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CRT HV wire repair ?

I have a bad and good CRT. I want to swap out BAD CRT with the (known compatible) good one.

The CRT's HV wires have a special plug/jack into the HV multiplier (flyback) so there is no flaky splicing to worry with.

The good CRT has (too) short HV wire. The wire does not reach the HV multiplier (flyback).

I was told that i can carefully cut under silicon blob where HV wire attaches to CRT and unsolder wire then solder the long one in place ?yes/no? Then re-cover with silicon. Let silcon dry/cure (**** completely ****) !!!

Questions :

  1. Is this a feasible repair ?
  2. What silicon do i buy (from local hardware?) ? is that special silicon ?
  3. Good CRT has 2" copper tape over the silicon blob / HV wire. a. Do i need to replace this tape ? b. can i use aluminum tape like for duct work ? :) that is the real Aluminum tape with just sticky stuff (no foam /vinyl/etc) c. How can i get old piece copper tape to stick back ? d. Any alternatives to the copper tape ?
  4. Any special cleaning or surface prep needed to do this repair?

thanks for any help, robb

Reply to
robb
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What kind of CRT is this that the wire is soldered on? I've never seen on that didn't have a metal cup that the wire just clips into, not saying they don't exist, but I've yet to ever come across one.

The copper tape is used as shielding, you can buy it from a lot of different places, just do a google search. You ought to be able to stick it back on with double sided plastic tape if the original adhesive is not reusable.

Reply to
James Sweet

never seen on

saying they

out of a Tek o-scope

robb

Reply to
robb

Personally, I think that at last initially, I would feel inclined to leave the factory connection to the good CRT alone, and go down the splicing route. If you do a really nice job of soldering the two wire tails side by side with a generous 'blob' of solder to make sure that there are no spikes, you shouldn't have an intitial problem with corona discharge. When you are happy with the solder joint, use a piece of insulation sleeve, slit lengthwise, to cover the join. Before making the soldered joint, slide a couple of lengths of hetshrink tubing over the lead. When you have your slit tubing in place over the joint, work a bit of silicon rubber into the slit, around the joint, then shrink the first piece of tubing over the whole joint. When that has cooled down, slide the second (slightly longer) piece over the whole lot.

I have spliced several high voltage wires of various types over the years, using basically this method, and have never had a problem. And at least if it doesn't work for you, you've then still got the damage-riskier option of trying to get a good bond at the actual CRT connection.

Arfa

Reply to
Arfa Daily

The OP wants to be careful with splicing in a scope. I reckon that any point in the HV lead that is not contiguous might have the possibility of generating some RFI which could have consequences when measuring delicate signals. I'll assume this is also the reason the anode cap is taped over with copper.

Reply to
Meat Plow

Meat Plow wrote in news: snipped-for-privacy@news.alt.net:

ever since TEK began making their own CRTs with the ceramic bell,they have affixed the anode lead to the CRT bell. I've seen maybe one failure of that joint in my 21.5 years there.Usually,it's because some customer tried to measure the anode V by digging under the silicone rubber seal.

While at TEK,I had to splice a few 634 monitor anode leads,and we used a silicone rubber tubing to go over the soldered splice,then heatshrink over that to keep it in place. 10KV or more has a way of finding any pinhole or leakage path and making arcs,carbonizing a better path,etc.

But I missed the reason WHY the OP wants to splice the CRT anode lead.

--
Jim Yanik
jyanik
at
kua.net
Reply to
Jim Yanik

we used a

heatshrink over

pinhole or

anode lead.

Hello Jim,

OP here. The reason .... I want to replace a BAD CRT with compatible GOOD one. The GOOD CRT has an HV lead that is too short.

The HV Anode Plug will not reach the socket on the HV multiplier that is sitting inside the PS. It is about 1.5 '' to short with HV lead pulled taught.

I read that one can cut the CRT anode silicon cover , unsolder the long lead and then solder long lead to GOOD CRT and then recover with silicon.

I am asking ...

  1. is this possible or feasible ?
  2. What silicon do i use (from local hardware store) ? "RTV" is not there just %100 silicon sealer
  3. is there any special surface prep to perform ?
  4. What can i do to replace or re-glue the 2" copper tape that was covering the silcon anode mount point ?

and any other ideas i did not list, robb

Reply to
robb

Well for the foil tape you might be able to use aluminum foil tape which is for air duct work. They sell it at most hardware stores. Well at least it is common here in the US, don't know about the rest of the world since HVAC isn't as common other places.

Mike

Reply to
Michael Kennedy

"robb" wrote in news: snipped-for-privacy@corp.supernews.com:

I'm afraid I don't have any answers to those questions.Sorry.

--
Jim Yanik
jyanik
at
kua.net
Reply to
Jim Yanik

The only way that I can see it generating any RFI, is if the joint is not good enough to be corona-free. Based on what Jim says at the bottom of the thread, removing the lead from the actual CRT does not seem to be the 'done thing' - so I'm guessing that there must be a reason for that. Based on that assumption, I would still think that it was better to at least try to do a good job on a splice initially, rather than risk 'doing a job' on the new CRT that left it useless. I would have thought that there is just as much potential to do a joint at the CRT end that corona'd and generated RFI as there is of having the same happen at a splice - yes ?

Arfa

Reply to
Arfa Daily

I suppose anything is possible. Jim gave good advise on splicing but then he's done it a few times.

Reply to
Meat Plow

Personally I would probably splice the wire then carefully cover the splice with silicone, let it cure, and slide heatshrink over that. If the connection on the CRT is easy to get to, then solder it there. Cover it with ordinary *clear silicone*, not colored, not latex. Let it cure for 48 hours before applying power. For the copper tape, any number of glues will work, contact cement, spray adhesive, double sided tape, etc.

Reply to
James Sweet

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