This amp has two IRF5305 and two IRFZ44N on the outputs. I found that one of the IRF5305's is shorted. I then removed all of the outputs to confirm they are ok, which they seem to be. When powering this amp with out any outputs installed, the power LED pulses and it makes a "squeaking" sound.
This is the first Class D amp I have attempted to work on. Does this amp require good outputs to be installed in order to power up correctly OR is there some other problem upstream from the outputs?
The attached picture was taken just after I removed the one bad output.
This is the first Class D amp I have attempted to work on. Does this amp require good outputs to be installed in order to power up correctly OR is there some other problem upstream from the outputs?
The attached picture was taken just after I removed the one bad output.
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If the half with the missing output is causing DC to appear on the speaker terminals, it could be going into protect.
With all of the outputs removed, I am not measuring any DC on the output terminal. Should I re-install the three good components and re-check for this?
Both pins 9 & 10 look identical on the scope, but I wouldn't call it a square wave. It looks more like a dirty sine wave that apears in rhythm with the audible pulsing of the LED.
Set the scope to 5v/div and 2ms/div. Do you see groups of pulses that deflect the trace to about 2 vertical divisions?
I can not seem to capture a good photo since the deflection is lighter and it is difficult to time it (it isn't always in the center of the scope). The same deflection is also present when the probe is placed right on the B+.
Remove the two rectifiers to see if it will power up without going into protect. Confirm that you have a square wave output on pins 9 and 10.
Powers up without going into protect when rectifiers are removed, but there is no square wave output on either pin 9 or 10.
I do not have significant voltage on Pin #12 either.
I do not have significant voltage on Pin #12 either.
LEG 1 = 12.09V = B+
LEG 2 = ~.900V but drops rapidly to ~.600V then slows down but keeps falling then slows down more at ~.450V I didn't wait and see if it quit.
LEG 3 + 11.52V
LEG 2 = ~.900V but drops rapidly to ~.600V then slows down but keeps falling then slows down more at ~.450V I didn't wait and see if it quit.
LEG 3 + 11.52V
It appears that the transistor may be defective but the voltage from base to emitter is right at the threshold so it's possible that it's not quite being driven into saturation. Is the collector voltage of Q663 at or very near ground (0v)?
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