Crossfire amp help please cfa-602

[joesch1999]

when i got the amp I replaced q301, q304, q302 and q306 as well as the tl494cn because everything was shorted

 

[joesch1999]

1. 0.00
2. 4.99
3. .06
4. 4.99 goes down when amp powers up to 2.74
5. 1.46
6. 3.68
7. 0.00
8. 12.40
9. .22
10. 0.00
11. 12.40
12. 12.40
13,14,15 4.99
16. -.01
All positive except pin 16

 

[joesch1999]

seems like a cap is leaking maybe

 

[Perry Babin]

I think you may have the second 8 pins reversed. Re-check them.

 

[joesch1999]

yeah I did sorry it's fixed now

 

[Perry Babin]

8 and 11 should have 12v. Re-check.

 

[joesch1999]

yeah it is 12v I know pin 4 is supposed to be under 1v I have tried in the past to ground it and all that happened was a couple of the pnps burned up

 

[Perry Babin]

Correct. Pin 4 needs to be near ground. In some amps you can ground it but not in all. Re-read #28 on the Power Supply Troubleshooting page.

Confirm that the collectors of the PNP driver transistors for the power supply FETs are directly connected to ground.

 

[joesch1999]

ok heres what i got after rereading and understanding best I could.
pin 10 goes to a 217 ohm R then to a 10uf cap then to a 20 k R then to a 32 k R then to a A1268 Korean i think pnp, gate is 21v base is 13v emitter is 20v.
pin 9 goes to a A1266, korean pnp collector is .44 base is 0v emitter is .36

also measured it in diode check black lead on base collector, is .393 emitter is .096

appears shorted but if I remember right i had it out and that was what the socket came up as.

 

[joesch1999]

that is with black meter lead on neg post red on part

 

[joesch1999]

On the 1268 just before the amp goes into protection it spikes at 21v

 

[Perry Babin]

Are you sure you traced the circuit correctly? Pins 9 and 10 should be connected to identical circuits.

 

[joesch1999]

yes I am pin 9 zeros out on the base of the four a1266's grouped together Q306 q305, q406 and q407 after further investingation pin 10 goes to where i said

 

[Perry Babin]

The power supply won't work that way. Pin 9 should go to two 1266s and pin 10 should go to two 1266s. Two 1266s driven from pins 9 and 10 go to each side of the amp. Are there any jumpers or re-routed traces?

 

[joesch1999]

sorry about all the confusion on my part pin runs the way I explained about and runs threw resistor, then goes to the base of all four of those 12.66's and on one of the sockets at the base it zero's out something is messed up

 

[Perry Babin]

In the attached image, there are purple and green dots. None of the green points should be connected to any of the purple points.

 

[joesch1999]

Once the amp sets a while things go to normal like you have there apply power thats when they all zero out on the base, you turn power off wait five or ten min and it goes back to the way you have it could one of those diodes be reversing or a cap that is shorting in the power supply area

 

[Perry Babin]

You have pin 16 at -0.01v. Does it ever drop lower than that?

I've seen these ICs do strange things when the voltage on one of the input pins was below the voltage on pin 7.

 

[joesch1999]

no pin 16 always 0.01

 

[Perry Babin]

What's the resistance between pin 7 and pin 16?