"MD" ha scritto:


"Geoffrey S. Mendelson" wrote in message
...
In article , Bob M. wrote:

The rest of your symptoms are very strange. I can offer no help at all.
Obviously something is wrong, but I can't even begin to tell you what to
look for.

They are very common. Kenwood potted the main PLL in a rubber compound
to isolate from thermal changes and mechanical shock. In plain English to
slow down the effect of temperature changes and prevent frequency jumping
if you tapped the radio, or when mobile went over a bump.

The TS450's do NOT use the compund that caused so many problems in the
TS440's. I have owned both.

The fix is simple in theory and is documented on the Kenwood web site.
You remove the shield from the main PLL, remove the rubber compound,
replace any parts damaged due to corrosion and readjust the PLL.

AS I said there is no compound in the 450.


If you are experiencing a row of dots on your display, this is a sign your
VCO is out of lock. If you can borrow a service manual, it is very easy to
realign.



That's right!
In fact I read again carefully the istruction manual, while
looking for the service one. I was so used to the disabled beep,
frankly annoying, that I didn't hear the error message!

First of all, I replaced the lithium battery, but this in fact
has nothing to do with the symptoms. Anyway, I put a battery
holder in place of the soldered contacts, thus in the future it
will be a 5 minutes work to change the battery. Apparently, I
didn't damage any cmos circuit...

Then, when I powered the rig, all parameters were of course
reset, so the beep was enabled and I noticed that when the
display became a row of dots, the speaker played "UL" in Morse
code. This is the error message for "PLL unlocked".

I unmounted then the CAR board and opened the case of the PLL
board, which is right under the CAR (and both under the speaker).
I detached and attached again all connectors, to be sure it was
not a bad contact.

Then I measured the 5V and 8V pratically everywhere and the
voltages where there. Unfortunately I don't have a frequency
meter with me now and the only I have was bought at an hamfest -
never sure it worked well...
So I used an handheld, for higher frequencies, and another HF rig
I have, for the lower ones. Using these radios as probes, I found
that the VCO is probably working well: I tuned to 995 kHz and,
since the first IF is at 73.050 MHz, the VCO should be at exactly
74 MHZ. And there I found it!
Moving the tuning to 1995 kHz of course moved the VCO to 75 MHz
etc.

The PLL unit should also provide a fixed 64.220 MHz signal for
the second IF, and this one was missing! No signal, or probably
on a different frequency. This is the first real problem I have
noticed.

Then I checked on the CAR unit the 8.375 MHz for the third IF and
the 455 kHz for the sideband detector. Both were present, even if
peraphs somewhat lower in frequency (I estimated 453 kHz). This
could be the cause for the distorted reception in SSB.
Also the fixed 20 MHz signal was there.

So, what I need now is to know how to realign the PLL unit, to
obtain again the 64.220 MHz signal that is missing (but for this
I will also check again cables...).

Thanks for now to everybody.

I have also read the advice about sending the rig to a Kenwood
service center. Well, this is the first thing I tried, but
apparently it looks very complicated in my country to be serviced
by Kenwood at the moment...

James