[Kenwood] 850S

[Ron & Madhavi]

Hello,

I decided to make this posting only so it might help someone on this list
troubleshoot a 850 with similar symptoms to those I had. BTW, most of these
problems are very well documented at N6TR's fine site dedicated to the 850.

I bought the radio from a K0 is Greenbay, who sold it as MINT. He claimed he
used the radio only for spotting during contests.  BTW, this was a 2xxxxxx
serial no unit, WELL KNOWN for DDS failure. Back then I didn't know the
stigma attached to 2xxxxxx serial no. 850s! When the radio arrived I noticed
the following.

1) Monitor function stops after warm up
2) Erratic slope tuning
3) Distorted Audio on transmit after half hour or so
4) Receiver audio seemed muddy

What followed soon after was the transmitter going completely dead. However,
much my surprise, I found that the radio transmitted normal when I had the
DSP100 kicked in (bought a few weeks later). A few weeks later the receiver
also went dead and this time the DSP100 didn't help!

Back in Sri Lanka, with no repair facility, I was left looking at a dead
radio and not knowing how to find the components or for a start, where the
problem was!. The many posts I made here and elsewhere didn't bring much by
way of tech advise. However, a fellow ham very kindly offered to fix it if I
shipped the radio or the boards stateside.

Finally, I consulted N6TR, "ham of the year 2003"  Thanks to Tree, I now
have a fully functional 850s. Tree, replaced all 4 DDS chips in a faulty
board he had and sent it to me. I still have to send my faulty board to him
to figure out if all or how many 6631s were bad. Incidentally, Kenwood
themselves realized this quality problem back in the 90s and started to use
the 66312s in their later production runs. The carrier board (that Tree sent
me) swap cured ALL my problems.

Tree truly desrves the award and has shown immense ham spirit and a
willingness to assist DX stations in "distress" !!!
.
DON'T buy a 2xxxx 850 unless the DDS has been changed. If it has lasted so
far, it will most like fail eventually.Watch out for these symptoms. The
monitor may seem a function you can live without, but it is an EARLY
warning. In my case, the seller was smart! It is quite possible that not all
6631s will fail, but unless you alrealy own a 2xxxxx  srerial no. 850, I see
NO REASON to gamble with buying one! I thought mine was a deal at 650$ with
a pair of optional filters thrown in!

Always reserch your radios before buying them. There are many hams here who
can tell you that certain production runs were known for certain  faults,
how to determine year of manufacture etc (perhaps the name of the JA YL who
assmbled them?!!!!!!).

73,
Ron, 4S7RO