Punch 601s

[Hexhclass]

Amp has rail and regulated voltages but no output.I see audio on all the op-amps.

PC-4333-B

Any suggestions?

 

[Perry Babin]

DCV on all terminals of the LM339?


Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:

 

[Hexhclass]

I see 19v on pin 8 11 and 12 of the 494

Pin 1: 0.031
Pin 2: 4.67
Pin 3: 19.78
Pin 4: 0.273
Pin 5: 2.094
Pin 6: 4.94
Pin 7: 3.676
Pin 8: 4.014
Pin 9: 4.94
Pin 10: 4.94
Pin 11: 7.56
Pin 12: 0.001
Pin 13: 4.67
Pin 14:4.67

 

[Perry Babin]

Recheck. Either something changed while checking or the diagram (which is for an 801S but is the 4333) is wrong. 2 numbers don't seem right.

 

[Hexhclass]

Only voltage that change was pin 7, now has 4.17v

 

[Perry Babin]

It still seems a bit strange but let's check something else. Do you have audio reaching C201 and C304?

 

[Hexhclass]

I see audio on both caps

 

[Perry Babin]

DCV measured directly across the 5.11k resistors R206 and R306.

 

[Hexhclass]

0.000v across both

 

[Perry Babin]

If you bridge Q11 collector to emitter do you get clean audio? Don't connect a speaker until you have confirmed that there is no DC on the output.

 

[Hexhclass]

I get clean audio but it is drawing 3.4a with in line limiter.There is no dc offset.

 

[Perry Babin]

Try adjusting the bias controls to see if the current will decrease.

 

[Hexhclass]

With both port closed it draws 1.5 amps

 

[Perry Babin]

Remove the jumper. Will it power up?

Were you starving it for current previously?

 

[Hexhclass]

It was always powering up just no audio.

With the jumper removed no audio.

 

[Perry Babin]

Measure the DCV on D10 and Q11. For each one, black probe on the emitter of the transistor being measured then the DCV on the base and emitter.

 

[Hexhclass]

Q11
B: -0.005
C: -18.99

Q10

B: -0.027
C: 20.13

 

[Perry Babin]

Do you still have 5v on pin 14 of the LM339?

Lift those two transistors and check them. Q10 looks like it's shorted or leaky.