memphis 1000d

[Perry Babin]

Have you tried installing the outputs?

There may be no problem.

 

[timwebb]

i tried it.one group of 640's get hot and it has dc current on the speaker terminals. i pulled the driver cards out it does the same thing.

 

[Perry Babin]

Are they new transistors?

 

[timwebb]

yeah i just got them in.

 

[Perry Babin]

How much DC voltage is there on the tabs of the output transistors (no driver board in the circuit)?

 

[timwebb]

on the card behind the opamps the two pins labeled output and sync has that same signal as before.

 

[timwebb]

12.3 volts

 

[Perry Babin]

With the black probe on the amp ground, what is the DC voltage on the secondary center tap of the power transformer?

 

[timwebb]

12.5v

 

[Perry Babin]

Measure the resistance between the B+ terminal and the secondary center tap with no power applied. What's the resistance?

 

[timwebb]

0.5 ohms

 

[Perry Babin]

The transformer appears to be shorted. Do you see any windings that appear to be darkened?

If not, try twisting the transformer while measuring the resistance. Does the resistance ever go significantly higher?

 

[timwebb]

yes it does the resistance goes very high.

 

[Perry Babin]

You'll need to find the short. Do you have a current limiting resistor?

 

[timwebb]

yes.

 

[Perry Babin]

Insert the resistor between the B+ line and the amp's B+ terminal. Connect the ground from the power supply to the secondary center tap. Make no other connections to the amp. Apply power and twist the transformer. You should hear it arc and you should see a spark where the short is. You'll need to insulate it at that point.

 

[timwebb]

doing it now.