Vacuum tube display: Tektronix 2455 - Page 1
Forum section: electronics / repair

author: bat
author_rank: Regular Contributor
timestamp: March 05, 2024, 06:45:54 pm
content: Hi everybody,Recently my Tektronix 2455 died. The power supply pretty much grilled, smoke started to spread all over the house. The smell was really bad, it also scared me alot since i never touched or serviced scopes. Though, i have common sense, I know safety precautions.I'm asking if anybody knows how i can properly dispose of the vacuum tube display. Because it seems that it too, has sadly died. I remember having a talk with a colleague, he had mentionned that you must snap the glass end of the vacuum tube to properly dispose it.If you guys know anything about what i'm asking, i'm all ears !

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: March 05, 2024, 07:25:34 pm
content: I highly doubt the CRT is the issue. Likely a bad cap from the PSU? I personally wouldn't go as far as to scrap the scope entirely. There's still a good chance of saving it. If you really don't want to keep the scope anymore, you can just set it up for sale at a low cost in the buy/sell/wanted section of this forum.Edit: also what makes you think the CRT has gone bad?

author: bdunham7
author_rank: Super Contributor
timestamp: March 05, 2024, 07:38:12 pm
content: Don't snap any glass, you risk getting glass everywhere quite violently. CRO display tubes need to be reclaimed by qualified recyclers that are very specialised because the funnel part contains lead.I would really doubt that the scope is junk, you may have just had the line filter caps go up in smoke. Even if you don't fix it, there are probably people that would want it for parts. You're too far away otherwise I'd happily "recycle" it for you.

author: bat
author_rank: Regular Contributor
timestamp: March 05, 2024, 07:59:24 pm
content: Well, the whole voltage power supply board is grilled for one, including the back connector that goes on the CRT. The CRT is broken for sure because i can definetely hear stuff inside, perhaps residues of filament ? It may be something else.I haven't extracted the tube out yet. I am trying to get this part out so that it can be properly disposed.And yes, I am looking give or sell the parts, everything else is pretty much perfectly working. I can only note that the front potentiometers definetly need to be changed, they are tired from the constant years of use.

author: factory
author_rank: Super Contributor
timestamp: March 05, 2024, 08:04:40 pm
content: Looks like it needs a good clean, then look for RIFA madness paper capacitors and Schaffner mains line filter, these can also contain paper capacitors, these capacitors fail releasing lots of smoke. They are located in the PSU section. The electrolytic capacitors in the PSU can also fail with age, some of them leak corrosive electrolyte other the PCB.And if you don't want to do this yourself, put it up for sale complete, there are popular scopes and people will be interested in fixing it, or using it as a source of parts for repairing other scopes.David

author: bdunham7
author_rank: Super Contributor
timestamp: March 05, 2024, 08:25:43 pm
content: Quote from: bat on March 05, 2024, 07:59:24 pmYikes! I guess that does seem like it is junk. Post some photos of the carnage if you can. And be very, very careful with the CRT--wear safety glasses, gloves and long sleeves at least when you take it out as it may be even more dangerous than normal if it is damaged.

author: factory
author_rank: Super Contributor
timestamp: March 05, 2024, 08:38:10 pm
content: Some pictures would be a good idea, it just looks like HV dirt from the picture in the first post.The HV board with CRT connector can usually be found for sale online, I believe the CRT is shared between a few of the later Tek scopes.David

author: bat
author_rank: Regular Contributor
timestamp: March 06, 2024, 08:19:58 am
content: I will post some more pictures when i'm at home.I won't fix the scope, the HV board is a bit expensive but not so hard to find and the CRT is more expensive.It sucks because I was given this scope by my employer who upgraded to digital scopes, there was no other 2455 so they did not keep it for spare parts, i had the opportunity to take it home. My employer was happy that I could finally practice electronic diagnostic even though it's not my jobI had it for a long time, I used it to fix my electronics and also learned how to use scopes with this one by doing all kind of stuff on it.If I had enough money I think i'd repair it but I think i'll save up some money and upgrade to either, digital scope or analogic memory scope.Just so you guys know, i'm a noobie in electronics, i'd rather have a smaller scope at home than a 2455, even tho I loved it alot :'(

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: March 06, 2024, 07:14:33 pm
content: Stuff inside the CRT doesn't mean it's bad. I had a Tektronix 2213 that had a piece of loose metal inside. The tube worked perfectly, and was really healthy. Nothing wrong. I would really like it if you donate the scope to someone near you instead of scrapping it if you really can't keep the scope. Very likely fixable scope.But by noise from the CRT you mean that the glass is broken? I doubt you need to de-vacuum the CRT if it has already imploded. Then I guess there's no hope of saving the scope.Anyways, here's the process to de-vacuum the tube. Take the tube out very carefully, then wrap it in a few layers of cloth. This is to prevent personal injury if the CRT implodes. Then clip the little nose or wiener at the end of the CRT neck. This will de-vacuum it. If the tube didn't implode, you can put the CRT on a shelf as a decoration if you want. I did that with one tube that had its filament blown.

author: CaptDon
author_rank: Super Contributor
timestamp: March 06, 2024, 09:25:01 pm
content: Nipping off the evacuation nipple is the best and safest way to allow atmosphere back into the C.R.T. How in the hell did the back end of the C.R.T. become damaged??? It is probably fine unless human intervention f--ked it up. Not like any electrical malfunction damaged the c.r.t.!! You could have set the input to 120vac and plugged it into 240vac and likely not damaged the c.r.t. (unless it had a filament transformer that was mains operated.

author: inse
author_rank: Super Contributor
timestamp: March 06, 2024, 09:40:08 pm
content: Scientific CRT destruction, rather boring:https://youtu.be/DEPo2SvOHPA?si=eVxoj879FzmUgk_P

author: factory
author_rank: Super Contributor
timestamp: March 07, 2024, 11:59:07 am
content: Quote from: CaptDon on March 06, 2024, 09:25:01 pmI don't believe it is damaged, from the only picture it just looks very dirty, as all HV areas in scopes & old TVs, monitors do.The CRT is this one;https://w140.com/tekwiki/wiki/154-0850-01The HV board is the one attached below (picture of one I had, no pic on tekwiki), it does have a couple of small yellow axial tants on it, which sometimes burn up.David

author: Zenith
author_rank: Frequent Contributor
timestamp: March 07, 2024, 12:53:25 pm
content: I'm late pitching into this and can only repeat what everyone else has said and which I agree with.The horrible smell is probably Rifa capacitors.The CRT may be dead, but I doubt it.The scope is probably repairable, and if not someone would value it as a source of spares and even pay for it. It would be a shame to throw it away.The way to make a CRT safe is to nip and break the small tube at the rear used to evacuate it. I don't believe you should be considering that.If you are determined simply to discard it, but do so responsibly, in the UK there are general disposal centres with sections for fluorescent tubes, asbestos, electronics and small electricals, and one for TVs and monitors. The TV and monitor section always has a few CRT based units, and I assume they are geared up to dispose of them safely. I can't see why recycling an oscilloscope would be different to dealing with a CRT based monitor. I assume the decheteries in France are much the same.If you decide you can't fix it and don't want it, it would be far better to sell it or give it away. Look at ebay prices for this and similar items. There's also the Buy/Sell/Wanted section on this forum.