The only switch contacts I saw was one wafer switch
right in front of the PBT housing. I did not see any obvious issue with
any of the components on the assembly surrounding the switch. I cleaned
that switch and the IF switch is scratch-free and positive now, but the loss of
signal in the narrow position is still an issue.
The PBT appears to be right to me. Well, at least
it is not hugely off. I've not tested it with my full attention but I have
checked and I get equivalent tone at the dot at either end of the arc associated
with the bandwidth that is selected.
- Keith -
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Friday, July 28, 2006 3:01 PM
To: Darwin, Keith; [email protected]
Subject: Re: [drakelist] Progress on my R-4A.
Hopefully, for your sake, the passband tuning unit is not in need of
alignment. I doubt very much that bad caps are to blame for your troubles that
is unless you can see that some or one of them has broken off a piece. However,
there are switch contacts involved in the assembly so there is a possibility
that cleaning those contacts may solve the problem. I would not use DeOxit in a
spray can, I'd use the other type in a bottle with an applicator. If the
passband tuning knob points to the center of the semi circle in the narrow
position, that would pretty much confirm the unit is aligned properly. There is
some attenuation as you decrease bandwidth due to the reduction in coupling
capacitance from each resonating L/C section. Since I'm not home now, I can't
say how much. Also check the other positions for the same response as described
for the narrow position. For me, it's best to check SSB response for the same
pitch or very close to it from lower to upper. If you feel l ucky, try following
the procedure outlined in the manual. Perhaps the best way to describe the whole
process is very touchy. Having done it successfully myself, I can only say it's
not something I'd look forward to again!
-------------- Original message --------------
From: "Darwin, Keith" <[EMAIL PROTECTED]>
I spent some more time with the R-4A last night. I carefully sprayed DeOxit into the AF & RF gain pots, and the wafer switches; esp the IF bandwidth switch. The rig does work better now. Things are better now.Unfortunately, the IF bandwidth issue is still there. A signal that is S9 in the 3 widest positions drops to about S5 or lower in the .4 position, even when I correct the pass band tuning to peak the signal. Any ideas of what the cause may be? I'm assuming bad caps in the LC IF filter but looking at the jumble of parts around the IF bandwidth wafer switch, I'm not thrilled about trying to replace them.- Keith KD1E -
