Powerbass XTA500D

Perry Babin · 2012-12-01 9:36 pm

You need to use the secondary ground when measuring voltage on the secondary side of the power supply.

The base of Q5 is driven by pin 1 of U6 through R25 and R32. The voltage on pin 1 of U6 was essentially 12v. It would be difficult to get anything more than 12v to the base (black probe on Q5 emitter and red probe on Q5 base).

Try this... Black probe on secondary ground. Red probe on each terminal of the driver board. Wiggle the driver board. Does the voltage on any of the terminals vary when you wiggle the driver board?

S Merlington · 2012-12-01 10:05 pm

now this amp isnt powering up again its pulsing in and out of protection mode and the fets are heating up..

Q18 is a A1381 I took it out to check it and forgot which way it goes in ..

1 pad is connected to the B+ would leg 1 of that transistor be connected to B + ?

S Merlington · 2012-12-01 10:17 pm

Ok leg one does go to the B+ i dont understand why its going on and out of protection mode now i did nothing to the amp

Perry Babin · 2012-12-01 10:22 pm

Try pushing the driver board (gently) forward or backward and then applying remote voltage. Does pushing it either way allow the amp to power up?

S Merlington · 2012-12-02 6:33 am

i dont get this amp..

The amp still is pulsing in and out of protection mode and all the power supply fets heat up ..

I havent done anything to the amp ..

Trying to wiggle the driverboard does nothing..

S Merlington · 2012-12-02 6:46 am

Ok something on the output driverboard is defective since when i pulled it the amp powerd up perfectly..

With the audio driverboard removed the D1302's still are being driven on ..

With the audio driverboard removed and black probe on leg 1 of D1302 and red probe on Leg 3 i get 0.60 volts..

what leg would i need to track back to see if i can find the problem?

Perry Babin · 2012-12-02 7:33 am

Look back at the two partial schematic diagrams that I posted. You need to find the equivalent circuits in your amp. Q1 would be the likely fault.

S Merlington · 2012-12-02 7:43 am

Ok ill look back at the 2 circuits..

What voltage should i have across the D1302's when i place black probe on Leg 1 and red on Leg 3 ??

I replaced the driverboard with a known working 1 and the driverboard issue is solved now just the voltage issue on the d1302'S

Perry Babin · 2012-12-02 7:54 am

Something well under 0.6v. 0.0 would be ideal.

Perry Babin · 2012-12-02 7:57 am

This is OT but... I can't remember the thread. Was it you looking for a replacement for a diode marked B2 (or something similar)? If so, post a link to the thread.

S Merlington · 2012-12-02 8:07 am

That was another amp..

Well i found that problem now i get 0.01 volts on the D1302's

Next thing is now i get -115 volts on the output terminals..

Perry Babin · 2012-12-02 8:10 am

Did you repair the other amp?

If you have DC offset without the driver board, you either have leaky outputs or a bad connection on the resistors connected to the outputs (or possibly a solder bridge).

What was the problem?

S Merlington · 2012-12-02 8:21 am

Someone had the wrong Diode in D 1's location

Powerbass XTA500D

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