Let me guess, the capacitor was a RIFA cap?
Every Tek scope that I have seen and have checked the X class
suppression capacitors on has at least shown fracture marks in the
epoxy coating if it was of the RIFA type. In the worst case they
have burnt out totally! I have also seen problems with these in
Philips scopes
For what it is worth RIFA still appear to make these caps exactly
the same (don't know if they still come with this nice feature).
Farnell sell a large range of X class caps and if you really wanted
to you could probably replace the cap with the same RIFA cap. I
think I would be going for a different option though given the
issues I have seen. The only problem you may have is manufacturers
have tended to be able to reduce the size of these caps which means
for some values getting the same pitch may be hard although I have
had success in finding suitable replacements for all the caps I have
needed to replace.
Cheers,
Chris
--- In TekScopes@..., "tom jobe" <tomjobe@...> wrote:
Hello Gary,
For what it's worth...
That same capacitor, 285-1222-00, was also used in the military
version of
the 2235, It was used directly across the incoming AC lines just
before the
full wave bridge rectifier as part number C904, and it did not
have a
resistor in series with it..
I have a few partially stripped military 2235 mainboards, and they
are all
missing C904, so I would guess that it must have been a component
that had
problems.
Other 22XX scopes I looked at use a .0022 uF (2200 pF) 250 V
capacitor for
C904.
tom jobe...
----- Original Message -----
From: "Garey Barrell" <k4oah@...>
To: "Tekscopes" <TekScopes@...>
Sent: Thursday, September 18, 2008 7:55 PM
Subject: Re: [TekScopes] 2215 Problem
Stefan -
It's not right across the line. It's in series with a 470 ohm
1/2W CC
resistor (which now measures 19 ohms) and looks like a "snubber"
across
the AC line "after" a series inductor. There's an MOV (250VAC)
and a
.001 cap across the line just after the fuse on the "line" side
of the
inductor. This unit is rated for 220 primary power, although
it's never
been used on anything but 120VAC.
73, Garey - K4OAH
Glen Allen, VA
Stefan Trethan wrote:
I'm assuming this was the x-capacitor (across the power line)?
If so the very same thing happened to me and a fluke 8842a. It
had just
come
from singapure, and worked just fine for a few hours
beforehand.
The cap leaked a nasty brown liquid (and acrid smell). It
stained my
fingers
for days. The cap was actually inside a Schaffner brand mains
filter
module.
Anyway, if it was the x-capacitor, you should replace it with
a rated x1
capacitor for mains filter purposes.
ST
On Thu, Sep 18, 2008 at 11:06 PM, Garey Barrell
<k4oah@...>wrote:
I was using my 2215 for an hour or so the other night, and
moved over
to
the desk to look at something else. About 30 minutes later I
heard a
"sizzle - pop" and smoke comes rolling out the back of the
cabinet!
Both sides! I walked over and turned up the Brightness, and
had a
trace. So I shut it off, took it out of the case and did a
close
inspection. Nothing! I couldn't find my small TORX bits
(don't ever
move.......) but everything looked fine. So I turned it back
on,
measured the supply voltages and all were right on..... Scope
seemed to
be operating normally!?!?!
Today, I found my little TORX bits, and removed the inductor
(the
HUUUMMMMMM) from the back panel and lo and behold, on the
main board
underneath the inductor cover was what remained of C926,
fanned out
like
a Rolodex. P/N 285-1222-00, 0.068 uF @ 250 VDC, 20%. This
is a tiny
rectangular 1/4" x 3/4" by 1/2" high epoxy thing. Of course
none of
the
million and a half capacitors that I have will even come
close to
fitting mechanically.
So. Anyone have a source for these things, or perhaps have
an "extra"
one.
help.....
--
73, Garey - K4OAH
Glen Allen, VA
------------------------------------
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