Ok back to basics for a second so i dont blow anything up that I dont want to replace. I just want to confirm; Q1 is an 2SA1038 PNP transistor. Leg 1 is the emitter, Leg 2 is the collector, and Leg 3 is the base? You think it is safe for me to short Legs 1 and 3?
Datasheet
http://pdf1.alldatasheet.com/datasheet-pdf/view/83333/ROHM/2SA1038S.html
It looks like C5 is connected directly to legs 1 & 3 and has posibly been replaced at one point.
Datasheet
http://pdf1.alldatasheet.com/datasheet-pdf/view/83333/ROHM/2SA1038S.html
It looks like C5 is connected directly to legs 1 & 3 and has posibly been replaced at one point.
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The break between the 33k resistors and the main board disconnected the DC offset protection from the protection circuit.
I'm not sure what the exact threshold is (and it probably varies a bit) but the protection circuit would need to see more than 1v to shut down the amp.
I'm not sure what the exact threshold is (and it probably varies a bit) but the protection circuit would need to see more than 1v to shut down the amp.
On the LM358 (And with the PRNW2 off the PCB). Should I be seeing these voltage readings?
LM358; IC3
1: 0.008
2: 5.5
3: 0.008
4: 0
5: 5.5
6: 9.7
7: 0.008
8: 10.98
With the PRNW2 back in the PCB and the amp in protection mode the LM358 measures this:
LM358; IC3
1: 9.4
2: 5.5
3: 11
4: 0
5: 5.5
6: 9.7
7: 0.008
8: 11.08
LM358; IC3
1: 0.008
2: 5.5
3: 0.008
4: 0
5: 5.5
6: 9.7
7: 0.008
8: 10.98
With the PRNW2 back in the PCB and the amp in protection mode the LM358 measures this:
LM358; IC3
1: 9.4
2: 5.5
3: 11
4: 0
5: 5.5
6: 9.7
7: 0.008
8: 11.08
That's normal.
When you checked Q1 for leakage, did you have approximately 3M ohms when forward biasing the junction (B-E and B-C) and OL when you reversed the probes?
Did the meter read OL no matter the probe position when they were on the emitter and collector?
All of this would be with the meter set to ohms.
When you checked Q1 for leakage, did you have approximately 3M ohms when forward biasing the junction (B-E and B-C) and OL when you reversed the probes?
Did the meter read OL no matter the probe position when they were on the emitter and collector?
All of this would be with the meter set to ohms.
The only two readings I get off Q1 iswhen I reference COM of the meter to Leg 3. Testing from Leg 3 to Legs 1 or 2 gives 4M ohms. There is no leakage; IE in reverse and all other orientations the meter shows OL.
B-E (Red on E) gives me 4M ohms.
B-E (Red on B) is OL
B-C (Red on C) gives me 4M ohms.
B-C (Red on B) is OL
E-C in either direction gives OL
From this, Q1 has good mesurment and no leakage.
B-E (Red on E) gives me 4M ohms.
B-E (Red on B) is OL
B-C (Red on C) gives me 4M ohms.
B-C (Red on B) is OL
E-C in either direction gives OL
From this, Q1 has good mesurment and no leakage.
When you removed Q113 and Q213, did it still go into protect?
I just removed Q113 and Q213 just to make sure and the amp still turns on in protection mode. Thats with all other circuits in place.
That disconnects the module from the rest of the over-current circuit so it appears that the module may have problems. Removing Q1/2 disconnected the module from the DC offset circuit and the amp still went into protect. Those are the only two protection circuits driving the module.
It's a simple circuit so I'd suggest that you reproduce it using discrete parts.
It's a simple circuit so I'd suggest that you reproduce it using discrete parts.
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