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Sansui 990 clicks of relay in phono mode

daveyh

daveyh

Super Member
OK. Here's one for you. I have a Sansui 990 that clicks off the relay on the left channel when the volume is turned up. No sound except very low volume. The right channel is nice and clear. When I unplug the right channel RCA connector and and leave the left plugged in and turn up the volume it clicks off the speaker relay. Both channels work in mono on the phono but no stereo in phono. FM and CD play stereo and it sound fine. What's going on?
 
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You've already answered that you have a problem in the phono stage, left channel.

To truly get an answer you will need to start probing for DC, compare voltages to the SM, and possibly a scope.

Hopefully others have had similar issues or know of known problems. Alternatively consider rebuilding the phono stage. I believe on the 9090 there is plenty of room, not too difficult. Best to find the problem first though. Service manual should have everything you need.
 
I just did that earlier and it still does it. Recapped it and checked the resistors. The SM I have is not very clear, Thought it might be something I missed that someone else has had happen to them. Looks like more probing.
 
daveyh said:
I just did that earlier and it still does it. Recapped it and checked the resistors. The SM I have is not very clear, Thought it might be something I missed that someone else has had happen to them. Looks like more probing.
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That makes this a lot more tricky... There isn't much on that EQ board, just a simple IC. AUX and the tuner are confirmed working. From your description it really seems to be isolated to the phono stage.

Did you do this work because you were trying to remedy this issue or is this a problem after you have worked on it?

Remove the jumpers for pre-amp/power in, lets keep the power section out of the equation. You're on a dim bulb right?

Pin 53 is your Left channel out
Pin 54 is your Right channel out

There is not much in-between the input and 53. Since you have already recapped it with presumed good capacitors its a bit of a head scratch...

Make sure 34 is getting 36V DC.
Make sure 49 is getting 13v (12.6v) DC

How do the voltages on on IC01 look?

upload_2021-4-10_22-47-23.png


upload_2021-4-10_22-48-9.png
 
I am on a DBT. I recapped it to resolve any problems that was occurring. I only use new Nichicon capacitors on all my units directly from mouser. I even replaced the two IC's BA312's with new ones because I am planning on this being used as my part of my main system so I should have correct voltages? I ordered the new IC's and had a few extra on hand so I used them to replace the old tired ones. I even re-flowed the solder joints. I never buy anything from auction sites. Only reputable suppliers.

The attachment you sent will help greatly. Thanks a bunch! I will check the voltages first thing tomorrow and post my results.
 
daveyh said:
Recapped it and checked the resistors. The SM I have is not very clear,
Click to expand...
The C03/04/11/12 Tantalum caps are prone to failure. If you've swapped them out, make sure to get the polarity correct. They're small and tricky and sometimes polarity is just marked with a tiny '+' on the positive lead.

BTW: The 880/990 service manual from HIFI Engine is a rather clean scan. Much better than the equivalent 8080/9090 service manual.
 
daveyh said:
OK. Here's one for you. I have a Sansui 990 that clicks off the relay on the left channel when the volume is turned up. No sound except very low volume. The right channel is nice and clear. When I unplug the right channel RCA connector and and leave the left plugged in and turn up the volume it clicks off the speaker relay. Both channels work in mono on the phono but no stereo in phono. FM and CD play stereo and it sound fine. What's going on?
Click to expand...
The relay doesn't click off just one channel... You have a problem for sure in the phono section, or selector switch. If only one speaker is off when the relay clicks, you also have a bad relay with one set of points welded together.
 
I have already put a brand new relay in. I recapped the protection board. All other modes work fine including AUX. All voltages check out OK according to the SM and the post MIJ_Pioneer provided. The amp pin voltages on the IC's are the same on each channel. I am going to look at the selector switch again. Cleaned it already. Any other ideas??
 
daveyh said:
I have already put a brand new relay in. I recapped the protection board. All other modes work fine including AUX. All voltages check out OK according to the SM and the post MIJ_Pioneer provided. The amp pin voltages on the IC's are the same on each channel. I am going to look at the selector switch again. Cleaned it already. Any other ideas??
Click to expand...
Yeah, if only one channel clicks out, and it is a new relay, you have a solder bridge somewhere. And it would be nice if all details are known from the start instead of sending people on wild goose chases not knowing what was previously done.
 
Skywatcher said:
Yeah, if only one channel clicks out, and it is a new relay, you have a solder bridge somewhere. And it would be nice if all details are known from the start instead of sending people on wild goose chases not knowing what was previously done.
Click to expand...

I am trying to solve this problem with help from others. I do not expect you or anyone else on this board to solve it for me without doing my part in trying to fix it and post results. I am posting as I go considering everyone ideas in trying to resolve this. If I posted it had totally been rebuilt would that change the problem? I do not think so.
 
daveyh said:
I am trying to solve this problem with help from others. I do not expect you or anyone else on this board to solve it for me without doing my part in trying to fix it and post results. I am posting as I go considering everyone ideas in trying to resolve this. If I posted it had totally been rebuilt would that change the problem? I do not think so.
Click to expand...
It will indeed change every suggestion from a "possibly" failed component to a "possibly" dirty switch, and everything in between... That's a lot of wasted time going on wild goose chases. That doesn't change the fact (as you explained it) one channel keeps playing then the relay clicks... You messed something up and have to go back over your work. That is unless you simply didn't explain it right...
 
Dirty switch I guess?? Sprayed the tape record switch again and this time i used CRC Dry electronic cleaner with no residue flooded it followed by DeOxIT 5 and worked the control. It came out of it. It now plays in both channels in phono. Still don't know what caused the relay to kick out and go into protection on the RCA input for the left channel phono but it works fine now, Stereo vs. mono situation now works. Aux, FM and phono. Thanks for your patience and all your help!
 
daveyh said:
Dirty switch I guess?? Sprayed the tape record switch again and this time i used CRC Dry electronic cleaner with no residue flooded it followed by DeOxIT 5 and worked the control. It came out of it. It now plays in both channels in phono. Still don't know what caused the relay to kick out and go into protection on the RCA input for the left channel phono but it works fine now, Stereo vs. mono situation now works. Aux, FM and phono. Thanks for your patience and all your help!
Click to expand...
Recheck the DC Offset. Something spiked it for the protection to kick in like that.
 
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