MTX Thunder 5601

[S Merlington]

Ok ill replace it and let you know what i come up with

 

[S Merlington]

replaced it heres what i get now

Pin 1:0.02
Pin 2:0.00
Pin 3:0.00
Pin 4:-15.34
Pin 5:0.00
Pin 6:0.00
Pin 7:15.34
Pin 8:15.34

 

[Perry Babin]

You appear to have a solder bridge between 7 and 8.

 

[S Merlington]

Pin 1:0.02
Pin 2:0.00
Pin 3:0.00
Pin 4:-15.34
Pin 5:0.00
Pin 6:0.00
Pin 7:0.00
Pin 8:15.50

 

[Perry Babin]

DC on speaker terminals?

 

[S Merlington]

measured directly across the speaker terminals i get 0.02 volts

 

[S Merlington]

Wondering should i plug the preamp board in and test for audio?? Or should i use jumpers on the pins?

 

[Perry Babin]

Install shunts on the preamp board connector as shown (after confirming that there is no DC on the pins). With the jumpers in place, does the amp produce audio?

 

[S Merlington]

On the top row of the 2 pins closet to the wires for the fan i get -15.79 volts on both pins..

Bottom row of pins 1st pin closet to the rail caps i get -0.89 volts

other pin i get -0.48 volts

 

[Perry Babin]

On the pins with the shunts installed in the photo, do you read any DC?

 

[S Merlington]

Yes I have DC on thoose pins..

The 2 tops pins with the red arrow pointing to them both pins have -15.34 volts on them..

The 2 bottom pins with the yellow arrow pointing to them i have -0.82 volts on both of them..

 

[Perry Babin]

There is a problem with the op-amp near the RCAs.

 

[S Merlington]

TL072C

Pin 1:-15.36
Pin 2:-15.37
Pin 3:0.00
Pin 4:-15.31
Pin 5:0.00
Pin 6:-15.31
Pin 7:-15.52
Pin 8:-15.52

Also R318 got hot a came unsolderd from the board ..

Its a 100 ohm resistor?? Just trying to confirm

If the op-amp appears defective i will replace it ..

Have a few things to do so ill work on this amp later tonight

 

[Randy62]

Yes R318,R319 are 100 ohms.They are current limiters for the 074.They should have +/- 15volts.If you have a TL074 I would go ahead and replace it.Usually when those resistors go it means the op-amp is bad.

 

[S Merlington]

Ok replaced the op-amp and the 2 100 ohm resistors R318 R319

On the top row of pins I get 0.00 volts

On the bottom 2 pins i still get -0.45 volts on both pins (red arrow pointing to them)

 

[Randy62]

Are you getting good audio output from the amp with the jumpers in place?

 

[S Merlington]

With the jumpers in place i get clean audio out of the amp..

 

[Randy62]

Inspect the preamp board for bad resistors etc..If it looks good remove the jumpers and try the amp again.Carefully.
With the preamp board connected.

 

[Perry Babin]

The resistors that typically fail are 10 ohm, marked 10R0 and are connected to the power supply pins of the various op-amps.

If you replace all of the defective resistors and you don't get clean audio, see if any of the op-amps are heating up or if you have more DC voltage across any of the 10 ohm resistors (possibly indicating that one op-amp is drawing more current than it should).

 

[S Merlington]

Perry,

I get clean audio from the amp with the jumpers installed..

I removed the jumpers and plugged the pre amp board in..

The pre amp board is dead i get no lights on the display for the pre amp board and the amp doesnt have output with the board installed..

Any ideas what to check next?