COM-120B deviation meter fail

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mogman
Posts: 127
Joined: Tue Aug 05, 2008 2:25 pm

COM-120B deviation meter fail

Post by mogman »

I am getting a deviation meter fail during self test, it appears to be reading deviation fairly accurately even with the failure.
I am assuming this is a recap situation and wondered which board I should start with.
Thanks!
jry
Posts: 481
Joined: Fri Feb 06, 2004 3:14 pm

Re: COM-120B deviation meter fail

Post by jry »

There are a number of boards in the COM-120 that need to be recapped.

The deviation test loops the 1khz audio through the GEN back to the RX so anything in that loop can cause the failure ...not really a pure Deviation Meter test ...more of a system modulation test.

I would start at the front panel and check the caps there as well as inspecting the display power supply.

Work your way back and inspect each board.

As mentioned before you cannot just replace the caps but you may have to remove the surrounding components and clean off the PCB and parts.

The leakage can affect the resistance values and OP AMP operations.

not a trivial repair by any means and often requires a significant amount of time and expertise to correctly repair and recalibrate.
mogman
Posts: 127
Joined: Tue Aug 05, 2008 2:25 pm

Re: COM-120B deviation meter fail

Post by mogman »

Thanks, I don't suppose there is a list (value etc.) of suspect caps so one can have them in hand.
jry
Posts: 481
Joined: Fri Feb 06, 2004 3:14 pm

Re: COM-120B deviation meter fail

Post by jry »

easier to inspect the boards and see exactly what you need
usually end up using SMD Aluminum CAPS
100uf 6v 47uF 16V 10uf 16v 1uf 16V ( maybe 50V ) IIRC
Mostly the 47uF and 10uf.
Usually the non polarized are OK so it's typically the 47uF and 10uF polarized
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