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18th Jun 2011, 5:44 pm | #1 |
Octode
Join Date: Dec 2010
Location: St Ives, Cambridgeshire, UK.
Posts: 1,180
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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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18th Jun 2011, 6:00 pm | #2 |
Heptode
Join Date: Jan 2004
Location: Stockport, Greater Manchester, UK.
Posts: 827
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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. |
18th Jun 2011, 6:13 pm | #3 |
Octode
Join Date: Dec 2010
Location: St Ives, Cambridgeshire, UK.
Posts: 1,180
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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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Invisible airwaves crackle with life. Or they should do. BVWS Member |
16th Mar 2012, 6:40 am | #4 |
Retired Dormant Member
Join Date: Jun 2009
Location: London
Posts: 14
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Re: Reformer circuit issues
Can anybody point me to where I can find the schematic/thread for this project?
Thank you Regards Joe |
16th Mar 2012, 9:33 pm | #5 |
Pentode
Join Date: Jul 2006
Location: Bedfordshire, UK.
Posts: 211
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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 |
16th Mar 2012, 10:58 pm | #6 |
Rest in Peace
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
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Re: Reformer circuit issues
I have had a look at the circuit. What is the purpose of C1?
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16th Mar 2012, 10:59 pm | #7 | |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
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Re: Reformer circuit issues
Quoting from the notes to the circuit:-
Quote:
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17th Mar 2012, 3:51 pm | #8 |
Rest in Peace
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
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Re: Reformer circuit issues
So, why smooth it? The test capacitor will do all the smoothing required.
Trevor |
18th Mar 2012, 9:36 am | #9 |
Dekatron
Join Date: Nov 2003
Location: Near Leeds, West Yorkshire, UK
Posts: 4,609
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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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Mike. |
19th Mar 2012, 12:09 am | #10 |
Dekatron
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,086
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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). |