G-9000DB Distorted sound on left channel (Solved)

Golanr

Active Member
I have this receiver for 6 years now and had no issues with it.
Last week the left channel started sounding distorted, even on headphones only, which means this is happening prior to the amplifier side of the house. It starts getting distorted after 10-20 seconds. I did notice that without touching anything, the distortion will go away after 1-2 minutes for about 10-15 seconds and then comes back again. I cleaned all pots and switches with DeOxit D100. I also cleaned and played with the CONNECTED/SEPARATED switch on the side, but again, since this is happening while also listening to headphones only, I did not expect it to fix the problem.
I decided to go for recapping, hoping I have a bad capacitor. I changed all the caps on the F-2799 Tone & Flat amps board as well as the F-2796 EQ Amp board, all capacitors met specs :dunno: but I replaced them all anyway using Nichicon Audio Gold where possible. That did not solve the problem.

Looking for ideas where to go from here, I plan to replace all capacitors and relays on F-2809 Power supply but not sure it will help as well.

Thank you,
 
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It sounds like dirty contacts in the speaker relay. Using headphones, tap the relay with the back of a screwdriver or something non metalic. If the sound goes up and down when tapping, its dirty contacts. Check also any switch like a main in-pre out coupling swith if it has one.
 
It sounds like dirty contacts in the speaker relay. Using headphones, tap the relay with the back of a screwdriver or something non metalic. If the sound goes up and down when tapping, its dirty contacts. Check also any switch like a main in-pre out coupling swith if it has one.
Thanks Tom, but how would the speaker relay affect the headphone output? In my case, I turned off both A and B speaker sets and listened via the headphone, problem still exists. Also, I took apart the decoupling switch and cleaned it. But again, isn’t that switch responsible only for the connection between the preamp part of the G-9000 to the Amplifier part?
 
The headphone sound still comes through the speaker relay. Its just that there are resistors in series with the headphone jack that drop the level, so you don't blow out the headphones.
 
The headphone sound still comes through the speaker relay. Its just that there are resistors in series with the headphone jack that drop the level, so you don't blow out the headphones.
I did not know that and I'll give it a try :) any idea if the headphones connect to relay A or B?
 
Yep, the Main power amp drives the headphones through a couple of large resistors.
The speaker relay supplies the signal.
It sounds to me like you have a dodgy relay.
 
It doesn't really matter. The sound from the relay goes through 220 ohm resistors usually from eack channel to the headphone jack. In parallel the wires from the speaker relay also go to the speaker switch assembly, allowing the A or B speakers to play.

It could also be bad components, but it sounds more like a dirty relay
 
I am not sure if it is the same as the G-9000, as I can't find a schematic specific to the G-9000DB, but there is a specific relay RL03 that connects the headphone socket to the main output, via 2 x 220Ω resistors, and it is completely independent of the 2 other speaker relays, RL01 & RL02.
 
I am not sure if it is the same as the G-9000, as I can't find a schematic specific to the G-9000DB, but there is a specific relay RL03 that connects the headphone socket to the main output, and it is completely independent of the 2 other speaker relays.

I think you might be right actually John, two speaker relays and a headphone relay.

The only difference between the 9000 and 9000DB is the Dolby decoding circuit in the tuner, everything else is the same.
 
It doesn't really matter. The sound from the relay goes through 220 ohm resistors usually from eack channel to the headphone jack. In parallel the wires from the speaker relay also go to the speaker switch assembly, allowing the A or B speakers to play.

It could also be bad components, but it sounds more like a dirty relay
The problem happens via both the left speaker and the left headphone. Now that you are saying that the headphones are driven via the same power amp (add the resistor in between) I'm trying to prepare for, what if, replacing the relay will not solve the problem.
 
Actually following up after John and other comments. I answered the question from experience with all sorts of equipment, but not looking at the G-9000 schematic.
Yes the unit uses 3 relays for speaker functions. I have never seen this but it appears Sansui decided to rely on the relay 1 and relay 2 to hold the load for the 120W speakers, and use them being switched on by a lower rated speaker switch, rather than having a heavier switch like the ones used by others. Relay 3 is interesting, in that 2 of its contacts supply the signal for headphones, while the other 2 contacts are used for the green/red led protect indicators. Sansui's 9090db and 8080db used a single speaker relay with 3 contacts. 2 contacts were for the speakers themselves, and the 3rd contact was used for the protect function (Relay supplied flashing red through the NC contacts, and solid green through NO contacts when relay energized. Relay 3 will not energize unless protect is OK. And dont believe relay 1 or relay 2 will energize even if speaker switch is pressed when there is a protect issue.

So to make a long story short, I think you should still check relays (all 3). Try Relay 3 first with headphones. While doing relay 3 also observe if the Green light starts to go on and off when tapping the relay. Then relay 1 for speaker A and relay 2 for speakers B.
 
The problem happens via both the left speaker and the left headphone. Now that you are saying that the headphones are driven via the same power amp (add the resistor in between) I'm trying to prepare for, what if, replacing the relay will not solve the problem.
Golanr,
Reading more closely now I am not sure that "relays" are your problem, but they can be many times. I am just trying to give you hints on what to look for an items as the cause, or "eliminate" it as being the problem. If tapping the Relay 3, and then relay 1 and 2 don't show any change to your symptoms, then the relays can be eliminated as a possible cause of the problem. Relays in my experience can get very spotty and intermittant such as front panel switches do. The sound could be good, then distorted, than good again. If components fail they usually fail one way or the other, and don't go from good to bad to good again, although poor solder connections can cause a problem similar to what you have. (transistors can become intermittant, but usually relating to noise. If they open or short, they usually stay that way.
 
Thanks Tom! While I still have the power supply board out, I'll replace all 3 relays as well. I remember tapping on all 3, multiple times and at different times, with no luck. I'll try one more thing (after reassembly) and try to connect the G-9000 to an external power Amp (use the the G-9000 as the pre-amp) and see if the problem persists or go away. If it goes away, I will know that it's the amplifier area and continue looking there.
 
You also need to get in and clean the crap out of the CONNECTED/SEPARATED switch, this switch is the cause of 95% intermittent issues with this G series.
Its a bit difficult to get to and you really need to give a decent cleaning.... even if it not the issue here, it will become an issue at some point, so definitely worth cleaning.
 
Thanks Tom! While I still have the power supply board out, I'll replace all 3 relays as well. I remember tapping on all 3, multiple times and at different times, with no luck. I'll try one more thing (after reassembly) and try to connect the G-9000 to an external power Amp (use the the G-9000 as the pre-amp) and see if the problem persists or go away. If it goes away, I will know that it's the amplifier area and continue looking there.
If the tapping doesn't show the intermittancy I would bother replacing them. Plus you will have a hard time finding them. I usually remove, dismantle, clean and polish contacts, test and reassemble and reinstall. But if you cant hear any change with your headphones on tapping relay, and dont hear any change tapping on relay 1 or 2 with speakers A or B, you shouldn't replace the relays.
 
If the tapping doesn't show the intermittancy I would bother replacing them. Plus you will have a hard time finding them. I usually remove, dismantle, clean and polish contacts, test and reassemble and reinstall. But if you cant hear any change with your headphones on tapping relay, and dont hear any change tapping on relay 1 or 2 with speakers A or B, you shouldn't replace the relays.
Got these at Mouser
653-LY2-0-DC24 X2
653-MY4-02DC24 X1

I'll finish recapping the Power Supply Board and test the G-9000 as a Preamp if that does not help. I'll update on progress (probably next weekend :))
 
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Attached is the list I created so far, for all the caps, trimmers and relays I have replaced or will be replacing soon. Work is still in progress, but I thought someone might find the list useful. The power supply board is still out (I'm waiting for my Desoldering gun to arrive) and then, after replacing the Bias and DC voltage trimmers, I will adjust them as well, as suggested by Paul. I'm going for eliminating the 2.2KΩ trim-pots and replacing the 100Ω with Bourns 25 turns pots.
 

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Power supply board caps have been replaced, but the inconsistent distortion on the left channel still happens. So, I'm turning to the next boards (2806X2, 2807,2808 & 2014x2)
On the first 2806, I found C02 (should be 33uF25v) at below 3uF (Finally 1 bad cap after replacing dozens of them :banana:).
I replaced all the caps, also eliminating the 2.2KΩ trim-pots and replacing both 100Ω with Bourns 25 turns pots. any recommendations on how to set the trimpots (for both bias and DC voltage) before I start measuring? Also, do I measure bias where I marked in red in the photo?

upload_2018-3-3_9-37-1.png
 
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If you don't have a variac, just leave them centered. That is where the trimmers are set when new. Yes, those are the bias test points. 16mV between them.
 
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