JVC M90 Power Indicator

[Will]

Hello everyone. I just noticed that my M90 Power Indicator light is not working, when turned on. Is this an easy fix?

 

[Transistorized]

Hi Will

Could be a loose wire going from the indicator to the amp board. The power LED along with the Stereo LED are on the same board. Power LED plug into the Amp Board and Stereo LED into the Tuner.

Its not very common for these LEDs to fail but you can check the LED with an Ohm Meter to make sure its not open. Remember it is a Diode so it will only read with the correct polarity (RED +) (BLACK - ) on your multimeter.

Other than the Amp board not sending power to the LED its fairly straight forward. You can test that while powered on with a Volt Meter also.

Picture Below:

 

[Will]

Thanks. I found a pinched wire.

 

[Will]

Pinched wire:



The repair:

 

[Will]

What! It's still now working. Hmmm. I examined the circuit board and noticed 4 resistors that appear to be bad. One was near the power indicator wire connection on the circuit board. The others were near too. I believe they are bad because they look burnt or melted and the colored stripe are not visible. I could be wrong though.

 

[Transistorized]

I do not have a schematic but my next step would be to place my meter on DC volts and measure the voltage at the Amp board connector to see if it is outputting any voltage.

 

[baddboybill]

Norm from Analog alley has the M90 service manual to check out.
https://www.analogalley.com/osccart/product_info.php?products_id=570&osCsid=5b617ae4a145bd24f77ff8d03d712125

 

[Will]

I do not have a schematic but my next step would be to place my meter on DC volts and measure the voltage at the Amp board connector to see if it is outputting any voltage.

Okay I will give that a try.

 

[trippy1313]

One of the Kings of all boomboxes, definitely worth getting the menu for.

Nice job getting in there and hunting around. I'm getting the impression you've done at least a little electrical work in your years as a DJ?

 

[Will]

I do not have a schematic but my next step would be to place my meter on DC volts and measure the voltage at the Amp board connector to see if it is outputting any voltage.

I did the test with the multimeter and found that the board connector was loose. The connector shakes like a lose tooth. I tested the wires to and the light came on.

 

[trippy1313]

Success!!! That thing 100% then? Or does it probably need belts then done?

 

[Transistorized]

I did the test with the multimeter and found that the board connector was lose. The connector shakes like a lose tooth. I tested the wires to and the light came on.

I'm not surprised. Most of the time they get loose from the wire being pulled to release the connector. It may have cracked solder joints or a damaged solder pad on the underside of the board.

Well now you know what the issue is

 

[caution]

What! It's still not working. Hmmm. I examined the circuit board and noticed 4 resistors that appear to be bad. One was near the power indicator wire connection on the circuit board. The others were near too. I believe they are bad because they look burnt or melted and the colored stripe are not visible. I could be wrong though.

Even though you got it working, I'm still curious about these resistors you saw that looked bad, do you have a picture of them?