Kenwood TS-830S VFO failure
Henry Gernhardt/Andrea Winship
I went to go tune into the Breakfast Club this morning, and upon turning
on the venerable rig aforementioned, noticed that there was no RX audio
and the digital display was blank. The VFO appeared to simply be dead,
as the VFO LED indicator above the display unit was not illuminated.
This unit had also shown some ``jumping'', described as a bad ground in
the AF unit according to a kenwood ASB I dug up. I also noticed in the
service manual where the display circuitry blanks if the PLL unlocks.
Would a bad ground such as described in Kenwood ASB-0840 also cause the
problem I am experiencing? Any other ideas? My test equipment consists
of a DVM, and I would like to avoid the expense of professional repair.
Thanks,
Henry C. Gernhardt, III
KE4PIB
Doug Smith
><hcg...@earthlink.net> wrote: Folks---
I'm kinda wild-guessing here as it's been MANY years since I've worked on an
830, but... I'm tempted to suspect something less exotic..
The fact that the VFO LED isn't lit suggests to me that the rig thinks
you've selected the external VFO. I'm gathering from context that you don't
*have* an external VFO. That would certainly explain the display blanking and
the receiver not working!
Is there some kind of jumper plug that goes in the external VFO jack if you
don't have the external VFO? (might that plug have become dislodged?) If
not, some Kenwood radios have also fastened switches to the DIN jacks;
plugging something into the jack activates that switch. Maybe that switch
is flaky on the external VFO jack?
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com
Henry Gernhardt/Andrea Winship
> The fact that the VFO LED isn't lit suggests to me that the rig thinks
> you've selected the external VFO. I'm gathering from context that you
> don't *have* an external VFO. That would certainly explain the
> display blanking and the receiver not working!
It would make sense, but there has never been a ``dongle'' on the
external VFO jack. The only switch I can see in the schematic is S21,
and that is not listed in the service manual under the parts list, nor
can I find it on any of the boards in the SM. Digging a little further,
it's almost as if the fixe channel switch is stuck, although I don't see
how the switch could have failed closed.
Michael Neverdosky
The good news is that the problem is likely to be dry grease in the
bearings of the VFO. Many older Kenwood radios show this problem and
regreasing the VFO bearings fixes it.
The bad news is that getting the VFO out of the 830 is a pain as you
have to remove the front panel.
If you are in central FL, I can help you.
michael N6CHV (in Sanford FL)
Henry Gernhardt/Andrea Winship
> The good news is that the problem is likely to be dry grease in the
> bearings of the VFO. Many older Kenwood radios show this problem and
> regreasing the VFO bearings fixes it.
I understand that you've had experience, but that doesn't make sense to
me. It seems that the display and LED would still be functional even if
there were dried grease---that the VFO would have SOME output. How is
it that this would cause the blanking I am experiencing?
> The bad news is that getting the VFO out of the 830 is a pain as you
> have to remove the front panel.
I've seen the exploded view. Ouch.
> If you are in central FL, I can help you.
Thanks, but I'm in central KY. Would you happen to know anyone in
Central KY who could help?
Doug Smith
><hcg...@earthlink.net> wrote: I understand that you've had experience, but
>that doesn't make sense to me. It seems that the display and LED would
>still be functional even if there were dried grease---that the VFO would
>have SOME output. How is it that this would cause the blanking I am
>experiencing?
I think the fact that the LED is out suggests a simpler problem - that the
radio thinks the external VFO is selected. Of course, if there is no
external VFO then it isn't going to work very well<grin>.
Is there some kind of jumper plug that's supposed to go into the external
VFO socket if you don't have the second VFO? Is it possible that jumper is
loose or missing? Also, there may have been a little switch fastened to the
inside of the external VFO socket used to connect & disconnect the internal
VFO; maybe that switch is flaky?
(I would think that dried grease would only stop the VFO at some frequencies
- that as you tuned across the band it would intermittently start and stop
working. But I don't have a whole lot of experience with the 830.)
Henry Gernhardt/Andrea Winship
> I think the fact that the LED is out suggests a simpler problem - that
> the radio thinks the external VFO is selected.
I've checked both the schematic in the manual and the PC board layouts
in the service manual, and the only thing I can come up with is S21,
which is the external VFO control switch, but does not appear on any of
the diagrams in the service manual.
A new development:
This morning, I decided to take some time to look about on the inside of
the unit. I removed the top cover and powered the unit up. The display
came on, VFO light lit, and everything. With the power remaining on, I
then proceeded to replace the cover and reattach all the connections.
It seemed to be working. This afternoon, again, it wasn't working. No
display, no VFO indicator. Power off, I removed the cover and applied
power. It worked.
I don't understand how this could be happening---it seems to me that it
must be some sort of mechanical failure (cold solder, bad ground, etc.)
on one or more of the boards. It could also be a PLL unlock, as the
unit sends a blanking signal, taking out the numeric display, if the PLL
unlocks---but what would taking off the cover do to rectify that?
Whatever it is, it's very intermittant and _VERY_ annoying.
Any ideas as to where I should start sticking probes? :)
Michael Neverdosky
>
> Michael---
>
> > The good news is that the problem is likely to be dry grease in the
> > bearings of the VFO. Many older Kenwood radios show this problem and
> > regreasing the VFO bearings fixes it.
>
> I understand that you've had experience, but that doesn't make sense to
> me. It seems that the display and LED would still be functional even if
> there were dried grease---that the VFO would have SOME output. How is
> it that this would cause the blanking I am experiencing?
Just having *some* output from the VFO is not good enough. The output
must
be in the proper frequency range and of enough amplitude, otherwise the
PLL looses lock and the display goes off.
The confirming point is if you have the VFO jumping freq, first a little
then getting worse and it gets better for a while if you spin the dial
lock to lock a few times. Eventually the only cure is cleaning and
greasing.
There are other *possible* causes but given the age of the radio and
design
this is both the most likely and the easiest to fix cause.
I have seen this in a TS-120, a couple of 130's and a couple of 830's.
On the TS-130 you can pull the VFO without even removing the top cover.
:-)
> > The bad news is that getting the VFO out of the 830 is a pain as you
> > have to remove the front panel.
>
> I've seen the exploded view. Ouch.
>
> > If you are in central FL, I can help you.
>
> Thanks, but I'm in central KY. Would you happen to know anyone in
> Central KY who could help?
Can't help there, sorry.
michael N6CHV
Michael Neverdosky
even a bad solder joint at one of the jacks on one of the pcb's.
If the display is on with the cover off, check to see if the frequency
changes smoothly as you turn the dial. If it is smooth then the grease
is likely *not* the problem.
michael N6CHV
Henry Gernhardt/Andrea Winship
Thanks for all the input. After hearing the probable necessity of
cleaning and junction checking, and recieving a couple of suggestions
from a friend, I called AES. As it turns out, 95% of their squirrely
VFO cases are resolved by a good cleaning.
I thank everyone for their patience and input, and appreciate all you
have done. It looks like, since I don't have the desk space and
organizational skills, I'm going to let the pros clean it out for me.
Thank you again,
Brian Waldron
>
>The bad news is that getting the VFO out of the 830 is a pain as you
>have to remove the front panel.
I had the VFO out of my 830 and did not have to remove the front panel.
I undid the screws for the counter unit and moved it aside a little.
The VFO itself comes out after removing the four screws from the
corners of the VFO that hold it into the front panel.
Cheers,
Brian
Mark
Henry,
This sounds to me like a classic "dry" solder joint. We have sold many of these
units and I have come upon similar issues on two or three occasions. Once fixed
they just run and run! Other Kenwood radios such as the TS930 and TS940 are also
well known for this problem as are Yaesu rigs of similar vintage.
GL with the fix!
VY 73
Mark, G1FYC / M5ACG / G0TYA
J M Noeding
wrote:
>
>This sounds to me like a classic "dry" solder joint. We have sold many of these
>units and I have come upon similar issues on two or three occasions. Once fixed
>they just run and run! Other Kenwood radios such as the TS930 and TS940 are also
>well known for this problem as are Yaesu rigs of similar vintage.
>
>GL with the fix!
>
>VY 73
>
>Mark, G1FYC / M5ACG / G0TYA
>
and 'dry solder joint' often use to be a particular joint where a
particular component often had to be be installed late in the mounting
process...., any idea about such cases?
Remember an early Standard C158 (?) had this particular problem, an RF
choke in audiofilter after clipper wasn't soldered in one end. Usually
almost impossible to trace unless you had been told where to look
73
Jan-Martin
Henry Gernhardt/Andrea Winship
> >This sounds to me like a classic "dry" solder joint.
> and 'dry solder joint' often use to be a particular joint where a
> particular component often had to be be installed late in the mounting
> process...., any idea about such cases?
If you happen to know where to look, that would be wonderful. As it
stands, I turned the unit on yesterday, and it seemed to be working
perfectly. Same today. I will eventually want to send it in to have
the VOX circuit fixed, but for now, I would like to keep it here as it
is my _ONLY_ HF rig.
BTW: Any ideas on the VOX circuit? It simply doesn't work---no QSK, no
sidetone, no VOX, no matter the setting of the VOX gain control (which
is also the VOX switch, assuming VOX is on).
Mark
Henry,
The only advice I can give is to thoroughly check over each circuit that has
failed using a magnifying glass to check for these dry solder joints. They are
notoriously difficult to locate any other way.
GL!!
Mark