Volume on Sansui G-5700 cuts out

[TwoFooted]

I picked up a Sansui G-5700. Initially seemed to work fine. Come to find that when the volume gets over a certain level it goes out.

So say I start with the volume at 0, as I go clockwise up to 6 clicks up the dial, everything is fine. Once I get to 8 or so, it goes out. Originally I thought it was making a static-like scratchy noise. Bad pot, right?

I bought some DeoxIT and cleaned the volume pot (which, man, hard enough to get to itself). That did nothing. But once the top was off I noticed something, that static-like scratchy noise wasn't the sound of a bad pot at all. There is a relay in the middle of the board and it was literally clicking/vibrating really, really loudly.

I saw in another thread where it might be bad contacts and you can just pull the plastic cover off the relay and hit it with some cleaner and it might be fine. I would try this but I can't seem to get the plastic cover off. Is there a secret to this?

Also, after poking around, it seems these boards are pretty weird and getting them fixed is down to luck and alchemy. I am not well versed in either. I'm not well versed in electronics to be honest. But if it's not the relay itself, what's the best bet for what's causing the problem? If there is just a bad cap on that board, that I can probably handle replacing (although on just a quick visual inspection there are no obvious failures). If it's anything beyond that, this might be a loss.

Thanks

 

[ghazzer]

Hello, and welcome to AK.

The F-2980 board is definitely finicky!

If the Safely Operate light is not flickering then I would probably suspect the coil in the relay or maybe dirty contacts. Either way, I'd replace the relay and also check ZD601

Cleaning the contacts would only be a short term solution.

Try to resist temptation and don't try to fix anything else until you get this one solved. It is a hard lesson to learn.

 

[TwoFooted]

Hey ghazzer:

Thanks for the reply.

The safety light flickers when the relay vibrates/clicks. What should I infer from that? (It's fine—solid on—when at low volume).

 

[ghazzer]

It is probably not the contacts or the coil in the relay.

I would check the inputs to the HA12002 chip and see if one (or more) of them go out of range when the relay starts to chatter.

 

[TwoFooted]

Thanks ghazzer. This is probably turning into after-the-holidays-when-you-have-some-spare-time project. Will report back.

 

[ghazzer]

The "data sheet" for the HA12002 is available on line, but send me a PM ("conversation") if you cannot find it. It lists the ranges for the inputs that determine "Safely Operate".

 

[TwoFooted]

Thanks, found the data sheet for the IC. Also on the same Google search came across this thread:

http://audiokarma.org/forums/index....2980-bd-in-g-6700-getting-tired.632127/page-2

So clearly you have some experience in this area. FWIW, about half that conversation is above my pay grade, but I think I can get started. Like I said, this might be waiting until after the holidays (limping by on a used Integra with its own issues but can be 'coaxed' into some stable operation).

If it helps: when I change the following input setting on the receiver (both push button switches out)

Tone: Defeat
Subsonic Filter: Off

I can get the volume a little louder before it starts to cut out.

 

[ghazzer]

Experience I have, but it is success that has eluded me.

My approach would be to monitor the inputs to the HA12002 chip, one set at a time. Start with the volume low and increase it until the relay clicks out. If the measured voltage(s) at that set is OK, move on to the next set. If you find a set that goes out of tolerance when the relay opens, try the Tone & Subsonic Filter buttons and see if that set falls back within spec.