Re: Little ceramic trimmer caps that always break... A fix.

Paul Amaranth

I could type 40 wpm on a manual typewriter all day with very few mistakes.
I suppose that dates me.

Now I can't type a line without a couple of typos. My theory is that as
the cost of a mistake decreases we just get lazy. Making a typo in
an editing program has essentially zero cost (other than finding and
fixing it). Add in spell check and you don't even have to remember
spelling (I'll ignore auto-correct).

Age has nothing to do with it. That's my take and I'm sticking with it :-)

Thanks for your service notes Chuck. Whenever I see one I file it away.
They're always full of useful information.


On Wed, Aug 19, 2020 at 09:09:42AM -0400, n4buq wrote:
Mid-sixties here and having some of the same issues. I work with a lot of various systems and am constantly crossing up numbers and letters (or conflating one system's numbers with another, etc.). Very annoying. I have had to resort to carefully rereading what I've typed to pick out the nits (just like I did for this one). It is indeed frustrating if not downright embarrasing at times.

Barry - N4BUQ

----- Original Message -----
From: "Chuck Harris" <cfharris@...>
Sent: Wednesday, August 19, 2020 7:58:25 AM
Subject: Re: [TekScopes] Little ceramic trimmer caps that always break... A fix.

It is becoming a touchy subject for me. All my life I have
been a very fast touch typist. I spent a lot of time writing
programs, and later writing documentation, and could always
type quickly and effortlessly...

But in my 60's, I am noticing coordination problems in my typing,
I "slur" my shift control, and swap adjacent letters.

FG504 can become FG540, Chuck can become CHuck...

I even do a little weird thing where small common words, like
"the" come out backwards "eht", and other words always gain an
extra letter, such as "ratio" always getting typed "ration".

I always find it amusing when I type a long treatise on some subject
or other, and the only comments that get made are about a misplaced
comma, or a typo.

I am getting older. I can't see as well as I once did, I cant type
as well as I once did... And I don't like it.

I am working through a couple of FG504's. If I can help, just ask.

-Chuck Harris

Colin Herbert via wrote:
No, the typo doesn't matter in so far as that is what it was. I was just
curious because I am trying to get a FG504 working correctly and not doing
too well at the moment. I didn't mean to insult you or anything like that;
please forgive me if that's what it came over as.

-----Original Message-----
From: [] On Behalf Of Chuck
Sent: 19 August 2020 13:22
Subject: Re: [TekScopes] Little ceramic trimmer caps that always break... A

Honestly, does it really matter that I mistyped FG504?

I am talking about ceramic trimmers that exist in
hundreds of Tektronix instrument models.

-Chuck Harris

Colin Herbert via wrote:
Do you mean an FG504? I can't find any FG540 on TekWiki.

-----Original Message-----
From: [] On Behalf Of Chuck
Sent: 19 August 2020 05:15
To: TekScopes
Subject: Re: [TekScopes] Little ceramic trimmer caps that always break...
A fix.

Just to clear up some confusion:

This note is about subminiature ceramic disk type
trimmer capacitors. Tektronix equipment from the
1980's onward is littered with these little timebombs.

It is a "modernization" of the old style ceramic
trimmers that had a silver plated half circle on
the lid that was soldered to the adjusting screw.

In this case, the silver plating is inside of the
trimmer, and the ceramic disk is held on by very
temperamental magic. The moving ceramic disk sticks
to its ceramic base, and the magic disappears.

-Chuck Harris

Chuck Harris wrote:
Hi All,

Just a note. As happens to all of us, one of those
little ceramic trimmers in an FG540 was broken. The
screw turned and turned, but the ceramic disk on top
didn't. It was frozen solid.


I didn't have a spare, so I removed the trimmer, and
found the ceramic disk frozen solid to the ceramic
base... no trimming going on here!

First, I put the capacitor into some IPA to soak for
a bit. There was more than enough stinky flux on
the cap, so I think the flux was gluing the cap stuck.

After it soaked for a while, I was able to turn the
disk with my fingers... don't use tools, it will break!

I put it in for some more soaking, and twisting, until
it was good and clean.

Next, I took a small dot of cyanoacrylate glue, and
spread it around the screw. A small dot, not a flood.
[If you can't control your glue bottle, put some CA glue
on a piece of plastic, and use a toothpick to bring a dot
to your trimmer.]

Then finally, I gave a rag a squirt of "Kicker", a CA
glue accelerator, and put the rag near the trimmer... The
kicker's fumes are enough to harden the glue almost
instantly. If you don't have any kicker, just let it set
a while, it will harden from the moisture in the air.

I gave the screw a twist, and all was back to normal.

-Chuck Harris

Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows

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