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I'm using a cheap little SMSL Class-D amp driving the modded Pioneers at work for video editing. Would I hear a difference with a Class-A Pass Labs clone? Probably, but my office gets too hot already.

I'm not great with remote diagnostics, so hopefully someone with more experience will chime in. That said, I think anything prior to the volume pot would not cause a buzzing when the volume is down all the way.

It looks like those are installed correctly. It looks like there are resistors missing in the bottom center of the photo and I see trimmers have been added. I'm guessing that's to adjust the bias? I wonder if these mods are part of the problem.

Very odd that you can't hear it with headphones, but you can with speakers. The headphone jack is fed right from the speaker outputs, just through a 150 ohm resistor. Is it just in the Right channel, or both?

I can only speak for my own tastes & ears, but I think the Murphy version has a much smoother sound. This might seem too mellow for some, as they don't have an exciting peaked up treble or overly punchy (or bloated) bass. These Peerless tweeters don't compare to more expensive options that...

No worries - happens to me too. Prepare to be amazed at the difference in the sound.

You're in luck. There are no 2.0mH inductors in this design. It calls for (x4) 0.50mH 20 AWG. You can use the Dayton version that are only $4.39 each. https://www.parts-express.com/Dayton-Audio-AC20-50-0.50mH-20-AWG-Air-Core-Inductor-Coil-257-036?quantity=1

I notice the BOM calls for 25v main filter caps. Anyone else think that should be a 35v cap?

I'm relatively new to tuner tweaking and still learning, but I'll bet going through the front end procedure in the SM will do wonders. Side note that may be of interest: I have a Kenwood KT-7500 that would not tune into any signal without noticeable distortion and never in stereo. The dial...

Well, I'm stumped. Hopefully someone can chime in who has experience with this amp & I hope it's something fairly simple that you can resolve quickly.

For DC offset, check pins 12 & 13. Those are the L & R output lines coming into the protection board. It sounds like Q2 is sensing some DC at the output of the amp(s) and doing what it's designed to do. The description in the SA-6800 manual does a better job of describing things and the circuit...

Go for it! As for caps, I'm in the same camp as onwardjames. I'll bet you won't have even close to $50 worth of in caps. You might now find every value in the KW series. One guru I follow uses PM or PW for power and KL or films for the audio path.

"This will repeat if the amp is left off for a long while but if turned back on soon the protection circuit doesn't release." Sounds like something heating up is causing the issue. Check the DC offset ahead of the relay once it goes into protect to rule that out as a cause. If that's fine, I...

That is a lot of kit for $155! Having all those features in an affordable handheld would have been considered impossible a few decades ago.

I've heard some say you just need enough bias to get rid of crossover distortion. But to know where that threshold is for a given output device, you need a scope. What's the penalty for exceeding that threshold by a factor of 3 or 4 as long as the outputs are not getting too hot?

I may be incorrect here, but I was under the assumption that R51 & R52 were part of the offset adjustment, while R69 & R70 (12 ohms) are in the bias stack.

Sorry for the late reply. You are actually looking just fine. Point-to-point crossovers can look messy, even in some commercial speakers. I try to use a star ground approach, but that can't always be accomplished on bigger crossovers.

Correct on both. I had some surplus trimmers in the parts drawer, but one of the multi-turns from Mouser or Digikey should work great. I did preset mine before installing and I feel they are more reliable than the open style Pioneer used in the larger receivers.

No problem. I was curious to see if there would be any difference. Madisound's 15 AWG Sledgehammer inductors have holes on each end of the laminate. If you are in a pinch and need a slightly higher value, you can use steel bolts to raise it nearly 10%.

Either one is fine. I just measured a 1.5mH steel-core and then placed a .40mH air-core directly on top of it. I saw no difference on my cheap little LCR meter.

The 434 is a great little receiver. You are in good hands. I think Larry chimed in to help me with my first one a few years ago. These have jumpers that can be cut to set the bias, which in my case was off a fair bit after replacing transistors. You can make this fully adjustable by replacing...

You should be fine if you keep the iron core down at the bottom under L2. The rule of thumb is 3 inches, but since these are in series to make an effective 1.5mH, it's not a problem.

Glad to see it's working properly before and after trying the tape monitor. That points to a simple case of dirty switches, which is fairly typical for these old receivers. I know I've replaced 2sc1344s with the ksc1845 with no issues, other than me installing them with the wrong orientation...

Since you have both channels working when the Mono switch is engaged, the problem is upstream from there. Do you have both channels if you connect your source to one of the tape monitor inputs? If so, I wonder if the selector switch is dirty or has a fractured wire.

No reason it wouldn't work, but I don't know if those are what might be considered HiFi. We had similar small amps all over the TV station I worked for. They were connected to rack panels with crappy whizzer-cone speakers, so ultimate fidelity was not the focus. Durability was key.