Kenwood KA-9100 popping

IMO the greatest concern with wire-wraps is breaking the wire that emanates from the bottom. The wire is fragile solid core and not very large. Repeated turning and re-positioning of a small board puts stress on those wires.

Also I would not add solder to the wrapped wire. Even if the outside of the wire appears to have some corrosion, the actual metal-to-metal contact areas between wire and post corners were originally gas-tight, so I would assume that without exposure to the atmosphere, those areas are still clean. Large amounts of heat needed to make solder flow in and around that much metal (wire wrap + post) would cause expansion and later contraction that, to my OCD way of thinking at least, might disturb those connections. Why take a chance...

If a wire-wrap joint is suspect, one could always put a meter probe on the wire and another on the post, after scraping away surface oxidation those areas. If there is a problem then unwrap, clean everything thoroughly, do a partial spiral wrap as tight as you can, and apply solder+flux generously.
 
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Yeah, it makes sense that you wouldn't want to put a lot of heat to old wire connections. I'll just double-check everything before I put it all back together. And the meter is a good suggestion for evaluating connections. If necessary, I have a wire-wrap and un-wrap tool somewhere in my tool box. I'm waiting for one more cap from Mouser that didn't make it onto the list of the first order. I think it's C-6, which they were out of when I ordered. It should show up Monday or Tuesday, then I can put some fire to the unit again and see how she flies. Thanks for the input.
 
Okay, I'm nearing frustration break-down. The board is back together, along with reflowing all the wire wrap legs before reassembly. I turned it one, first with a DBT, then hooked it up to some signal. From the beginning, the left channel seemed a little hinky. But it cleared itself up finally, such that I assumed it was dirt in one of the controls, which I played with for a while. So it ran in my shop flawlessly for a couple hours. I unhooked it and transferred it into the room I use it in, hooked it up to signal and turned it on. Within five minutes it started popping again, just like before. Except that this time I made a point of making sure it was coming from both channels. It wasn't. It's coming from the left channel only. So now I suppose I need to rebuild the left channel board, correct? It looks pretty accessible, but I'd like some input, if anyone can weigh in on this mess.
 
Yeah, tarior, I just didn't pay close enough attention and thought you were referring to the power supply. My mistake. I was rushing, which is never a good idea, and thought, "Okay, both channels [which I now don't think is the case] and figured you were talking about the other board. However, just for fun, I hooked the unit up as a pre and ran it through my B & K amp. Everything worked fine, except that, once it warmed up, I think I heard the relay keep clicking every few seconds. It didn't affect the sound out of the amp, but the clicking was obvious. Before, when I ran the unit normally, the pop came up again, but I can't say whether or not the relay clicked. Does this make any sense to anyone? It could be the arcing of whatever component is failing that is causing the relay to kick out, but it still surprised me. Either way, I'm going to rebuild the right and left boards now. I just need to make up a purchase list. I've consulted what I've found on this site, but if any of you have lists of equivalents for the boards, I'd appreciate it, even if only to double check myself. Then I'll get it to Mouse and maybe even get this thing back up to snuff.
 
Yeah, it happens.
I've worked probably four of them, and they all had the same problem. The very first one got me, though, some years ago. It was only popping on one side, so I only fixed that side. That was a mistake, as I basically did the other side under warranty. Nowadays, I just replace the transistors in question even if they aren't acting up.
 
That's my plan. Since I'm going to invest any time, it would be stupid not to do both sides at the simultaneously. Besides, I'd be reluctant to make any changes in one channel and not the other, purely for purposes of eliminating the possibility of audible differences. I have the lists of equivalent transistors offered by others on AudioKarma, so I feel confident about that part of the fix.
 
Relay chattering - hope that it's not the relay driver transistor but it probably is.(Qz2, KSC2690AYS is a good sub). It's on the diode board under the right hand pair of filter caps. I'd make certain that is what you're hearing before digging in - it's not fun. (well it is in a twisted kind of way) Accessing it requires unsoldering that pair of big caps. Unfortunately it seems to be a common issue.

I suppose it could be really high DC offset - you can check at pin 7 on the left amp board and pin 8 on the right.

One of the better free service manuals here - very clean. https://www.vintageshifi.com/repertoire-pdf/Kenwood-5.php
 
Well, I don't know if I'd call it chattering. It happens about every 10 or so seconds, if that makes a difference. But I'd sure hate to have to dig that far into the guts of the thing. That board looks to be buried pretty badly.
 
It's most likely the DC appearing on the speaker outputs that is making the relay open and then close again when it subsides. The protection circuit is functioning as designed.
 
What about the caps? Just one to one replacements? Or are there recommended substitutions? And thanks for the help. I'm trying to get my Mouser order in today.
 
I just took a quick look at my own KA-9150 (I don't take notes for crap), and refreshed my memory. Q5-Q8 were replaced with KSA1220AY, along with Q11,12 with KSC2690AY. No other semis were replaced, nor do I recommend it unless you have evidence that they have failed. I mean, you can, but I really don't like to shotgun semiconductors without a good reason.

Just use the same uF values on the caps, you can go up on voltage rating, but not down. Panasonic FC, or any other high temp, low-ESR capacitor is perfectly fine.
 
Ceramic caps rarely fail. I leave them be, unless I have a reason to change them.
 
Well, I pulled all the old components off of the two boards, but one of the transistor trace solder pads was damaged. The transistor had a leg bent over and attached with a lot of solder. In order to get the leg loose, I just continued to use my de-solder wand and twisted the transistor from the other side. No matter how much solder I pulled out of the connection, the one leg just wouldn't let go. It was in there so solidly that it finally pulled the pad loose. I've never had to fix a PCB in that way. Do any of you have any suggestions as to how to repair the damage?
 
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