[Drake] T-4XC Relay Problems

[msmith@licor.com]

Hi Mike,

I send this to the list in case it might explain someone else's wierdness
too. This may not be your trouble, but I helped a local ham find his T-4XB
trouble that had the same symptom.

What he had was a failed filter cap on the bias supply in the AC-4. The
bias supply had so much ripple that it got to D10 via R94. D10 rectified it
and biased V10B on and energised the relay. It is pretty easy to check for
and the filters for the bias supply in the AC-4 are a pair of 20uf, 150V,
easy to find replacements. I used a very small 47uf 160 part that I had on
hand on mine when I could not set my bias and found my filter bad, though
it was not turning on my relay. I think it has to get pretty bad to turn on
V10b.

Besides ripple on the bias supply, you can also see what the maximum
negative voltage you can get is. If the filter(s) is (are) bad it will not
make it to -60 or -65V.

It is worth a try. This particular problem seems to me to be the most
prevalent in the XB, XC transmitters, or at least this is what I hear about
the most. If this was it and you need one of those 47uf 160V caps let me
know and I will toss one in the mail to you.

Hope it helps.

Michael Smith
N0XY




>Hello All!
>T-4XC Relay Problems
>My C-Line transmitter had been working well until
>recently when the relay started kicking in
>intermittantly, and it would usually kick back off on
>its own after a few seconds.

>advice, comments, flames, etc.