SB-104A receive alignment

[multi-volti at MULTI-VOLTI.COM]

It's been a long time, but I remember an alignment for another board that
had tuneable filters for various bands, I think 10 M because of the wide and
sectionalized BW. It needed a spectrum analyzer because when misaligned the
board would sometimes 'take off' and create alot of spurious garbage.

I don't remember if it was the same board, but there were band pass filters
on another board that had fixed value L & C pi-networks. Over time the
toroids would drift in value. Because the parts were largely unavailable at
that point, we would do a couple of things out of desperation.

One was to swap the front and rear section inductors in the hopes that this
would shift and misalignment in the opposite direction. I don't recall the
inductors being accessible to spread or compress turns - I think they were
wax potted in a fiber cylinder. Usually the problem was not meeting rated
power at all, or at one end of the ham band. Sometimes swapping positions of
equal nominal value inductors helped. Another was to substitute a small
ceramic trimmer capacitor that spanned the value of one the fixed capacitors
in the filter for the band that had trouble, and tune it for max power,
balancing it at the CW and SSB frequencies. Less frequently, we'd put a
trimmer on the other side of the inductor also. I can't remember, but I
think the output capacitor was where we'd start.

Even 'though numerous parts were no longer available, it helped to have
other things to experiement with. That was in the days when they charged a
flat fee to fix the radio no matter what (sometimes you got a L-O-T of labor
for that $99 flat fee on an SB-104A), regardless of how much people
complained about the fee.

Murray

----- Original Message -----
From: "John Farrington" <jfarr at LIVINGSTON.NET>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Wednesday, August 07, 2002 12:45 AM
Subject: Re: SB-104A receive alignment


> H Hugh Flint wrote on the Heath list:
>
> >I need a copy of the SB-104A "G" front-end board  alignment procedure.
> >Un-fortunately all of the manuals and information I have pertain to the
> >older original version SB-104 board.
> >
> >Obviously much of the alignment procedure is the same, however it would
> >be most helpful to have the board and the information jive...
> >
> >Thanks to anyone who can help!
> >
> >Hugh Flint - KF7LN
> >hflint at skyride.net
>
>
> The 104-A's "G" receiver front-end board was a completely different design
> from the one in the original 104, and was shipped from the factory
> preassembled and prealigned; there were no alignment instructions in the
> SB-104A manuals.
>
> No doubt Heath had an in-house service manual, but I've never heard of its
> being released to the public. If anyone has access to a copy, I'd
> appreciate their letting me know if copies can be made.
>
> Even with the service procedures for the G board, I would think that
> getting the bandpass shapes right for all its filters would require more
> and better test equipment than most people have at home.
>
> 73
>
> KE5ZB
>
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