Punch 200ix

[seankane]

Hello everyone.

I recieved a punch 200ix for repair. I opened the amp and it had a previous repair attempt made on the power supply.

I replaced all the power supply fets with IRF3205's and 4 new 47 ohm gate drives.

I also replaced the 1A and 2A driver transistors for the power supply.

Both channels test fine with nothing out of tolerance or shorted.

When power is applied nothing happens, no led light and amp does not power up.

I am not getting any gate voltage to the power supply fets and I am sure thats why it is not powering up.

Can anyone tell me why I am not getting any gate voltage to the power supply fets?

[Perry Babin]

Do you have voltage on pin 12 of the 494 in the power supply?

[bdgf2004]

you should probably check for pulses on pins 9 and 10 on the x94 ic chip

[seankane]

Originally Posted by Perry Babin

Do you have voltage on pin 12 of the 494 in the power supply?

Pin 12 of the TL494C has 13.18 vdc

I installed a new led and there is something I must add. The amp powers up for a second with the light on then the led light slowly fades out and the amp powers off.

I have installed a new remote terminal and there is a good connection to the board that is not an issue.

The old light was so dim I couldnt see it with the light on my bench turned on and by the time I got around to testing for gate voltage the amp was already powered off.

Soooo it does power on for a second then just slowly powers off.

Any ideas???

[seankane]

Just wanted to add pin 12 of the 494 still has 13.18 vdc even after the led light goes off.

This is with power and ground hooked up and the remote hooked up.

[Perry Babin]

Do pins 3 and 4 remain at or near ground?

Do pins 8 and 11 remain near 12v?

[seankane]

Originally Posted by Perry Babin

Do pins 3 and 4 remain at or near ground?

Do pins 8 and 11 remain near 12v?

TL494C power, ground, and remote power applied led out produces these readings.

Pin 1: 0.032 vdc
Pin 2: 7.73 vdc
Pin 3: 0.117 vdc
Pin 4: 8.21 vdc
Pin 5: 2.830 vdc
Pin 6: 6.53 vdc
Pin 7: 0.00 vdc
Pin 8: 13.20 vdc
Pin 9: 0.000 vdc
Pin10: 0.000 vdc/ then sometimes will read -13.95 vdc
Pin11: 13.20 vdc
Pin12: 13.20 vdc
Pin13: 8.25 vdc
Pin14: 8.25 vdc
Pin15: 8.25 vdc
Pin16: 0.000 vdc

The LM339M reads as follows:

Pin 1: 0.064 vdc
Pin 2: 7.74 vdc
Pin 3: 13.20 vdc
Pin 4: 2.939 vdc
Pin 5: 4.31 vdc
Pin 6: 4.37 vdc
Pin 7: 8.25 vdc
Pin 8: 0.473 vdc
Pin 9: 5.75 vdc
Pin10: 8.25 vdc
Pin11: 8.23 vdc
Pin12: 0.000 vdc
Pin13: 0.064 vdc
Pin14: 7.40 vdc

There is no voltage to the op-amps

There is no rail voltage from the rectifiers

There is no voltage in and out of the regulators

[Perry Babin]

If nothing is pulling pin 14 up, the 494 is defective.

[seankane]

What do you mean when you say "pulling pin 14 up" ? Should it be getting more than 8.25 vdc? I am not quite sure I understand what you are saying.

[Perry Babin]

Pin 14 should be 5.0v, not 8v. If nothing external is pulling the voltage up on that pin, the IC's internal voltage regulator has failed.