Tektronix 2465B CRT pin bent - Page 1
Forum section: electronics / repair

author: jonpaul
author_rank: Super Contributor
timestamp: August 22, 2019, 09:39:22 am
content: Hello all:Here is a photo of the CRT VERT plate and term in a newly received 2465B.the area around the term is VERY delicate and affects Vert transient response. I have NEVER seen a CRT pin bent like this.CRT light up and seems normal.1/ Anyone seen this before?2/ Will the bend compromise glass to metal seal and make it susceptible to future leaks?3/ Could the pin angle be from adjustment of transient response or more likely inexperience and sloppy handling?MANY THANKSJon

author: tautech
author_rank: Super Contributor
timestamp: August 22, 2019, 09:43:19 am
content: A gorilla has been there before you, that’s all.

author: jonpaul
author_rank: Super Contributor
timestamp: August 22, 2019, 10:17:02 am
content: Hi again, I shot 4 better images:http://crypto-museum.org/TEK/2465B_CRTPIN.pdffirst 2 suspect bent pin unit, last 2 another normal unit.Really hope the veteran 2465Bers can comment!Bon journee,Jon

author: Gyro
author_rank: Super Contributor
timestamp: August 22, 2019, 10:38:48 am
content: I've seen it before where somebody has accidentally yanked sideways on one of the deflection plate leads. The CRT was still fine many years later.The one thing I'd say isDON'Ttry to straighten it. The glass seal looks to have survived the original bend but it will almost certainly chip if you try to straighten the pin again.It wouldn't have been done deliberately to trim transient response, too risky. I doubt that it will have significantly affected the transient response anyway, but if it has then I'm sure you could overcome it by careful adjustment of the wires going to the pin contacts (don't damage the hybrid!).

author: David Hess
author_rank: Super Contributor
timestamp: August 22, 2019, 11:46:28 am
content: Someone bumped or snagged it.The frequency response can be trimmed by adjusting the lead dressing but Tektronix never bent the pins as part of it.If the CRT still works, then the pin is fine so far but straightening it risks cracking the glass to metal interface.

author: Gyro
author_rank: Super Contributor
timestamp: August 22, 2019, 01:46:43 pm
content: ^ I wish I had your insight... oh wait!

author: tkamiya
author_rank: Super Contributor
timestamp: August 22, 2019, 06:22:04 pm
content: I had one like that. I grabbed the pin with a needle nose and straightened it. I held in such a way that force won't be magnified in the area that touches the glass. It's a judgement call if you should or shouldn't.I can't imagine any of that will affect performance though. I would just leave it alone just to be safe. I did mine on already broken unit.

author: tautech
author_rank: Super Contributor
timestamp: August 22, 2019, 10:12:23 pm
content: Quote from: tkamiya on August 22, 2019, 06:22:04 pmYep.And if the clearances are still sufficient for the ~100V on each plate leave it be.

author: med6753
author_rank: Super Contributor
timestamp: August 23, 2019, 02:18:38 am
content: I have experience removing/installing Tek CRT's and if you aren't careful guiding the CRT in or out you will tweak the deflection plate pins. As long as they aren't bent too bad and there's sufficient clearance I'll leave it alone. But I have had to straighten at least one or two and you need to exercise extreme care. Chipping the glass is a possibility but I would worry more that the pin would fracture and break off. In your case there's plenty of clearance and it's not causing an issue so I recommend you leave it alone.

author: james_s
author_rank: Super Contributor
timestamp: August 23, 2019, 03:03:34 am
content: I would definitely leave it alone. If it works don't be tempted to mess with it, you'll really be kicking yourself when you hear that *crack* Hiisssssssssssssssssss.

author: rf+tech
author_rank: Frequent Contributor
timestamp: August 28, 2019, 03:07:45 am
content: Those CRT termination inductors and pins are purposely bent at the factory.The proximity effects between the inductors and leads is part of the flat-top fast rise-time pulse response optimization.

author: med6753
author_rank: Super Contributor
timestamp: August 28, 2019, 02:46:20 pm
content: Quote from: rf+tech on August 28, 2019, 03:07:45 amWhat page is that on? I can't find that same reference in the 2465 service manual.

author: MarkL
author_rank: Unknown
timestamp: August 28, 2019, 05:49:48 pm
content: Quote from: med6753 on August 28, 2019, 02:46:20 pmPage 5-17.If you have different numbering, it's in the section titled "DYNAMIC CENTERING, CRT TERMINATION, VERTICAL GAIN, ".

author: med6753
author_rank: Super Contributor
timestamp: August 29, 2019, 12:55:30 am
content: Quote from: MarkL on August 28, 2019, 05:49:48 pmThanks, I found it. But note that it says to move the inductors for best response. It does NOT say to bend or disturb the pins on the CRT itself.

author: tautech
author_rank: Super Contributor
timestamp: August 29, 2019, 01:00:04 am
content: Quote from: med6753 on August 29, 2019, 12:55:30 amYep, so we get back to what I said in the first reply, gorillas on the loose !

author: med6753
author_rank: Super Contributor
timestamp: August 29, 2019, 02:46:44 am
content: Quote from: tautech on August 29, 2019, 01:00:04 amYep, damn gorillas.

author: jonpaul
author_rank: Super Contributor
timestamp: August 29, 2019, 12:16:00 pm
content: Hello all, mille mercis for all the fine and useful comments, from the veterans and mavens!I am familiar with the transient response adjustment of the CRT leads and termination, but I have never seen the leads bent like this, usually they are nearly straight. Agree a gorilla was there.As the A5 board is pulled out for NVRAM work, and PSU is bad, this project is offline for some months.After reassembly and repair of the PSU, I will check transient response for the characteristic 5 ns bump.Certainly the CRT pin seal will not be disturbed.I will send photos of the results.Bon journéeJon