[Kenwood] TS-820S Guru

[Cecil Acuff]

Greetings list members,

Do we have a resident Guru on the TS-820S.  I have one that was given to me 
in rough shape.  It had taken a lightning strike but surprisingly the damage 
was limited pretty much to the power connector, voltage switch, RF connector 
and one of the finals.  The unit, if I can finish it is destined to be used 
as a Club loaner for new hams that are licensed through our VE program in an 
effort to get more new hams exposed to the joys of HF.

I have fixed pretty much everything except one nagging problem that has me 
scratching my head.  You power up the radio and all is great.  Great 
receiver performance, all controls work as expected, full power out.  But 
after a key down the receiver returns with greatly reduced sensitivity. 
It's not the typical AGC decay....it stays that way until you cycle the 
power on the radio.  Once you do that all is back to normal...until the next 
time you key the radio.  Doesn't matter which mode, doesn't matter if you 
are putting out power or not...as a matter of fact it will do this trick 
with all the tubes out of it...so no driver or finals.  I've been through 
the antenna relay scenario and it's not that.

I've found the power cycle fix can also be duplicated by lifting one of the 
power supply leads momentarily, supplying the RF board that plugs in 
vertically.  Can't recall at the moment which pin it is but I can go into 
those details as needed later.

I have spent hours troubleshooting RF board and thought I had the problem 
cornered on a couple of occasions...even to the point of replacing a couple 
of transistors I thought had problems but no joy.

I'm really not sure what to look at next.

Has anyone seen this problem before?

Can anyone offer suggestions as to what else I should be looking for....I've 
checked voltages all over the board with no real clues.

I'm so close to having this thing wrapped up and in somebody's shack....

Any help would be appreciated!

Cecil Acuff
K5DL