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Old 7th Jun 2009, 6:37 pm   #21
FRANK.C
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Default Re: Capacitor reformer project

Quote:
Originally Posted by jimmc101 View Post
500v across adjacent pins of a 0.1" pitch 'Molex' connector
The connector certainly don't look up to the job.
But after saying that, I have an AC version of this unit monitoring the output of my variac/lamplimiter the output often reaches 260V AC. Its been working for about 3 years with no problems yet.
I guess if there kept dry and clean there OK.

Frank
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Old 25th Jun 2009, 7:49 pm   #22
David G4EBT
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Default Re: Capacitor reformer project

The 500V meter in this project comes in a little box, with sparse instruction printed on the box. Red and black leads are to power the meter, (which is also backlit), and which if I recall correctly has a supply voltage between 9 - 15V. (9V in this project). The blue in the HT+ input being measured, the black in negative.

Any malfunction of the meter probably means that it's had more than 500V applied to it. I killed my first meter through inadvertently applying a little over 500V - they don't like it up 'em. Luckily, they're surprisingly cheap - less than a tenner including post from China.

Until I came across these little digital meters, I toyed with the idea of mounting a small multimeter mounted behind a front panel cut-out and set permanently to the >500V range - (These little yellow meters are sometimes two for a fiver).

I didn't follow the layout as shown in Radio Bygones and I used a plastic case rather than a metal one. I used all new components, and as to a "high voltage" potentiometer, the standard pots fron Maplin et al are rated at 500V 0.4W.

Initally I was going to use a secondhand mains tranny culled from an old set to give 250V, rather than two new transformers 6V + 6V tranformers back to back to get the 250 V (whch then doubles to 500V). I settled for new transforers as they're so cheap.

The reformer given good service since Feb this year.

Hope that's of interest anyway.
David, G4EBT
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Old 25th Jun 2009, 8:25 pm   #23
Colin
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Default Re: Capacitor reformer project

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Originally Posted by David G4EBT View Post
I toyed with the idea of mounting a small multimeter mounted behind a front panel cut-out and set permanently to the >500V range - (These little yellow mters are sometimes two for a fiver). David, G4EBT
I've used these cheap meters in the past for a number of projects. I remove the circuit board from the case and cut off the meter section. It's not difficult to hard wire the meter to permanently display the required range. They make useful and very cheap digital meters. In fact I have a small boxfull of them bought for 99p each at a local car boot sale!
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Old 26th Jun 2009, 5:02 pm   #24
David G4EBT
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Default Re: Capacitor reformer project

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Originally Posted by Colin View Post
Quote:
Originally Posted by David G4EBT View Post
I toyed with the idea of mounting a small multimeter mounted behind a front panel cut-out and set permanently to the >500V range - (These little yellow mters are sometimes two for a fiver). David, G4EBT
I've used these cheap meters in the past for a number of projects. I remove the circuit board from the case and cut off the meter section. It's not difficult to hard wire the meter to permanently display the required range. They make useful and very cheap digital meters. In fact I have a small boxfull of them bought for 99p each at a local car boot sale!
Excellent Colin! That was what I had in mind, but as yet I've never got round to attacking the PCB with a junior hacksaw. I assumed that the "switchery" would be essential, and that there would also be series and parallel shunts on the PCB which would be needed for the desired range. EG, for the 500V+ range a high value series shunt, or say a 10A range, a low value parallel shunt.

At the cheapo prices these little jobbies can be picked up for, there isn't much at stake!

Nothing ventured nothing gained

Thanks for adding the pics Colin.



Regards,
David G4EBT
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