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IIRC, when a TV CRT ages, the electron emission of a small circular spot on its cathode decreases.
Boosting the heater voltage heats a larger ring-shaped area, leaving the semi-dead spot in the middle.
Since the electron emission then takes place from a ring-shaped area, the onscreen image's focus is no
longer as sharp as it was.

I dimly recall (pun intended) servicing a console? black-and-white TV which had a very dim screen and *three* boosters
connected in series. The set's frugal owner reluctantly agreed to getting a rebuilt CRT installed.

73--

Brad? AA1IP

On Wed, May 5, 2021 at 05:44 PM, ChuckA wrote:

I've had good luck using a Sencore CR-70 restoring a TDS-648A and a

HP3562A CRT....

Hi Chuck,

do you, or anyone else, have an idea what the Sencore and other
rejuvenators are actually doing?

cheers
Martin

Are you sure that the plastic itself has changed color? If looks like the grey spots are collected in depressions of the plastic's texture, which suggests that it is a separate material that has been worn away by handling. Admittedly, his interpretation is contradicted by the fact that we don't seem to see the discoloration on the screen, metal, or beige plastic parts, but I had very similar grey spatter on a 475, which was removed using isopropyl alcohol (and a generous amount of elbow grease).

I would try soaking the case in IPA and then rubbing with a soft cloth or paper towel. Maybe start with just the fold out foot and see how it works.

-- Jeff Dutky

I'm on the opposite side of the country but don't you have some sea ports
there and a navy base? (Also large airports and/or universities) If so then
I can guarantee that there are a lot of civilian companies near them that
support them and that have very sophisticated TE and that also frequently
discard their old equipment for newer models. Seek out those companies,
see if they have surplus disposal auctions and also see if they just send a
lot of the TE and other electronics to electronic disposal companies for
recycling. Seek out those disposal companies see if they will sell any of
the "scrap" to you. It's not like shopping at Sears where you can go in
and pick the exact model that you want, it's more like digging for car
parts in an automotive junk yard, but can guarantee that you will find and
then *want* things that you never imagined! You have to persistent and
probably have to visit them over and over and over so be friendly to them
and *respect* their property and equipment and don't leave a mess behind or
they won't let you return. They never know what is coming in in advance so
you need to visit them over and over again, so I said, stay on GOOD terms
with them.

IMO shopping on Ebay is for people that are too LAZY to go out and look
for the items that they want. It's more convenient and you won't have to
get your hands dirty but it is expensive. OTOH when you start getting into
really specialized TE such as HP 3458 meters, then you're probably not
going to find one locally and you may have to resort to E-Greed. But hang
onto your wallet if you do!

Also have you tried placing WANT ads on Craigslist, Facebbook
Marketplace or in the newspapers not only in your town but everywhere
within driving distance? Years ago, even before E-bay, a friend of mine
installed an incoming 1-8oo number on his phone line. Then, even though he
lived several states away, he placed I-want-to-buy-HP want ads in all of
the newspapers surrounding several of HPs biggest US manufacturing plants.
He had hundreds and hundreds of calls from people who had worked at HP, or
one of their family members had, and they all had HP items that wanted to
sell. He had an account with UPS at the time so he would buy their items
and have them drop them at UPS and UPS would send them to him. The key to
his operation was to make it as simple and as easy and as cheap as possible
for the sellers to sell and send their stuff to him. No E-bay, no PayPal,
no (then very expensive) long distance phone calls. Just call his 800
number, tell him what you had and if you made a deal, then drop the item at
UPS and he would send you a check or money order. If you're willing to
drive and pick up the item in person, then I think that this approach would
be extremely effective for buying from people that have old big heavy TE
that they don't want to test or have to box up and ship. IMO you would be
MUCH better off picking scopes up in person since you could be sure that
they didn't get damaged in shipping and avoid the expensive packing and
shipping fees. Buf it that is impossible, then you could have the seller
drop the bare item off at UPS or FedEx and, for a fee, they will pack it
and ship it to you. Beware the fee though! The last time that I did that,
UPS charged me $100 just to box up a HP 9826 computer and that was at least
20 years ago! If you're going to have equipment sent to you, you might
also consider getting some very well built boxes and sturdy foam that the
TE will fit into and then ship the box and the packaging to the seller so
that they can pack the TE into it and then return it to you.

On Wed, May 5, 2021 at 8:54 AM Lawrance A. Schneider <
llaassllaaass@...> wrote:

I live in the willy-wags of Maine. About the only way go getting anything
is ebay or CraigsList. If someone else lives in Maine, I'd like to know
how they (you) get anything without resorting to the above.

Thanks, larry

I've cleaned up the CA plug-in with a toothbrush and warm, soapy water, and it looks almost new now. I've used DeOxit on the switches, which improved the switch feel 100%, but the vertical position pots (and assume the other pots) are quite gummy and stiff, and I don't see a way to get lubricant into them. Do I need to disassemble the pots, or are they not sealed?

-- Jeff Dutky