MA Audio 4000

Status
Not open for further replies.
I've got this amp which some repair dude didnt know how to fix very well. It appears all the power supply fets were replaced. Nothings shorted, but the amp wont power on correctly. It sorta appears that the drivers were replaced, but then again I'm not 100%.

Pin 5, 9 and 10 of the TL494 look abnormal when the amp is powered through a resistor.

Through the resistor, the amp only gets 6.14v across power terminals. If I supply 13v to rem, the amp tries to power up;

TL494
Pin 1: 0
Pin 2: 3.609
Pin 3: 0.063
Pin 4: 0.055
Pin 5: 1.270
Pin 6: 3.354
Pin 7: 0
Pin 8: 5.93
Pin 9: 2.065
Pin 10: 2.183
Pin 11: 5.92
Pin 12: 5.96
Pin 13: 4.87
Pin 14: 4.86
Pin 15: 4.84
Pin 16: 0.302

I *think* this amp may need new drivers in the ps but not 100% sure
 
This amp:

20120211_104703.jpg



I removed the PS drivers and the amp can accept full 13v power. Upon inspection of the TL494:

Pin 1: 0.015
Pin 2: 3.700
Pin 3: 0.078
Pin 4: 0.070
Pin 5: 1.397
Pin 6: 3.507
Pin 7: 0.014
Pin 8: 12.70
Pin 9: 3.210
Pin 10: 3.197
Pin 11: 12.70
Pin 12: 12.75
Pin 13: 5.02
Pin 14: 5.02
Pin 15: 4.84
Pin 16: 0.014

20120211_104656.jpg


Pins 5, 9, and 10 appear on the scope way way faster than they should, as I can only measure the signals a 1uS which seems odd.

Pin 5 at 2v/div and 1uS:
20120211_104447.jpg


Pin 9 & 10 at 5v/div and 1uS:
20120211_104547.jpg
 
I think this amp may be OK. It has a tough time powering on my 7A power supply, but on my 12A it comes up without issue. It will not power up with my current limiter.

Regulated voltage is +-12v, rail voltage is +-67v

Think it may be fair game to put this amp back in the sync for some load tests?
 
Status
Not open for further replies.