Hey all,
I decided to take the plunge and try to repair some of my old car amps (instead of just building speakers from time to time) as hobby projects.
I recently picked up a Punch 45 (HD), and after replacing the junk wire the PO had connected to it (with what looked like telephone crimping stuff) I got it to power on, but I have a high amount of static like crackling noise from the right channel. Initially, I thought it was due to the loose rca inputs- (and there may still be a problem with the inputs) but I tacked them back to their mounting surface (where they had become detatched) with a bit of solder and the noise continues.
I did alot of searching before posting, and found one old, dead, unresolved post where someone had a similar problem with an RF amp, and Perry had asked him to measure the resistance between the input rca shields/sleeves. I checked the resistance between the shields on this P45 and now that they're tacked down, they read 0.6 ohms between them.
So, what would be next?
I thought I would post this as a diy tutorial for others to follow who might be interested, and I will be reading on the bcae site as well. If there are any other sites that might help me repair a RF amp (or any other amps) I'd really appreciate the info. Thanks in advance and have a good week- John
I decided to take the plunge and try to repair some of my old car amps (instead of just building speakers from time to time) as hobby projects.
I recently picked up a Punch 45 (HD), and after replacing the junk wire the PO had connected to it (with what looked like telephone crimping stuff) I got it to power on, but I have a high amount of static like crackling noise from the right channel. Initially, I thought it was due to the loose rca inputs- (and there may still be a problem with the inputs) but I tacked them back to their mounting surface (where they had become detatched) with a bit of solder and the noise continues.
I did alot of searching before posting, and found one old, dead, unresolved post where someone had a similar problem with an RF amp, and Perry had asked him to measure the resistance between the input rca shields/sleeves. I checked the resistance between the shields on this P45 and now that they're tacked down, they read 0.6 ohms between them.
So, what would be next?
I thought I would post this as a diy tutorial for others to follow who might be interested, and I will be reading on the bcae site as well. If there are any other sites that might help me repair a RF amp (or any other amps) I'd really appreciate the info. Thanks in advance and have a good week- John
Hi Perry, Thank you very much for responding. No, there isn't any corrosion- in fact, compared to many of the pictures I've seen of damaged amps, this one appears to be in pretty good shape. No burned spots, no broken traces, etc.
If it's noisy. you'll have to trace the signal to see where the noise is getting into the system.
Look on the HBPIM board right behind the RCA jacks and look at the 2 10uf 16v aluminum capacitors and see if there is any brown spots around them.
Ive purchased two 75hd's and a 45hd in the past month. All have ruptured caps on the PIM. Boards aint cheap either. Eventually when i quit buying broken amps, i'll order replacements. Lol. First thing im gonna do when i get new boards is replace the aluminum caps with low profile leaded radial caps. Ill just keep the leads short and heat shrink em.
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Hooked it back up to power and realized that the crackling, popping static noise was in both channels- and... whatever was failing, failed. Pop, smoke. Now it's dead...
I didn't have burned spots before, but I do now...
I didn't have burned spots before, but I do now...
Very bummed about this- my first project up in smoke (literally.) Would it be OK to try and post a picture of the burned spots for feedback/direction from y'all?
Hope this works. This is a macro of the whole board with purple arrows showing visble burns
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I've spent the last 3 hours trying to post photos of the P45s board to this thread- and even though they are sized properly- it's a no go. The pictures are in my "gallery" in diyaudio, however so...
Here's a link to the photo of the board in my gallery:
I've spent the last 3 hours trying to post photos of the P45s board to this thread- and even though they are sized properly- it's a no go. The pictures are in my "gallery" in diyaudio, however so...
Here's a link to the photo of the board in my gallery:
It appears that you allowed an unfused remote wire contact one of the speaker wires. What color wire connected to that terminal of the plug?
One last macro of the burned side. Used 2 desk lamps and no flash to try and get light while eliminating glare.
No, the transistors weren't clamped- just the aluminum plates were in place behind them. The whole thing took about 3 seconds to go from crackling static like before, to smoke and burns on the traces...
No, the transistors weren't clamped- just the aluminum plates were in place behind them. The whole thing took about 3 seconds to go from crackling static like before, to smoke and burns on the traces...
I'm sure you're both right (and a genius.) The old electrical tape I had wrapped around the remote turn on lead had fallen off- and while the speaker wire connections were covered, they were not covered real well- because the tape is losing adhesion. So it is entirely possible it made contact with either the black or orange wire... (forehead slap)
Look at the pin that's connected to the burned trace. Does that go to the black or the orange wire?
That's not one of the active speaker wires so the output transistors may have survived. You may not need to do anything other than repair that trace (if it's actually burned open) to get back to where you were.
Please read the basic repair page (link in sig line below), paying special attention to the information in the yellow box.
Please read the basic repair page (link in sig line below), paying special attention to the information in the yellow box.
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