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).

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

"Tim Wescott" wrote in message
...

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.

Good suggestions. I would add that you should find out if it happens on all
bands (you didn't say). If so, then the VFO or premixing circuits may be the
problem. If you know the VFO frequency you can listen for it on another
receiver, with an antenna wire close to the VFO box. You can make a simple
RF probe for your voltmeter. Here is a link:
http://www.io.com/~n5fc/rfprobe1.htm You don't have to worry about the exact
voltage now. Just find out where the voltage drops when the radio quits
working. Start at the output of the VFO and follow the signal through. In
addition to a part that fails when it gets hot, you may also find a bad
solder connection on a circuit board, that also fails when it gets hot. Or
the pin on a connector may be corroded (or loose, and bending enough under
heat to break the connection). If you follow the signal from the beginning,
you will eventually find the place where it stops. Then you know where to
look. (Hint: Look for signs of overheating, like a dark place on the bottom
of a circuit board.) Bad solder connections are sometimes very hard to see.
If you suspect one, you can reheat it and see if that fixes the problem.

73,

"PM"

The FT101ZD is "THE" most popular rig for an 11 meter conversion that I
know of. Yup, she's a hybrid. Along with all the superb advice given, I'd
like to add watch the interboard connections. Sometimes a little
re-dressing can cure a lot of problems.

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

Thanks for those firsts advices.
At the first time, we have found some bad solders, but probably
not all the ones.
We have remplaced the electrochimic capacitors in the main power
supply, they were very "tired".
When the problem arrives, the reception is cut on all bands but
sometimes, the frequency counter continue to display good numbers
only on some bands.
We're going to continue to climb this mountain, meter by meter.
Thanks.

Guillaume.

Hi,
fixed similar case some years ago, the reason was that one contact inside
VFO assembly had never seen solder. It was wrapped but not soldered, all
other contacts were OK.

After the fix everything worked fine. I do not have the serial number, it
was a friend's rig that has since been sold.

73!
Ari

"Willy" kirjoitti viestissä
...
Thanks for those firsts advices.
At the first time, we have found some bad solders, but probably
not all the ones.
We have remplaced the electrochimic capacitors in the main power
supply, they were very "tired".
When the problem arrives, the reception is cut on all bands but
sometimes, the frequency counter continue to display good numbers
only on some bands.
We're going to continue to climb this mountain, meter by meter.
Thanks.

Guillaume.