Autotek MM 4000.1

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If you're getting rail voltage, pin 1 on the 7500 has to be dropping below 2.5v. It's not important now but you may want to look at it again in case you need to see this type of pulse in the future.

Do you get positive and negative rail voltage (re-check both sides)?

Did you confirm that you had positive and negative rail voltage when the driver boards were out of the amp?
 
When i first try to power the amp up i get both positive and negative rail voltages but after 5 secs the rail voltages all switch to positive on both sides..

Without the driverboards out of the amp i get both + - 115 volts of rail on the outputs..

With the driverboards out i measured the voltages on the pads for the driverboards..

On all 21 pins for 1 board voltages look good..

On the pads for the other driverboard PINS 6 and 16 have pulsing voltages and thoose pins connect to where the tace has been cut..
 
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Ok i found 3 problems in this amp finally..

i wanna deal with one problem at a time..

1st problem is what ever is making the amp shut down is on both audio driverboards..

2nd problem is on pad 6 and 16 for 1 of the driverboards i get pulsing voltages..

3: not sure if this is a problem or not but the + - 15 volt regulators are only putting out 11 volts..

Pads 6 and 16 for the driverboards go thru some 47mh chokes then go to a d1303 muting transistor the muting transistor tests fine but the middle leg is pulsing the same voltages..


What should i check to see why i have pulsing voltages there?
 
Check the two halves of all 4 driver ICs as shown in the attached image. Do you read anything below 1000 ohms in any of the probe/pin combinations?
 

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