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Problem: Cobra 200 GTL with no output power

Pilsener

Member
Mar 28, 2008
21
2
11
My Cobra 200 GTL got the well-known failure of the RD16HHF1 driver transistor.
This has been replaced, but I still get no output.

I have a good and strong signal all the way to one side of C 641 (left side of it as seen on the diagram).
On the "right side" of C 641, the signal gets weaker and weaker for each component.
No input signal is measured into the final stage transistors, and there is no output power and no
reading on the meter.

The 2SC2290's has the required voltage of 13 VDC on their collectors.
They,however, measure open circuit between collector and emitter only one way when measured with a multimeter i diode-test position.
Is this normal ?
No short circuit is measured on either of them.

No excessive current draw in RX mode. Only 0,35 A. And no heating of any components.

Tips are very welcome.
 

I didn't pull up the schem to see where that cap was in the circuit. Do you have output from the replaced FET? Its possible that a trace came loose while replacing the RD16. I've taken to installing them with a bend up in the leads, then back down to a single point on the board to avoid having to slide something under them to lift them up later if the RD needs to be replaced again.
 

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