[AMRadio] Stock or modify? BC rig "value"


Todd, KA1KAQ ka1kaq at gmail.com
Wed May 31 09:26:16 EDT 2006


On 5/30/06, Phil Galasso <k2pg at worldnet.att.net> wrote:
>
> ----- Original Message -----
> From: "VJB"
> > Several people have asked me, over the past 10-15
> > years, whether it is "better" to preserve an old
> > broadcast transmitter as-is or modify it to make it
> > more useful in a second life on the ham bands.
> >
> > I wholeheartedly say modify it !
>
> Whenever I have acquired a broadcast transmitter, I spent many weekends
> REMOVING some totally atrocious mods that were installed by "engineers" over
> the years. Some of these were done under time pressure in order to get the
> transmitter back on the air in a hurry, but most of them seriously
> compromised safety. If they were done for that purpose, the transmitter
> should have been fixed properly at the earliest opportunity, during an
> overnight maintenance shift.

I thought the 300G was pretty "clean" and free of such things until I
got it home and went through it well. One of the biggest kludges was
the addition of a large Gates motor-controlled rheostat used for
cutting back the output power. This in place of using the front panel
control for changing power, perhaps because the 'improved way' was
easier to remote? End result was the hacking up of the black HV wiring
on the big caps, spliced back together and taped with black tape.
Hmmm......the original insulation is a lot thicker than the tape used
to cover the splice.

A recent post to the amfone board resulted in a couple of sources for
the black HV wire, so now I can replace it all. This is one of those
'fixes' meant to be permanent, no doubt thinking the tape was
sufficient insulation.

> Worse are some of the mods made by hams who think that they know more about
> engineering practices than do the people who design transmitters for a
> living.

My friend Ray, KC1BT is a retired BC engineer. He told me astory about
another engineer (also a ham) who spent days and days on the phone
with Collins re-designing the new transmitter the station had just
bought back in the 60s. Said engineer considered he was far more
qualified than the engineering staff at Collins. Not sure if his ham
experience made him think this way or what.

> I personally prefer to keep my broadcast rigs stock, using them on 160. The
> only mods that I have ever made in these transmitters are slight changes to
> tuned circuits to get them to hit 1885

This is my preference also, since I have other rigs for bandswitching.
Just as well, with my limited knowledge and experience in re-designing
such things! Removing the old mods and getting things back to Square
One is more than enough torment for me.

> The worst mod that I often see (and one that would cause me to fire a
> subordinate at work, if I caught him or her doing it) is the defeating of
> door interlocks. These are there for a reason. The plate transformer in a
> typical 1 kW tubed transmitter can deliver sufficient voltage and current to
> run an electric chair. YOU COULD GET KILLED! With ONE exception, every
> broadcast transmitter that came into my hands had the interlocks jumpered
> out.

Yep, both of the examples I have are the same. Fortunately the pieces
were all still there in the 300G (so far as I can tell), and they will
be reinstalled once everything is set and ready to go. I have to say
that there are times, or have been times for me, where a temporary
bypass is needed to observe arcing or other problems not seen with
doors closed and HV on, but these times are very few, and VERY
temporary. When W1UJR was over recently to give me a hand with the big
rig, I asked many questions about the need to do this before we got
into it. Once satisfied that there was no other way, we proceeded
carefully, located several problem areas, repaired and tested, then
restored the interlocks. I'm always paranoid around juice in general,
and HV specifically. Once is all it takes.

> Granted, these transmitters probably have little intrinsic value. In fact,
> the most I ever paid for a broadcast transmitter was $1! But I still like to
> restore them to near-pristine condition, much as car collectors enjoy
> restoring vintage cars. Some of the broadcast transmitter mods that I saw on
> the Internet remind me of installing a Yugo engine in a Lamborghini!

This certainly makes a case for any real value being in the eye of the
beholder. As soon as the first BC mod was drilled into the rig, any
perceived "collector value" was compromised. Yet another reason to use
and enjoy this old gear rather than placing some unrealisitic
expectation of great value on it. For me, the value lies in the
preservation, restoration, use, and enjoyment of these fine pieces of
radio history.

~ Todd,  KA1KAQ



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