than double the capacitance that it should be okay right off the bat that's a troublesome error now let's look at the second tone cap which is 10 times the capacitance of the first and see what its value really is as we saw was supposed to be 0.005 and instead it's 0.010 it's double the value it should be it should be 0.005 okay so both of these tone capacitors are incorrect let's install the proper ones and check the resistance of the two pots and see if that makes any difference okay both tone caps have been replaced let's see if this helps at all [Music] i think it is a little bit clearer but it's still not right okay so let's keep looking for ways to improve the tone i was looking at the coupling caps between the preamp tubes and the phase inverter and instead of 0.1 they're 0.047 so you know as you go up in value on your coupling caps you let more and more low frequencies through so if anything the 0.047 should help the problem not cause it so we'll leave those in place and move on over here to the phase inverter and we see this 0.0001 microfarad cap probably to cut down on oscillation uh and then when i looked in at the value on the cap it's 0.0015 which is about 15 times greater than it should be so let's find a 0.0001 microfarad cap and put it in here and see if that helps and by george i just happen to have an nos sprague 0.0001 microfarad cap so let's install it okay the little cap is installed right there so let's see if that helps at all once again i think pretty good size step in the right direction we're starting to get some real clarity here uh but it can probably still be improved upon so let's keep looking at our schematic in our circuit as an experiment i'm going to reduce the value of this tone cap to ground the one that we replaced earlier i'm going to go with a less than half this value 0.002 microfarads that will reduce the amount of trouble going to ground let's see how that sounds well i think that's a little better a little more clarity and trouble i've got one more uh idea one more trick up my sleeve let's see how that works here's that final bit of trickery we're going to bypass the one meg volume control pot on the microphone channel with a .0001 microfarad cap that will allow all the high frequencies to bypass the uh volume control and go on in to the phase inverter and as you will see just this tiny little shortcut here is going to make a big difference in the amount of treble that we hear from our output tubes okay i'm plugged into the microphone channel volume is at 4 out of 12 and you can see the little bypass cap right there now listen to the enhanced trouble [Music] that's with the volume control set right at the mid range this is minimum treble control maximum trouble [Music] a little harsh but that's the way you want it when the extremes of your tone control are a little too far in either direction a little too much trouble to the right a little too much base to the left then the you can find the ideal uh adjustment right in between okay so we're back to the mid range [Music] just crystal clear plenty of trouble now here's my plan i'm just going to jumper this volume control here leave the other one alone and that will give a really broad spectrum here of tone uh because you can plug into the microphone inputs for treble enhance and you can plug into the uh instrument inputs for a more mellow tone now i'm going to hardwire in that bypass cap on the microphone volume pot and then i'm going to demonstrate all of the tone possibilities using the tone control and the two different input jacks we're plugged into the instrument input which does not have that treble enhancement we're up at a volume setting of 5 out of 12 and i'll go through all three settings on the tone control [Music] [Applause] so [Music] now we'll repeat that procedure but plugged into the microphone jack that has the bypass cap [Applause] [Music] [Applause] [Music] [Applause] [Music] let's take a second here to discuss the difference in bias values when you have the amp plugged into the current limiter or into the wall receptacle in this case you see the readings that i got plugged into the current limiter which yielded a mean plate dissipation of 6.16.9 watts for the 6l6 gcs when i plug into the wall outlet i get a mean plate dissipation of 18.4 watts that's a difference of 8.9 percent now on this particular amp that difference is not terribly significant but on your higher wattage amps say 24 to 100 watt amps this number will go way up and it makes a huge difference so you really need to do your final bias in the manner with which the amp will be used and in almost every case that will be plugged into the wall outlet so this then would be the bias that the customer would experience uh with the amp plugged in at his house now as i said the tubes that came in this were 606 gcs which are not appropriate uh for this particular amp circuit so i'm going to plug in a pair of 6l6 gbs which are identical to the g's as far as performance characteristics and let's see what our bias is with the proper tubes uh installed in the all right you can see that the plate current is higher with the gbs with the gcs in place we had a average of around 48 milliamps here we got around 50 milliamps okay so a little more plate current plate voltage is right about the same about three volts less uh so we're running around 18 watts here the plate dissipation but here is the huge difference with the gcs the maximum plate dissipation is 30 watts in a cathode biased amp like this one maximum plate dissipation on gbs is 19 watts so we're operating right at the maximum if we use gbs or we're operating at around 60 percent of maximum if we use the gcs now we know from the experiment i demonstrated in a previous video that operating uh output tubes at sixty percent of maximum yields pretty darn good tone so you can use the gcs at sixty percent of max and get good tone or you can use the gbs at absolute maximum plate dissipation and get probably very good tone also so to me it's kind of a toss-up but i'll say this the gcs are going to last a lot longer and they're going to sound good i'm very strongly tempted to leave the gcs in this and let it operate at 60 percent of max rather than returning it to the customer operating at a hundred percent of maximum plate dissipation with a pair of gbs the third possibility would be to greatly increase the value of the bias resistor and bias the gb is down at a much a lower more conservative bias of value um but then the customer is going to have to pay for a pair of vintage uh 606 gbs a new uh high wattage bias resistor i think it'd just be easier cheaper and make perfectly good sense to let him use his tubes biased at 60 percent and get great tone with that said it's now time to button this jewel up and uh get ollie and jack awake from their catnip naps and uh get them tuned up and have them play a few tunes for us okay uh so if that sounds good to you then stay tuned well here's the setup for our audio demonstration we have the sm57 microphone aimed at the left hand jensen 10 inch speaker the sm58 aimed at the right hand speaker so we're going to get a true stereo signal and if you're listening in stereo uh with headphones uh or with separate speakers this will be the left channel this will be the right i'll have ollie and jack play three or four tunes uh first through the microphone channel and then to the instrument channel we'll also use both single coils and humbuckers okay so sit back and get ready for our audio demonstration of the 1950 fender super amp [Music] [Music] [Music] [Music] [Music] [Music] [Music] [Music] [Music] do [Music] [Music] [Music] [Music] do [Music] [Music] do [Music] [Music] [Music] do [Music] [Music] do [Music] well i guess that about does it uh for this video on the mighty 1950 fender super amp i hope you enjoyed it no doubt some of you are wondering why i didn't completely uh retweet the entire cabinet and make it look like it just left the factory well to be honest with you i think that would have been darner era felony to do so if you look at the surfaces on this amp the wood has just a mellow glow to it of age that just cannot be faked every a little nick and cut and scratch on the surface his testimony to its 70 years of hard work and good service and far be it for me a mere mortal to try to hide all that under about 10 dollars worth of cloth i'd like to take a few moments to thank our patreon patrons and paypal contributors for keeping us on the air and advertising free for another month if you'd like to join them i'll put links in the video description to allow you to do so i also wanted to thank max in sweden for that fantastic tube shipment he must have spent four days packing them up it took me about two to unpack them but really max we appreciate it tremendously also i'm sure a bunch of you were aware of the fact that since our last video we surpassed the 100 000 subscriber mark which is just uh something we never dreamed would ever happen and i sincerely want to thank you all for making it possible jack and ali and casey were all really excited uh at the prospect of receiving a nice plaque from youtube commemorating the achievement of our channel but sadly since we do not allow advertising in our videos and do not share the revenue with youtube we are not eligible to receive any sort of awards or plaques but that in no way diminishes the fact that three cats an old codger and a fat old hound dog named rusty combined with one hundred and two thousand people from all over the world got together and made it happen thank you well we're irrigating the backyard as we must do out here in the desert let's see if rusty still has his old ball retrieval instincts rusty here's the ball ready here goes there it is rusty go get it boy rusty okay here's rusty here's the ball a deadly combination ready there's the throw rusty go get it boy oh god it's beautiful good work good work rusty you haven't lost it good retrieval rusty here's your cookie while the boy hasn't lost his appetite

Channel: Uncle Doug

Views: 47,650

Rating: 4.9482603 out of 5

Keywords:

Id: 5Sq0bOPlwdA

Length: 68min 38sec (4118 seconds)

Published: Mon Jun 28 2021

Reddit Comments

[u/buefordwilson]

Uncle Doug is great. Been subscribed to his channel for some time now since first discovering it.

[u/drroub]

I ❤️ Uncle Doug. I can fix a damned thing, but after four or five of his videos, I’m thinking about where he’s going to put that reverse feedback.

[u/mikePTH]

That is soooooo cool.

[u/thenagat]

UD is THE master teacher of amp repair & building on YT. After selling my ac-15 last August to fix my car, I was without an amp and sad. Seven months and a bunch of videos later,3 I found myself surrounded by 4 killer home made amps! Even made a few bucks from one! I wasn’t sad anymore!!