Kustopm 250-4

[mross001]

Here is a photo of the "new" power switch and the green and red wires.

[52 Bill]

Here is a photo of the "new" power switch and the green and red wires.

This looks like the original photo that you posted.

The red and green wires used to go to the original power and polarity switches. Tape them off or cut them off at the resistor. Unless you find original switches you do not need these wires.

These loose wires have nothing to do with the signal loss.

[mross001]

ok thanks. So I assume that there are many reasons that there is no out put from the two pre-amp boards.

[52 Bill]

Have you tested the power amp output? On the back of the amp is an RCA jack. Sometimes they are marked as power module output or something like that.

Plug a signal into it and see if you hear the sound through the speakers. You can use a guitar or an mp3 player, etc. If you can hear it, then the power amp is working as well as the main power supply. If you don't hear it, then start by checking the power supply voltages.

Do you have a voltmeter and do you know how to use it? Connect the black lead to the metal chassis and use the red lead to measure the dc voltage at the two brass terminals where all of the red and green wires are connected. There should be +12 volts dc at the red terminal and -12 volts dc at the green terminal.

Have you tried cleaning the Molex connectors that connect all of the boards together? This is a common problem in there Kustom amps. With the amp off and unplugged, pull each plug from the board and spray a little DeoxIt on the connectors. Then plug and unplug the connector a few times to burnish the contacts clean. Do that for every one of the connectors and then test to see if the signal is passing through the amp.

[mross001]

Reply

Have you tested the power amp output? On the back of the amp is an RCA jack. Sometimes they are marked as power module output or something like that.

Plug a signal into it and see if you hear the sound through the speakers. You can use a guitar or an mp3 player, etc. If you can hear it, then the power amp is working as well as the main power supply. If you don't hear it, then start by checking the power supply voltages.

Do you have a voltmeter and do you know how to use it? Connect the black lead to the metal chassis and use the red lead to measure the dc voltage at the two brass terminals where all of the red and green wires are connected. There should be +12 volts dc at the red terminal and -12 volts dc at the green terminal.

Have you tried cleaning the Molex connectors that connect all of the boards together? This is a common problem in there Kustom amps. With the amp off and unplugged, pull each plug from the board and spray a little DeoxIt on the connectors. Then plug and unplug the connector a few times to burnish the contacts clean. Do that for every one of the connectors and then test to see if the signal is passing through the amp.

No rca jack on back. To module input 1/4".

[52 Bill]

No rca jack on back. To module input 1/4".

Oh well, then I guess I'm out.

[Jazz P Bass]

Check the header voltages.

http://music-electronics-forum.com/t40070/#post392708

[mross001]

Oh well, then I guess I'm out.

CHecked voltages at those terminals +11.60 -11.60 ran a check of the resitors, diodes etc all see to be within spec for listing on schematic for the power amp.

[Jazz P Bass]

O/k, so you have the IC power voltages.

Now you have to find where the signal fails.

Do you have a setup for injecting a 100mv signal into the input jack?

If so, follow the schematic & look for signal at each output pin (pin 1 & 7) according to the schematic.

Find the point that it stops & you are half way there.