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 Post subject: Capacitors for a Victor VE 12-15
PostPosted: Nov Mon 18, 2019 3:29 pm 
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Joined: Sep Sun 22, 2013 2:23 pm
Posts: 135
Location: Columbus Ohio
Hello,
Around thanksgiving a Victor VE 12-15 I bought will be delivered and once it comes I’d like to have it up and running for the holiday season. In the last couple weeks I’ve learned quite a bit about electronic repair so I feel fairly confident in my ability to restore this set. However, I’m a little confused on what capacitors to replace those in the set with.

Below the schematic says that I’m going to need 4uf, 2uf, and 1uf capacitors.
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E9852EC4-A5CB-4CAE-9DDD-AA99B462299A.jpeg [ 422.64 KiB | Viewed 184 times ]


However, I keep reading that these capacitors have to be of a very large voltage rating. Like VERY large, potentially 800v? I’d like to simply find a drop in replacement for each capacitor rather then putting capacitors in series with balancing resistors if possible but I’m really looking for input on what replacement would be best. Looking on Mouser.com all of the high voltage Film capacitors are boxy capacitors that don’t quite resemble the cylindrical polypropylene caps I’m used to seeing. For example, would something like this make a suitable replacement for the 4uf caps?: https://www.mouser.com/ProductDetail/Vi ... rgzg%3D%3D
Or should I be looking for the more familiar polypropylene film capacitors with lower voltages (say 600v) and put them in series. If I do this should I use balancing resistors? I’ve seen arguments that say to include them and others that say they won’t matter?

Another question is that the VE 12-15 has a very compact cabinet with a ballast tube and tubes that generate lots of heat. Should I have to pay much attention to the heat rating of the capacitors on this one? 100 degrees Celsius should be enough, right? Lastly, as far as replacement wiring goes I know that this set also has asbestos wiring to address the heat issue (would feel more comfortable replacing it at some point). What would a suitable replacement of wire be, I’d like to keep the appearance original and would prefer using non asbestos cloth wiring, but would this create a fire hazard?

Any input on these questions as well as any tips tricks or advice on these early “Tomcat” amplifiers would be much appreciated! I’ve never heard a working one in person, so I can hardly wait :lol:

-Thomas Pappas


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 Post subject: Re: Capacitors for a Victor VE 12-15
PostPosted: Nov Mon 18, 2019 5:14 pm 
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Joined: Jan Mon 16, 2012 4:15 pm
Posts: 5903
Location: Near Brandon, Iowa
800V? Not likely for power supply B+ filter caps. Cite your source for that figure.


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 Post subject: Re: Capacitors for a Victor VE 12-15
PostPosted: Nov Mon 18, 2019 5:23 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 37559
Location: Livermore, CA
I would be careful on this on. Output tube is a number 10. This tube can operate with 425 volts on the plate. If the tube is pulled and power supply is brought up B+ may far exceed this as the ballast will not drop much line voltage.

A 216 rectifier can handle 550 volts on the plate.

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 Post subject: Re: Capacitors for a Victor VE 12-15
PostPosted: Nov Mon 18, 2019 6:58 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 14386
Location: S. Dartmouth MA 02748-1225 USA
I have refurbished a couple of these "Tomcat" style power supply amp.

You don't have to be concerned about the asbestos wiring. Unless the insulation is fraying into dust. To replace that wiring used braided fiberglass appliance hookup wire for electric stoves. Do not use a silicone wire, that has a tendency to hardened after a few years.

Be wary, electric stove wire is monel, cannot be soldered, have to use compression connectors and a "tulip" crimper...

There is also a hard asbestos mat under all the electronics placed on the base. That too can be replaced with a Fiberglas/ceramic mat available at stove shop, McMaster-Carr, etc

The ballast drops as much as 40 volts. The transformer primary is 85 volts. The ballast will regulate from 95 to 125 volts. Keeping the primary at 85 within a volt. At 124 volts input the filament of the ballast will be a bright red. If the line voltage gets higher it will become yellow, that is too much. If the line voltage is that high then some other means to reduce the line voltage must be used. Preferably a bucking transformer but keep the ballast. The intend of the ballast is to keep a near constant voltage on tubes like the '99 which are sensitive to line fluctuations. Volume would go up/down with line voltage changes.

If you need a more spare ballasts advise, I have too many...

Tip, clean a COLD ballast then re-install with gloved hands. Like the newer quartz bulbs the glass is somewhat sensitive to finger prints and may shatter if deposits are left behind.

There are two parallel filaments in the ballast, both must be intact to operate properly. A broken ballast will burn up in a few moments if used, it is filled with hydrogen gas...

The filter caps must be rated for 1kv volts continuous. Old school paper caps could surge to 1.2kv and be fine.

Use new hardwood blocks cut to size to secure new smaller caps under the same existing clamp, paint them black for "looks".

What happens when the ballast is cold there is a surge in voltage at the time of the lighting of the rectifiers. The initial plate voltage at the 210 will be about 900 until it warms then drop to 525. If the caps can't handle that they will expire...

I was fortunate to use 1kv mineral oil filled caps for that purpose. These are still available but will run FWIR $70 each. You can use 1kv metalized. If you decide to series caps it will be hard to find 8 mf in a 630 volt cap. to get 4mf If so balancing resistors are not required as the metal film does not have an electrolyte. I do not recommend using electrolytic caps in this power supply/amp.

Flip the OEM 216 rectifiers and replace with the type 281 (81). The 216's are hard to find and are not as robust as the '81. BTW this was an RCA recommendation...

https://www.americanradiohistory.com/AR ... 3-1928.pdf

AND

https://www.americanradiohistory.com/AR ... 9-1930.pdf

This "type" of supply was used in many models, variations in the voltage dividers and output tubes used.

There is also some "missing" data in the Gernsback manual as well.

YMMV

Chas

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 Post subject: Re: Capacitors for a Victor VE 12-15
PostPosted: Nov Mon 18, 2019 8:03 pm 
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Joined: Sep Sun 22, 2013 2:23 pm
Posts: 135
Location: Columbus Ohio
Chas wrote:

The filter caps must be rated for 1kv volts continuous. Old school paper caps could surge to 1.2kv and be fine.
Chas


Would two of these in series work then for 4uf? https://www.mouser.com/ProductDetail/KE ... 99LcIzE%3D

And these for the 2uf?
https://www.mouser.com/ProductDetail/EP ... 6I5Q%3D%3D


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 Post subject: Re: Capacitors for a Victor VE 12-15
PostPosted: Nov Mon 18, 2019 8:46 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 14386
Location: S. Dartmouth MA 02748-1225 USA
Tpapp54321 wrote:
Chas wrote:

The filter caps must be rated for 1kv volts continuous. Old school paper caps could surge to 1.2kv and be fine.
Chas


Would two of these in series work then for 4uf? https://www.mouser.com/ProductDetail/KE ... 99LcIzE%3D

And these for the 2uf?
https://www.mouser.com/ProductDetail/EP ... 6I5Q%3D%3D
https://www.electronics-tutorials.ws/capacitor/cap_3.html

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 Post subject: Re: Capacitors for a Victor VE 12-15
PostPosted: Nov Tue 19, 2019 11:18 pm 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3247
Location: Lexington, KY USA
Don't put film caps in series. You can get parts with plenty high enough voltage ratings at reasonable prices

Parallel connection is OK, and is what was often originally used for higher capacitance values in early radios.

For instance, a quick search turns up a 2uF 1500V polypropylene cap for $2.29 at Mouser:

https://www.mouser.com/ProductDetail/KEMET/C4AQSBU4200A1YJ?qs=sGAEpiMZZMv1cc3ydrPrF95ZAHiPXMKgUY7Ze8fHUAcY59auXQGhiw%3D%3D

Just wondering: has someone seen any info on series connection of film caps? I suspect that equalizing resistors might be more important than for electrolytics. The normal voltage breakdown mechanisms are very different.

Ted


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