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


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.


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