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Old 18th Jun 2011, 5:44 pm   #1
Andrewausfa
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Default Reformer circuit issues

I had a bash at making Pauls capacitor reformer this morning. A simple circuit for my second project after a lamp limiter or so I thought!

It functions very well except aahh... that I'm getting only +/-115vdc on the output whichever way the switch is thrown. I've taken it apart five or six times now, checking for wiring issues and can't work out what is wrong so I'm getting a bit frustrated Clearly it's dropping too much voltage somewhere but I've got to the stage where I can't see the wood for the trees.

I've attached a photo showing the project, as you can see it's laid out almost exactly as Pauls suggested layout with just the addition of a 250v neon in the Live line and the replacement of the 10k 7w resistor with an 11w. I've drawn in black pen the wiring connections.

Top of R1 is reading 132v AC
Top of D1 - 115VDC
Top of D2 - 113VDC
Top of D3 - 0
Top of D4 - 0

Black and red wires go the outputs, green and brown to the voltmeter inputs at top of box.

Any ideas?

Thanks _ Andrew
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Old 18th Jun 2011, 6:00 pm   #2
G8UWM-MildMartin
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Default Re: Reformer circuit issues

You have indeed put a neon in the live line!
That's what's wrong.
You want the lamp in parallel with the live and neutral instead.
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Old 18th Jun 2011, 6:13 pm   #3
Andrewausfa
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Default Re: Reformer circuit issues

Aaaah! Damnations. Thanks for clearing the wood and trees Martin, that's something that just didn't occur to me

Andrew
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Old 16th Mar 2012, 6:40 am   #4
gulfstream
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Default Re: Reformer circuit issues

Can anybody point me to where I can find the schematic/thread for this project?

Thank you
Regards
Joe
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Old 16th Mar 2012, 9:33 pm   #5
Ricardo
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Default Re: Reformer circuit issues

Joe,

I think you will find the information for Paul's reformer project at the following link:

http://www.vintage-radio.com/project...-reformer.html


Best regards,

Richard
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Old 16th Mar 2012, 10:58 pm   #6
TrevorG3VLF
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Default Re: Reformer circuit issues

I have had a look at the circuit. What is the purpose of C1?
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Old 16th Mar 2012, 10:59 pm   #7
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Default Re: Reformer circuit issues

Quoting from the notes to the circuit:-

Quote:
The mains supply voltage (220-240V AC) is half wave rectified by D1 and smoothed by C1.
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Old 17th Mar 2012, 3:51 pm   #8
TrevorG3VLF
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Default Re: Reformer circuit issues

So, why smooth it? The test capacitor will do all the smoothing required.

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Old 18th Mar 2012, 9:36 am   #9
Mike Phelan
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Default Re: Reformer circuit issues

Only if/when it has sufficient capacitance.

Remember that there is a string of zeners to stabilise the voltage and they might get a bit warm on the positive half-cycles on an unsmoothed input.
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Old 19th Mar 2012, 12:09 am   #10
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Default Re: Reformer circuit issues

I don't see any point in smoothing the supply. The zeners don't stabilise the voltage, they limit it. The leakage prevents the voltage from going near the final value until the thing is reformed. Also, if the capacitance is low then you have a problem because unreformed capacitors should have a higher capacitance than rated - the reforming process steadily reduces it (as the dielectric thickens).

In fact there is a disadvantage. My experiments show that capacitors reform faster if you keep discharging them, something that many circuits you see don't do (although best results may be to do this somewhat slower than 50Hz - but I haven't had time to study this effect fully yet).
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