Need a little help with a Tek 422  - Page 1
Forum section: electronics / repair

author: ultimatekaiser
author_rank: Newbie
timestamp: October 24, 2019, 04:12:24 am
content: Hi, I realize I'm new and that this is my opening post, and I'm a bit sorry (and embarrassed) to make my first post a plea for help. but I'm not sure where I can turn to to find parts. I recently got a pair of Tek 422s (one of the nuvistor versions, and one that is not ironically) and the older one is still working fine. the newer one is working but if I pull out the 10x mag I lose my trace. I need to take a look at that, but unfortunately the newer one, appears to have a rather unfortunate malady where some of the knobs are bent. I straightened the shafts of the potentiometers involved, but that's when I noticed that one of them is actually completely missing. The horizontal positioning knob has been cleanly broken off, shaft and all ironically. and I was hoping someone here might have a parts unit that I could pilfer a replacement fromas I have no idea where I could source such a thing from anymore. God only knows how it was broken off. the intensity knob is broken too. though it's fortunately only the plastic part on that one. if anyone has parts they'd be willing to share, It'd be much appreciated so I can get these both up and running again! the power supplies appear to both be good as well for the most part as they do power up. Though the batteries are of course long shot to shit. (20 very old NiCd D cells that i had to remove and wrap in plastic for safety so they didn't get Cd powder all over.)Ironically, the older one is in better shape overall than the newer one and short of a recal, is pretty usable! :p I'm amazed every time I open up old Tek units like this. Even as a fairly novice electronics guy, I can't help but see a work of art.

author: andy3055
author_rank: Super Contributor
timestamp: October 24, 2019, 05:08:54 am
content: Try this link:https://www.ebay.com/itm/Vintage-Tektronix-Oscilloscope-Parts-Knobs/273976549133?hash=item3fca465f0d:g:hcAAAOSwPJVdX2kZ

author: ultimatekaiser
author_rank: Newbie
timestamp: October 24, 2019, 07:09:21 am
content: Thanks Andy. That solves the problem with the intensity knob. Those grey ones appear to be correct. Now to tackle the broken potentiometer. It is labelled as a dual 50K ohm sharing the same shaft. number 311-0470-000. I've done a couple searches in places I know, but I haven't come up with anything. I'm rather worried I won't be able to get one short of out of another unit.I also noticed the neon for the power light is out too. though thankfully it's the only one of the four. But that's obviously a minor thing. If anyone has a good one, I'd be very thankful.

author: andy3055
author_rank: Super Contributor
timestamp: October 24, 2019, 04:00:00 pm
content: Can you post a picture of the broken potentiometer?These guys are supposed to be in Oregon. First time i came across them though! Since you can use Paypal, it should be safe.http://www.vernonianorthern.com/TekParts/Tek311Page.phpUnfortunately, there is no phone number. Here is the main page where there is an email link (t.anderson46@frontier.com):http://www.vernonianorthern.com/TekParts/TekParts.php

author: james_s
author_rank: Super Contributor
timestamp: October 24, 2019, 04:07:22 pm
content: Is the neon lamp something other than the typical NE-2 sort of thing?

author: jdragoset
author_rank: Frequent Contributor
timestamp: October 24, 2019, 05:18:05 pm
content: I've used an NE-2 for re-bulbs on my 422's.You have to remove the back cap, un-solder the old bulb and solder in the new bulb, work fast as the cap is thermoplastic.Those bulbs are powered with a wire from a remote 120k resistor and I've found at least one indicator wire pinched during unrelated re-assembly.The dual H position pot is sort of a luxury, giving a coarse/fine adjustment on one shaft.A single 50k, such as 311-0580 or 311-2146 with fixed 22k ohm resistors for the fine would at least allow the coarse adjustment.https://www.ebay.com/itm/Assorted-Tektronix-potentiometers-311-xxxx-00/143209999491?epid=17030221176&hash=item2157fb2c83:g:jyUAAOSw7ttcheGfFor the over-the-hill Ni-Cd pack I subbed two of these in series from Battery Mart.12 Volt 3.2 Ah Sealed Lead Acid Rechargeable Battery - F1 TerminalItem #: SLA-12V3-4 | In StockPrice: $16.95Some dremel tool work was needed to the original Nicad pack frame

author: jdragoset
author_rank: Frequent Contributor
timestamp: October 24, 2019, 06:04:02 pm
content: 50 k dual 322-0979, single shaft.https://www.ebay.com/itm/Assorted-Dual-and-Triple-Tektronix-potentiometers-311-xxxx-00/143210002116?epid=17030221176&hash=item2157fb36c4:g:aioAAOSw-RFchdaE

author: ultimatekaiser
author_rank: Newbie
timestamp: October 24, 2019, 07:47:12 pm
content: Thanks so much for all the help guys. I really appreciate you taking the time to help a newbie like me! That last pot might work. I'll have to see if I can get dimensions just to make sure it'll fit. I could probably go with a modern bournes, but I was hoping to use the correct original part if I can in order to make it look as historically correct inside as I can. I could always cannibalize a third, but I was simply hoping I wouldn't have to do that. I figure someone somewhere has got to have a parts unit that likely still has it inside. I can't imagine it's something commonly replaced unlike maybe a tunnel diode or cap or something like that.I attached a picture of the broken one on my desk.

author: jdragoset
author_rank: Frequent Contributor
timestamp: October 24, 2019, 08:49:58 pm
content: Those on the Ebay sites are 1/4" OD threaded part and 1/8" shaft OD.

author: andy3055
author_rank: Super Contributor
timestamp: October 24, 2019, 09:18:02 pm
content: Did you check the site I mentioned? They have it for $11.75. $3.75 shipping via USPS. You can email and see if he will respond.If it was me, I would take it apart and put a new shaft. Very easy.http://www.vernonianorthern.com/TekParts/Tek311Page.php

author: jdragoset
author_rank: Frequent Contributor
timestamp: October 25, 2019, 01:13:34 am
content: Test the DC supply with something like this:https://www.ebay.com/itm/Tektronix-161-0149-00-12-V-OF150-Series-OTDR-Cigarette-Lighter-Adapter-New/222810308641?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649I can pix the pin-out/polarity if needed for testing.If it works on 24 volts DC, buy two Battery Mart batteries.There're not very many of the AC/DC versions that work out there so every rehab is good.Albeit the small screen & low frequency response (10-15 MHz), these are great units, very rugged & :-without fan cooling air, stay very clean inside.https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif

author: ultimatekaiser
author_rank: Newbie
timestamp: October 25, 2019, 03:43:54 am
content: yeah I saw your link. Andy. I just didnt see the Pot the first time. I found it and ordered one. thanks a ton. that should likely be most all i need parts wise.I did test the power supply. it seems to be ok on DC on my bench supply. I'll look in more detail soon

author: andy3055
author_rank: Super Contributor
timestamp: October 25, 2019, 03:47:48 am
content: Quote from: ultimatekaiser on October 25, 2019, 03:43:54 amOk, great to know. If the shaft is plastic or even aluminum, you can repair that and keep as a spare.

author: ultimatekaiser
author_rank: Newbie
timestamp: October 25, 2019, 04:10:44 am
content: yeah I didn't think to take it apart. That's very true. If I could find a shaft of the right diameter. now I'll jsut have to dig that power neon out. it's hidden down in there a little ways. not looking forward to pulling the trigger board out to get to it. it's in kind of an awkward spot to get to. These are neat scopes. I did notice that DC testing the nicd terminals on my current limited supply I get a short. there is a diode in there that seems to be shorted. fortunately i have spares of that though. hopefully nothing else is broken. powering it up on the DC input it runs fine. haven't tested the AC part, but I imagine it's probably fine too.