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.
That resistor connects between the primary and secondary grounds.
What is the resistance between the B+ terminal and any of the non-bridging speaker terminals (nothing connected to the amp)?
What is the resistance between the B+ terminal and any of the non-bridging speaker terminals (nothing connected to the amp)?
Twist/push/pull on the power transformer while measuring the resistance. Does it ever drop to near 0 ohms?
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?
Do you see anything that could produce any of the situations mentioned above?
With the rca shield resistors pulled out, I measure 47k ohm from b+ to rca shield. but a short from b+ to where these resistors connect to.
The 'point where these resistors connect to' should read 0 ohms to the non-bridging speaker terminals.
It reads 22k @ those points and the resistor getting hot reads 0ohm to b+ on the coil side and 0ohm to ground on the other
I double-checked on a similar amp here. The end of the resistors NOT connected to the RCA jacks should read 0 ohms to the non-bridging speaker terminals. You likely have an open trace somewhere in the secondary ground.
I think you were right about the a shorted transformer, all legs of the red/orange coil read 0 ohms to B+. And its a mono amp there is no bridging, would that matter about the rca to speaker terminal reading i cant find anything open except the trace to the heatsink.
Connect the meter from B+ to one of the secondary center tap wires. If it's shorted, it will read 0 ohms. Try twisting/pushing/pulling on the transformer. Does the short make/break intermittently?
Rewinding is no fun, it's best to avoid if possible.
Rewinding is no fun, it's best to avoid if possible.
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.
Referencing measurements from my pcx-2200 there would definitely be a short in this pcx-1500 transformer then.
Is the coating on the transformer rubbery or hard like epoxy?
Before you do anything else, push all of the windings that exit from the bottom of the transformer down and away from the transformer. Does that break the short?
There appears to be a dark area in the windings (near the center of the core). Is that the light or does it look dark?
Before you do anything else, push all of the windings that exit from the bottom of the transformer down and away from the transformer. Does that break the short?
There appears to be a dark area in the windings (near the center of the core). Is that the light or does it look dark?
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.
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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