old school Ppi pcx-1500

Oldskoolamps

Member
2016-01-27 12:35 am
I have this precision power pcx-1500 and it turns on and works but not like it should. I opened it and found 2 burnt resistors behind the inputs for the rca sheilds & i have some replacements. But the problem is that as soon as i apply the remote voltage to power on there is a resistor getting extremely hot immediately, (no speakers or rca hooked up) its the one right between the 2 coils, what is it for & how do i fix this? Could it just be out of tolerance? I cant accurately measure it while its installed, meter fluctuates. For the rca sheilds I tried 47ohm & 47kohm & left it open but no change.
 

Oldskoolamps

Member
2016-01-27 12:35 am
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The resistors that are getting hot typically fail when voltage is applied to the secondary ground. It's often from a shorted transformer (doesn't seem to be the case here), when 12v from an outside source contacts the RCA shields or when one of the speaker output wires (bridging terminals) contacts ground.

Do you see anything that could produce any of the situations mentioned above?
 

Oldskoolamps

Member
2016-01-27 12:35 am
Yes there is a short from B+ to rca shields. But idk why, I cant find anything wrong, what could cause this? I took it out of the case and the trace from ground to the case was fried and open.
 

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Sorry but "secondary center tap?" Pretty sure i know what you mean but dont want to act like i do & be wrong, ive never had a transformer problem yet in my repairs. that would be the side between the coils right. From reading your transformer page the red and orange wires should be separated to induce voltage right? but I get 0ohms from B+ to All of the connection points on the red\orange transformer. These coils are Very secure not much wiggling is possible, I can't break any short.
 
Try as i might i can not locate or break the short in the windings, should i remove it? And see 1) if i can locate the short /2) if there is still a short on b+ to secondary taps? (Could anything else even cause this short?)

The coating on the top outer layer is silicone-like.

I dont see a dark spot in the center, or any spots that looks like it was getting excessive heat.
 

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