BGW 500D HELP

[Econolett55]

I need help identifying the transistors for this power amp. I'm experiencing issues with the left channel in which the volume is either near quiet or fluctuates up and down or pops then goes back quiet. I Isolated the issue to the amp and not the pre-amp. I deoxit the gains but still did nothing. Any ideas?

 

[cademan]

It doesn't sound like a transistor problem to me. If all these transistors have the same numbers, test them with a multimeter just to make sure they all read the same.

Just google how to test a transistor with a meter.

Check for cold or loose solder joints.

 

[chazix]

volume is either near quiet or fluctuates up and down or pops then goes back quiet

Welcome to AK.

I agree it doesn't sound like a transistor problem. I believe this amp has a relay for speaker protection, and the symptoms seem consistent with the relay getting flaky. If the sound clears up after briefly cranking up some volume, and/or if the symptoms change when you tap on the relay, it's a slam-dunk. Best fix is to replace the relay.

 

[Econolett55]

It doesn't sound like a transistor problem to me. If all these transistors have the same numbers, test them with a multimeter just to make sure they all read the same.

Just google how to test a transistor with a meter.

Check for cold or loose solder joints.

Ok will do so.

 

[Econolett55]

Welcome to AK.

I agree it doesn't sound like a transistor problem. I believe this amp has a relay for speaker protection, and the symptoms seem consistent with the relay getting flaky. If the sound clears up after briefly cranking up some volume, and/or if the symptoms change when you tap on the relay, it's a slam-dunk. Best fix is to replace the relay.

Ok that is a good sign. When I crank up the the gain it does a quick blast then goes back quiet, but it doesn't click (unless its not supposed to). Also the right channel is perfect.And could I clean the relay like a regular reciever relay? This is a huge freaking relay compared to the ones in my monster recievers.

 

[GordonW]

If it is a transistor- I would suspect one of the lower-level signal or driver transistors, before an output transistor.

A bad output transistor would probably lead to enough DC offset, to trip the protection circuit.

Regards,
Gordon.

 

[chazix]

could I clean the relay

I'm not at all sure I understand the "quick blast then goes back quiet", so my guess that the relay is at fault might be wrong.

You could certainly try burnishing the relay contacts, and if that eliminates the symptom, then at least you know the relay is the culprit. The usual AK advice is that replacement is a more reliable fix, but I've been known to settle for contact burnishing, as long as the contacts don't show any signs of actual pitting.

 

[Econolett55]

If it is a transistor- I would suspect one of the lower-level signal or driver transistors, before an output transistor.

A bad output transistor would probably lead to enough DC offset, to trip the protection circuit.

Regards,
Gordon.

OH MY God! You are absolutely right! I'm too young to be forgetting this ****.

 

[Econolett55]

I'm not at all sure I understand the "quick blast then goes back quiet", so my guess that the relay is at fault might be wrong.

You could certainly try burnishing the relay contacts, and if that eliminates the symptom, then at least you know the relay is the culprit. The usual AK advice is that replacement is a more reliable fix, but I've been known to settle for contact burnishing, as long as the contacts don't show any signs of actual pitting.

Thanks I asked this because just like the output transistors this LARGE relay is near unobtainable. Probably more easier to find the relay then the transistors though.

 

[Econolett55]

UPDATE: I cleaned and deoxit everything. It's ALIVE!!! Sounds better too! My ESS AMT 1Cs really shine now with the Soundcraftsmen pe2217 preamp. I tested everything and nothing is really out of "tolerance". Easiest piece of audio I've ever worked on. Thanks for everyone! help!