| Products > Test Equipment |
| Tektronix 2235 repair thread |
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| tautech:
--- Quote from: bd139 on March 07, 2019, 11:04:06 am ---If that doesn't work I'll see if I can find a suitable focus pot. Seem to be unobtainum. It's a 5M AB modpot which has to withstand 2KV. --- End quote --- Not at all easy these days so maybe a strip and clean might be an option. 5M will most likely be a carbon track so could just be real dirty and wiper needs a tweak. In the D83 I had a HV zener in the CRT socket went leaky and needed replacement, check for that. IIRC it was 150 or 175V rated and set up the grid bias or something. Might be on the PCB in your Tek. |
| bd139:
Nothing in tube base at all. Straight wired. Have checked bias everywhere for jumps - nothing :( The tube bias and blanking is totally stable. I just disconnected the deflection plates and anode and powered it up again and it's 100% stable as well, just dull obviously. No jumping or anything. I have already replaced the multiplier with another one and the issue persists exactly the same. I just found my HV probe after digging around in the cupboard for nearly an hour as well. The PDA voltage is 7.1KV (about right) and not jumping. Totally stumped! |
| tautech:
Time to pull out the isolated push stick and give things a poke ? Dry joint perhaps ? |
| bd139:
Possible. I might take the tube out and inspect it as well. Look for flashover. Wonder if it got gassy |
| med6753:
--- Quote from: bd139 on March 07, 2019, 12:09:20 pm ---Nothing in tube base at all. Straight wired. Have checked bias everywhere for jumps - nothing :( The tube bias and blanking is totally stable. I just disconnected the deflection plates and anode and powered it up again and it's 100% stable as well, just dull obviously. No jumping or anything. I have already replaced the multiplier with another one and the issue persists exactly the same. I just found my HV probe after digging around in the cupboard for nearly an hour as well. The PDA voltage is 7.1KV (about right) and not jumping. Totally stumped! --- End quote --- Gee...almost sounds like it's the CRT itself. Perhaps a loose internal element? Try carefully tapping the neck of the CRT while powered up and see what happens. |
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