[ARC5] BC453 repair

[Tim]

The dreaded Tin Whiskers?  Been there, done that...LOL


On Fri, Aug 22, 2014 at 7:07 PM, J Mcvey via ARC5 <arc5 at mailman.qth.net>
wrote:

> I finally got around to fixing the "new to me, 28V virgin" BC453 today .
> It started out pretty straightforward with a quick ESR cap check showed the
> usual suspects  needing replacement ,such as the .22X3 ,etc. I replaced the
> 10W diver resistor that someone has removed , lubed up the dynamotor and
> applied 24 volts with anxious anticipation of hearing some beacon stations.
> All I got was a brief cackling, then silence- NO JOY!
>
> I pulled the 12K8 grid cap and was encouraged when I was able to get noise
> by touching the cap. When the cap wire was put back, it went silent again.
> I thought it was the RF stage but everything checked out.
>
> It turned out that the oscillator was dead, in fact I was surprised to
> find the osc plate at 2.6 ohms to ground! Why, might you ask? They plate
> tune the oscillator stage, so there is B+ on the gang variable! There must
> have been a tiny speck of metal shaving in there somewhere which I could
> not see, before or after blowing it out with air which cleared the short.
>
> Once that was done the receiver was howling away with a 50 microvolt
> signal lead laying on the bench about 3 ft away and no antenna.
> I've got some more cleaning and tweaking to do, but I'm a happy camper
> now, knowing that the radio is basically in very good shape.
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