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Given it seems to be standard (especially since we see it in the schematics) my guess is, due to it's proximity to the amp board, it was put in place as a noise filter. Obviously from its size, it wasn't meant to smooth AC ripple, which leads me to the noise filter assumption. Still, why there...

From the schematic, pin 8 of both power amp boards is tied to pin 22 of the power supply board (supplying 50vdc). There is only one capacitor, C9, at 1uf, 80v that is tied to this circuit. From memory, I'm guessing it was on the left-hand amp board. Not a factory mod that I can tell, since it...

What's are the voltages on the pins of the PA3004 both on and off the DBT?

Sorry for the delayed response. Yeah, if the solder is butchered, it may mean that board has been previously pulled out for repairs (hopefully done correctly and not glob-soldered), so I'd replace the cap (or at least test it). Still odd why one amp board has the cap and the other doesn't...

I'm almost certain I've seen these before. I always assumed it was a factory modification (as Mark pointed out) since it looked, well, factory. I believe both capacitor leads have black insulation covering them?

I replaced R241 & R242 with 240K-ohm resistors, which brought DC offset in both channels down to nearly zero, with P & Q jumpers removed and VR5 & VR6 centered. I read some older posts from Mark about the +41.5v & -41.4v power supply differences (I had a 0.5v difference) contributing to the...

Crickets. Chuckle-chuckle. I do miss Mark being around (Audiokarma's own "Soup Nazi"!). And Merlynski. Haven't heard any updates on Mark, but I'm hoping he's on the mend.

Hello, all I have a Pioneer SX-880 on the bench that is exhibiting high negative DC offset. The receiver originally had two blown 1-amp fuses: FU2 & FU3 (I chuckle whenever I see FU2). I found D26 shorted, as well as Q29 & Q30 with shorted junctions. All were replaced with correct modern...

It looks like the correct PCB socket for the MY4DC48(S) is a PY14-02, in stock at Mouser. Also, it looks like a harder-to-find Idec RY4V-UDC48V relay might be a direct replacement for the Omron relay.

Wow, I think I just bought the last MY4-02-DC48 relays on the planet. Found 3 at RS Online - all the other usual places had zero in stock. I guess once my stock is depleted, it will be the (S) version with a socket unless there is a better alternative?

I agree. Pull the right channel STK module and see if the relay clicks in.

I've had a function switch polluted with whatever gunk the previous owner sprayed in there, causing similar issues to what you're experiencing. I couldn't flush it out with Deoxit, so I ended up removing the switch from the board, taking it apart and cleaning all the contacts by hand.

Who knows? And I had previously powered the receiver up (on a DBT) and somehow didn't burn up anything. I did manage to get it repaired and working, again.

I've refurbished somewhere between 100 and 200 of these receivers. Here's a classic solder-job from someone trying to "repair" a function selector switch (I got this repaired, amazingly-enough). BTW the two smaller screws that go through the bottom cover and attach to the bottom of the...

I installed E202 diodes in my last attempt at eliminating the FETs as the problem so I simply left them in place after finding the bad MZ-140 zener diode. I saved the original 2SK34 FETs as good used replacements. Which brings up another thing - using my Peak DCA55 semiconductor component...

Found it. D28 was shorted. Pretty sure I checked D28 yesterday, but I may have been testing the wrong traces. Transistor heat sink glue had oozed over it during the assembly process (not sure if this aided it its demise) and it was kind of a pain to get out. If anyone wants to take a stab at...

Well, I'm back at this, again, with a different SX-880. I've got +58v & -58v in to each of the 2SK34 JFETs, but only about +3v & -3v out, respectively. I replaced both JFETs with NTE312 JFETs and E202 diodes and am getting the same result. I've checked for proper grounding, etc. but am...

Would anyone be willing to share their copy of the RS-2015 service manual? I'm having zero luck scouring the internet for one. Thanks!

My apologies but I have no notes on what I did to resolve the issue. The nearest I can recall is that I likely went through the alignment procedure another time or two, then finally got it. Some tweaking of T251 outside of what's specified in the manual may have done the trick.

The Pioneer SX-790 and SX-890 (black-face versions) use the same cover, as well.

Old ECG or NTE cross-reference manuals are your friend. 13-23824-1 crosses to an NTE 319P, which is a TO-92 case NPN transistor. IC = .05a BV CBO = 40v BV CEO = 30v BV EBO = 4v HFE = 80 PD = 0.26w FT = 300 Others here on AK can likely recommend a correct replacement based on this info. I've...

Today, I tried tracking down grounds to pin 5 of the flat amp, but there was nothing there (with exception of the original ground wire from that pin to the nearest ground terminal that I removed, since it looked like it was soldered in by an amateur). I finally Googled the SX-850, looking for...

The last thing I was going to do today was recheck my power supply voltages, but I ran out of time. Just now, I started thinking about the ground issue and realized I didn't look upstream from the flat amp. Looking at the schematic, I see pin 5 of the flat amp is supposed to be tied to ground...

Hi, Larry Yeah, that's what it acts like. Here's a photo of the pre out / main in connectors from the back side. The yellow and green cables go directly to the amp board, with no other connections to those points. You can see the capacitor from the ground to the frame ground screw. I've...

Hi, Mark. I forgot to include that with my original post. Removing the jumpers makes no difference. It's odd, with the jumpers removed, I can still make the protection relay engage/disengage by grounding/removing the ground on pin 20 of the flat amp (or pin 2 or 6 of the tone amp).