Rick OM:
>When I hook the antenna coax thru the amp, the receive
>signal drops completely off.
In order, my guesses are: 1) Dirty (open) relay contacts,
2)something shorted to ground in the RX path, 3) broken wire in the RX
signal path.
Assuming the relay is de-energized (in RX mode), you likely have
dirty relay contacts. They do tarnish in a high-humidity area, etc, but here
in the desert we more have problems with dust; either can cause
hi-resistance/sig loss. I use the red "Cramolin" liquid on relays and
bandswitch contacts with great results. Using the standard safety
techniques, try ohming out the contacts to see. Maybe ohm-out the RF IN to
the RF OUT and wiggle the relay, see if it is stuck/dirty etc. Maybe check
also to see the RF path isnt grounded (Murphy's Gremlins LOVE things in
storage!)
I just rebuilt another ham's SB-1000, and include this additional
info in case it helps:
Mine had no "back-EMF" diode across the T/R keying; installed a
1N4001 on the jack. The 160m wafer on the bandswitch was melted; ordered
the whole switch from Ameritron ($55) as they said they didnt sell just
wafers. Theirs came with a bronze-looking washer for using on 1 of the wafer
contacts; this apparently is a corona or arc-suppressing device that is
missing on the Heath switch.(If you're interested in an anecdote about
Ameritron's little game with the wafer/switch, let me know). And the HV
winding had a breakdown to the 12v winding. Ordered the transformer from
Ameritron also ($115). Peter W. Dahl also makes a dandy replacement, bigger
& more $. The Ameritron tech said nearly all of the replacement transformers
sold go to Heathkit owners, apparently Heath used a cheaper supplier.
Cleaned it up, tightened some loose nuts & connections in the RF
path in the tank ckt
The SB-1000 now works FB; it needs to have the tank taps or turns
spacing adjusted a bit to improve tuning. No arcing, no loss on RX and I
can get out of it what they claim. Personally I find this pushing the Eimac
ratings a bit, so I drive and tune it for a comfortable 500W out on 120VAC
supply.
73 de Jim, KF7E
Jim Henderson
jhenders@tdrss.wsc.nasa.gov
jhenders@zianet.com
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Sponsored by: Akorn Access, Inc. & N4VJ / K4AAA
|