Ampeg BA210 Shut-off Issue

[cjenrick]

dude, you need to read the first post more carefully, details are important>

"I took it to a local amp guy here in Reno who gave the amp a once-over, changed a couple output transistors and attributed the popping sounds to "dirty" electrical power in my home, since the amp made no noises in his shop."

the amp tech should have replaced all the power transistors, especially since they were MOSFETS.

[MarkusBass]

dude, you need to read the first post more carefully, details are important>
"I took it to a local amp guy here in Reno who gave the amp a once-over, changed a couple output transistors and attributed the popping sounds to "dirty" electrical power in my home, since the amp made no noises in his shop."
the amp tech should have replaced all the power transistors, especially since they were MOSFETS.

Yes, you are right. I may have language problems. For me statement like: "I earned just a couple of dollars" means: "I earned some dollars". But for you it means: "I earned just 2 dollars". Sorry, if my understanding is incorrect.
But please note that Bill asked:

I will ask, when did the local guy change the two output transistors and give this a once over?
It doesn't look like any of the outputs have ever been changed.

and he never got an answer. If you look at the photo, it is possible that the transistors were never changed on the board. And it's good because it was not needed. Most probably the amp tech wanted to justify some charge for taking care of the amp. So the question that is still open is: was anything changed on the board? This can be easily answered by posting a photo of the bottom of the board (and not the top). For now, we don't know it.
Sorry for misunderstanding .

Mark

[DrGonz78]

The two mosfet output transistors on the right have very shiny legs. Almost looks like someone applied solder on those legs or something. Perhaps tech was lazy cut the legs off to remove and replace with similarly snipped legs of some new outputs. Perhaps he had his eye's on a tube amp repair and did not want to take the time to do the job right?

[MarkusBass]

That's true. I haven't noticed that. They look different.
Please note that the amp uses two MOSFETS of type "N" and two MOSFETs of type "P". So changing just two (a couple) of them makes sense. But for me it seems that the problem was not properly diagnosed and not properly fixed. And now we are discussing whether there was anything changed in the amp, or just a couple of transistors (just 2), or 4 of them should be changed. This is not needed.
A good picture of the bottom of the amp could help.

PS: I checked the dictionary and "couple" means "pair" - exactly 2, not 2 or a little bit more as I thought. My bad .

Mark

[cjenrick]

no worries bro, just people trying to help people,

[MarkusBass]

I was looking for a photo of the amp I was fixing but I cannot find it. Here is a picture of another Ampeg amp that had similar problems:



Just take a look at how the 10W resistors are soldered. This fix was so simple that I even didn't make any notes of it. Maybe it's the same case (although the OP claims that the resistors are OK in his amp). And of course there was no need to replace anything else .

Mark

[J M Fahey]

PS: I checked the dictionary and "couple" means "pair" - exactly 2, not 2 or a little bit more as I thought. My bad .
Mark

Oh, no need to apologize .
Couple means two in Formal Speak but here we are using IN-formal speak as fas as I can tell.
Just checked none less than the *Oxford* Dictionary, and I found, besides the formal definition of course:

informal An indefinite small number.
‘he hoped she'd be better in a couple of days’
as pronoun ‘we got some eggs—would you like a couple?’
as determiner ‘just a couple more questions’
‘clean the stains with a couple squirts of dishwashing liquid’

Dictionary.com says:

Idioms
14.
a couple of, more than two, but not many, of; a small number of; a few:
It will take a couple of days for the package to get there.

I bet we are talking informal English here ; otherwise the pickup Forum guys might be actually talking about

[MarkusBass]

Thanks for the support. For me "couple of days" means few days (somewhere between 2 and 6). But on this forum it's not the first time when "couple of transistors" means exactly 2 transistors. And this confuses me because I know rather this informal meaning of the term.

I bet we are talking informal English here ; otherwise the pickup Forum guys might be actually talking about

So the guys on the pickups forum are not talking about cars? I always wondered how they make cars using winding machines

[Enzo]

Hey my car really winds, man...

[Ba55playa]

Dang! Sorry its taken so long for a reply.
Enzo, those things really were right under my nose, right? I'm going to have to get more familiar with the myriad types of electrical components out there; I was looking for a banded resistor and didn't even look at those white rectangles. I have a lot to learn.

I double-checked the solder points for R66 & R68 and found no issue. I put a meter on the respective legs and found those two resistors measured 333 ohms, where the other 4 same resistors all measured 0.6 ohms. I pulled them both off the board and re-measured and got the same result. I know we were talking about a mechanical connection issue but this doesn't seem right to me at all. Could it be that while the resistors are still cool the amp works okay but once they heat up they increase in resistance then begin to cut-out the power supply?

[Enzo]

When facing potential solder problems, we just resolder them with a dot of fresh solder. Looking at them only goes so far. SO what is the current problem, I forget what we were doing. So the six power resistors all measure OK.

If you have resoldered all of those resistors, and reassembled the amp, does the problem still exist?

[Ba55playa]

Enzo. I did resolder the resistors. The six power resistors do measure OK. I am going to put it back together and re-check.