Quote:
Originally Posted by TinCanAlley
Okay, I'm trying to fix an IBM Monochrome Monitor from '82. I have the Sams Photofacts service manual and have been following the diagnostic steps. I got only so far before I found something odd and no explanation for it in the SM.
I tested the power supply section and all readings looked good. So I moved to the horizontal output section and that's where I ran into a problem. The SM said to check for 24.7V at the emitter of the TR24. I got a reading of 27. Then it said to check the collector of TR24 for 14.9V. I got 27V again. Both the E and C have 27V. The SM only notes what to check if the voltage is missing, not if it is wrong or, in my case, the same. Now TR24 is what I always considered a HOT based on the package TO-3, but in this SM it is a transistor and the HOT is package TO-220.
Yes, my knowledge is limited, but I'm trying to learn. That's why I always defer to the expertise here. If you need more info, as I'm sure I've left out something needed, just let me know.
I wanted to attach the SM, but it is too large.
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it would really help if you can link the Schematic on someplace like imgur or other such site, I have not seen one of those monitors since my very young teen days, and do not have quick access to docs, what I DID find, is CLOSE, but most likely not correct, there is NO way for the V at that point to be that high if the regulator is working correctly, the schematic I found shows 24.7 going into the regulator and 14.30 out, this goes to the HOT, but as mentioned, it's most likely CLOSE but not exactly what you have.
https://i.imgur.com/RLFCEKB.png