Rockford Punch 500S

[seankane]

I have a Punch 500S I recieved for repair.

Upon powering it up it has a dead short. Everything tested good, power supply and outputs.

I found a "bare" spot between 2 of the transformer legs where the coating has wore off. I seperated the 2 legs with a screw driver spreading them apart to break the contact.

The amp powers up and idles fine and produces audio. Do I have to replace the transformer or can I put something on it to insulate the 2 legs from ever touching again?

I have a few used ones laying around, but it seems like a waste of time and money if I can fix it in a simpler way. Any help would be great.

Thanks again..............Sean

[seankane]

The board number is PC-3082-D

I have included a pic of the board as well.

There is a bare spot on the bottom sheet metal cover like it was rubbing on the cover and finally shorted out. I cant believe it didnt short the power supply.

Maybe I could use and epoxy or silicone to re-insulate it, and some small spacers to seperate it from the bottom cover?

[Perry Babin]

If you know precisely where they were shorting together and can get an insulator in place so that they cannot short together again, I see no reason to replace it.

In the future, use a plastic tool to separate the windings. The Menda 35622 is a good choice. Make sure that you get the genuine Menda tool, buy a few extras and don't pay more than a couple of bucks a piece for them.

Edit:
I'd replace that if you have another one and you intend to sell it.

[seankane]

Thanks for the heads up Perry. Look at a close up of my photo and you can see the 2 legs right in front of the second and third rail cap.

The amp works fine now, but what about the bottom cover issue? Am I gonna have to de-solder it anyways and move it closer to the board or can I do what I asked in my previous post?

[Perry Babin]

The fact that several windings that are tightly wrapped on other windings have had their enamel burned makes me believe that there's a good chance that it will short again. Of course, you're there and can see the windings close-up so you'll have to make the call.

I don't think you can insulate those windings unless you unwrap them, lay down an insulator and then re-wrap them.

[seankane]

I agree with you it should be replaced.

In the future where is a good source to by torroid cores and windings. I would like to be able to wrap my own in case of a reapir that it was needed for?

What specifications do I need to know before ordering such parts?

[Perry Babin]

CWS bytemark has cores. I generally try to use 'P' material cores but 'F' and '77' material is all that they'll likely have.

Match the core size.

You'll need a dial caliper to determine the gauge you need. Magnet wire comes in 1/2 gauge sizes (12, 12.5, 13, 13.5...) so you need to get the right size. Many times, there is not additional space on the core to use larger wire.

You can buy wire from many sources. Ebay has some magnet wire. Amidon and Surplus sales of Nebraska have a larger selection.

I use the high-temp insulated wire but it's harder to strip than the solder-strippable wire that most manufacturers use.

[seankane]

Ok thanks Perry.

One more question, I just unwind the old one and copy the lengths or do I benefit from more windings?

[Perry Babin]

Length isn't a good way to determine how to re-wind it. Professionally wound transformers are typically would very tight and if you use the same length, you'll likely have too few windings. You must count the turns.

If you increase the number or secondary turns, you may get more power from the amp but you'll also make it more likely to fail if driven hard. Unless you're experimenting for your own use, wind it as it was originally wound.

It's not practical to change the number of turns on the primary.

[seankane]

Ok Perry understood, good info. Thanks for your help!!