Need help or advice with a problem running 4 speakers on my SA7500

[euphemismos]

I recently connected a second set of speakers to my SA7500 integrated and it sounds great running all 4. However, I noticed something strange... The left speaker (connected to the "B" terminals) stays on continuously no matter how I set the speaker selector control. In other words, the other 3 speakers behave as they should relative the the setting, but left speaker B continues to output sound even when the selector switch is set to the "off" position. I checked my connections and everything is as it should be. Any advice on where to start troubleshooting would be greatly appreciated.

 

[euphemismos]

Is it possible that my speaker relay needs to be replaced?

 

[efzauner]

If you download the service manual from hifiengine and look at the schematics you will find that the relay is before the speaker selection switch and is independent of it. When the relay is energized by the start up and protection circuitry, the speaker selection switch has ultimate control. Open it up and check the switch. Check the binding posts and connections. If this is the first time you ever do this maybe you have discovered a factory error. Maybe the Left B speaker is wired wrong.. maybe there is a short somewhere. Definitely NOT the relay.

 

[euphemismos]

Thanks for the info. My knowledge on this is limited. I knew about the start up relay, in fact I had that replaced when I had the amp re-capped (by a local tech) a few months ago. I thought maybe there was another "speaker" relay (I know, crazy right?). At this point, I think it may be the switch itself. Although, with only speakers "A" connected, the switch is working as it should. It's only one channel of speaker "B" that is continuously on. Binding post connections are correct (externally). Are you saying it could be wired wrong internally? Could a "short" result in this problem where the speaker is always on (even when the switch is in the off position)?

 

[BOUXY]

A & B are separate switch positions. B position might need a good cleaning if it is dirty and causing your problem

 

[efzauner]

something is causing the Left B speaker to be connected to the left channel all the time, regardless of the switch position. I cant tell you more. Someone will have to take a look. By "short" I mean a connection that should not be there. As simple as a bent out of shape contact on the rotary switch. Maybe a wire pigtail got bent and is contacting something it shouldn't. We can go on and on guessing.. this should not be difficult to troubleshoot once you open it up. We are not talking bout tracing faulty transistors.. just following wires... The speaker switch should even be an open affair. If you purchased it used, maybe there was a problem with the switch and someone bypassed it. Who knows.

 

[efzauner]

A & B are separate switch positions. B position might need a good cleaning if it is dirty and causing your problem

cant see how dirt will cause a permanent connection... usually causes a disconnection and noise.

 

[BOUXY]

cant see how dirt will cause a permanent connection... usually causes a disconnection and noise.

There are many things we can't see that could cause this problem I just offered my opinion right or wrong simple as that

 

[euphemismos]

Thanks to both of you guys for your responses.

 

[efzauner]

There are many things we can't see that could cause this problem I just offered my opinion right or wrong simple as that

Well, not really. Something has to physically connect Left B speaker to the Left B speaker output after the relay. There are not too many ways this can happen. I have looked at speakers switches and can't think of ways that dirt build up on the speaker selector switch could cause this permanent connection. Attached is the diagram for the speaker switch from the service manual, as well as the copper side of the PC board where the relay is and were the speaker switch connects. The other plausible fault would be some short on this foil as you see the Left B trace is very near the amp output trace. So that would be a another place to look.

 

[N8Nagel]

It's possible the speaker selector switch is mechanically falling apart. My tech finally tracked down the intermittent problems with my Luxman R-1120, apparently he had to disassemble the selector switch, glue some crap together, and reassemble it. I'd been in there myself and never spotted the problem.

 

[petehall347]

could be a broken wafer .
or someone bypassed the switch and hoped it wouldn't be noticed

 

[kvining]

Take both top and bottom covers off, turn receiver upside down and shake it, see if loose screw that fell in last time it was worked on falls out. Get big magnifying glass, check selector for same jammed up in switch.