EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: philo on April 06, 2023, 07:25:38 pm
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Hi! How are you? I've got this tektronix 2213 which doesn't show anything on screen unless I press the "BEAM FIND" button (and the SEC/DIV rotary switch on XY, on the rest of SEC/DIV option you can bearly see the trace) and a short horizontal trace shows at the right of the screen. I do have apparently some trouble at the horizontal amp. With the BEAM FIND button unpressed I get at the H+: 85v and at H-: 15v, when BEAM FIND button is pressed I get at H+: 40v and H-: stays at 15v aprox.
I recently got this scope being sourced as non functional, the only two faulty components I could found where: Q386 (vertical output transistor) was leaky because it measured a reversed diode from emitter to collector, and R379 vertical output resistor 340ohms was open. I've individually measured out of circuit almost every transistor related to horizontal and vertical circuit: Q763 Q753 Q747 Q780 Q785 Q789 Q736 Q730 Q731 Q720 Q770 Q779 Q775.
I'm really lost, all resistors and caps measured related seemed fine. Removed SEC/DIV rotary switch from A12 sweep board and completely cleaned it with no changes.
All PSU output voltages are OK. If you need any measures taken please let me know. Thanks!
PS: attaching photos of both channels getting body noise with tweezers on XY setting in SEC/ DIV
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Looking at page 173 of the manual
https://w140.com/tekwiki/images/1/1c/070-3827-00.pdf
So are you saying -15V is at point 24, I only see the negative 8.6 rail close by, and they say it should be +47V between the (-) Hor drive BJTs. And there's a resistor divider path to -8.6 right there too. Is that -8.6 rail really working ? nevermind, +15V. I'm trying to make some of the circuit ion the sim, but IDK what BJT's or FETs to use, to try and see the DC biasing.
When it was all in 1 piece, did you measure any of the voltages around there, there's a bunch listed in the schematic ?
What was the history of it, did it work before, did u just buy it ?
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go to tekwiki, w140, DL complet service manual for the serial number
DO NOT fiddle with transistors yet! Very unlikely!
Usually just control and contact clean g, then PSU, perhaps recapping...
Use troubleshooting flow chart,
first check every power supply DCV and ripple
Next following proceedure for check HV supply.
Notice that many scopes shipping is poorly packaged, one drop by the freight carrier and the CRT can be damaged.
jon
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I've downloded the 200 and something service manual, in which I couldn't find the vertical circuit. It's just briefly explained, i cleaned twice with contact cleaner the rotary switches. PSU caps where almost all replaced, all voltages are on spot. HV I'm not able to measure it, it is produced cause I can discharge the anode but don't know if 8kv are getting there. Thanks!