WTB (or trade 3D printing services for) : Tektronix 2225 crt x ray shield  - Page 1
Forum section: electronics / general

author: JenniferG
author_rank: Frequent Contributor
timestamp: February 28, 2017, 11:42:08 am
content: For some reason my Tektronix 2225 is missing the crt x ray shield on the back of the unit.Any of you have one or more tektronix 2225 (or compatible) units laying around that you use for parts?I could really use that x-ray shield.. don't want to get cancer!I'd pay $10 for it plus shipping. Or trade 3D printing services.Thanks,Jennifer

author: jpanhalt
author_rank: Super Contributor
timestamp: February 28, 2017, 01:07:53 pm
content: I have a Tek 2235 (mil version) that I use for parts. CRT and shield (I believe) are in Cleveland, and I cannot access them right now, but can check on tomorrow. I do not have the parts manual (only op manual), so I do not know if it is compatible. It has been several years since I disassembled it.If it is compatible, I do not need it nor foresee needing it (I have two operable 2235's).Do you have a way of checking compatibility?Feel free to PM me. If compatible, it will be free. You only need to reimburse shipping.John

author: JenniferG
author_rank: Frequent Contributor
timestamp: February 28, 2017, 01:53:26 pm
content: Thank you, I'll look into it the best I canI am such a newb so I might end up just asking someone else hereI only need the round silver (aluminum?) can thingy in the back before you open up the metal case but after you pull off the back plastic tan panel.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 28, 2017, 02:12:27 pm
content: That is what I was thinking you needed. My unit's is like a small measuring cup on the back of the chassis. Will pull it and get some dimensions tomorrow. Contingent, of course, on being able to find it. I think I know where it is. I have been in the process of moving.John

author: JenniferG
author_rank: Frequent Contributor
timestamp: February 28, 2017, 02:15:08 pm
content: I am trying to get ahold of hte service manuals for both 2225 and 2235 and compare part numbers for that piece, if they even mention that piece in those books. I asked dave for a copy of the 2225 manual. Have to look into finding the 2235 service manual now.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 28, 2017, 02:22:43 pm
content: This appears to be a good link to the service manual for your device:http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Tek/2225%20SM.pdfI am scanning it to see if that part is called out. See: Pages 195 and 196.And here is the 2235 from the TEK site:http://www.tek.com/manual/2235-service-manualThey certainly look similar. So, there is hope.John

author: Tom45
author_rank: Frequent Contributor
timestamp: February 28, 2017, 02:36:49 pm
content: The Tek Wiki has a 2235 manual but no 2225 manual:http://www.w140.com/Artek Manuals is a great place to get high quality manual scans. They have the 2225 manuals:http://artekmanuals.com/

author: james_s
author_rank: Super Contributor
timestamp: February 28, 2017, 04:32:25 pm
content: I don't think it's an xray shield, there's no way you'd get a significant amount of xrays out of a scope tube, the anode voltage is nowhere near high enough. More likely it's a shield to keep external interference out of the tube. You need around 40kV before the xrays are hard enough to penetrate the glass.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 28, 2017, 05:04:27 pm
content: There is a metal dome on the back case, which I believe is what Jennifer is referring to. I agree it is more likely an HV shield or shield for something else (not X-rays). There is also the shield around the tube per se which serves as anti-implosion or magnetic shield.In any event, that part of the two instruments is pretty similar, so I will retrieve and photograph for identification tomorrow.John

author: JenniferG
author_rank: Frequent Contributor
timestamp: February 28, 2017, 05:57:33 pm
content: I appreciate it, thank you. I was referring to what I saw on the label on the back of the rear plastic panel, that resides over the capped area. Now that I re-read maybe it wasn't referring to that can/cap thingy. I guess I jumped to conclusion because it was in the same area as it.

author: james_s
author_rank: Super Contributor
timestamp: February 28, 2017, 06:05:09 pm
content: That's a required warning label on anything with a CRT using more than a certain anode voltage. It's mostly a holdover from early TV sets before they used leaded glass to make the CRT envelope. A fault condition could cause the HV to increase to levels where significant x radiation was produced. The HV rectifier tubes in early color TVs were another source, the radiation could be significant if you sat near the TV as kids often do. In addition to the warning label, they are required to have protection circuitry that will shut down the HV if it exceeds a set value. The scope is not going to irradiate you but it still has to have the warning. The shield is important or it wouldn't be there but not for that reason.

author: tkuhmone
author_rank: Regular Contributor
timestamp: February 28, 2017, 06:12:03 pm
content: I do have Tek 2225 scope. Not for sale, but I can take measurements of the metal cup, if you cannot get info from other sources. I assume dimensions for tek2235 part will arrive later...

author: JenniferG
author_rank: Frequent Contributor
timestamp: February 28, 2017, 06:20:27 pm
content: Thanks for claryfying about the radition.And thank you guys for sharing links to both the 2225 and 2235 service manuals.I scanned through them and found the labeled parts diagram. Turns out the part is a match.Here is a screenshot from the 2225 service manual:And here is the screenshot from the 2235 service manual:

author: PA0PBZ
author_rank: Super Contributor
timestamp: February 28, 2017, 06:47:30 pm
content: Lexan is polycarbonate, so not metal and not useable as an X-ray shield.

author: jpanhalt
author_rank: Super Contributor
timestamp: March 01, 2017, 05:30:47 pm
content: Hi Jennifer,Back from Cleveland...First image ("muffin pan") is what I thought you described in your original post.Second image ("Lexan") is the clear piece of plastic on the right. It snaps onto the tube socket. There are two aligning pins. Then that assembly snaps into the black plastic piece on the far left.The muffin pan simply provides physical and electrical protection from the protruding end of the CRT. It is attached with stop nuts to two screws (6/32?) that are swaged or spot welded to the chassis panel. Center to center distance is about 3.65".The Lexan simply covers the end so of the female terminals of the tube socket. It is probably mostly to protect from unknowing fingers probing the live terminals.Hope this helps.John

author: JenniferG
author_rank: Frequent Contributor
timestamp: March 01, 2017, 06:11:26 pm
content: Thanks for clarifying. I probably misread the diagram. I'll snap a photo of how the back of mine looks now.Also notice the rear panel on my 2225 is busted bleh. Missing screws for it as well. If anyone knows which screws I need to buy I'd appreciate it

author: JenniferG
author_rank: Frequent Contributor
timestamp: March 01, 2017, 06:14:36 pm
content: Can I run it just as is? Without the rear panel and the muffin thing? I am not worried about safety, I won't put my hands back there when it is on.

author: jpanhalt
author_rank: Super Contributor
timestamp: March 01, 2017, 06:49:02 pm
content: 1) Always ensure safety. My day job was in a lab where we worked with all sorts of bad things, including at one point Legionella and HIV before they were identified as such. No one ever contracted a disease from the lab under my watch. That does not mean one should be hysterical about safety either. (I am now retired.)2) Your scope is probably safe to use so long as you are aware of its defects. The muffin cup is a shield to prevent contact with the rear of the tube if you open the case. You have the Lexan protector. So, the cup adds mostly physical protection.3) I would be sure the rear case is reinstalled, even though it is broken. I would not operate that scope without its case intact. If you have the urge, you might put a layer or two of 6-oz fiberglass using epoxy resin on the inside to reinforce it. Then be sure to cut ventilation slots in it while the layup is "green." Green is that state between when the epoxy is no longer sticky but is bendable and not fully hard. I typically use an overnight cure epoxy. The green stage usually occurs after the excess in the pot is hard, but before overnight. For the epoxy is use, that is usually after a few hours. You could also use a polyester resin, but it might attack the plastic of the back. I am just much more comfortable with epoxy. There is a vinyl ester resin that behaves somewhere between epoxy and polyester. It gives a longer working time than polyester typically gives. It uses the same catalyst as polyester. Automotive or boat places are good sources for such resins.John

author: JenniferG
author_rank: Frequent Contributor
timestamp: March 01, 2017, 06:56:50 pm
content: Thank you. So I don't need to bother you mailing me the muffin then as long as I have the back on I guess.By any chance anyone know the length and type of thread I should get to screw the back panel on? Sorry for all these questions. Gah. Thank you.

author: tkuhmone
author_rank: Regular Contributor
timestamp: March 01, 2017, 07:13:42 pm
content: Quote from: JenniferG on March 01, 2017, 06:56:50 pmdo you mean those two screws, that are located in the middle of plastic cable quides, I see two torx headed screws on my tek 2225 back cover.-> In tek2225 service manual, figure1 (cabinet) part number 4. <- is this the one ?

author: jpanhalt
author_rank: Super Contributor
timestamp: March 01, 2017, 07:44:27 pm
content: When I take something like that apart, I save the mechanical stuff, as it is often the most expensive and hard to find. I am sure I have the exact screws for your unit in a tin can along with hundreds, maybe thousands of others.That said, your scope is standard American (SAE NC and NF thread as I recall), Common sizes (smallest to largest) are 2-72, 3-48, 4-40, 6-32, and 8-32. There may also be some #10 sizes. Of that group, the very most common are probably 4-40, 6-32, and 8-32. The 2-72 is pretty small. Big parts of the case may be 10-32 (most likely) or 10-24. They will probably be Phillips head and a variety of head styles. My recommendation would be to go to HD, Lowes, or a local hardware store get one one or two of each thread size in a length you can handle (1/2" will work), then find out which ones fit. Some of the smaller hardware chains have racks and racks of screws (Hillman brand?). Whether the screw is Phillips or slot won't matter for functionality. Phillips are easier when assembling as they stick on the end of the screwdriver, and you don't have to worry about the driver slipping out of the slot.If the screw goes into a threaded hole, then you need the correct thread. If not, then just get something that will fit. Be sure the screws are not too long, as the end might touch an electrical part that you don't want it to touch.The service manuals may actually list the screw sizes used.John

author: JenniferG
author_rank: Frequent Contributor
timestamp: March 01, 2017, 09:36:54 pm
content: Thanks a bunch. Actually found the exact screw (they give all dimensions) in the service manual as you said they mightBF is gonna hit Ace Hardware for me

author: PointyOintment
author_rank: Frequent Contributor
timestamp: March 01, 2017, 09:38:30 pm
content: In the manual it looks like the screws that hold the back on are 2× item 1-4, described as "SCR,ASSEM WSHR:6-32 X 1.25,PNH,STL,TORX" which are inserted through 2× item 1-5, "RTNR,POWER CORD:POLYCARBONATE GRAY" (which looks easily printable). Pages 193 & 194 of the PDF. As a novice in the world of fasteners, I'd interpret that as a screw with an attached washer, size 6-32 × 1 1/4" long, pan head (?), Torx drive, not sure what STL means (probably not produced by stereolithography). Does that seem to match?Edit: You beat me to the post button. Looks like it's already taken care of.

author: james_s
author_rank: Super Contributor
timestamp: March 01, 2017, 11:16:55 pm
content: A hardware store ought to have something that will work, but it probably won't be torx. If you want something close to an exact match McMaster-Carr is great for this sort of things. 6-32 is a very common screw though.

author: JenniferG
author_rank: Frequent Contributor
timestamp: March 01, 2017, 11:27:02 pm
content: BF got the exact screw, not sure what head he bought maybe phillips. That's okay though.It's screwed on securely now.. feels solid and doesn't wobble despite it being cracked.So I am gonna run it without the muffin on the back of the lexan crt shield thingy, if no one ojbectsThanks again for the help.

author: JenniferG
author_rank: Frequent Contributor
timestamp: March 01, 2017, 11:31:39 pm
content: Here's a photo of my 2225 I just snapped on my workbench (err kitchen table) -- figured I'd share with you guysI still need to dust it. But I am happy with the condition. Spent $150 on it about 4 years ago from local electronics shop.

author: jpanhalt
author_rank: Super Contributor
timestamp: March 01, 2017, 11:37:27 pm
content: Good luck. Have fun. I will be making blueberry muffins this weekend.Oscilloscopes are addicting. That is why I have so many. I built my first one from a Knight kit in the 1950's. It has been long lost.John

author: JenniferG
author_rank: Frequent Contributor
timestamp: March 01, 2017, 11:41:20 pm
content: Quote from: jpanhalt on March 01, 2017, 11:37:27 pmMmmm.. blueberry muffins... with actual real blueberries!Wow built your own scope back in the 50's.. impressive! Sorry you lost it.. maybe you can find it some where, perhaps the unassembled kit.. that'd be awesome.

author: james_s
author_rank: Super Contributor
timestamp: March 02, 2017, 12:53:06 am
content: Wow that's a nice looking instrument, it looks brand new.I remember lusting over those in catalogs when I was a kid. They cost far more than I could afford at the time.

author: David Hess
author_rank: Super Contributor
timestamp: March 02, 2017, 12:59:52 am
content: Quote from: JenniferG on March 01, 2017, 06:14:36 pmThe rear panel is removed when the rack mount kit is used so there is no problem operating it without it; it is just inconvenient. If it sits on your desk, then you may never notice that it is missing.The cap on the back of the CRT is just for safety.With some plastic welding cement, that rear panel can be mostly repaired.