The drive circuit appears to be OK.
If you don't have a limiter, a 5 amp fuse may work. I don't know what to expect from your cordless drill battery so that's why I'd prefer the limiter.
The next safest thing would be to desolder the center legs of the rectifiers and confirm that you get approximately ±25v DC on them.
If you can't desolder them without damaging them, you can power up with them in the circuit. That will power up the audio circuit so you'll have to be very cautious.
See if you can find an old headlamp (automotive, not camping type).
If you don't have a limiter, a 5 amp fuse may work. I don't know what to expect from your cordless drill battery so that's why I'd prefer the limiter.
The next safest thing would be to desolder the center legs of the rectifiers and confirm that you get approximately ±25v DC on them.
If you can't desolder them without damaging them, you can power up with them in the circuit. That will power up the audio circuit so you'll have to be very cautious.
See if you can find an old headlamp (automotive, not camping type).
That should work. Use the high beam and common terminals. They should be the opposing terminals (low beam is at a right angle to them).
It will be inserted between B+ on the amp and the positive battery terminal. When you initially power the amp up, the light will glow brightly then dim.
Only leave it on for a few seconds. If the Z44 isn't soldered down, monitor its temperature carefully while the amp is powered up.
It will be inserted between B+ on the amp and the positive battery terminal. When you initially power the amp up, the light will glow brightly then dim.
Only leave it on for a few seconds. If the Z44 isn't soldered down, monitor its temperature carefully while the amp is powered up.
When you say "only leave it on for a few seconds" don't I need to take readings?
I'm assuming that the lamp remains at near full bright as if you connected it directly to the battery.
Confirm that you don't read 0 ohms across the B+ and ground terminals. It should be a constantly changing reading.
If that's OK, desolder the center legs of the two rectifiers and try powering up the amp. Does the lamp do as expected?
If you see bright-dim with the rectifiers out, solder them back in and...
Flip the board over and measure the DC voltage across the 4 large resistors connected to the 3rd legs of the output transistors.
You'll need to place the probes, apply power, get the reading, remove power. Do this for each of the 4.
All should read 0.000v DC.
I may not be back here tonight. If not, I'll check back tomorrow.
Confirm that you don't read 0 ohms across the B+ and ground terminals. It should be a constantly changing reading.
If that's OK, desolder the center legs of the two rectifiers and try powering up the amp. Does the lamp do as expected?
If you see bright-dim with the rectifiers out, solder them back in and...
Flip the board over and measure the DC voltage across the 4 large resistors connected to the 3rd legs of the output transistors.
You'll need to place the probes, apply power, get the reading, remove power. Do this for each of the 4.
All should read 0.000v DC.
I may not be back here tonight. If not, I'll check back tomorrow.
Well for some reason, I couldn't get the headlight to come on anymore. I was verifying 12V at the terminals of the amp. I lifted the amp to look at the power LED and low and behold, it was lit up.
I didn't leave it on too long. I didn't notice any heating of the Z44. At this point, I will leave it alone and see what you have to say. I work 12 hour shifts the next two days so it will be late when I get home.
Thank you very much for all of the help you have given me. When I get further instructions from you, I will perform them when I can and report back.
Are you going to be able to connect a signal source and speaker (any speaker) where you're working on the amp (out of the vehicle).
OK. Next tests out of the vehicle...
Confirm that R136, 163, 236 and 263 are within tolerance.
If they are, rotate the bias pot for each channel until the lamp just barely begins to increase in brightness then back off just a bit. Both channels should begin to increase the brightness at approximately the same point in the rotation.
Remember to monitor the temperature of the z44 through this.
If that all goes to plan, measure the DC voltage directly across each pair of speaker terminals.
Confirm that R136, 163, 236 and 263 are within tolerance.
If they are, rotate the bias pot for each channel until the lamp just barely begins to increase in brightness then back off just a bit. Both channels should begin to increase the brightness at approximately the same point in the rotation.
Remember to monitor the temperature of the z44 through this.
If that all goes to plan, measure the DC voltage directly across each pair of speaker terminals.
Earlier question about flux...
For larger solder connections, there is generally enough flux in the solder. For SMD parts, you use such a short length of solder that there may not be enough flux. search ebay for Kester 186 951 reflow flux needle bottle xbox. The amber flux is messier but easier to work with. The clear flux flows too easily and, in my opinion, smells awful. Order both and see which you prefer. You want a dispensing bottle that has a metal needle.
For larger solder connections, there is generally enough flux in the solder. For SMD parts, you use such a short length of solder that there may not be enough flux. search ebay for Kester 186 951 reflow flux needle bottle xbox. The amber flux is messier but easier to work with. The clear flux flows too easily and, in my opinion, smells awful. Order both and see which you prefer. You want a dispensing bottle that has a metal needle.
I think this is the first time I've ever seen a value that low. Looks like the schematic says .1
Something weird is going on. The headlight is no longer lighting up. I verified it works by hooking straight to the battery. I have it hooked in series with the positve line just like before. The Z44 still isn't heating up though. (a good sign I imagine)
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