HELP......electronics guru needed !

Looks like Q8 and R39 have gotten hot too.

 

Board #132887

 

This machine may have turned itself into a parts machine..... not what I needed right now.

 

The power output was surging before the unit died.. acted as if it had a pulse unit..it doesn't.. then POOF.... it died.

 

This place repairs these. I'll keep searching.

Servicing Miller | EIC Repair

 

Sorry to hear about your problems. I have a couple of questions, how often do you remove the side panels and blow it out good ? Does your 250 have fan on demand ? I'm asking because about 15+ year's ago my 250 started acting up and my local service guy said blow the @#$& out of it because the metal dust shorts out the PC boards. You in fact might not have had a component induced failure but rather a contamination induced one. Not sure if I can be of any help but if you need to compare anything or ??? I'm more than willing to get mine all naked for ya ! Probably overdue for a blowing out anyway !

 

Pretty hard to troubleshoot over the net, send it to me if not in a hurry?

You more than likely smoked the FET and generally any input caps I would go and replace.

EE by trade, firewood hack on the weekend

 

Constant fan...... Preventitive maintenance....lol.... What's that ???

 

Not in a major hurry.... I can send it to you if you want to take a look .... How long might you think you would need it ?

Have a job coming up in late January that I will need a tig on... But can always borrow one.

 

Just re-read this thread, I would follow that guide @GrizzlyAdam posted earlier. Before powering it up, I would also replace that clearly fried resistor. Too bad Radio Shack is closed, Digikey is where I get most things like this.

I can take the board and give it a quick eye test, meter check, but not a full functional test. You might be best trying what you can. It would take me one night to take a crack at diagnosing.

 

Does it matter if the new resister is smaller physically ?? I have not been able to locate 1 that is the same dimensions...

 

Physically, no, as long as it fits. The power/ load/ ratings are what matters.

The last fix I did had a physically smaller component, but it was rated better than what was put in the subwoofer. Actually it was rated as what Polk should have put in it too begin with. It's been great since.

 

My supplier is checking on a replacement board, based on that number. Will let you know when I know.

 

I agree with Horkn. The new resister should have the same wattage rating and ohm rating.

 

Ok... I found the resistors... but having trouble to match up the 9a 50v transistor. Any help on that one ? Would a 60 v or 100v one work ? So many different kinds.

 

Is it an NPN or PNP transistor? If you can get a part number for it you could look it up on DigiKey.

 

I don't know if NPN or PNP.. How can you tell ?
The Miller part # is 109 156 but have no luck finding anything more about it. (That number is also on top of the transistor)

This is turning into a personal challenge.... I'm going to win this one !

 

Do you have the schematic?