Tek TDS 520D Acquisition Board Problem

[tnsguy]

Hello,

I was recently given a Tektronix TDS 520D DPO scope. The two main channels do not work but the two aux channels do. Each input has a multi-chip module that interfaces to the acq main board. On the main board is what looks like a multiplexer to take the 4 inputs and send the signals off to two A/D's.

Does anyone know where I can find information on the multiplexer and MCM's or have suggestions on how to proceed with the repair?

Thanks

 

[shrtrnd]

I don't have a manual on this scope, but I've got a lot of time-in on Tektronix scopes.
You probably have a circuit problem, but before I do anything, I go through those cheap pushbutton switches on the front panel. MANY times, when they fail, they hold-out the circuit you're trying to activate.
May not help you, but consider looking at them.