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| Tektronix455, high voltage transformer |
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| doban:
Hello friends. I want to check the high voltage transformer of the tektronix455 oscilloscope, code 120-0984-00. Any help or information about the transformer is welcome. Thank you. |
| doban:
Or does anyone know how I can check if it's good? Thanks. |
| adam4521:
I have a working 455 oscilloscope, I guess I could do some ohms measurements on the windings (in-situ) if you wanted to compare. You have a copy of the service manual PDF? There is a lot of information in there with test point voltages etc. |
| doban:
The oscilloscope didn't break for me. That's how I got it from a friend. Yes, please make measurements on the windings for comparison, when you have time. I have documentation, with measurement points. The defect is, the transistor Q552 burns - short between the base -collector-emitter and Q556-short only between the base and the collector. I only have one pair of transistors. When starting immediately, the +32VDC fuse blows and both transistors burn immediately. I can start the measurements if I remove T550 and U550 from the card? Thank you very much. |
| adam4521:
I wouldn't remove the transformer unless you have higher certainty that it has failed -- at that point it is curtains for the scope unless you have a parts/donor unit! I would be suspicious of the zener diodes VR552 and VR553 and diode CR552. Are you happy that they are ok? They are holding up very big voltage swings -- if anything fails there I could easily imagine them breaking down your transistors. Unfortunately it might be a few days before I get bench space and time to open the cover of my unit and take ohms measurements -- will do my best to find some time this week. |
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