Dumont RA102 "Clifton" restoration

[Kamakiri]

Just a beautiful set. Wow.

I remember there was something historically significant about the Clifton, but for the life of me I can't remember what....

[compucat]

That is a well designed set. Those Cliftons always remind me of early British or pre-war sets. The chassis are quite roomy to work on. I wish the RCA chassis I have on the bench right now was so uncluttered. I will be eagerly following the restoration progress on this one. Done yet?

[bandersen]

Nope, not done yet I'm just starting to put together a parts list. For sure I need to get a whole bunch of 475volt or higher 10uF and 47uF caps.

Does anyone know of a domestic source for 500 volt 105C Rubycons ? They look like very good quality caps with a loaded life of 8,000 - 12,000 hours Most generic caps are only 2,000.
Digi-key and Newark list them but the minimum order is 1,000 pieces !

http://www.newark.com/rubycon/500bxc...00v/dp/54T7071

[Geist]

Hi All;
Bob, maybe You could contact Rubycon direct and talk to a Sales Rep, maybe someone there could either get the quantity you want, or tell you where you could get what you want.. Good Luck !!!!
THANK YOU Marty

[bandersen]

Good idea. I also found some in the UK for £1.325 (about $2) each for a quantity of 20.

They don't ship internationally, but I might be able to have someone in the UK order and ship them for me.
http://uk.rs-online.com/web/p/alumin...tors/7497366P/

[bandersen]

I finally realized that Nichicon makes a 10uf, 500v cap with similar specs to the Rubycon and they are readily available from Digi-key.

About a buck each if you order 25 or more: http://www.digikey.com/product-detai...892-ND/3664442

This set uses an even dozen of them.

[bandersen]

My order of caps has arrived. I tried to get the highest grade caps at a reasonable cost.

All the electrolytics are rated for 105C or 125C and 8,000-10,000 hours life. Generic caps are typically 85C and 2,000 hours.

The white caps are metallized polyester Mallory 150 series. The box caps are Y2 rated AC line filter caps.

I'll hold off on ordering any resistors until I test them.

[compucat]

That set is definitely worth the upgraded caps. I'll bet it is quite reliable once it is restored. Love your YouTube restoration videos by the way.

[vts1134]

I just recently found your Youtube videos also, good stuff.
Have you figured out how you'll rebuild the paper caps? My next set uses caps that are similar and I'm not sure how I'm going to rebuild them yet.

[bandersen]

My only thought so far is to use some plastic tubing to enclose the new cap, paint it brown or dip in brown wax, and wrap a replica paper label around it.

[bandersen]

OK, so it's only been 13 years. Let's get after it!

Now I'm in a house with a large workbench rather than the cramped apartment.




Plenty of room the get both chassis up on the 8' long workbench


Very roomy and easy to work on. I've already replaced a few of the caps in this photo.
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Although the service info lists most of the carbon comp resistors as 1/2 watt, they are all the size of 1 watters. Only one tested out of spec so far.

[bandersen]

Easiest recap ever.


Boy are these "SEALDTITE" caps garbage!


Now as for the eight twist-loc electrolytics... They are trivial to unmount as they barely twisted the tabs.


However, I was quickly reminded why I stopped attempting to restuff them.


Instead, I'll finally give CE Manufacture caps from Amplified Parts a try.
Just over for $300 for eight caps but I figure the labor savings are worth it. Plus, it will look authentic and no need to reroute wiring or install terminal strips.

I had to get creative for some to get the need values, but I think it'll be OK.
For example, I need a dual 40uF @475 which they don't carry.
So, I ordered a 4 X 20uF @475 and I'll tie some sections together.

[bandersen]

While I wait for the electrolytics to arrive, I poked around with the Mallory Inductuner.
The shaft was frozen as they commonly are from hardened grease.
The cover is impossible to remove without some major surgery, but I was able to get into enough to flush out the old grease and spray in some new lube. Also cleaned the roller inductors.




It's moving freely now and I couldn't resist hotwiring the dial lamp for a preview.

[bandersen]

I pulled out the power supply last night and gave it a look over.


I find it interesting that all the tube sockets and held in my screws rather than rivets. Same goes for the terminal strips on the main chassis.


The 10,000 volt HV/EHT supply is an RF type and regulated using an 0C3 gas tube for a reference. A 6SN7 tube is the blocking oscillator and the HV output is sampled using a 180M voltage divider. The coil primary is driven by an 807 tube - precursor to the 6BG6. The only early B&W set to have a regulated supply to my knowledge.
The 807 has gone to air so I'll need to track down a replacement.


Also, the B+ delay relay coil is open


Not much work needed down here otherwise. The brunt of the B+ filtering is done by two huge filter chokes. Just three 40uF caps do the rest.