Fred McKenzie wrote:
In article ,
"clive & kristi ingram" wrote:

hi. i've got a hallicrafters sx-42 that has developed a strange s meter
problem.the receiver works on all bands but the s meter works normaly only
on the first 2 bands,broadcast band and band 2 (1.6 to 5 mc). when I switch
to band 3 (5
to 15 mc) and bands 4, 5 and 6 i hear signals but the s meter indicates
zero. occasionally
there will be a very slight negative indication with the needle moving below
the zero. it
must be getting ok avc on the first 2 bands but not on the others. does
anyone have any
suggestions?

ci-

My understanding is that the S-Meter is measuring a negative voltage
(AGC) that is developed at the AM detector, and is used to limit the
amplification of an earlier stage.

For the meter to read down-scale, there could be either a vacuum tube
that is "soft" or a DC Blocking capacitor that is leaking. You may find
a tube that has positive voltage on its control grid. That could either
be caused by the tube or the capacitor that feeds it.

Fred
K4DII
Yes but the meter reads correctly on two bands so the tubes / capacitors
must still be ok. It's possible that there are capacitors tied to
specific coils that get switched between bands, but my bet would be that
you have a high resistance contact on the band switch. Get some switch
cleaner spray and have a go at that switch. After spraying the contacts
rotate the switch back and forth around the bad positions to get the
cleaner to do it's work. Also check the coils for an open winding, or a
bad solder joint that has gone high resistance between the coil and the
band switch.