QSC MX3000a power supply repair

[Seeber]

Servicing a QSC MX3000a with one side of the two dual power supplies out. My real question is procedure to remove the main board. It's not clear from looking to proceed with or without large heatsink. PS, Service manual not available from QSC factory. Link posted previously here to schematic on QSC site is dead.

 

[JonSnell Electronic]

Here is the service manual; QSC MX3000A SM Service Manual download, schematics, eeprom, repair info for electronics experts

 

[Greg32]

Hi Seeber, how did you go with with the servicing? I need to recap an mx3000a shortly. Greg

 

[Seeber]

Happy to help if needed. I found a shorted bridge, that was it but did recap. The disassembly was easier than first looked and straightforward. Pretty easy to work on overall.

 

[Greg32]

Did you have to unmount all the transistors to disassemble?

 

[Seeber]

You don't have to detach transistors from the big heatsink. Get the service manual and look carefully. There are two heatsinks, one for each channel, held together with straps and screws on the sides. To get into the unit remove the lid including 4 screws on top that hold the top heatsink. On the bottom there are 5 screws holding the heatsink for channel 2.

 

[Greg32]

That's good news, I have now got the service manual, and main caps will be here monday, will start recap and service then. Thanks Greg

 

[Greg32]

Recap went well, I used exactly the same value in uf and ripple current. I did an 8r power test afterwards and got 85vrms on both channels, just a hair over 900w. Greg