Yes, I did both to verify. At first, I thought that one of my "quickie" high pass caps (two computer power supply caps series tied cathode to cathode) had half failed. Jumped out the cap, no change. Switched speaker to other channel, sounds good. Swapped RCAs, bad channel sounds good on the other amp channel. I actually left it that way for a day or two, both rear speakers running off the right channel and the sub still bridged. Verified the symptom on the bench for a minute before removing the bottom cover.
Anyway, after failing to reproduce the symptom, I did some toothpick corrosion removal and fired up the Weller. Spent an hour or so with the heat and flux, shined up all kinds of dull/flaky looking micro solder, as well as all of the big 3 pin things. Reflowed power transformer while I was at it. Gave it an alcohol and paintbrush wash and rinse.
Let it drip dry for a bit, blew it off with air, fired it up at about 10 volts and let it warm up at idle current to evaporate any hiding liquids. Since the new power supply has a 3 digit ammeter, I used it to rough set the bias on each channel. Turned bias pots down until idle current bottomed, increased bias until it rose 1 digit in the meter for each channel. Went back with the fluke and leveled all of the source resistor readings.
Anyway, after failing to reproduce the symptom, I did some toothpick corrosion removal and fired up the Weller. Spent an hour or so with the heat and flux, shined up all kinds of dull/flaky looking micro solder, as well as all of the big 3 pin things. Reflowed power transformer while I was at it. Gave it an alcohol and paintbrush wash and rinse.
Let it drip dry for a bit, blew it off with air, fired it up at about 10 volts and let it warm up at idle current to evaporate any hiding liquids. Since the new power supply has a 3 digit ammeter, I used it to rough set the bias on each channel. Turned bias pots down until idle current bottomed, increased bias until it rose 1 digit in the meter for each channel. Went back with the fluke and leveled all of the source resistor readings.
Hooray, new problem. I installed the amp back in the car after I woke up the other day. Worked great until this afternoon. Got in, as soon as the head unit woke the amp, left front channel squealing. Switched off, unplugged the input cables, left front still oscillating as soon as the amp power up. Power down, connect the other 3 RCA inputs, disconnect LF speaker, other 3 channels make clipped music.
I disconnected the remote wire and drove home, pulled the amp. May have time to look at it tonight.
I disconnected the remote wire and drove home, pulled the amp. May have time to look at it tonight.
Ok, I only had a few minutes to look at the amp tonight. No bad RCA inputs, the shields all measure good: front and pass throughs all measure zero ohms between each other, and 100 ohms to the rear input shields.
What I found tonight is that I need more power supply to duplicate the symptom on the bench. The instant the remote wire is pulled high, the amp tries to oscillate and trips the current limiter, emitting a short "blip". The current limiter kicks in and the amp stops oscillating. It then acts normally. Starts at about 0.6 amps, then idles around 1.2 amps. Can't catch the blip on the old crt scope I'm using now, I'll have to dig out the fluke.
What I found tonight is that I need more power supply to duplicate the symptom on the bench. The instant the remote wire is pulled high, the amp tries to oscillate and trips the current limiter, emitting a short "blip". The current limiter kicks in and the amp stops oscillating. It then acts normally. Starts at about 0.6 amps, then idles around 1.2 amps. Can't catch the blip on the old crt scope I'm using now, I'll have to dig out the fluke.
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We don't know. Came back to it this afternoon with the scope meter and a lawnmower battery. It's behaving perfect again. Twiddled knobs and switches, played it quiet, and loud, with and without the battery. The thing sounds good. I unplugged it and gave it an alcohol shower and a nice painting down while it was warm.
While it wasn't raining, I put it back in the Saturn, upside down without the bottom cover. If it malfunctions again, I can troubleshoot it in situ and get this one figured out while it's in a bad mood. Played it in the car for a while and the only thing that doesn't sound great is the improvised high pass caps, kinda grainy sounding. I'll be making a proper 12db for the rear speakers if I don't put a dedicated subwoofer amp in the car. If I do, I will be running the fronts and rears off the active high passes built-in.
While it wasn't raining, I put it back in the Saturn, upside down without the bottom cover. If it malfunctions again, I can troubleshoot it in situ and get this one figured out while it's in a bad mood. Played it in the car for a while and the only thing that doesn't sound great is the improvised high pass caps, kinda grainy sounding. I'll be making a proper 12db for the rear speakers if I don't put a dedicated subwoofer amp in the car. If I do, I will be running the fronts and rears off the active high passes built-in.
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