1960's Tektronix 422 Oscilloscope re-cap - Page 1
Forum section: electronics / repair

author: lordvader88
author_rank: Frequent Contributor
timestamp: October 02, 2017, 10:17:08 pm
content: Just got it, it supposedly worked and show both traces at least, so the seller said. ATM I need to solder on a 3-pin plug, I only have modern ATX style and they don't fit.But it will also be full of 1960s electrolytic caps (I've taken off the back cover and the big input filter elec. caps there look ordinal, metal-can, big axial type fitting perfectly in the holders.I don't have near enough random big elec. caps of mains input levels. I have the schematic.So far just using sandpaper to clean off the rear plug. And know what side has the fuse on it, and the fuse is fine. Haven't looked at the sch. yet tho, how are the switches connected, idk yet. The plug retapticale/pot seems to be riveted to a back plate (that I've unscrewed) so I could just solder onto the plug posts for now or cut the inside wires.........the add said it had no plugSHould I power it up for a minute? I most confirm what the seller said of it working condition.

author: lordvader88
author_rank: Frequent Contributor
timestamp: October 02, 2017, 11:27:29 pm
content: It looks well used, actually well abused, all scuffed up, scratched up, even FP knobs/buttons melted. I measured the 4 big caps I can see, they measure right with a DMM.But I'll replace all them anyways, not worth the risk, they wear out

author: The Guy
author_rank: Regular Contributor
timestamp: October 02, 2017, 11:36:40 pm
content: Quote from: lordvader88 on October 02, 2017, 11:27:29 pmI have one of these.... and it works just fine. No recap needed whatsoever. These are very sturdy long lasting pieces of equipmentVery beautiful little scope

author: lordvader88
author_rank: Frequent Contributor
timestamp: October 03, 2017, 01:20:39 am
content: It never worked. I screwed it back together with the fully chasis back together, and soldering in a 3prong plug. 115V measured across its plug, pulled a little FP switch out, that says 'power' and waited a few moments, no traces,,, the CRT gives off a tiny amount of light.... but no hint of traceswait now I (lack of CRT light is bad) but I never tried centering anyting....still hope yet

author: lordvader88
author_rank: Frequent Contributor
timestamp: October 03, 2017, 01:29:33 am
content: it doesn't work. wired in 115V, and the CRT screen gets a ;little brighter, but thats itorange pwr light comes onI had a bit of a trace for moment after playing with some buttons.Intensity/focus/etc seemed to do nothing

author: The Guy
author_rank: Regular Contributor
timestamp: October 03, 2017, 01:18:18 pm
content: Do you have the service manual? First thing to do is to measure the output power supply voltages at those line nodes.Start by getting the service manual athttp://bama.edebris.com/manuals/tek/... I think they have it.

author: lordvader88
author_rank: Frequent Contributor
timestamp: October 03, 2017, 06:28:44 pm
content: Yeah thanks I have it.And just plugged it in today for 1/2 second, and heard a weird noise like scratchy rumbling....and some smoke/wax wafted out the side. The fuse never blow, but did warm up.It begins. Hope I didn't wire mains in backwards, I put hot on the fuse side. there'a an X cap, then a common (or diff.) choke., fuse then transformer.The longest it was plug in and on was last night for maybe 30s-1minToday it wasn't even turned on.Sounds like a capacitor going

author: Cyberdragon
author_rank: Super Contributor
timestamp: October 03, 2017, 08:15:41 pm
content: Getting the mains backwards shouldn't cause a problem, transformers and X caps don't care. The noise was either a cap shorting out and burning up or something high-voltage arcing over and burning up (hopefully not a transformer), just look for physical damage somewhere.

author: The Guy
author_rank: Regular Contributor
timestamp: October 03, 2017, 08:35:47 pm
content: yea... also check for burned resistors... mine had 3 carbon comp resistors burned up in the power supply when I first got it.

author: lordvader88
author_rank: Frequent Contributor
timestamp: October 04, 2017, 11:10:07 pm
content: Yeah and I have 2 very different schematics (at least at the PSU) for a Tek 422, both with the Tektronix name all over the pages and called 422, maybe 1 is a lab model or something, mine doesn't have an x-cap or choke, its just a fuse, and a thermal switch straight into the trans.I have the right schematic, and the pictures match. However I'll wait till tomorrow when I get a small lightblub limiter, setup, the thing uses about 25W, andI'll fire it up and very quickly check a few voltages off multiple secondary outputs.

author: The Guy
author_rank: Regular Contributor
timestamp: October 05, 2017, 02:28:50 am
content: Before firing it up again i suggest to perform a very detailed visual inspection. I like to use an 5x optivisor, helps a lot when trying to find screwed up stuff.Visually check every carbon comp resistor, transformers and caps from the power supply. There is a high chance of finding the source of the noise that way i think.I´m not expert but i´ve successfully restored three scopes last month (with the invaluable help from the guys here), and currently i am restoring my fourth