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 Post subject: how to test Eimac 4PR60C 8252w tubes
PostPosted: Apr Mon 20, 2009 8:41 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 629
Location: barre, vt usa
i got a couple eimac 4PR60C transmitting type tubes. i have no way to test them i would like to see if at least the firmaments are intact does anyone know which pins i use to check that.


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PostPosted: Apr Mon 20, 2009 8:51 pm 
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Location: Mt. Airy, Maryland
SHould be almost the same as a 4-65 which should be googlable.


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 Post subject:
PostPosted: Apr Mon 20, 2009 9:16 pm 
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Joined: Oct Sat 20, 2007 3:36 am
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Location: Southern NH, 03076
There should be continuity between only two base pins which are the filament.

The tube is not a pulse 4-65A, rather a replacement for the 715C and 5D21. They dont make good RF linear tubes.

Carl


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 Post subject: Re: how to test Eimac 4PR60C 8252w tubes
PostPosted: Apr Wed 13, 2011 3:18 pm 
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Joined: Apr Wed 13, 2011 3:14 pm
Posts: 1
Hello,
I am in need of some new old stock 4PR60C
Do you have any for sale??
Thanks
Dick Gross
352 592 7800


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 Post subject:
PostPosted: Apr Wed 13, 2011 9:23 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3680
Location: Monterey California USA
I think you need a fundamentalist preacher to check the firmaments.

A VOM will suffice for the filaments. :twisted:

_________________
WB6NVH
California Highway Patrol Radio
Bell System Mobile Telephone History
http://www.wb6nvh.com


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 Post subject:
PostPosted: Apr Thu 14, 2011 1:12 pm 
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Joined: May Sat 22, 2010 4:42 pm
Posts: 2987
Those tubes were designed to switch 17,500 volts at 15 amps! ( but only for one microsecond, every millisecond )

You're going to have a really hard time testing them. Do you have a 17KV power supply, capable of 15 amps? Do you have a grid pulser, capable of 1200 volt at 3 amp pulses?

Marvellous tubes, with gold-plated grids and all, but really hard to test or use for anything.


Last edited by Ancient_Hacker on Apr Thu 14, 2011 1:17 pm, edited 1 time in total.

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 Post subject:
PostPosted: Apr Thu 14, 2011 1:16 pm 
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Joined: May Sat 22, 2010 4:42 pm
Posts: 2987
>I am in need of some new old stock 4PR60C
>Do you have any for sale??


There are quite a few 715's for sale on eBay. They're the same tube I think. There are also 4PR60's for sale on eBay but they guy wants 189 Euros for each. But the ad says they have a large quantity of them, so they're likely to be talk-downable.

Watcha doing, rebuilding a WW2 radar?


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 Post subject:
PostPosted: Apr Fri 15, 2011 6:31 am 
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Joined: Oct Sun 11, 2009 10:06 am
Posts: 1441
Location: British Columbia
The only way to test them really, is to load them and take readings.
Here is an 826 that I'm de-gassing before service. Turning the plates red to orange for a few hours usually does the trick. (The plate de-gasses the tube.) These tubes will work fine in HF service but will ionize powder blue in VHF if not heated for a good while. I have found this procedure brings back maybe 50% of the 826's I have tried. The same can be done for 4-65's. You will need a variable bias and high voltage supply though.

Image

Here is the little "foot warmer" they reside in. :) 65 Watts of screaming power :lol: AM.... 2 meters of course.


Image


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 Post subject:
PostPosted: Apr Fri 15, 2011 3:19 pm 
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Joined: Oct Sat 20, 2007 3:36 am
Posts: 14393
Location: Southern NH, 03076
Ive been regettering tubes such as the 100TH, 250TH, 304TL, 3-500Z, 4-400A, 4-1000A, 6C21, and others in a similar way.

Since gas can ignite and sustain a destructive plasma arc the HV must be fairly low, I run 800-900V variac controlled.

The bias is also on a variac and in order to get orange anodes it must be a positive polarity on many tube types. A chassis with several different sockets was built with forced air chimney cooling using Eimac chimneys or large Coleman glass as needed.

Some tubes wont be completely restored and others have required 12-24 hours which really heats the basement and spins the meter but considering the price of tubes its been worth it. Some such as the 3-500Z that still showed a bit of gas at 3500V in an amp are fine at 2500V in another amp such as a SB-220. Customers are happy when I save them almost $400 for a pair of new ones and I stress that they have to run them hard at least monthly to remain good.

Carl


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 Post subject:
PostPosted: Apr Fri 15, 2011 3:25 pm 
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Joined: May Sat 22, 2010 4:42 pm
Posts: 2987
Note that you can reduce gas in some tubes by running the plates really hot, but it has the opposite effect on others!

It depends on the kind of plate material-- some like tantalum do absorb and bond to gases at high temps, but others like plain old nickel or steel release gas.

Similarly, you can restore emission on some tubes by running the filament really hot, but this hurts other tubes.

The ones that are helped are the ones with pure tungsten or thoriated tungsten filaments.

But if the filament or cathode is oxide-coated, things are much iffyer-- you might burn off some contamination off the oxide, OR you might evaporate some of the oxide and redeposit it on the grids, which is a bad thing.


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