No problem Greg.
I'm sure you're not the only one who's misidentified something wearing the wrong (or no) glasses in the past!
( I've done it myself in the not too distant past! )
My advice re fault finding still stands, read the theory of operation info about the CRT subsystem, especially about the "DC Restorer" circuits, before wading in.? They are not difficult to understand, but can confuse people who are not used to that sort of circuitry, where a DC signal modulates an AC feed, that is then rectified to re-create the original DC signal, but offset by an overall (often high) voltage.
A HV probe and meter is useful, but not essential.? I have often used a standard DMM "floating" at up to -20kV when working on TWTA power supplies, to check filament voltage regulation and cathode/grid bias.? So long as they are well insulated from the surroundings, have good HV rated leads, and (*Important!*)? You don't touch it when the volts are on, you can setup and measure just about anything.
The cathode end of a Tek 465 'scope is only some -3kV if that, but it is best to make the connections when powered off, rather than try to do it with the power on.?? A good thick plastic sheet should be OK to insulate the DMM, or place it in a glass beaker (a UK Pint Glass for example!)? But if in any doubt, don't do it that way, make or purchase a HV probe and lead assembly.
Tantalum cap's.?? If all the LV rails are present and correct, I'd not bother doing a shotgun-change, but if one rail is missing or low, you need to find out why.
Note, that the various low voltage DC regulator stages rely on each other, especially in as much as only one of them has the initial voltage reference.? That rail is then used as a reference for the others.? Again, check the theory of operation section of the manual.
You could also disconnect the raw DC supply to the HV oscillator while hunting down any LV issues, to save the CRT from more stress.
I have also in the past, substituted a resistive load or small bulb instead of the CRT heater, so the HV section and controls can be de-bugged with the tube cathode cold, so no beam, but you'll need to find out what load the CRT heater/filament usually presents, to get in the right ballpark.? To much, or too little load, and the HV regulation won't behave correctly.
Doing that can save the CRT screen in the case of uncontrolled beam intensity, but of course all the usual High Voltages are still present, so take care.? And no, you wont "strip the cathode" doing that.
I have an old 465 (and 468) here, both still working well, and as far as I know, with the original tantalum and electrolytic caps still present.? It is prolonged lack of use that causes electrolytic failures over time.? Tant's don't like current surges, but the Tek PSU stages all have current limiting, so surges should be managed. When they reach the ripe old age those in the 'scopes I have, it's likely they'll outlast me now.
I have in the past pulled the current limit sensing transistor from a "troubled" regulator stage that was collapsing, to find the errant Tant'...? It was often amazing (a) how long they'd run before "going nova", and (b) the amount of smoke they create if you don't power off ASAP when they do let go!?? Not damaged a PCB doing that, but don't leave such an instrument powered like that un-attended!
There was a period back in the early 70's, where a lot of them were fitted the wrong way round into the PCB.? I suspect all of those have been found and replaced by now.
Note!? Removing the big PSU Elctrolytics needs great care not to damage the PCB.? If the DC rail ripple spec's are OK at minimum AC line input voltage, leave well alone.
Lastly, the 465 is a great general purpose 'scope, and well worth repairing.? Also, except for a few rare custom parts, (HV transformer, PDA HV Multiplier, Input attenuator modules, and some mechanical parts) are relatively easy to source parts for.
Have Fun.
Dave 'KBV (Ex Tek UK bench service when the 465 etc were current products.)
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