What Value of Trimmer Capacitor?

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sickboy
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What Value of Trimmer Capacitor?

Postby sickboy » 03 Jan 2017, 22:17

Hi, I have this "NYCE FC-155S" frequency counter and meter but the frequency readout is way off.
The trimmer cap that should adjust it has went pretty erratic (tried switch cleaner). Can anyone hazard a guess at the value of a replacement? No markings on the component itself..
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dt307
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Re: What Value of Trimmer Capacitor?

Postby dt307 » 04 Jan 2017, 00:18

No idea but if it was mine
Try a red trimmer from an old CB about 2-20pf
If you find its not enough a green trimmer 6-30pf
Just put a fixed value in to temp get the amount you need. So say you put 20pf and the meter is close to where it needs to be then a ceramic trimmer that's around 10-30pf give or take will do.
Or you could use a fixed value of 10pf in parallel with a red trimmer that would give you the range of 12-30pf
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sickboy
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Re: What Value of Trimmer Capacitor?

Postby sickboy » 04 Jan 2017, 00:34

Thanks Chris, helpful as always!
Cheers!

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DX-Digger
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Re: What Value of Trimmer Capacitor?

Postby DX-Digger » 04 Jan 2017, 01:52

Not sure why it would need such a beefy trimmer, is it sampling RF through it or is it just pulling a reference xtal?
In which case it could be the xtal that's past its sell by date. A circuit diagram would help.
Try what Chris suggested but do it on low power.
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sickboy
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Re: What Value of Trimmer Capacitor?

Postby sickboy » 04 Jan 2017, 09:46

DX-Digger wrote:Not sure why it would need such a beefy trimmer, is it sampling RF through it or is it just pulling a reference xtal?
In which case it could be the xtal that's past its sell by date. A circuit diagram would help.
Try what Chris suggested but do it on low power.



Thanks, yes there's a 10.00MHz crystal connected to the trimmer. I'll swap that out as well, thanks for the help :)

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Re: What Value of Trimmer Capacitor?

Postby cb4ever104 » 04 Jan 2017, 09:57

dt307 wrote:Just put a fixed value in to temp get the amount you need.


That's what I have done in the past . Once you know the rough value then just buy a variable that covers it .

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Re: What Value of Trimmer Capacitor?

Postby sickboy » 04 Jan 2017, 16:43

Thanks again lads. Nipped into Maplin for a 10MHz crystal, then used a 15pf cap and a red trimmer from scrap board, and that's the meter back in service.
Really appreciate the advice :clap:
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Re: What Value of Trimmer Capacitor?

Postby dt307 » 04 Jan 2017, 18:18

love a happy ending ....... :D

only the flux left to clean off ;) ;)
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