Trimmer capacitor queries
 

Hello all.

I have a few small air-spaced variable 'trimmer' capacitors, obtained some
years ago for a project (one of many) which never got off the ground. They
are in excellent condition, apart from the inevitable silver tarnish. I
thought I might eBay them, but first there are some things I need to find
out.

It may seem a daft question, but are the plastic dust jackets merely to
protect them until they are installed on a PCB, or are they intended to
remain on afterwards? The access hole for the trimmer screw seems to suggest
the latter, whilst the fact that the two halves are held together with
adhesive tape seems to suggest the former.

You can see a photo here - http://tinyurl.com/6qr7m .

My next task is to identify the value of the two types that I have, one with
5 movable vanes and one with 7. They are identified on the adhesive tape as
TL 10 followed by 24/3 and 24/4 respectively, which doesn't tell me a fat
lot. The problem with Googling is you can have simply too much information,
and this is the case here, so I need to narrow down my search in order to
make any progress. Does anyone have any idea where I should be looking?

Failing that, I'll have to blow the dust off the old GDO (it really does
have a grid and not a gate!), fish out some VHF coils and some fixed
capacitors, and do it the hard way!

--
Rick G4BLT

On Tue, 24 Aug 2004 09:12:16 +0100, "Richard Sterry"
wrote:

It may seem a daft question, but are the plastic dust jackets merely to
protect them until they are installed on a PCB, or are they intended to
remain on afterwards? The access hole for the trimmer screw seems to suggest
the latter, whilst the fact that the two halves are held together with
adhesive tape seems to suggest the former.

I'd leave the covers on if I were you.

You can see a photo here - http://tinyurl.com/6qr7m .

My next task is to identify the value of the two types that I have, one with
5 movable vanes and one with 7. They are identified on the adhesive tape as
TL 10 followed by 24/3 and 24/4 respectively, which doesn't tell me a fat
lot. The problem with Googling is you can have simply too much information,
and this is the case here, so I need to narrow down my search in order to
make any progress. Does anyone have any idea where I should be looking?

You don't need to establish the value to sell 'em, although it may
help. But the kind of people who will go for this item are probably
not that bothered. They could easily be 24pF., but it's hard to tell
without any scale to the picture.

Failing that, I'll have to blow the dust off the old GDO (it really does
have a grid and not a gate!), fish out some VHF coils and some fixed
capacitors, and do it the hard way!

Fixed inductors, I think you mean...

--

"What is now proved was once only imagin'd." - William Blake, 1793.

Paul Burridge wrote:
On Tue, 24 Aug 2004 09:12:16 +0100, "Richard Sterry"
wrote:

It may seem a daft question, but are the plastic dust jackets merely to
protect them until they are installed on a PCB, or are they intended to
remain on afterwards? The access hole for the trimmer screw seems to
suggest the latter, whilst the fact that the two halves are held
together with adhesive tape seems to suggest the former.

I'd leave the covers on if I were you.

I have since learned that these are for protection from solder splashes etc.
during assembly, and are removed afterwards.


You can see a photo here - http://tinyurl.com/6qr7m .

My next task is to identify the value of the two types that I have, one
with 5 movable vanes and one with 7. They are identified on the adhesive
tape as TL 10 followed by 24/3 and 24/4 respectively, which doesn't tell
me a fat lot. The problem with Googling is you can have simply too much
information, and this is the case here, so I need to narrow down my
search in order to make any progress. Does anyone have any idea where I
should be looking?

You don't need to establish the value to sell 'em, although it may
help. But the kind of people who will go for this item are probably
not that bothered. They could easily be 24pF., but it's hard to tell
without any scale to the picture.

I like to provide as much info as possible. There are two different sizes,
one with 5 movable vanes and one with 7, and as the size and spacing of the
vanes is the same I would expect their capacitances to be different - unless
I'm missing something, which is perfectly possible!


Failing that, I'll have to blow the dust off the old GDO (it really does
have a grid and not a gate!), fish out some VHF coils and some fixed
capacitors, and do it the hard way!

Fixed inductors, I think you mean...

The fixed capacitors are for calibration purposes, the values of the
inductors being unknown (just airpspaced coils). BTW, the GDO is a Heathkit
GD-1U - heavy, mains powered, but works a treat!

Rick