Hi all,
  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:
http://groups.yahoo.com/neo/groups/TekScopes/photos/albums/158207078/lightbox/1026393052
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!

Dan

On Saturday, December 7, 2013 10:58 AM, Don Black <donald_black@bigpond.com> wrote:

I'm not so sure. Yours may be faulty, these are tested good so they must be a rare animal.

Don Black.

On 08-Dec-13 2:31 AM, Daniel Koller wrote:

 

I'll check and see what's in there.   And when I take them out, I'll sell them on e-bay to an audiophool!!
http://www.ebay.com/itm/4-TUBE-AMP-CAPACITORS-0-1uF-400V-Sprague-Bumblebee/171185528791?_trksid=p2047675.m1982&_trkparms=aid%3D333005%26algo%3DRIC.FIT%26ao%3D1%26asc%3D177%26meid%3D3232141210003616509%26pid%3D100009%26prg%3D1088%26rk%3D1%26rkt%3D5%26sd%3D181276706729%26

(No affiliation with the seller!)

Dan

On Friday, December 6, 2013 11:27 PM, Chuck Harris <cfharris@erols.com> wrote:

Most of the time with the 545, the problem is the

              black beauty oil/paper

tubular capacitors used for the HV filters.  They

              always go bad, and if

they haven't been replaced, you must replace

              them.  Ceramic is fine.

There is also a BB cap that is in series with the grid

              feedback winding,

and another in parallel with the plate winding.  Both

              must go.

-Chuck Harris

Daniel Koller wrote:

Howdy,

The recent discussions on HV repairs has me

              thinking I should look into the issues

in my 545 (not A or B, old style square case).  

              It works very very well, but

about half of the time, increasingly more, the HV

              circuit will not oscillate.  If

I pull the plug-in out and drop it back in, it

              will work.  I know this is not a

recommended option!  Alternatively, if I shut it

              off and wait for it to cool, it

will work when I turn it on with about the same

              probability, or a little less.

Once the scope is on it's up to spec.

The 6AU5 is not brand new, but is good.  It was

              replaced recently with no

improvement.

So, suggestions as to where to start on this

              intermittant problem are welcome.  Is

there anything I should look for or measure that

              might indicate what is getting

tired?

Dan

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