Fairchild 670 Restoration

[Di_Sousa]

Hi,
I'm starting a restoration on a  Fairchild 670.

I need to replace the Can Filter Caps at the back, but I'm having some problems in finding replacements,
I'm trying to avoid modifying the unit, so I would like to keep the capacitors in the original sockets and pinout.

The capacitor values are:

C305  -  140uf / 350v

C306  -  140uf / 350v

C307  -  60uf + 60uf / 450v

Does anyone know of where could I find replacement capacitors?

Thanks

 

[radiance]

What are they? Polyester , electrolytic ?? Where are these caps being used in the 670?

Have you tried searching RS, Farnell, digikey or other online stores alike? Maybe ebay?

 

[bruno2000]

cedist.com
Best,
Bruno2000

 

[idylldon]

cedist is the wholesale arm of Antique Electronics.  If you don't have an account, you won't be able to order on that site.  Their regular website is www.tubesandmore.com, and you don't need an account to order on that one. 

Cheers,
--
Don

 

[hop.sing]

In Europe you could try:
http://www.die-wuestens.de/
Best Tobias

 

[abbey road d enfer]

Hi,
I'm starting a restoration on a  Fairchild 670.

I need to replace the Can Filter Caps at the back, but I'm having some problems in finding replacements,
I'm trying to avoid modifying the unit, so I would like to keep the capacitors in the original sockets and pinout.

The capacitor values are:

C305  -  140uf / 350v

C306  -  140uf / 350v

C307  -  60uf + 60uf / 450v

Does anyone know of where could I find replacement capacitors?

Thanks

I don't think you'll find exact replacements. Technology and normalisation have happened since then. You could replace the 140uF with a dual 100+100uF 500V (both sections in parallels) and the dual 60uF with a dual 50.
Someone may point out that the peak rectifier current will be higher than expected, but it should not matter, because the 670 is waaayyyy overengineered and the difference between 140 and 200u is not much considering the safety margin a designer is expected to take.
As an example:
http://www.tubeampdoctor.com/de/shop_Kondensatoren_TAD_Gold_Cap_radial/
Not the cheapest source, but just so you have an idea...
The 500V rating is a bonus.

 

[njm]

I restored a 670 earlier this year. I used 4 individual caps and bolted the extra one inside the chassis. Drilled a couple of holes....oops!

From top to bottom on the 670 the caps are C305, C306 and C307. C305 and C306 are wired in series with R305 and R306 as balancing resistors to make what is basically a 70uf 700v cap. Voltage there is 450V so you could use something like a 70uf 500v cap there to replace both of those. Then the extra space gained by removing that second cap leaves room for using inividual caps for C307a & b instead of a dual one.

You could just use 80uf 500v for all three caps

 

[mata_haze]

I restored a 670 earlier this year. I used 4 individual caps and bolted the extra one inside the chassis. Drilled a couple of holes....oops!

From top to bottom on the 670 the caps are C305, C306 and C307. C305 and C306 are wired in series with R305 and R306 as balancing resistors to make what is basically a 70uf 700v cap. Voltage there is 450V so you could use something like a 70uf 500v cap there to replace both of those. Then the extra space gained by removing that second cap leaves room for using inividual caps for C307a & b instead of a dual one.

You could just use 80uf 500v for all three caps

HOw come I did not see it????  8)

 

[Di_Sousa]

Thanks you so much,
I'm trying to find capacitors with the same value and pinout so that I don't have to modify the Fairchild unit.

I'm not allowed to drill any holes, and the owner wants  it as original as possible.

 

[Biasrocks]

I'm not allowed to drill any holes, and the owner wants  it as original as possible.

Those caps have a tolerance of +/- 20% when new, take that into consideration when finding modern equivalents.

140uf = anywhere from 112uf to 168uf.
60uf = anywhere from 48uf to 72uf.

You get the idea.

I would say that erroring to the high side is your best bet.

You can also stuff modern caps inside of the old cans to maintain the vintage look.

http://www.nmr.mgh.harvard.edu/~reese/electrolytics/#rebuild

If your looking for direct replacements, you may have to get them custom manufactured. $$$$

Mark

 

[njm]

I think Mr Sir Clive Kavan told me he had a set of the exact replacements. NOS
http://www.clivekavan.com/contact.html

 

[emrr]

Those caps have a tolerance of +/- 20% when new, take that into consideration when finding modern equivalents.

Those caps probably have a tolerance of -10%/+100%.  +/- 20% is a more modern concept.  If owner is real tweaky about minimal change, measure them.  Anything higher than spec, try to match or go slightly higher.

  Njm is right on.

  Assume pin-out means these are 4 pin plug in caps in octal sockets.  There's a well established tradition of restuffing those, and I've seen commercially restuffed ones done within the last 15 years.  Common among anyone restoring old gear.  This is definitely the piece to do it right with, pay someone to stuff the caps if you must. 

 

[emrr]

Was just looking at the manual for a GE limiter from the early 1950's, and the Sprague plug in electrolytics are -10%/+250%. 

 

[Di_Sousa]

Thank you so much,
I'm trying to find some NOS, if the contacts fail I think I will re-stuff them keeping the vintage looks and having modern caps inside, thats a really great idea.

 

[CJ]

if you want nos 670,

you need pcb cap, 4uf

toxic but everything e\was toxic in the 60's

wat up?

4 uf pcb

i have one, can not ship,

regulations against cancer

use to be pcb's on every 240 xfmr. now what

what about the gold cardboard , where do i get that?

only 220 fairchids made, money loser, so be carefull

build the 660,

is narma still alive?

 

[Di_Sousa]

I've lost my hope in getting exact replacements, so I will go the alternative routes!