Harman Kardon PM665 Repair & Restore - Part 1

so harman kardon pm 665. this is the big brother to the pm 655 that i did and uh mismarked it originally on the video when i put the title i accidentally put it as a 665 but it was a 655. and one of the main differences other than wattage this one's 100 watts per channel i think the 655 was something like either 60 watts or 65 watts 80 watts something like that but that one had a single power transformer this one is a dual power supply so it has two power transformers in it and it's of course higher wattage it's still from that same era pretty much now i've had i've had several harman kardon's of this era on my bench and a couple things that seem to be uh consistent through this era is first of all the build quality of these the components the circuit design everything is really good this has a fantastic phono stage you can switch between moving magnet moving coil it has the capacitor of trimming for the cartridge so this has a really good phono stage what i don't like about these is i've noticed that the circuit boards are very brittle they crack very easily and the circuit traces will crack and get hairline cracks that are very hard to troubleshoot and i've had several that have done that these little switches here by the time they get this age they're extremely delicate and they fail pretty easily these ones look to be all good which is good another thing that happens is these are nice aluminum knobs but the little plastic inserts as you can see come unglued i think what happens is the plastic shrinks with age and then people try to super glue them and super glue just does not work between this anodized aluminum and the plastic you really have to use something like jb weld or jb quick and put a thin coating of it on there and glue these back together so all of these are loose unfortunately it looks like somebody got a little bit happy with the crazy glue and now the plastic is glued to the shaft on a couple of these so that might be a big problem if we have to take this apart but uh other than that you know the like i said some the build quality is just not up to par with some of the older models of gear that they made but it's an excellent amplifier they perform very well and they're they're worth having i mean honestly it as far as performance goes so we're going to go through this one i have no idea if it works or to what degree it works but we're going to clean it up we're going to do all the tests on it try to restore it as best we can and go through make sure it's aligned properly and then give it a good test and see how it performs so if that sounds interesting to you stay tuned and that's what we're gonna do all right one of the things i've noticed is these speaker terminals are all bent and that may have happened in shipping this was pretty pretty well packed when it was shipped honestly but these things if they're not screwed in and these were all threaded out you see that whenever you ship these make sure these are screwed down and make sure you properly put foam around here so that nothing can press against it um or these are very flimsy they'll they'll bend very easily these banana plugs so you got to kind of watch these binding posts here so we'll have to see if we can straighten those out and make them a little better the fuses again i always like to check you know this is how we find some clues this is supposed to be a 5 amp when you're running it 110 volts or a 2.5 amp if you're running it at 240. and this is a 5 amp fuse which is good and we'll check this other one one fuse for each power supply this kind of gives you some clues you know if there's a somebody put some aluminum foil around a fuse in here and you could see this one's a different type of fuse so it has been replaced at one point in time uh let's see 250 volt 2.5 amps you see so we have two different fuses here well it's rather dusty in there but wow look at these massive transformers now remember this is 100 watts per channel so each one of these this great big transformer is just for a single mono 100 watt amplifier so this amp will have all kinds of headroom and you can see nice big capacitors those are what 10 000 rpm or 10 mike ten thousand rpms ten thousand microfarads each and we can see there's your rectifiers to them with nice heat sinks on them nice big heat sinks for the power transistors and that's another thing is on the pm 655 the transistors are those uh mt 200 type though the long narrow ones with the pins coming out the sides and they're mounted up underneath i believe and the heat sinks sticks up like this but the transistors are underneath you have to flip the unit over and you can see these ones are mounted traditionally like on the side of the heat sinks you can see over here inside the shield this is your phono stage it's all shielded and covered in here which is excellent and you can see what i'm talking about i'll zoom in a little bit for you you have to be very careful working on these amplifiers when you look see how thin that circuit board is and just the type of material they make it out out of it will break very very easily and you can see in here let me get a little pointer you see all these little right here these little connectors those are connectors that connect the front board to this bottom board here and they can and you can see how tiny some of those tracks can get and they will you'll get these little micro cracks inside there from these flexing it's very delicate and when they do that you get these intermittent problems where the amp will cut out and it can be a real bugger to get in there and try to find where the little crack is so what i like to do is i like to go through all of these and just reflow all the solder joints and make sure they're all on there really good before we turn this back over to someone the good news is we don't have a lot of that glue that you see in things from this vintage and none of the trans or none of the capacitors look like they're bulged or anything like that or leaking but we of course will recap this uh but i think we have something to work with the nice thing is it doesn't look like there is any service done on it we have a nice alps potentiometer with and the knob came off of it as well so yeah i think this will be a good project now before we get started just a quick word and this is an actual pm 665 there's also another model called the 665 vxi it's a newer model uh instead of 100 watts per channel it is 150 watts per channel different different circuit inside somewhat but generally very sim shares a lot of similarity but it's a newer version i just gave this thing a preliminary once over before i plugged it in and it in fact does have a lot of the characteristic issues that these things suffer so for instance if we look over here and put some light on the subject and when we lock down the camera and if we zoom in you can see down here a lot of these little circuit traces kind of have rings around them you can see and they're somewhat loose some of them are good but i found a few of them if we go over to the phono stage and rotate that around let's see if i can get some light on the subject for you there and if you look down here these ones are really bad you can see that these are just moving around loose see that one's just totally loose see how it's broken that one's broken real bad that one's broken this one's bad it's broken that one's completely desoldered so you can see all the components how they come loose this is something that you'll see a lot of and whenever you go and work on one of these harman kardon's from this era the 655 is the same way and i suspect a lot of the other ones as well from this era are all like that so a little word of warning anytime you're going to restore one of these make sure you go through all the circuit boards i know it sounds tedious and it is to a little bit but these are great amplifiers and they're worth the effort go through check all the boards make sure there are no little cracks in the tracks that's the worst problem you'll have on these they're very hard to troubleshoot if you have that but go through and touch up all the little solder joints and just take your time i mean this is a hobby for most of us you know take your time do it right and this will be a great amplifier so we're going to do that where before we do any of that though even with all that we're going to power this up and just check some things and we're going to play around with the schematics on this video or at least on this series we'll say if we do more than one video here and most interesting is the protection circuit and we're going to discuss how it works some of the advantages and disadvantages and we're going to see how some of the principles they used in this protection circuit have been used in the past if you recall the back macintosh mc 2100 series that i did some of the things they used for that some of the carver gear that that you see uh there's a some of the principles they use for the protect circuit and that is similar so very unique very neat and we'll look at some of those things well let's power this up and see if we have any dc on the speaker terminals i have this meter connected to left channel and this one connected the right channel to look at dc millivolts and the first thing we're going to do is we're going to plug this in and turn it on and we're going to look at the dim bulb i have this bulb on which is 110 watt bulb and we'll just see if it lights up as the caps charge and then drops down all right power coming on that's a good sign and the protect relay didn't click in ha fooled you all there is no protect relay on these the protect circuit does not have a relay on the outputs we'll get more into that later all right let's look at our dc well that's not very good 300 millivolts on the left channel and 747 millivolts on the right channel i would say that is some pretty horrific dc offset and looks like it's climbing as we go now i have all the controls set you know at center range i have the volume all the way down and we are just getting really really bad dc offset that's why you don't just put these on your bench and connect them to a set of speakers and start playing it now this is one of the things that's a problem with this design let's talk about why okay schematic time some of you love this some of you hate this but we're doing it the first thing you notice here is your protect circuit and we'll get more into what this does here in a minute but looking up here here's your main power amplifier and when they drew this schematic they actually showed the signal path in this dark this dark thick line this kind of shows you your signal path coming from the inputs going all the way out to the speaker for the left channel the right channel is just the same but they're just making it easier for you if you look here here's your pair of outputs so you have two npns and two pnps it's a complementary class a b amplifier and right at this midpoint this is where the where your speaker output is this should be zero volts in a perfect world it never is but it should be very low just a few millivolts if properly adjusted and normally what most protect circuits will do is one of their functions will be to monitor this output here at this at the mid point of these transistors and if your voltage if you your dc offset gets more than maybe about a voltage drop of a diode like 500 millivolts 300 millivolts somewhere around there or a little higher it will actually drop out a relay set of relay contacts that are in series with your speakers and it'll prevent dc from getting onto the speakers with this particular amplifier that's not necessarily the case now the way this works is if it sees too much dc which we're not quite there yet in this instance what it will do is it's supposed to you see these little fets here these little i think these are jfets i'd have to look them up but what they do is they can actually clamp down the signal going into the amplifier to prevent it from driving into clipping so this this amp should do very well with not allowing clipping to take place and not allowing dc to get on the terminals when you overdrive the amplifier the problem with this is is if something shorts like let's say one of these transistors dead shorts that dc voltage right here can go straight through those transistors and straight out to your speakers and blow your speakers now this isn't the only amplifier in the world that does that a lot of them do if you go way back a ways on some of my videos i did a series on the ad com gfa 585 which was actually a very high-end amplifier in its day and i know some of you say it's junk everybody has their opinions anyway whatever it's a powerful amplifier and a lot of people really like them including myself but they're the same way there is no there is no protect circuit for hard dc on the outputs and if the output transistor is short in that amplifier you will if you don't blow the speaker uh blow the fuse the line fuse for the power supply you're basically going to vaporize your speakers and that's one downside of these but in theory the way this is supposed to work is it's never supposed to let these transistors turn on to the point where they can put a dangerous amount of voltage out to the speakers now is 700 millivolts dangerous to your speakers uh i wouldn't want to have upwards of one volt sitting dc on a on a voice coil of a speaker constantly because that will put heat on that voice coil unnecessary amounts of heat more importantly though with that level of dc offset this thing is going to have horrific distortion especially at very low vol low volume levels and at high frequencies and so definitely that's something that we're going to want to address early on now part of that could be because of our cold solder joint problem that a lot of these suffer from if we have a loose connection it could affect the voltage at one of these transistors and it could throw off that dc offset it also could just be that it's out of adjustment but what i usually find with this kind of design is if it's that far out on both channels i you can adjust the pot and a lot of times you adjust the the control for the dc offset and bias and you can get it to come in and then it'll just move again on you it'll move around and that's because you're not fixing the actual problem in there you're just trying to mask it by adjusting it out temporarily but again if you have a leaky transistor if you have a cold solder joint something you know bad connection somewhere adjusting your dc offset and bias won't fix it so really you have to go through and find out why i normally don't like to just go in there and willy-nilly adjust these when they're way out like that if this was a few millivolts higher than spec then i would say it's just a matter of adjusting the pots but in this instance it's that far out there may be something more to it than that we'll have to look but anyway that's just a little primer of what we're going to get into on this i want to really take my time on this one and go through everything and when we're done i want to have a perfect working pm665 amplifier that's going to be reliable and last a long time okay we have the amplifier on we have it connected to the dummy load and i have a one kilohertz signal into the auxiliary input the current limiting is on still and i don't know i have all three bulbs in so it's very you could see how dim they are and that's because when we start turning the volume up we are going to see we don't want too much current limit because we want to see the amp actually you know put out a clean signal you're still not going to be able to drive the amp hard like this because the bulbs will limit the current but that should get us to where we need the first thing you'll notice if you look on the scope there's your dc offset so you can see where right on the line there is where the uh where our zero volts would be same here but you can see this the left channel is or the right channel is a lot worse than the left and that's what we were seeing if you remember now you got to times this by 10 because i have the times 10 divider or my 10 to 1 divider set up on my dummy load for the scope output so technically if you want to look at you go to 20 millivolts per division there sorry and i turn the wrong knob 20 millivolts there now you can really see how far off we are that's 200 millivolts per division we're at because of the times 10. so you can see right here we're almost 100 millivolts and here you can see 200 and right here would be about 300 300 millivolts roughly little of 350 something like that so it's pretty close and again now that there's a speaker load across there and it's not an open circuit that loads that down a little bit which is why you're not getting quite as bad as it was with open terminals all right let's bring this back up to about 2 volts per division and of course i messed up my time here but and you can see how just noisy noisy this all is and you can see this channel is really bad let's turn the balance control up look i just touched the balance so we have dirty controls for starters and that may not just be a control that might be again a bad see there solder joint on that board i'm tapping the actual board on the where the tone control and everything is so yeah this is what i'm talking about on these these harman kardon's you really got to kind of clean them up but what i want to do is turn this way down like crazy way down and i want to look at the you can see how this thing just doesn't like let me change my trigger hold on a second okay we set our trigger a little bit different here and we're at 100 millivolts per division now so this is a very small signal and you can see even with that dc offset on the speaker terminals you can see that there's really not any crossover distortion that we can see and again we're getting to the limits of an oscilloscope here oscilloscopes don't like looking at really really low voltages they're a high impedance input they can you know you're seeing noise there and so forth so your that is a function of the scope and the wires and everything connected to it but anyway i see a little bit of oscillation right there and right there and one right there and one right there i don't know if that's just again if that's just noise on the cables or if that's something significant in the amplifier we'll have to look and see but definitely we need to check some solder joints and do some cleaning of the potentiometers before we can go any further with this but the good news is it is working the amplifier is passing a signal and you can see just your dc offset in a perfect world this would be up here we're not going to play with that yet we're going to clean the controls and go over the solder pads and everything and kind of see what kind of improvement we can make just by doing the basics now a lot of times i have a lot of people that are experienced at working with amplifiers they even do have done this for a living or whatever they're way better at it than i am and invariably they get very frustrated with the videos and say hey why are you doing that that's so in you know so any efficient that's a you know such a long way around to do something this is the way you should do this well understand that i do this for entertainment understand that if i did the same thing the same way every time on every amp these videos would get very boring very quickly and people who are new to this uh hobby would not really see very many different ways of doing things that's why each video i do i try to do something a little bit different and use a different technique that may not be the most efficient or the best technique for this particular case but i want to demonstrate it so people can see different ways the idea is to get people to be able to think to be able to know diff that there are different ways of troubleshooting and checking things and doing these restorations there is no one set way that you have to do and that's why i do that so yes there are probably better more efficient ways i can do this but we're going to go through this process and we're going to learn as we're doing it all right let's go through and do our basic clean up the solder joints and clean the controls and let's see what happens after that in the process of taking the face plate off i kind of felt some heat and i came over here and touched these two heat sinks and the right one was quite warm i mean not hot but i mean for being on just for the few minutes that you saw it at very low milliwatts of output these were both quite warm and shouldn't be that warm that fast so that tells me not only is the dc offset wrong but the bias is way off as well these amps will idle a little bit warm because they're class a b meaning there is a little bit of idle current on all of the transistors even when the when the amp's sitting at idle but it should never get that hot that fast when the heat sinks warm up within the first couple minutes of turning it on and they get really warm that's probably too much bias and the amp is running closer to class a than it is class a b so and i did a lot of videos on amplifier classes and things you can go back and check those but the other thing is you can remove the face plate without removing the knobs and that's important on these amps because again like i said these plastic inserts that are on here you can see they pull right off these little plastic inserts you can see somebody tried to glue them with super glue and that never works with this type of plastic and what will happen is these will really get stuck on there and it's really hard sometimes to pry these off without damaging something especially damaging the face plate but harman kardon was nice enough to make the holes larger than the actual knobs so you can take this face plate off and leave the knobs on and then that gives you the ability to get into this in behind here if you need to very carefully to get something to if you need to pry these off it makes it a lot easier just be careful you know not to hit any of these switches the other thing you're going to find out is these tiny teeny little switches here are extraordinarily delicate and fragile so be careful with them they get dirty very easily and they need cleaned but they're just little plastic switches and i they fail a lot and they're really really hard to find if you need to replace one so be very careful with all of these little tiny switches now to get this out the way i did it was i took the front face or the front plate off you can see right here many screws later everything comes out and then you have a lot better access you don't have to try to shove everything back here and twist it to get it out you can see the way these are put together these ribbon cables are solid wire and they're very stiff so they don't bend very easily and they are barely barely soldered in there if you look how tiny the solder joints are on there it is very easy you can see for those to crack loose when you're moving this around so it's up to you if you want to work on the amp this way or if you want to work on it by disassembling if you're just trying to do a repair you can take that front plate off which just other than taking the screws out isn't very bad and you can kind of move this up like this and just work on the part that you need to work on if you're just trying to do a repair we're going to do a restoration and we're going to recap this and and clean the controls properly and everything so i'm going to choose to take these ribbon cables off now i have the proper desoldering equipment to do it safely so i'm going to do that and then i'm going to take this top board set it aside and then i'm going to take this other board out and get it out on the bench where we can properly work on it because we really have to this is the main part of the amp that has a lot of problems on it i see a lot of issues with you know these tracks cracking in the solder joints and everything so you want to make sure you do as much as you can to correct any little problems that might be there before you put it all back together and you have to go take it all back apart again if you did if you missed something so i'm going to kind of scrutinize this because again there is a difference between a restoration and just a repair all right so let me get these ribbon cables apart and get these two boards separated and we'll get to work all right holding the camera at an odd angle here but we have the board out i'm not going to remove these ribbon cables it's just extra work and i can get to what we what i need here i can see after bumping the camera where if you look kind of in there you can kind of see how the heat shrink wrap has like pulled away from the bottom you can see how on the these ones here that's not the case i'm looking through the camera but and some of that could just be for manufacturing but also if we look closely in this area you can see that these components have gotten really warm and again that's probably just the way the circuit is made or it could be that some of these capacitors or these transistors are leaky and are causing excessive current to be drawn either through these diodes or through these resistors so we're going to have to go through and measure all of this and make sure it's good we'll have to check these transistors and of course they're very difficult to check for leakage unless they're in circuit and working and that's a big pain because you have to put everything together to test it so this is one of those instances where so much work to take one of these apart where now that you're into it you might as well replace it this whole board can be repopulated with components which we're not going to do but we can at least put the caps and most of the you know check the resistors replace the bad ones and do these few transistors up here very inexpensively so for for what the parts are going to cost it's worth it now if i were doing this for a living if i were doing this for a customer where i'm charging by the hour i would probably leave these all as is verify that there's no problems in here clean it up clean the controls and as long as it's working put it back together but since we're doing this for fun it's a hobby take your time and let's replace the components and then we know that they're going to last another 30 years so i'm going around this hot area where it looks like we've had extra heat and i went to check this diode and take a look it's just falling out loose and you could see they're all just coming apart now that one's mostly in there that's pretty tight those are tight but you can see what i'm talking about on these boards i don't know what it is about these harman kardon's but i've seen this like i said i'm not an expert on hk but i've worked on i don't know four or five of them now including this one which isn't a whole lot but i always seem to see this on this generation of equipment so just some things to be aware of if you're going to restore one of these be prepared to take the time and go through all of it to make sure you don't get it all together and find a bunch of other problems looking on this side of the board here's one of those ribbon cables and you can see it's just falling off it's all cracked so and again a lot of the televisions that were built in this era too had this same issue i think it was just this process and this type of circuit board they were using on a lot of these pieces of equipment this was something pretty prevalent in that era that mid 1980s era okay here's one of those capacitors that was in that overheated area and you can see it's supposed to be if it'll focus 25 volts 220 microfarads and if we check it on the es or the lcr meter yeah it's only reading 130 and that's only at 120 hertz if we go up to kilohertz which no big deal we don't really for this particular use but if we connect this in here yeah it's down to 92. so these caps are bad now the blue ones those blue ones i showed you that are kind of in the audio path for instance here's a 47 microfarad i mean that's excellent if you compare that to a brand new nichikon fine gold at one kilohertz that's about the same as it would perform all right i have all the capacitors replaced now i'm looking at these transistors i have you focused in on this one look at this guy right here see it right there this one here is ready to break loot well this one's loose here this one's loose here it this board is completely filled with bad solder joints so we're just gonna have to go through all of them now i'm gonna pull some of these transistors that were in that hot spot there and i want to make sure they're okay i may even just if i have good replacements i may just replace them just so we don't have to worry about i think the reason they got hot was because they weren't making good contact with the with the traces in there but then again if they were running hot they may be damaged so we're just going to replace them i think so i pulled this transistor out and it's a ks 2sa 965. so going online doing a little search i found that the 2sa 965 is of course a pnp transistor by toshiba and here's some of the specs and you can see i'll just let you take a look at that for a minute these are kind of a tall transistor they're they're 900 milliwatts so they're a little bit heavier duty and you can take a look at the collector base collector emitter voltages and i just so happen to have these let's see if i can get a get it to focus these ksa 916s i don't know if you could see that and if i look that up and i think i have the complement to them as well but looking that up you can see that almost identical specs we can go down the list but everything even down to the transition frequency is the same so that's a direct replacement which is good news because i had these and their compliment for the 2sa 965 is the 2sc 2235 and i'm sure i have the complement to these in there somewhere but if we look the complement to that one is a ksc would i say 23 16. so i wrote that down on my spec sheet here just so i remember and i found the 916s like i said i had those now i just need to see if i have those 23 16s as well all right i didn't have the ksc 2316s i'll need to order some more of them but i do have some of these ksc 2383s which are the same transistor pretty much except instead of 120 volt collector base and collector emitter they're 160 volts so other than that all the other specs are the same so these will work so i'm going to just use those and i only need two of these and two of these and that'll get rid of that hot spot by the way out of all of these transistors in this bag they were all bad i'm really bad i mean way out of spec these four were almost perfect they were in spec so these were the only four good capacitors on that board one of which was the one we tested earlier at the beginning so yeah these really needed it and i think some of them had some heat damage from all those loose traces and everything overheating anyway let's get these replaced so i've removed that zener diode that was real loose and the solder had come loose on it and it was in that hot spot and if we try to connect it in here to the meter and if you look at 2 milliamps it's reading 24.69 is a 24 volt zener and if i move to 5 milliamps then to 10 then to 15 you can see how it continuously goes up in voltage now if you take a brand new 24 volt zener and when they say 24 that's plus or minus a volt usually they're not always exactly on but if we look at this one you can see 2 milliamps 5 10 and 15. and you could see it stays right at that 23 volt range all the way across the board and doesn't drift so that kind of gives me the inkling that this this diode is bad it's been heat damaged and i just dropped it on the floor so it's gone but we need to replace these zener diodes thankfully we've got some of those when things get hot like that these semiconductors a lot of times they can be heat damaged like that and that's the result that's what will happen and as the amplifier runs and heats up and warms up that voltage will drift and it'll throw things off which will then cause the bias to change on those transistors which will cause them to heat up those heat up and then of course they heat the capacitors around them cause them to dry out and then they go bad so we're gonna we put all new transistors in just in that area and we put 105 degree celsius capacitors instead of the 85s that were in there so this circuit should be a lot more reliable and we soldered it very well so let's get those replaced and see what else we can find by the way it is normal to have some drift with as you increase the amount of current flowing through these zener diodes they will drift eventually but at that low of a current like that with that small of a change they should not typically drift that much they'll drift a little bit okay the zeners are replaced and i just took and cleaned that up with some alcohol but notice it's a good idea here when you replace these zeners to raise them up off the board just a little bit like that and that'll allow better airflow around them so they don't get as hot and that typically should help out now the everything else on there tested out good so we're going to leave everything else in there and i think we'll be okay i tried to clean off some of that scorch burn mark as much as i can but the the board is actually a little bit discolored but that won't hurt anything so the rest of this board is pretty much done and the only thing left to do now is to repair all the rest of the cracked solder joints on there let me shut this fume extractor off for a minute i think that last recording i did i didn't have the microphone on so it's probably going to be quiet i want to stop here for a minute and show you one of the reasons why the solder joints crack so much on these circuit boards i took and just removed the solder from this one connection right here and if you notice look how large the diameter of that hole is versus the wire that's going through it and that's one of the problems when you punch the holes too big for the for the lead of the component you're no longer kind you're no longer soldering the the wire to the pad you're actually kind of building a solder bridge over top of it which allows for for it to flex and crack loose so that's one of the things that will cause this if you're designing a circuit board for instance on key cat or eagle cat or whatever make sure that you you set the whole the hole diameter to be close to the lead diameter you don't want a big huge gap like this or it will make it very difficult and watch what happens when we solder this and i'm going to do this without the fume extractor so you can hear me and you'll see that when you solder it like this see what happens it doesn't like to fill in and when you do get it to fill in properly it'll make kind of a dome like that because it's somewhat making a solder bridge across the hole and instead of filling it in and if you do just fill it in this is so thin right here that just touching it you see what happened it opened right up and that's the problem a lot of times when these go through the wave soldering they don't completely fill in and you don't get a good joint there and that hole diameter is so big that it'll just from flat from the components flexing and the board flexing it'll just crack and that's why all of these are cracking like that so just something to pay attention to if you see something from this era that was made like this you really have to go through and make sure you get get them properly re-flowed now in some of the more modern boards you can get away with that if you have the plated through holes what's a plated through hole well plated through hole is when they after they drill the hole for the lead in the board they'll put a little they'll insert a little wire ferrule through there it's like a it's just kind of a little metal sleeve and it'll attach on on this side and go all the way through the board so when you solder this not only does it attach to the surface of the trace but it flows all the way through that plated through hole and fills the entire hole with solder and that makes a much more positive joint however when you don't have that on these it's really important to have the correct size hole for the lead you know people say tony you need a bigger bench you got too much clutter on there and you can't fit everything on there well i'll be honest at least for me i don't know about for other people that do a lot of this sort of bench work when i'm working on a project like this i want to have everything right next to me so i can reach it easily so i tend to put everything right next to where i'm working and it piles up and no matter how big my bench is i would still have that same clutter because i put everything nearby so you know cluttered bench doesn't necessarily mean you don't have enough room what it means is that you're just putting all your stuff within arm's reach so that's why you do that but i just thought i'd talk a little bit while i'm doing this i don't know if you want to skip through all of this boring stuff and again everybody has their way of soldering these things the best way would be to remove the old solder from every joint you know instead of adding to it but really this is flux core solder and it does a pretty good job of kind of reconstituting the old stuff this is an old enough machine that it's it has lead-based solder in it so you're not mixing leaded with lead free so really there's nothing wrong with this and you kind of don't want to get so much on there that you have a big blob and that's why you'll see sometimes after i put these on there i'll reflow them a second time right after right after the follow-up and it just kind of makes everything look a little neater i don't want to do that too much and when it dries when it cools it should be shiny it shouldn't be dull like like you see here see how dull that is now when we're done see how shiny it is that's what it should look like so i hope you can see what i'm doing probably some of you watching this on your mobile device probably your screen is too small see what happens there see how that how big that is and oversized for the league so what you have to do is fill that in and get it to bridge across there and that's what causes these problems so i think you get the point here every board in this amplifier is going to need gone over like this and even with that i've seen these traces are very very thin on these boards and not only are they thin they're narrow so again you have you still may have problems and you may have to go and find the crack in the trace somewhere down the road this is what you're getting into if you want to work on or restore one of these [Music] amplifiers from this era and it's not just it's not just these harman kardon's i mean a lot of things at that time were built with this type of board and this type of process it's just the era that these were built this is also right around that time that the capacitor blight that people talk about you can look that up actually i think even wikipedia has a little article on it and fortunately i don't believe these amps suffer from that they used very good capacitors that don't seem to have that chemical in them that causes them to leak like that but just be aware things from this era could possibly have those capacitors and it's a good idea because of that to do a complete recap on things from that era we remember i know some of you probably watched my video series on the ad com gfa 585 and you saw the damage those capacitors caused and uh yeah that was quite a mess wasn't it but again that was there's a lot of computers from that era too that had that problem i can't tell you how many of them we had we had with some of the ones that we have at work you know on some of the x-ray equipment they use a standard pc motherboard for the controller and they use a basic operating system you know like something microsoft based or linux based and the software is very specific to that particular motherboard you can't change the motherboard so you have to repair it and i'll tell you what that's a real pain because the solder is really hard to remove from those multi-layered boards and every capacitor on the board leaked so the only alternative you have is to repair it and that can be somewhat of a challenge sometimes you usually end up having to go to hot air or something to to get enough heat in that area and to get get the leads out but that's kind of what you have to do i guess and uh i'm looking around the camera here so i'm probably making a mess of some of this but i'll go back off camera and verify all these and make sure they're all good i'll look at them under the microscope possibly i don't know if i feel like setting it up it's nothing else i'll use a magnifying glass to make sure seems like no matter how much light you get you still can't see good enough there we go so we're about three quarters of the way through this now i'm getting a lot closer to finishing it but you know every board like i said has to be done like this because of the way this was done and again i'm not being critical of harman kardon because like i said this was this was that era electronics the way they were being mass produced at the time a lot of a lot of manufacturers had this problem and honestly some people might say this isn't worth it but if you've ever heard one of these amps harman kardon did a good job on the design of these the execution wasn't great because of the you know this issue but when you get them up and running they they really are an excellent sounding amplifier for certain tastes of course everybody has their preference what they like and don't like so let me finish this up i think i've bent your ear enough some of you like that some of you don't but we do a little bit of everything and you pick and choose what you want to watch you don't have to watch it okay i'm all done reflowing all the joints on the board and you can see it's just a complete mess with flux and so forth and i do not remove all of the flux i actually kind of like it on there this is a non-corrosive flux so it doesn't hurt the solder joints or the board and if anything it kind of protects it a little bit from corrosion so what i'm going to do is i will take denatured out or denatured or i use anhydrous isopropyl because there's no water residue and i'll go over and clean all of this and i'll flood it pretty well with the alcohol while i'm going through here and it'll just kind of take all that mess off and level it off and you'll just get a nice sheen on the board and it won't be sticky or anything like that it'll just be kind of a waxy feel but that board will last a long time like that and then you don't have to worry about trying to mop up all of the excess flux there's also flux remover spray and i have that and i use it sometimes and it'll remove everything from the board but i don't like to use it because sometimes it'll soak through the other side of the board and if there's any screening screen printing on there certain types of screen printing it'll remove and certain components like resistors and things it'll mess up the color bands and things not always but some of them so i like this method i'll show you real quick just in a small area how i do it we'll just go right here in the middle for instance and just kind of move it around like that and see how wet it is and when it when that dries when that even when the when it the alcohol evaporates that'll be just kind of a nice smooth shiny finish and that's all i'm going to do to the whole board when it's done it'll look pretty good and you know all this globby looking it's like this stuff up here will be gone i don't know if you can see it or not but you see all this kind of this stuff and everything that'll all be gone anyway that's what we're gonna do i'll clean it up off camera at this point i'm gonna end this uh call it part one and until next time i'm gonna wish you all peace joy happiness and good health in your lives and in part two we'll get this part put together and we'll do a quick test and make sure that the amplifier works from the front part and uh we'll go from there so until then stay well and we'll see you all very soon thanks a lot take care bye-bye

Channel: xraytonyb

Views: 19,588

Rating: 4.959712 out of 5

Keywords: electronics, vintage electronics, stereo, amplifier, harman kardon, PM665, PM 665, PM-665, repair, restor, restoration

Id: lb0tGANnyA4

Length: 60min 0sec (3600 seconds)

Published: Mon Mar 08 2021