tektronix 2335 repair

[aortiz557]

hey guys, I just finished repairing my tektronix 2335. It was an interesting experience, I documented the project in a log, maybe it can be of use to someone else. also, when looking for the service manual, don't look for a 2335, the manual isn't out there. use the manual for the 2336. the only difference is the 2336 has a daughter board for an optional lcd display that ties into the main board, but the layout for everything else is the same. looks like the file is too large to upload here so I'm just going to dump all my documents into a dropbox.

https://www.dropbox.com/s/tccra4ajzjcgftx/High-voltage-crt.jpg?dl=0
https://www.dropbox.com/s/b1jvoq7uyvps92l/hv-circuit%20z-axis%20excerpt.png?dl=0
https://www.dropbox.com/s/4fduzhxhnb0j1qn/tektronix%202335%20repair.docx?dl=0
https://www.dropbox.com/s/xzo36h5mcbx11po/tektronix_2336ya_sm.pdf?dl=0

first one is the hv/z-axis board schematic
second one is the failed capacitor highlighted
third one is the project log
fourth one is the service manual.

if anyone has one that they're working on and want me to probe any parts of the circuits for waveforms/voltages let me know! I'd be happy to help.

[tautech]

Welcome to the forum.

I read your service log, not bad, shame I can't say the same for your repair.
Better you find a suitable replacement cap, get a few if the scope has more, and make a tidy repair that you can be proud of. Long component leads in test gear are to be avoided. You probably used too hot a setting for the soldering iron to lift the pads like that. More practice required.

C108, C108, C108.......... add it to your OP.

[aortiz557]

yeah, It's not the best repair, I worked with the components I had on-hand. on top of temperature, I believe that the leads were also bent in a semi-wiggly fashion on that particular cap, the rest of them came out for testing with no problems. Had I taken the time to remove the board and straighten the pins out on the bottom it probably could have been avoided. All in all though, The scope was free and the repair was free I'll probably use this as a scope for audio repair. For anything high frequency or precision I have a DS1054Z that finally came in.

[tautech]

I'll probably use this as a scope for audio repair. For anything high frequency or precision I have a DS1054Z that finally came in.

While the 1054 might have features the Tek hasn't do not discount the quality of this 100 MHz CRO.

[aortiz557]

This is true, I suppose you can never really go wrong with a tektronix. but for any sort of accuracy i would really need to re-cap the whole thing and get it calibrated. A lot of the other caps were reading really high with an esr meter.

[aortiz557]

any suggestions on what to replace these polystyrene caps with? They're all over the place and most are rated at 200v. looks like i can cut the price down quite a bit if i don't go with axial caps, I was thinking maybe metal film and ceramic capacitors, but I'm not sure how that will affect things. Though I'd imagine it wouldn't make it worse.

[tautech]

any suggestions on what to replace these polystyrene caps with? They're all over the place and most are rated at 200v. looks like i can cut the price down quite a bit if i don't go with axial caps, I was thinking maybe metal film and ceramic capacitors, but I'm not sure how that will affect things. Though I'd imagine it wouldn't make it worse.

https://www.eevblog.com/forum/repair/pm3262-oscilloscope-repair/msg651054/#msg651054

[aortiz557]

awesome. I'll probably source my parts from digikey or mouser, I'm pretty sure they have a warehouse in texas pretty close to me. And today I got to go back to the t.v. shop i've been hanging out at. after desoldering about 50 caps i finally found one that read 4.7nF. I dont really trust the accuracy of my meter so it felt good enough to me. It's working pretty well now, with short leads, no more hanging wires. I did have to mess with the grid bias control though, the display was dimming as fast sweep rates, but it was just a hair of an adjustment. I also took the time to replace a bunch of missing screws and mounted everything back up. I'll probably order the new caps in about a month.