Mtx ta92001 distorted output.

[Perry Babin]

The 'regulator' isn't one part. You can measure the DC voltage on the power supply terminals of the op-amps for 2 of the regulators. Measuring from pad 5-8 of the opto-couplers will tell you if the other regulator is working properly.

 

[kfx5050]

Should all the transistors have that insulation between them and the heatsink? Two of the didn't. They was clamp directly to the heatsink

 

[Perry Babin]

Which two?

Has anyone been in it before you since it was working normally?

 

[kfx5050]

I believe so for the simple fact the security stickers over the corner screw was damaged and also one screw was missing. I purchased the amp not working. the person I purchased it from claims at work right before he was trying to sell it

 

[kfx5050]

Rec109 and REC101 are missing the thermal insulation pads.

 

[Perry Babin]

Do you have continuity between any legs and the exposed metal tab on the rear of the rectifier?

 

[kfx5050]

Do you have continuity between any legs and the exposed metal tab on the rear of the rectifier?

No continuities on rectifiers legs or tab.

 

[kfx5050]

The 'regulator' isn't one part. You can measure the DC voltage on the power supply terminals of the op-amps for 2 of the regulators. Measuring from pad 5-8 of the opto-couplers will tell you if the other regulator is working properly.

Are you referring to the opto couplers by the led400? I still have those pins jump together

 

[Perry Babin]

I haven't see that on the larger rectifiers but have on some of the negative TO-220 rectifiers.

Yes.

Leave the pins jumped together until the opto-couplers are reinstalled. It keeps the gates from charging on the outputs which could make them fail.

 

[kfx5050]

Op-amp by the preamp connector.
Pin8 +15.31
7 +145.6 mv
6 140.6 mv
5 142.7 mv

Opt coupler
-2.851
-2.851
-109.6
-109.6
First reading for the opt coupler is the one closest to the heatsink. The least reading is the one closest to the end off the amp

 

[Perry Babin]

For the op-amps, black probe on ground. Red on 4 and 8.

For the optos, black on 5, red on 8.

 

[kfx5050]

Pin 4 -15.32
Pin 8 +15 .32

Optos
-.382
-.382
+15.67
+15.67

 

[Perry Babin]

The regulator for the 0.38v optos is out.

 

[kfx5050]

The regulator for the 0.38v optos is out.

Where is that located?

 

[Perry Babin]

Which optos are the ones that have low voltage?

 

[kfx5050]

The first to are close to the heatsink

 

[Perry Babin]

Is D401 near those optos shorted?

Was the resistor that melted off of the board connected to D401?

Confirm that D401 is connected between terminals 5 and 8.

 

[kfx5050]

Set the meter to continuity to check to see if the resistor that melted off too see if connected to d401, no connection.
Pin 5 does have connection to one side of d401 pin 8 does have connection to the other side of d401

 

[kfx5050]

What's the appropriate setting to test that

 

[Perry Babin]

Post the reading on diode-check with probes one way, then the other.