[ARC5] Re-capping

[Kenneth G. Gordon]

On 6 Mar 2011 at 12:46, Richard Schumann wrote:

> Well, all this talk about checking capacitors has motivated me to
> purchase an inexpensive unit that will do the job.
> 
> For those of us on a 'Harbor Freight' budget, do they or another
> source have a reasonably priced DMM or something accurate enough to
> get the job done?

Unfortunately, not to my knowledge. 

What you need for this kind of work is some sort of instrument that can 
apply the rated voltage to the capacitor then measure any resulting leakage 
at that voltage.

Over the years, there were many, many such instruments built and sold by 
many companys. 

Sprague, for instance, sold one, and upgraded it continually, under the 
name of Tel-Ohm-Mike, which was a very good one.

The models were TO-3 through TO-6, as far as I know. 

IMHO, the best of the bunch was the TO-5, and this particular model 
always goes for a fairly high price on eBay.

Manuals for these are available on BAMA.

I use two different Heathkit C-3 units, one at work, and one at home, which 
I rebuilt some time ago and wrote an article that was published in Electric 
Radio magazine detailing both the C-3 itself, how to rebuild it when 
necessary, and how to use it properly.

The C-3 and its ilk not only measure capacitance (somewhat crudely, but 
accurately enough, i.e. within 10% in most cases), resistance, and leakage 
in capacitors, both paper and mica, and electrolytic, but they also measure 
"Power Factor" in electrolytics, and can be used to reform electrolytic caps.

Knight, Eico, and Lafayette, among others, had similar models.

The latest Heathkit version, as mentioned by Bob Maclin here, was the IT-
28, which was also sold as the IT-11 under a different color scheme.

This is an excellent instrument, easily available from eBay at regular 
intervals.

Some of those need to be rebuilt, but basically, they are perfect for this kind 
of work.

There is a fellow, a ham, who sells a kit on eBay to make the older Heathkit 
C-3 types as capable as the IT-28. I bought two of those kits from him.

One very interesting feature of the C-3 and its predecessors and some 
subsequent models, is that it uses both the 1626 triode VFO tube from the 
ARC-5 transmitter (as a rectifier) and the 1629 eye-tube as the indicator.

That kit I mentioned above re-configures the 1626 into an amplifier, and 
does other things to the C-3 to bring it more up to date.

Most of these units have the capability of reforming electrolytic caps too.

The Sprague units also can measure transformer turns-ratios.

Ken W7EKB