Hi Mike,
What I'm going to propose you is going to sound a bit crude, but it might
help.
If you have a receiver you can tune it to the frequency where the 555 is
operating and instead of using an RF probe, you can touch the
base/collectors of the transistors you want to test with your finger (naked
finger or helped with a small piece of naked wire or a paper clip
unfolded).
If there is RF at the points you are probing, the receiver will show it
instantly. It might help if your RX antenna consist in a short (3ft) wire
close to the 555 under test rather than a large antenna far from your shack.
With this technique you can check the presence of the heterodine xtal
oscillators or even the PTO.
Does it make sense?
73,
Carlos VK1EA
On Sunday, December 9, 2018, Mike Fishman NK8S <nk8sradio@gmail.com> wrote:
> Thanks very much for the replies and tips Gary and Steve!
>
> Steve, I don't recall when precisely it failed - I'm guessing I turned it
on and found it as is. I was using CW and the internal keyer
previously...will try and locate the reverse polarity diode to eliminate
that as the issue. Thanks again!
>
> Gary, I'm thinking I'll grab a kit version of an rf probe for the
multimeter and give that a try - thanks very much!
>
> Very 73, Mike NK8S
>
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