Just bought a Cornell Dubilier Capacitor Analyer Model BF-50
 

Hello Everyone, today I just picked up on Facebook Marketplace a Cornell Dubilier Capacitor Analyzer Model BF-50 and I was wondering what the concensus was about those as far as how they compared to the Solar version and the Knight and the Heathkit versions of the Capacitor analyzers?

The one i just bought is going to need to be electrically restored as it currently isn't in working order but it looks pretty straight forward and it looks like its all there, I paid $50 plus shipping for it so I don't know if that was a good price or not, but it seems like a pretty good deal to me compared to how much I've seen working Knight and Heathkit ones going for on eBay.

Any information would be appreciated.

Also how common or uncommon are 12A7 rectifier tubes? I'm curious because that's what this capacitor checker uses and its missing that tube.

I picked one up local a few years ago that I still have to get around to recapping. Even with all the tired caps I was still able to get it to work to some extent.
Quality wise it's excellent. The solid wooden cabinet is all nice and solid,
The push buttons selectors are very well built.

It'll test anything a Heathkit, Solar, Knight will do. As much as I like the Heathkit C3 I would say it's built far better.

You'll also have to do a recap on yours. It doesn't look too bad to do theres a few old dry electolytics in there for filters and a bunch of wax paper caps

Here's a manual I found for them.
http://hallmanlabs.com/wp-content/up...ers-manual.pdf


The 12A7 is 10 bucks or less if you shop around.

Thanks for the info, I think that the reason why the person I bought mine from couldn't get it to power on was because the 12A7 tube is missing.

the one I bought is missing its original leather handle but I think I could make a new one fairly easily with some leather from a local craft shop.

That baby came over on the Mayflower.:D
The 12A7 is a rectifier and low power output penthode. I have one!

Nice! Yes I saw the copyright date on the manual for the unit, 1938! :scratch2:

Yeah having no 12A7 would stop it dead in it's tracks. One half of it is the rectifier, and the other half is the amp.

The inside of yours is identical to how I remember mine right down to the blue electrolytics.

That's a good sign, that means it hasn't been fiddled around with much over the years. I ordered a 12A7 earlier today, so it should be here by Friday hopefully.

The only thing that does look a bit out of place is the big green power resistor that is below the push button switches.
https://i.postimg.cc/pLM0G0SD/Screen...22-54-01-1.png
Looks like it was changed. Seems kind of strange that there's no spaghetti and such long bare leads traveling across a metal switch.
Otherwise everthing looks the same as how I remember mine.

There's a big wax paper in there that need to be accurate. 2.4 mfd. 60 v. This is part of the bridge capacitors for comparing your cap under test in that range.

I'll check into that when it arrives. It was just mailed out, so it should be coming hopefully the same day as the tube.

Is that resistor supposed to be there?

As for the 2.4 uF 60 V cap, I saw that in the parts list in the manual you sent me, and I was trying to figure out if that was a paper or an electrolytic cap, apparently it's a paper cap by the sounds of it.

Does value of the replacement cap for the 2.4 uF 60 V cap have to be exactly the same as the original? I'm asking because I know that that exact value isn't made anymore, because 2.2 uF is a more common replacement value today.

There's a few highter wattage resistors in the circuit so it's likely suppost to be there. I just find how it's installed to be sloppy and not likely original.


All you'll need to do is parallel a 0.2 along with the 2.2 or whatever combination to get 2.4 mfd. The 2.4 mfd is one of the caps used for bridge reference and if it's off the dial will be off.

Should I use a regular film/mylar cap in the 2.4 uF 60 V cap position or would a NP electrolytic work there? Just wondering.

I don't know how a NP electolytic would work and you'd likely only be able to get 2.2 mfd and have to mix and match to make up the difference. You could try it. Myself I would stick to a film caps. Heathkit used big war surplus oil filled caps for this capacitor on the old model C1 condenser checkers.

I'll just see what I can come up with.

I looked up the schematic for the Heath-kit C-1.
It's dated 1948! I think Heath-kit would've never survived without those war-surplus parts and tubes. A 12A6 for a rectifier? They used them in a few kits as both a rectifier and an output tube. :D

Lol yeah. I forgot how they used the 12A6 as a rectifier. Just wire the grids to the plate and you're good to go. Come to think of it I think my tubes have JAN numbers on them. Those war surplus part must have gave Heathkit quite a edge allowing them to sell kits for far less than assembled equipment.

I loved mine till the transformer got some shorted turns between the some of the secondary windings and fried the wire wound pot for the main control. I still need to get around to rewinding the transformer. When it was working it was very accurate for both caps and resistors.

They must have got one sweet deal on all those post war parts. Might explain all the chicken head knobs on the equipment too. I wonder if the early scopes were running war surplus CRT tubes.....