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SS64 12th October 2009 03:44 AM

Memphis Belle st-1300d
 
OK picked this amp today for $80 at a swap meet.. the Amp physically is like a 9/10... Ok here is the problem.. It does not turn on.. Power supply checks out ok. No big burns on the board.. The only thing that was wrong is C741 next to the tl494 daughter board exploded.. there is almost nothing left of it... I think that it is a 10uf 50V because the one next to is the same value.
Can anyone tell me where to go from here? Should I just replace the cap and try it?

Perry Babin 12th October 2009 04:56 AM

Post the DC voltage on all 16 pins of the TL494. Place the black meter probe on chassis ground. Place the red meter probe on the point where you need to measure the voltage.

494
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:
Pin 15:
Pin 16:

SS64 12th October 2009 01:24 PM

OK I pulled it out of the sink last night to check the underside of the board for burnt traces.. everything looks good.. I'll get the pin voltages today perry..

SS64 12th October 2009 06:49 PM

Ok here are the voltages
pin1- 0.019
pin2- 0.082
pin3- 5.06
pin4- 0.041
pin5- 1.515
pin6- 3.774
pin7- 0.020
pin8- 12.64
pin9- 4.96
pin10- 4.96
pin11- 12.67
pin12- 12.67
pin13- 5.06
pin14- 5.07
pin15- 5.06
pin16- 0.020

all measurements taken in vdc.

Perry Babin 12th October 2009 07:48 PM

Do you have the voltage on pins 2 and 3 reversed?

Do you have positive and negative voltage on the rectifiers?

Do you have positive and negative 15v on the op-amps?

Do you get audio from any of the channels?

In the future, copy and paste the column of numbers I post. It will save time and if you have negative values, the colons are less confusing than the dashes.

SS64 12th October 2009 11:10 PM

Well It works I think the shorted c741 was keeping it from coming on..Idles at 2.583 amps..
Thank you for your help perry..


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