Mackie MA1400 thermal stay on

[mwenga]

Temperature light stay on even though the Heat sink is cold as ice.
I have a M1400 amplifier for some reason the temperature light stay on. I checked all my pre amp transistor and the output transistor all seem to measure fine. Also the temperature IC U1 (LM35DZ) it's okay. I have changed the LM339 IC as well . Still no changes. Any suggestions.

 

[JonSnell Electronic]

You don't say whether it is working or not.
If not working look for the DC offset.
If working, check the supply lines to the sense section.

 

[mwenga]

the unit stay on but no sound, I have check all my voltages. I have the +-16V and also my +-80V output transistor is stable.
what do mean "If working, check the supply lines to the sense section." because sense section I have changed the LM339 and also check for any open circuit resistors.

 

[mwenga]

I have the problem to be an open resistor. R205 100 ohm in the small board. I replaced that the temp light went off. unit work fine

 

[mwenga]

the problem which I found was R205 resistor was open, 100ohm, its on the small board. I change that and the unit work fine. thanks