Unusual Amplifier Issue

[Filmo]

Hello,
This is my first post. Thanks in advance for your advice.
I have a BGW 250D with an odd issue. In order to get it to power on and be functional, I have to pull the speaker wires out first, turn it on, and wait for the relay to click. Otherwise, it will either not produce sound from the left channel or else emit a loud screeching noise.
Once I get the relay to click on, I can reconnect the speaker wires and turn it on without a problem. The relay clicks again, and everything sounds amazing. In fact, this is the only amp that I have found which actually makes my AR speakers sound proper other than my (currently not working) AR AU.
I pulled out the relay, and the connections don’t appear corroded (in fact everything looks perfectly brand new inside - which is impressive for a 40 year old pro amp).
Any thoughts on why the relay would not work initially, but will do so after an initial start without speakers? Thanks.

 

[llwhtt]

Does that model use an octal plug to connect the amplifier boards to the power supply/housekeeping circuits? I think it does, try removing the plugs, cleaning, and re-seating the plugs. I've been stumped on my first couple of BGW repairs because of those plugs/sockets.

Craig

 

[NAD80]

Service manual is on HiFiEngine.com. Just register and download for free. https://www.hifiengine.com/manual_library/bgw/250.shtml This unit has the octal connector, and other connectors. Id say open the unit and clean all the connectors, as ilwtt advises. Filmo, Welcome to AK. Hope this helps.

 

[Filmo]

Thank you for the links, advice, and warm welcome. It looks like there are two sets of these octal plugs - one set in the back which relates to the inputs and then one plug on each side connected to the transistors. I am guessing that the left side transistor connection should be my focus, as this is the problem channel? The issue I described seems to occur regardless of whether or not anything is plugged into the inputs, so I don’t think I should bother with these. I’m headed out now to buy some contact cleaner. Perhaps the relay itself could be sticky and could use some as well? Thanks for your help.

 

[llwhtt]

When those channel connectors are the problem the amplifier does all kinds of strange things, nothing makes sense. Since the amplifier seems to function normally after you do whatever you do makes me think of those connectors. It's an easy first step as I've seen this many times over the years.

Craig

 

[Filmo]

Thanks Craig. I cleaned the octal connector on the left side and the problem seems to have disappeared. Then I took the opportunity to clean a number of other accessible connectors as well. Everything sounds great and it is trouble-free!

 

[llwhtt]

Awesome, simple fix. Those connectors probably haven't move since the amp was made.

Craig

 

[Capitol C]

What is wrong with your AR AU amplifier? I've been working on mine on and off, and they can be a little tricky to service.