[CQ-Contest] Wimpy TS820 ... pls help ...

KL7RA kl7ra at blizzard.gcgo.nasa.gov
Tue Sep 10 08:58:51 EDT 2002

Hello Jon

One thing nice about old radios like the TS-820 is they don't have
the mystery LSI chips and usually easy to fix. They also find mults
in a contest just fine, maybe even better.

Verify the HV is correct by the 820 panel meter. If one of the HV 
caps has failed it will indicate 400 VDC vice 800. Verify the screen
supply is okay and the 12BY7A cathode resistors R10/11 are still 
the same value. Verify a good ALC peak. 

If you are into troubleshooting RF circuits the IF unit will have 1v PP
of RF going into the TX mixer and 8 Vpp RF going to the driver. The
output of the driver to the 6146 grids is around 100 v pp. Another
place to verify transmitter operation is RF3 pin 6 on the RF unit. The
ALC voltage should be around 2 volts for 120 watts RF out. 

Good luck, the 820 is a fine radio and worth the trouble to fix. Kenwood 
sold a lot of them in the 70's. The 830 is even better, it forced people
like to me to give up our s-lines.

73 Rich  KL7RA

>This relates to second contest rig ...
>Got a second radio for the shack ... TS820 , RX works just fine, but
>on TX output rises from 0 to 30 - 40 watts max and then drops off fast
>as drive increases more ... output supposed to be 100w ... does this for
>all settings of loading control ... Sincerely request some hints as to
>what's wrong ... bad finals?   One bad final?   12BY7A replaced with
>new and same behavior ... Spare 6146 swapped out both finals and
>still same behavior ... probably something very simple ... Jon kb4zdu
>CQ-Contest mailing list
>CQ-Contest at contesting.com

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