I got a sundown sfb 2000d off of ebay. When I opened it up it had no power supply fets and 3 original output fets and 1 4115. The 4427 and gate resistors were blown also. I replaced the 4427 and the gates. Also replaced all the tl074cs. The power supply is up and running. On the output I'm not getting any switching and the clip light stays on. Nothing is getting hot. I probed the tl074cs and pin 4 I got +15.39 but on pin 11 I only get -12.05. Do I need 15 volts on both to get drive? Or is there something else I should be checking?
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+15 and -12 on the op-amps shouldn't be a problem but you should follow the negative supply line back to t its source to see if it's a -15v regulator and why it's not producing its rated voltage.
What output driver ICs?
What microprocessor?
^^^ part numbers
What output driver ICs?
What microprocessor?
^^^ part numbers
No idea what the microprocessor is. The driver ics are 20957s I think. Everything is marked out. And I haven't been able to find the regulators yet
Could it be c18? And r16? R12 reads 3.3 I changed it and still got the same reading so I'm guessing it's good?
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Are you sure it's a 20957? It's possible but I don't think I have anything on any Brazilian 20957 amps.
I did a search on here and that's what they said I think. As you know I don't know what I'm doing or looking for on any of this though. Thanks for the replies
Which terminals on the output driver IC connect to ground?
Does this amp have ±rail voltage or only positive rail voltage?
Does this amp have ±rail voltage or only positive rail voltage?
Pins 4,5,8,9 and 12. Hopefully they are not shorted because if they are the Irs20957s I couldn't find any. And I think it has positive and negative rails. Not sure. I saw this in the tutorial somewhere but can't remember where.
If pin 9 is grounded, it likely has only positive rails.
For the 20957:
What's the DC voltage on pins 1 and 2?
Do you see a square wave on pin 3?
For the 20957:
What's the DC voltage on pins 1 and 2?
Do you see a square wave on pin 3?
I used a scope with only the trace (no digital readout) for virtually 100% of my time working. A Tek 465B was my favorite even though I had other scopes with many more features.
If you drive a signal into the amp, do you see audio on the various op-amp output pins in the amp?
If you drive a signal into the amp, do you see audio on the various op-amp output pins in the amp?
Are the signals clean?
Are any of the op-amps heating up?
Have you tried operating all of the pots and switches through their entire range with a signal source connected and a speaker connected to the dead channel to see if the channel ever produced any sort of sound (even if it was just static/noise) or allowed a square wave to reach the 20957 pin 3?
Are any of the op-amps heating up?
Have you tried operating all of the pots and switches through their entire range with a signal source connected and a speaker connected to the dead channel to see if the channel ever produced any sort of sound (even if it was just static/noise) or allowed a square wave to reach the 20957 pin 3?