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Tek 465M Repair: Re; Tek 4654M No Trace, No +5V, No +95V Thread


Harrison
 

This is a new thread that is a continuation of the “Tek 4654M No Trace, No +5, No +95V Help” thread. I restarted the thread because of an error I made in the initial title, Identifying the unit (due to fat fingers) as a 4654M instead of a 465M. The initial thread has 64 posts. Thank you so much for all the comments and help. Because of those postings I have made good progress. All references in the original and this post are to an Air Force Tech Manual that I I found on line. I have tried to add it to the file section, hopefully that was successful.
After replacing C741, CR582, Q742, Q552, VR552 and VR553 I now have both the +5 and +95 banks back. I have a trace and a waveform when compensating a 10X probe and when checking it on a 6.5VAC wall wart I have a nice sign wave.
My current problem is that the above results are obtained with a leg of CR552 raised (taps in between Pin 3 of U550 and Pin 8 of T550). It appears that when I reconnect the CR552 leg it blows F558 and takes Q552 with it. Checking out the components in the feeds to U550 pins 1 and 2 all seem good.
VR552, VR553 and Q552 come into play when the high voltage regulator malfunctions (see manual page 4-25 paragraph (b) 4.). Could the HV regulator be an issue? The HV regulator is potted. I was thinking, could I build a new regulator circuit and piggy back it in place of the existing potted regulator. Thanks again for any and all help and advice.


adesilva_1999@...
 

If you plan on doing the U550 block, here is what I did:

https://groups.io/g/TekScopes/album?id=255419