Capacitor Tester and Reformer Unit - Stefan Niewiadomski

[SurreyNick]

I'd like to include in my 'things to make' a capacitor tester and reformer. If anyone has a construction article including circuit on one which they have personal experience of I would be most grateful to receive a copy. I came across one example which I believe might fit the bill. It was entitled the 'Capacitor Tester and Reformer' Unit by Stefan Niewiadomski and appeared in the Winter 2008 edition of the BVWS magazine. If someone has a copy of that article.....?

Many thanks

Nick

[Yorkie]

I built the reformer when it was first featured in Radio Bygone Nick. It was later featured in the BVWS Bulletin. I posted a thread in the 'Home Brew'section of this forum back in May 2011. It works very well and I've used it regularly since I built it almost five years ago. To get the 500V it  uses two back to back transformers with the low voltage secondaries wired together, then a voltage doubler to lift the 240V output from 'T2' to nearer 500V.

However, there's no reason why a mains transformer from a scrap radio with a 250V HT and 6v3 heater winding couldn't be used if to hand, as an alternative to the two back-to-back transformers. 

There was a error in the circuit in terms of the LT supply for the digital panel meter, which must not share the ground with the voltage being measured. If you look for 'Radio  Bygones Cap Reformer' you'll find the forum thread that expalins this,  with a diagram of the panel meter. (The reformer also uses an analogue meter for measuring the current).

Time has move on of course, so maybe the present digital  panel meters from China (and perhaps the one used by Stef?) don't have this requirement. It's not a  prblem.

I'm away from home till Saturday Nick, but when  I return home, I'll drop you an e-mail.

Hope that helps.

[Alan Douglas]

I built one about 40 years ago; it's described in my book on test gear but also shown in this discussion in the Antique Radio Forum:
http://www.antiqueradios.com/forums/viewtopic.php?f=8&t=276600
There are other suggestions in that thread too.

[Radio Fixer]

IMHO it maybe worth the effort reforming caps from the 60's on but I wouldn't bother for electrolytics before that. Its easy to put in new ones and even re-stuffing isn't onerous once you learn all the ways of doing it (and there are plenty). That way even if you don't use the radio often it should always safely work. Personally, I don't reform any but have left them in the odd 60's set that has come my way, that has been and will continue to be in regular use. Often the case for early FM sets.

Gary

[SurreyNick]

Oh, I didn't know that Gary. I just assumed (what's that old saying...if you ass-u-me you make an ass out of you and me) you could reform caps of any age. As I only work on pre 1936 units there's little point in my making one then
Nick

[Yorkie]

I'd certainly agree with Gary - I wouldn't consider trying to reform caps in pre-war radios - I'd re-stuff them. Most (not all) radios only use a two-section smoothing/reservoir cap plus an audio valve cathode bypass cap, as often as not, 25uF 25V. The later are invariably duff even on 1960s radios. Modern equivelents are puny in size so to preserve the appearance, depending on whether the set is worth the effort, I'll re-stuff the original one.

If the internal physical appearance of a set is considered worth conserving - and most who restore pre-war sets would assert that it is, you can get very compact electrolytics with good ripple ratings ffrom Farnell which comfortably fit inside the old can - every three section ones.

If you look under 'where to get sets and part' and 'caps for restuffing' you'll find at least one thread where thosse caps are discussed and their specs stated.

If the appearance isn't considered that important, the BVWS sells 'period sized' upright can multisection caps, as do other suppliers.

Most of the sets I've restored have been post war and apart from three Ekxo A22s have been of no great value. For such sets, a reformer has almost always done the trick for me.

Hope that helps.
 

[Alan Douglas]

You might reform pre-1940 electrolytics to passable working condition but they will be back to their original state in a few days.

[Refugee]

This thread is mine on the topic.
http://golbornevintageradio.co.uk/forum/...p?tid=3756&highlight=restuffing

I also did some with the slim capacitors that can be loaded into the new capacitor without even removing it from the chassis.
http://golbornevintageradio.co.uk/forum/...p?tid=3934

[Radio Fixer]

The BVWS also sells good electrolytics (high voltages and large ripple current ratings) for re-stuffing purposes (I always buy from them).

Gary

[AlanBeckett]

In general so do I although they 'aint cheap. However, you can rely on them.

Alan