In ,
(Eric Merlen) wrote:

Hello,

I bought an old Colt 480 to use in my car (40 channels, AM/SSB,
Circuit Board PTBM048A0X, pll-02A, 2sc1969 final) but it doesn't work.
Here are the symptoms:

1. When I turn on the radio, it seems to change frequency during a
couple of second before it stabilize.

2. The red led light up on transmit but there is no power on the
built-in meter nor on my external meter. I can not hear myself in a
receiver when keying in a dummy load.

3. When I turn the channel selector, the channel numbers change, BUT
the radio stay always on the same frequency.

4. The clarifier doesn't work.

5. The only thing I tried is to change slightly the position of the
VCO core. I can receive other frequencies by turning the core.

6. The frequency seems to be unstable when receiving.

A visual inspection inside show no sign of abuse, repair, mod or
damage. All wires seems well connected.

Problems 1, 3, 5 and 6 indicate a PLL problem. Problem 4 could be a seperate
issue, but is likely related to the PLL fault. The cause could be any number of
possibilities, but it sounds like the radio was tweaked by someone that didn't
know what they were doing, and turned the VCO control voltage out of capture
range of the PLL.

Problem 2 could be anything.

Do you have an idea of what I do?

Take it to a qualified tech.






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