Re: 545 HV won't oscillate 100% of the time.
My caps probably are bad. When I first got the scope around 1980, I learned about "black beauties" and had to replace them in the power supply, but I think I recall being told that the bumble-bee types were fine, so those stayed in. Now it looks like I have leakage from them in the HV power supply. See the attached photo here: http://groups.yahoo.com/neo/groups/TekScopes/photos/albums/158207078/lightbox/1517700781
The two shiny black 0.001 uF caps stand out because they are coated in oil. You can't see it on the photo, but there is a film of liquid oil between the middle cap and the 56K resistor below it. Those two are coming out but being a big fan of "don't mess with it if it ain't broke" I might leave the other caps in unless there is an obvious failure. Mind you, my scope works well when it does turn on.
But I've had some other modifications it seems. What's that square cap on the left and the 2.2K resistor doing there? I'll have to trace the circuit to see where they were put in and why. Maybe that was a long ago patch for the oscillator failure? Or the cause of it now?
I see now why I had originally thought my scope was much younger than it is - before I learned from the group here that the "brown" Teks were pre-1954. There is this circuit board in my scope:
Someone seems to have made factory improvements circa 1967. What was in its place before this? Is it possible my additional HV circuit components were placed in the same upgrades/refurbishment?
Back to the shop. I've got an hour before guests arrive!
On Saturday, December 7, 2013 10:58 AM, Don Black <firstname.lastname@example.org> wrote:
I'm not so sure. Yours may be faulty, these are tested good so they must be a rare animal.black beauty oil/paper
always go bad, and iftubular capacitors used for the HV filters. They
them. Ceramic is fine.they haven't been replaced, you must replace
must go.and another in parallel with the plate winding. Both
thinking I should look into the issues
It works very very well, butin my 545 (not A or B, old style square case).
circuit will not oscillate. Ifabout half of the time, increasingly more, the HV
will work. I know this is not aI pull the plug-in out and drop it back in, it
off and wait for it to cool, itrecommended option! Alternatively, if I shut it
probability, or a little less.will work when I turn it on with about the same
replaced recently with noOnce the scope is on it's up to spec.
intermittant problem are welcome. Isimprovement.
might indicate what is gettingthere anything I should look for or measure that