On Wed, 19 Oct 2011 06:16:31 -0400, JW wrote:


I never trust a 2 wire DMM when reading resistances less than an ohm or
so. Contact and test lead resistance always seem to be an issue. I would
expect that you'll find some around 5 ohms or more, though.


I wouldn't trust my exact measurements, but there was consistently
more resistance in two of the relays, which is obviously not good in a
high precision circuit.


Don't bother with the thin blue one, I've yet to see one of those go
bad...

I wasn't bothering with those for now, but it's good to know they
don't cause many problems. I suspect the blue ones are just for
switching between 50 ohm and 1M termination. They looked like they
would be tricky to replace due to their short pins, and they are a lot
more expensive.


You have to cut the RTV off from the side of the CRT, then cut inward
between the face of the CRT and the shutter. It still takes quite a bit of
strength to pull the shutter free. If it doesn't come free then cut some
more, lather, rinse and repeat. It looks fine without the gel, but it's a
gooey mess cleaning it all off the CRT and shutter. I use a soft plastic
scraper to scoop most of it up, then a lot of rags and isopropyl alcohol
to finish the job. Wish I knew of something that would attack the stuff
better.


It sounds like a mess, but at least you don't have to cut all of the
RTV off.

I know replacing the CRT with an LCD would be more sensible, but I
like the look of those CRT + LCD shutter displays. If anyone reading
this has an old TDS5XX, 6XX, or 7XX color CRT that they want to get
rid of, please contact me. I'm interested in anything that has a
decent looking color shutter and/or CRT. I'll even take a known bad
one for practice if the price is right. I'm located in the US.