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Photo of one unit in ad, lights on; sold another unit not pictured in ad? If this goes deeper than F604, I recommend either 1) an experienced tech or 2) if you're doing this yourself, make or otherwise obtain a DBT.

I am in the same boat. I seem to have narrowed to the volume pot, or at least near it. I took a pause on it to let my frustration dissipate (I accidentally broke one of the tower coils on the MPX board while I was messing around with the volume difference). I'll get back to it eventually...

'kay. Sounds different from mine, which is modulated by the balance pot.

Other dials or switches affect it? I'm watching eagerly, as I have something similar on my AU-505...

125 total seems pretty decent for time and effort, IMO.

What are you using for a source? I'd been driving myself nuts trying to figure out why I had semirhythmic sound coming out of my 2000 when I finally realized that by moving the cell phone I was using for an AUX source, the noise could be changed. It had been the phone to RCA plug interface...

The 5000(X/A) is a beast and totally worth it, IMO, but I'm fairly confident in my soldering abilities. I agree with Sansuiman that you need to do the mod, you'll just have to dig up some buried forum treasure to do so.

I've had both the 4000 and 5000a, and it was worth it. My 4000 had a blown left channel the seller concealed by using the MONO button and wiring one speaker to channel A and another to channel C. To this day I don't know if he was fooling himself or trying to fool me, but it was $45 so I bought...

There was a reason I didn't go with 22. I can't recall at this moment whether it was because it wasn't available at the time or if there was a fit issue. I went with 4+4 instead of 8.2 at the time because I was quite paranoid at the time about getting exact values and I just never re-adjusted...

The AudioCap Thetas are being used as a bypass across the main caps. I included them in my SP2000 refurbs per rek50's recommendation, but some would argue whether they were necessary or just adding extra expense and complexity. I would call them "optional" (but I've always put them in)...

Outstanding! Congratulations on a successful troubleshoot!

larryderouin is correct in all particulars... the 2SC458s are used for gain with low-noise, but unfortunately that transistor type did not age well-- even within 5-10 years they needed replacement, apparently, according to folks who were service techs in the 70s and 80s, because they became...

Yeah, not a fan of the filter board soldering design decision. Was my least favorite thing about opening this unit. I might be opening it back up up to add better power supply caps at some point, but I have two 2000s and a 5000x to nurse back to health first

Okay, you made me think there was something I didn't know about beyond the Sansui 7000 with your crazy "8000" typing. :) It makes way more sense that it was an Eight. And beautiful. Very jealous!

I mean... yes, that's always an option. And convenient for a manufacturer to say when they're putting out thousands of these a year and it's not necessarily an easy problem to diagnose and fix. Still want to try, though. It's a technical problem and should have an engineering explanation even...

I think Larry was saying that the voltages listed on the schematic at various points to check are in DC.

Yeah, I think that will be my next step. I did some quick measurements of the 1kHz drop across the pots a couple days ago and there seemed to be differences between left and right, but I need to get into better detail. At first I was wondering why the Bass knob showed discrepant values (same...

Good idea. Did that last night. DC voltages which are listed on schematic are matched within 10% of each other on both channels.

I would recommend opening it up for contact cleaning. I have found it challenging in the past to get Deoxit into the switches and pots without doing that first. Also recommend gently using a camelhair paintbrush to remove the accumulated dust of years from the innards.

I appreciate the input. I'm just not understanding how that can be. The output of the EQ board is left/right 78.4mV/84.8mV pk-pk: certainly could use some improvement, but it's within 10%, whereas the output of the tone board is a 50% drop on the left vs the right. All the transistors you...

Okay, filter this through several hours of frustration and a couple cocktails... I recently bought a Sansui 2000 as a parts unit... it was advertised as parts only because the face plate for the tuner display was popped out and needed repair (gluing). I have Dad's from his days in the Service...

Looking at the schematic... if you swapped the F1150 boards and the noise stayed on the left channel, the only possible problem to the right of the equalizer board is output transistors (those cans mounted to the heatsink on the back) or the output caps (those big 2200uF towers). You can't...

Hmmm... if you swapped the F-1150 boards (what I am guessing are the "amp boards") and the behavior stayed on the same channel, then it's not the 2SC458s (unless either the manufacturer or a subsequent owner substituted 458s for one of the other transistors on an upstream board, which sometimes...

Sorry, I thought you said the balance knob affected the issue. "Balancing to the right gets rid of the static and the right side plays normally the whole time". I must have misunderstood. tom3 is correct to suggest 2SC458... there's one on each output board and those are notoriously noisy...