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[AMPS] SB-1000 RX info, & more

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Subject: [AMPS] SB-1000 RX info, & more
From: (jim henderson)
Date: Fri, 21 Feb 1997 15:59:28 +0000
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

        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

73 de Jim, KF7E

Jim Henderson

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