Autotek sm3500.1 issue!

[Basshead1989]

Yes with the 10k resistor it still lights up constant on pin4&pin8

 

[Perry Babin]

Again, I was hoping that you'd see the LED flash which would mean that the comparator was triggering the protection circuit.

Try installing the LED in place of Q4. The negative of the LED would go to the Q4 base pad. The resistor would go to the Q4 emitter pad.

Does that flash the LED when you'd expect the amp to go into protect?

 

[Basshead1989]

Nope no flashing of the led that way either but amp seems to work fine with q4 out hmmm.

 

[Basshead1989]

Even purposely clipping the amp a bit to try and trigger the protection but it just stays playing and before I took out q4 even at such a low volume wear you couldn't hear it. It would shut down like clock work around the same time in the song on high or low volume.

 

[Basshead1989]

I also noticed when turning the current up on my supply that there a little audible pop on start up. Not real loud but noticeable if that helps at all.

 

[Perry Babin]

Well... Q4 and the over-current protection circuit has to be working. Are you sure that you have good transistors in Q2 and Q4?

Is it possible that something (besides the removal of Q4) changed since the last time it was shutting down?

 

[Basshead1989]

I'll try putting new fets in q2 and q4 maybe they were defective I've had new fets be bad in the past.

 

[Perry Babin]

For clarity, Q2 and 4 are bipolar transistors, not FETs.

 

[Basshead1989]

Yes I know it's a bad habit of mine wanting to call transistors fets sorry perry.

 

[Basshead1989]

Perry so I think it might have been a bad connection or stray solder fragments because after reflowing the output card. I found tiny little solder fragments in between resistors etc on the board and also when taking the card off the main board there was more Excessive solder under the header on the card. So I cleaned all of it up before the test you asked me to do so maybe that's what it was because its been totally fine since no shutting down and the popping quit. Even after putting new transistors in q2&q4 the old ones tested fine but I changed them anyways And after putting q4 in the pop noise went away.

 

[Perry Babin]

Did you use chipquik?

 

[Basshead1989]

No just hot air on the ic and desolding vacuum on the header. But all the fragments were all over the output board before I touched it and the header idk.