2023 Options for Capacitor Reformer/Tester

[Dazz100]

Hi
A capacitor reformer is a key item of equipment missing from my lab. There are a number of DIY designs for capacitor reformer/testing circuits floating around the internet, including on this site:
https://www.vintage-radio.com/projec...-reformer.html
and
https://www.vintage-radio.net/forum/...d.php?t=195127

The Silicon Chip Aug 2010 design still looks like the premium solution and the one I think I might build:
https://www.siliconchip.com.au/Issue...r+%2526+Tester

but there are others.

I found this simple one : https://www.pcbway.com/project/share..._0b3de257.html

Have I missed better options?

[McMurdo]

I just use a small light bulb in series with a DC supply and let it run intil the current has gone to nothing and/or the voltage on the capacitor is at its working voltage, no microprocessors involved of any sort

[David G4EBT]

Back in 2009 I built the Capacitor Reformer which was initially published in Radio Bygones, June/July 2008, and later in the Winter 2008 BVWS Bulletin, which can be downloaded from this link:

https://www.bvws.org.uk/publications...olume33number4

The reformer has given good service for fourteen years now, and to my mind, strikes a sensible balance between simpler 'no frills' designs, and 'OTT' designs such as Silicon Chip. Most of it is point-to-point wiring, but I etched a little PCB along the lines of that in the article, and a little tagboard.

For the power supply, it uses two back-to-back transformers, each with two 6V 1Amp windings. That arrangement provides both the HT and the LT for powering the digital panel meter. Some constructors might wish to cull a transformer from a scrap radio, and the article explains that option, but I used two new 6 Volt transformers coupled back to back (that is with the secondaries coupled together, so you put 240V into one transformer, and get 240V out of the other. A doubler circuit uplifts that to 500V (adjustable).

I obtained the transformers from ESR Electronics, a most helpful firm I’ve used many times over the years: Side Tag Transformer 0 - 6, 0 - 6V (2 x 1A) Order Code 301-045 £8.88 plus VAT + P&P: http://www.esr.co.uk/electronics/product...ormers.htm

The IRFBE20PBF MOSFET is available and in stock from RS for 67p Inc VAT + P&P at this link:

http://uk.rs-online.com/web/p/mosfet-tra...s/5429535/

The circuit in the BVWS Bulletin wasn't very clear, and contained a small error in that digital panel meters cannot share the same ground as that which the meter is measuring. Two meters are used in the design - a 0 to 10mA analogue meter for monitoring the current, and a 0 - 500V digital meter from monitoring the reformer Voltage.

Also, the original circuit didn't make it very clear how the 'Set Current' switch (SW3) was wired. I've attached a clear copy of the circuit, with both the grounding error of the 500V meter clarified, and the S3 wiring shown in green.

The article gives useful advice on the reforming process which I typed up and have attached below, which hopefully, if printed off, will be more legible.

With thanks to the designer, forum member Stef Niewiadomski, AKA 'Saddlestone Man'

Hope that's of interest.

[Uncle Bulgaria]

I've built the Silicon Chip one ('Everyday Practical Electronics' over here). They sell the board so it's straightforward. My only difficulty was making the transformer, but I got help from here to hold my hand through that. You'll find it rather easier getting the relevant Jaycar part down under, I expect.

It works well.

[Dazz100]

Originally Posted by Uncle Bulgaria

I've built the Silicon Chip one ('Everyday Practical Electronics' over here). They sell the board so it's straightforward. My only difficulty was making the transformer, but I got help from here to hold my hand through that. You'll find it rather easier getting the relevant Jaycar part down under, I expect.

It works well.

The Silicon Chip option looks good to me. The hurdle I face is the cost. The magazine shop charges $A10 for each of the two magazines. I only need the issue with the BOM, transformer winding instructions and circuit diagram, but I don't know which month(s) that is. Do I need both Aug and Sep issues? A programmed PIC is $A15. The PCB is $A20. Adding shipping and that comes to $A70 before buying parts.

Buying a cheap Chinese PIC programmer and blank chip is slightly cheaper than buying the programmed chip.

Industrial Solutions (Radio Spares), element14 (Farnell) and Digikey all sell into New Zealand, but the shipping cost makes small orders extremely expensive. The order has to be valuable enough to qualify for zero shipping cost.

I probably have most of the parts already, including the ferrite core and case.
Any I am missing are probably stocked by Jaycar that are just down the road.

[Uncle Bulgaria]

I programmed the blank PIC I bought using a programmer given away by a member here, which did help reduce the cost. I'd pass on the PICKit programmer except it's packed away somewhere while house-building. The parts list is all Jaycar as it's from the Silicon Chip magazine originally.

I got the magazine from the Internet Archive and have attached a PDF I made of the construction articles. The PCB is unavoidable (and I don't mind paying for a nice PCB when they did all the work on the article!)

[PaulR]

I bought a cheap basic unregulated 0-300v Griffin High Tension power supply, presumably ex- school as it had a sticky label on it saying it wasn't to be used by pupils(!).

I use it to apply a voltage to the capacitor, adjusting it to keep the current down until it reaches the desired voltage with low current - or doesn't. It has 6.3v sockets and is useful for various things.

[ian_rodger]

Here's a thread on one I designed a few years ago an Ardiuno rather than a PIC. Easy build if you are familiar with Arduino programming.

https://www.vintage-radio.net/forum/...d.php?t=144420

[Dazz100]

Originally Posted by ian_rodger

Here's a thread on one I designed a few years ago an Ardiuno rather than a PIC. Easy build if you are familiar with Arduino programming.

https://www.vintage-radio.net/forum/...d.php?t=144420

I like your design better than the Silicon Chip design.
I already use and know Arduino devices. I have never used PIC before.

Was the second controller to drive the inverter necessary or just easier?

[60136 Alcazar]

I built a capacitor reforming/leakage measuring tester many years ago. I still use it - it's in a metal box labelled "TV Convertor" (band iii to band i) which it does - it will convert any TV from working to non-working in a nanosecond! It uses an EF80 as series regulator and current limiter (max saturation current is around 14mA), and has a built in voltmeter (0-500v) to monitor the voltage at the output terminal. The voltage is turned on at 100v and progressively increased until the capacitor working voltage is reached. For reforming an in-line ammeter displays the current draw and the voltage is increased until the current draw reaches the maximum permissible for the applied voltage and capacitor value; if this is not the capacitor rated voltage, the reforming process is allowed to continue till the current draw (read leakage current) has fallen sufficiently low, and then the applied voltage is increased further, the process repeating till the rated voltage and leakage current are achieved.

[Chrispy57]

Hi John,
that sounds interesting - do you have a circuit diagram that you can share?

Cheers
Chris

[ian_rodger]

Originally Posted by Dazz100

I like your design better than the Silicon Chip design.
I already use and know Arduino devices. I have never used PIC before.

Was the second controller to drive the inverter necessary or just easier?

The second controller is not necessary, I was just playing with single chip micros at the time and liked that the Attiny85 could be programmed easily using an Arduino Uno (just 6 wires and a capacitor to connect) and uses a subset of the same commands.

A logic gate base multivibrator with complementary outputs could work just as well. It would need to have an inhibit input that sets both outputs low to avoid unnecessary power dissipation in the drive transistors and transformer, also some frequency adjustment to optimise voltage out from the transformer.

[60136 Alcazar]

Originally Posted by Chrispy57

Hi John,
that sounds interesting - do you have a circuit diagram that you can share?

Cheers
Chris

Leave that one with me - after all this time, I'd have to take it apart to find out!!

[Chrispy57]

Hi John,
very kind, but please don't go to all that trouble on my behalf, I was just hoping the diagram would exist and be easily photographed and posted if it was old-school hand drawn.

Cheers
Chris

[buggies]

Ian - apologies for not returning to your original thread.
I built it with only minor mods - works well and has had a lot use.
Just taken the pic attached.

[60136 Alcazar]

Chris

Attached is quick schematic of what's there. This re-used the mains transformer and 16+16/350V smoothing cap from the original TV convertor (dated 1956!). The preset may also be original. All the rest came from the scrapbox.

[60136 Alcazar]

..and the mains transformer secondary was 220-0-220 but with bridge rectifier across the full winding.

[jimmc101]

Handy for a quick check? 110V-2600V IGBT Voltage Capability Tester
I've checked mine up to 2500v and it seems accurate but with a fair amount of ripple.
Jim

[Dazz100]

Originally Posted by ian_rodger

A logic gate base multivibrator with complementary outputs could work just as well. It would need to have an inhibit input that sets both outputs low to avoid unnecessary power dissipation in the drive transistors and transformer, also some frequency adjustment to optimise voltage out from the transformer.

I am thinking direct drive from controller outputs to a pair of self-protecting drive transistors. Implement no-driver-short in software, or alternatively, use a half bridge driver device. The aim to keep the circuit as simple as possible.

[Dazz100]

Hi
I am going to make any further posts on this topic to the thread here:
Capacitor reformer and leakage current indicator