ZD9 is an 18v zener diode,R73 is a 10 ohm resistor (1206). R73 carries the battery terminal voltage and ZD9 insures that IC13(opamp for auto ton) and IC19(auto and high level on) do not exceed 18 volts. Changing these parts should take care of this problem.
R273,274 are 16 ohm zobel resistors, and most likely burned up due to oscillation in that channel.
Check R176-27 ohm and remove R174,274,R173,273 & R176 and power amp and w/o signal check with an oscilloscope. You will see low level oscillation or ac voltmeter on speaker term/s and the drive to the output inductors will show a square wave with obvious jitter, as if there is a small amount of signal.
C229,230-22nf and C231-3.9nf may be the culprit. Because you are seeing this on one channel only is a good sign that this is the case.
R273,274 are 16 ohm zobel resistors, and most likely burned up due to oscillation in that channel.
Check R176-27 ohm and remove R174,274,R173,273 & R176 and power amp and w/o signal check with an oscilloscope. You will see low level oscillation or ac voltmeter on speaker term/s and the drive to the output inductors will show a square wave with obvious jitter, as if there is a small amount of signal.
C229,230-22nf and C231-3.9nf may be the culprit. Because you are seeing this on one channel only is a good sign that this is the case.
ZD2 is an 18 volt zener, which should normally only see approximately 13 volts depending on the battery terminal voltage. This is the operating voltage for IC20-UC3843. It sounds as if this voltage is not getting to Pin 7 of IC20, which would be the reason why you are not seeing any signal on Pin 4 or Pin 6.
Check to see if R5-10 ohm is open and if Pin 7 is shorted to ground. If this is the case C23-10uf/25v may be shorted. This is a fairly common problem.
If this doesn't pan out, post the voltages around IC20,IC17,ZD1,Q1,Q2,Q10 (near the output driver chips)
Check to see if R5-10 ohm is open and if Pin 7 is shorted to ground. If this is the case C23-10uf/25v may be shorted. This is a fairly common problem.
If this doesn't pan out, post the voltages around IC20,IC17,ZD1,Q1,Q2,Q10 (near the output driver chips)
Have you replaced R274,273 and if so, do they burn up after amp powers up? Note post #2
Check Q14-BC807 for shorted collector to emitter. This may be the reason why amp powers up w/o the remote turn on signal.
Okay, if your looking at the PS gates you will see a very short duration pulse which may be tough to capture w/o a 100mhz or faster delayed sweep scope.If you have a good scope, you might be interested in the waveform at the top of the flyback coil. From your previous post the PS is working as it should.
Before you install the resistors, look at the squarewaves on the output coils w/o signal. In particular note the squarewave in the same channel as R273 & R274. You may notice the waveform will have some jitter as if a small signal is applied. If so follow instructions in post 2
Before you install the resistors, look at the squarewaves on the output coils w/o signal. In particular note the squarewave in the same channel as R273 & R274. You may notice the waveform will have some jitter as if a small signal is applied. If so follow instructions in post 2
When testing this amp on the bench, and in the audio turn on mode, it will turn on w/o signal. When properly installed in a vehicle this should not be the case. Without getting too deep into it, the vehicle install will provide proper grounding and eliminate any ground loops that will introduce noise that falsely triggers the audio turn on circuit.If the remote DC turn on work, you should be ok.
I may be mistaken about the resistors footprint, maybe 2010? I will check tomorrow to be sure.
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