MadMax
Joined: 26 Feb 2005
Posts: 3
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 Posted:
Sat Feb 26, 2005 2:15 pm Post subject:
Tektronics 2465 problem -TEST 05 FAIL 24- HELP! |
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Hello all! I need help on repairing my tektronix 2465B. After switching on it shows "TEST 05 FAIL 24" and never triggers in "auto lvl" and "auto" mode. Triggering is still possible in "norm" mode, but triggering voltage reading in upper right corner of CRT isn't correct (for example, when there is 1V RMS@50Ohms 150MHz, it triggers between -1.0 and apporox.1.70V instead of -1.4 to 1.4 V, vertical scale factor is setted to 500mv\div.). Triggering is still possible in "auto" mode only this way:
1) i must set LEVEL knob fully clockwise
2) i must change mode of triggering (for example, switch from AUTO to AUTO LVL and back to AUTO) or sweeping time
3) i must rotate _SLOWLY_ LEVEL knob counter-clockwise and stop it immediately when the scopr triggers. If i continue rotating and the scope distriggers, i must begin from step 1).
I downloaded service manual for it (.pdf file, 14 MB, 256 pages, without schemes) and found that "TEST 05 FAIL 24" means that "negative level is too negative, and positive level is not positive enough". Maybe anybody knows what did they mean and how can i correct desired levels?
I opened the scope and saw that it was opened before me. U800 (TEK 155 0241 02) maybe replaced before (there is visible traces of dedoldering\soldering), and U500 (a&b trigger - marked on board) fixed only with 3 nuts instead of 4. Type of U500 is TEK 155-0239-02. I unscrewed 3 nuts and saw that device is physically destructed a little- there is scratches, but all thick-film wires visible are tested with ohm-meter and are OK.
I switched the scope ON without U500, and it shows "TEST 05 FAIL 42" instead of 24. Triggering without U500 is impossible.
I put U500 back and the scope now works as worked before.
Please, help me to diagnose my scope or to get circuits! Ple-eeease!
Thanks a lot
Max
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MadMax
Joined: 26 Feb 2005
Posts: 3
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| Posted:
Sat Feb 26, 2005 2:52 pm Post subject:
a little to add |
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| I want to add that i measured power supply voltages on the connector between main board and power supply. +5,-5, +10, -15, 15, +42 and +87V are OK, and point "-15U" was at -18.8V. |
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