Please help. Tek 2335 Wiring. - Page 1
Forum section: electronics / repair

author: Henry Finley
author_rank: Regular Contributor
timestamp: September 09, 2015, 09:55:01 pm
content: I have disassembled my Tektronix 2335 and did not photograph it first. Now I'm down to 4 plug-in wires and I can't find where they go. I have included a photograph of where I am now. Can anybody help? Thank you.

author: tautech
author_rank: Super Contributor
timestamp: September 09, 2015, 10:30:34 pm
content: Welcome to the forum.Hehe, most of us have done similar.Especially in the days without smart phones etc.Back then a workbook was the standard way of keeping track of cabling along with cable marking tagsGenerally you can find where the wires live by further study of the Schematics and/or the Service manual.Once you get a couple sorted then it's normally obvious where the rest live.Good luck

author: Henry Finley
author_rank: Regular Contributor
timestamp: September 09, 2015, 10:38:10 pm
content: Thank you, but that isn't going to do it. For one thing, it may as well be the schematic to the Saturn 5 rocket, and I can't even see that kind of stuff any more. I'm hoping for some nice guy to take my photo and mark it.

author: Mephitus
author_rank: Regular Contributor
timestamp: September 10, 2015, 12:06:57 am
content: Heres a link to the service manual of the 2336, which is in the same family.https://www.dropbox.com/s/xzo36h5mcbx11po/tektronix_2336ya_sm.pdf?dl=0What you need should hopefully be inside. Hope this helps!

author: Henry Finley
author_rank: Regular Contributor
timestamp: September 10, 2015, 12:15:30 am
content: Thank you, I clicked the link, but you have to be a member or something. I've got the 2336 shop manual already anyway, and it tells me nothing. I can't believe this. The natural set that the wires have taken over the years is not leading to any pins to connect to. That's why I didn't photograph it. I've always been successful in letting the hardened shape of the wires lead my way. This time it isn't working. There's nothing there to connect to.

author: Henry Finley
author_rank: Regular Contributor
timestamp: September 10, 2015, 02:48:55 am
content: I found them! The pins in the main board I was hunting were nestled smack up against these 2 little 1/2 inch square circuit boards that were sticking up vertically from the main board. Almost impossible to see even with a magnifier and a light. Now everything is connected again in accordance with the curving of the wires as they naturally hardened into. Should work. The problem I was originally trying to find, and never could get to, was trying to find out why the little red variable knob in the middle of the horizontal sweep-time knob turns round and round but doesn't do any thing. Never did find that.

author: tautech
author_rank: Super Contributor
timestamp: September 10, 2015, 03:21:10 am
content: Quote from: Henry Finley on September 10, 2015, 02:48:55 amThat's the Variable s/div which should be set to the Cal position for normal use.They are connected to a pot by a long socketed shaft and a grub/hex screw.If yours goes round and round with no Cal (locked) position, either the physical connection has come loose or the Pot is buggered.

author: Henry Finley
author_rank: Regular Contributor
timestamp: September 10, 2015, 03:39:05 am
content: Thanks. I'd still like to get at that shaft, but haven't been able to. I took it all apart and had screws everywhere, but couldn't get the 2 big gray volts/div knobs off. I haven't a clue as to what holds them on, but they darn sure don't just pull off. So I had to button it up again. Sure wish I knew what holds those 2 knobs on there though. If I could discover that, I could get to the sweep time shaft and tighten up the setscrews. But that main circuit board won't come up till I get those blasted volts/div knobs off.

author: tautech
author_rank: Super Contributor
timestamp: September 10, 2015, 04:34:02 am
content: Some CRO's can be really tricky and very careful study is required when disassembly is not described in the Service manual. Sometimes wholesale PCB removal is required to access or even see how it is accomplished.I've seen scopes that the sweep control knobs could be removed while others are retained by locked collars on the shafts either side of selector switches.With a dual timebase there will be 3 shafts, the innermost connected to the Cal pot.I know that's not what you want to hear, but you need to be sure that the scope is in Cal and to do so you need to be sure the variable s/div knob is in the Cal position. Unless these Teks have an indicator light when not in Cal position, some scopes do.

author: Henry Finley
author_rank: Regular Contributor
timestamp: September 10, 2015, 04:48:13 am
content: Thanks again. This is a 2335 and I'm having to use the service manual for the 2336, which is quite similar. And in that manual it says the Volt/Div outer big gray knobs just pull off. But they sure as heck don't, unless they're glued on there or something. And I can find no evidence of any kind of clip from the backside. But one thing's for sure--those dadgum knobs are NOT coming off there. Beats the hl out of me.This is a great scope, in beautiful working order, and seems to be in calibration. All I really use it for is azimuth adjustments on tape recorders. But I've given up all that and had to get rid of everything to survive in this terrible economy. I just wanted to get under that circuit board to tighten up the sweep shaft collar so I can sell it on ebay and get a good price. Because everything on this scope works great, except that red variable knob going round and round on the sweep shaft.Extremely irritating.

author: jitter
author_rank: Frequent Contributor
timestamp: September 10, 2015, 04:44:15 pm
content: I googled "Tektronix 2235 knob removal" and got some images. It looks like the screw is on the side of the red cal knob, not the grey V/div knob. Once you get that off, the grey V/div knob can be pulled off too. If you had already removed the cal knob, then I would agree that maybe glue was used.

author: Henry Finley
author_rank: Regular Contributor
timestamp: September 10, 2015, 10:51:08 pm
content: Well, well, well--I fixed it. Man, what an ordeal. Those knobs do indeed just pull off, but not without a great deal of effort, and possibly have to be turned to a certain setting. I'm not sure about that. But I finally got the big circuit board out, although I tore off a couple of resistors underneath, because I disassembled it wrong. But after re-soldering them, I proceeded to find out why the variable sweep vernier was just going round and round. It has a long shaft that joins the pot with a collar with set screws in it. The set screws are 180 degrees apart, and somebody tightened one too far and the other was sticking out enough to get hung on the little shroud that encircles it. So I corrected that, and the variable sweep knob worked correctly.So I re-installed the circuit board, and buttoned the machine up, and it's sitting over here working pretty as you please. Thanks guys.

author: tautech
author_rank: Super Contributor
timestamp: September 10, 2015, 11:13:06 pm
content: Quote from: Henry Finley on September 10, 2015, 10:51:08 pmGood job, thanks for sharing.