From: wouk@alumni.cs.colorado.edu (Arthur Wouk)
Subject: Re: fixing shrinking :capacitor questions.
Summary:  do i have the right replacement?
Organization: University of Colorado, Boulder
Distribution: usa
Date: Sat, 7 Nov 1992 21:44:56 GMT



well, my monitor differs from the faq. definitely.

also the machine has been down a week. the crt is fully discharged.

i have discussed matters with someone with the same type of monitor as
the one i have. it is possible using various devices to get to the
point where the capacitor is available. this involved using an offset
screwdriver of the form:

   |
   |______________________________
                                 |
                                 |

this was needed for the following reason:

my case seems to be a little different. the plate the speaker is
mounted on is L-shaped, with the speaker in back on the  vertical
portion. the horizontal portion goes under the pc-board. the speaker
is screwed into the vertical arm of the L, not pressure fitted.

near the end of the horizontal portion of the L there is a SECOND
aluminum piece attached to it which goes parallel to the L itself, and
ends in a hook, which hook seems to lock into the main frame, just
below where the L-arm slides in. sort of like the following:


|
|
|------------------------------------\/ )
                           -------------


not quite to scale. the bottom piece is screwed to the horizontal
piece of the L, so i had to take the whole cage
apart! even if i remove the monitor from the base there will still be
a major problem of access. 

>entirely. The tricky part of the operation is to get the lower shield
>out. Remove the copper tape from the joints between the side of the
>metal frame and the lower shield - there are also a couple of strips

i don't have these copper strips: clue that my monitor is different.


anyway, one other person disassembled the mechanism which allows the
monitor to track sideways and up-down. i couldn't get that done.
however, the screws holding the locking plate to the L-shaped shield
could just be reached by the smallest offset screwdriver of my set.
loosening the two screws (it is tight work, since the lower plastic
case part interferes) permits one to remove the the whole piece.


anyway, it is now sitting there and i have reached the final state: i
am about to unsolder C411. i have bought a new capacitor, 4.7 uf, 63v
electrolytic non polarizing. it is about 1/8" in diameter and 1/2"
long.  can this be a proper replacement? it is what the local
electronic parts supply store offered when i asked for the above with
at least 25v rating.

from faq:

>	A 4.7 uF 25V non-polarizing electrolytic capacitor (C411) is
>bad.  C411 develops a high internal resistance and gets quite hot,
>which further causes it to deteriorate.  It may explode -- use
>caution.  C411 is located between L402 and T401 inside the monitor
>proper.  The value and voltage rating of this capacitor is not
>critical, "ESR" [equivalent series resistance] is however.

what is the appropriate equivalent series resistance?

>	Replace C411 with a mylar capacitor, 4-6 uF @ 25V or more,
>such as AT&T 535GA (4.22 uF @ 100V) or equivalent.  Mount on end with
>insulation on top lead.  Dress away from adjacent parts.


why do i have to mount on end with insulation on top lead if what i
have looks like:

                  ---
                  | |
                  | |
                  | |
                  ---
                 /   \
                /     \



where the things on bottom are the  two leads? how can i possibly
dress this away from adjacent parts?
-- 
arthur wouk 
internet: wouk@alumni.cs.colorado.edu
Newsgroups: comp.sys.3b1