Willy wrote:

73 to all.
I'm just on this forum for a few weeks and i have already a
question.
A friend of mine own an antique FT101ZD (latest model with WARC
bands) and his transceiver has a problem.
After a few minutes, the reception stops and the frequency
counter displays erratic numbers.
Sometimes, all becomes normal by leaving it OFF a few minutes (or
hours).
We think that probably comes from circuits common for TX and RX
like VFO or PREMIX, but we are a little lost.

If someone has some informations about this kind of problem, or a
logic method to find the solution, it would be very interesting
for us.

Hope you can understand my english.
73 and thanks in advance.


Guillaume

(Please, remove _nospam in my e-mail adress for direct answer).




First, don't apologize for your English -- as written it's better than
many native English speakers manage.

Second, I haven't worked on the FT101, but one basic procedure is to
identify a signal that should be there (like the signal out of the VFO)
and see if it's there and of the expected strength. If you have an
oscilloscope that's dandy, but an RF probe will be enough to make sure
that you have signal.

Having a problem that goes away like that is a plus, because you can put
your probe on a suspect signal and look for it changing as the radio fails.

It sounds like you've got some component failing due to heat. I _think_
the FT101 is a hybrid, with semiconductors and tubes -- is that right?
If so, the problem is either a transistor or diode that's on the edge of
failing but works at room temperature, or you've got some other circuit
fault thats getting something really hot. Once you find your problem
signal you can start looking for hot components (I use my much-burned
fingers), or you can get some freeze spray and look for components that
want to be cool.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com