The problem sounds all too familiar. I did work on a fair number of scopes in the series, but guys, it's been about fifteen years ago now. (~1985-2000) So maybe it's best I just bow out now.
Best of luck.
Doc
Best of luck.
Doc
Hey gang. No time to look into this today, but I'll get to it. Off hand I can say one thing I did was crank up the sweep rate and dial off the attenuation to see whether this wide-band trace thickening in channels one and two was really noise or something more periodic. The result was fairly inconclusive, but it did look more periodic than noise. It would be funny to finally find that the vertical amp module has been oscillating all along, or maybe no so funny. I'm not sure I can nail it, but will work on it in the next couple weeks. It really is a critical factor in getting this machine to do all it can do up to 300 MHz, which is twice as fast as any of my probes! I must say that I have worked around the problem so far in that the only circuits that I've been measuring that run that fast have been digital, and were mostly compatible with the limited attenuation options of inputs 3 and 4, and that's why I've not really had to corner this problem sooner...
I picked up an aerosol of deoxit today. Should have some time over the weekend to put into mine. I appreciate you digging in with me, hopefully we can finger it out.
Go easy with that stuff. I've been trying to fix electronic things for 30 years and rarely had Deoxit help for more than 6 months...
Hi All,
I would be cleaning contacts with Alcohol, nothing that will remain to gum up the works. I think that Tek is fairly specific about the use of cleaners ... Don't!
If you get any fluid into a trimmer cap, that's it. You will need to replace that capacitor. It's not worth the trouble to attempt to use a contact cleaner. If you are extremely careful (which means no spraying or pumping of chemicals into the works), you can use a no-residue cleaner that completely evaporates. This means that the oxides must be removed with paper, heavy paper (better) or similar. If you float the contaminate out, where does it go? Make certain you know exactly where anything you wash out is going to end up.
-Chris
I would be cleaning contacts with Alcohol, nothing that will remain to gum up the works. I think that Tek is fairly specific about the use of cleaners ... Don't!
If you get any fluid into a trimmer cap, that's it. You will need to replace that capacitor. It's not worth the trouble to attempt to use a contact cleaner. If you are extremely careful (which means no spraying or pumping of chemicals into the works), you can use a no-residue cleaner that completely evaporates. This means that the oxides must be removed with paper, heavy paper (better) or similar. If you float the contaminate out, where does it go? Make certain you know exactly where anything you wash out is going to end up.
-Chris
I bought the deoxit contact cleaner, which evaporates completely in my experience. I'll only be using this to clean the volts/div and sweep switches, removing the faceplate board from the unit completely. I'm not sure what other method to use to clean these. A tektronix tech in Israel claims that they have seen similar symptoms in aging scopes caused by these switches, so I thought I'd see if cleaning them gets results before wasting money on a replacement faceplate board.
Hi Justinlwtx,
The main concern is with any fluid getting into trimmer capacitors, or wicking into any other component. You need to control your delivery of the cleaner.
Business card stock is excellent for cleaning contacts. Put the cleaner onto the stock (no ink or colours in that area) and use that to deliver the cleaner and also to gently wipe the contact surfaces. I find this very effective. The contacts in Tek 2235 'scopes are much easier this way. You can also use a glass syringe (rubber swells a lot), or a dripper. The nozzle would be equivalent to that of a syringe.
For audio switches, you can use a contact cleaning solution, then follow that up with the no residue type of cleaner. Business card stock cut to the size you need does a very neat job. Of course, you always have to use your head with delicate contacts....
Always use the least amount of force to do the job and never force contacts. Also know when to accept that some switches are too far gone to repair. It really helps to have your beer or spirits after the job is done, never before! 🙂
Wishing you success, Chris
The main concern is with any fluid getting into trimmer capacitors, or wicking into any other component. You need to control your delivery of the cleaner.
Business card stock is excellent for cleaning contacts. Put the cleaner onto the stock (no ink or colours in that area) and use that to deliver the cleaner and also to gently wipe the contact surfaces. I find this very effective. The contacts in Tek 2235 'scopes are much easier this way. You can also use a glass syringe (rubber swells a lot), or a dripper. The nozzle would be equivalent to that of a syringe.
For audio switches, you can use a contact cleaning solution, then follow that up with the no residue type of cleaner. Business card stock cut to the size you need does a very neat job. Of course, you always have to use your head with delicate contacts....
Always use the least amount of force to do the job and never force contacts. Also know when to accept that some switches are too far gone to repair. It really helps to have your beer or spirits after the job is done, never before! 🙂
Wishing you success, Chris
I normally do. In this situation I didn't want to completely disassemble these 9+ position switches. Was blaming to spray the aerosol through the seams to flush them, then dry with medium air pressure.
Hi Justin,
-Chris
I wouldn't unless you can stuff something in to catch over and through spray. It doesn't take much to ruin your day ...
-Chris
Like I said before, I'll be removing the faceplate board from the unit to clean. If I'm bored enough I may go ahead and disassemble the switches, but last time I tried to reassemble one of these it turned into a very long week.
Experts,
is there any good known shop for replacement parts?
Personally looking to replace a scratched display frame with a new one..
Hp
is there any good known shop for replacement parts?
Personally looking to replace a scratched display frame with a new one..
Hp
Hi Hp,
Try Tektronix Electronic Test Equipment Parts in Canada. They rebuild and supply parts for Tek products.
-Chris
Try Tektronix Electronic Test Equipment Parts in Canada. They rebuild and supply parts for Tek products.
-Chris
Try Qservice electronics - obsolete parts for Tektronix test equipment
Honestly, as there are no new parts left for the old scopes, sometimes your own piece is in better shape than what you're buying.
Honestly, as there are no new parts left for the old scopes, sometimes your own piece is in better shape than what you're buying.
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