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Author Topic: 3-500z questions  (Read 22924 times)
KA8WEP
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Posts: 23




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« on: September 06, 2013, 01:52:05 PM »

I have a pair of 3-500Z tubes that are of the 3-500C variety.  Today I cracked the glass at the anode cap of one of the tubes.  It makes sense to replace the tubes as a matched set.  So, what do I do with the old tube?  It is suppose to have low hours.  The tubes came in my recently purchased Henry 2KD Classic amp.  Do I keep it as a spare?  What might be a reasonable price to sell it used?  Do I mount it with a 5 volt 15 amp filament transformer & use it as a space heater/night light?  (That's the only humor I can find for now.)
Thanks for your comments
Joe KA8WEP
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W7VO
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Posts: 192


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« Reply #1 on: September 06, 2013, 02:22:21 PM »

There is no harm in keeping it as a spare, except that the 3-500s like to be de-gassed every so often through drawing plate current, so you would have to stick it back in the amp and use it for a while every year or so.

I had a similar problem with my dual 3-500Z amp, (one tube shorted out), so I bought a new matched set from RF Parts and ended up donating the leftover "still good" tube to a friend of mine that needed a tube to get his his amp running.

Used 3-500s go from anywhere on e-Bay from $50 to $200. Bascially they are worth what you  can get for them. New Old Stock Eimacs seem to sell for the most, as some people want only the "Made in USA" name brand in their equipment.

I have had great service from my Chinese made RF parts 3-500Z tubes.

Good luck!

73;

Mike, W7VO
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W1QJ
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Posts: 1444




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« Reply #2 on: September 06, 2013, 03:22:39 PM »

I would say if the glass is cracked the tube is NFG!!!!!  It is good for a ornament and that is about it.
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WB2WIK
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Posts: 20561




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« Reply #3 on: September 06, 2013, 06:25:37 PM »

What's a 3-500C?

Do you mean 3-500Z?
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AH6RR
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Posts: 803




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« Reply #4 on: September 06, 2013, 07:04:08 PM »

What's a 3-500C?

Do you mean 3-500Z?

Steve it is a Chinese no name 3-500ZG see this site.
http://store03.prostores.com/servlet/henryradio/the-413/New-3-dsh-500C-Glass-Transmitting/Detail

Roland AH6RR
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K5RT
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Posts: 132




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« Reply #5 on: September 07, 2013, 05:07:48 AM »

Unless your amplifier has a means to measure current through each tube and adjustments to balance the current, it makes no sense to buy "matched tubes" for amateur radio RF power amplifiers.

Save your money.

I suggest buying a pair, just so the hours of use are the same, and keep the tube that is in your amp as a spare.

Vy 73
Paul
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W9GB
Member

Posts: 2613




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« Reply #6 on: September 07, 2013, 06:09:26 AM »

RF Concepts / Alpha TUBES
Tube, 3-500ZG, Glass Triode, Graphite Anode
We've been inundated with orders.  
The Interval from order to receipt of product is now approximately two weeks.


3-500ZG Tubes, Glass Triode, Graphite Anode,
Part Number VTU-3-500ZG-MP2
http://www.rfconcepts.com/PRODUCTS/tubes
$278.00 USD for Matched pair; $135.00 for Single tube

You can keep single tube as spare, re-sale price of
a used single tube has dropped due to Alpha Tubes current pricing.

DO NOT expect these low prices to last, if you need a 3-500ZG, now is time to buy.
« Last Edit: September 07, 2013, 06:23:12 AM by W9GB » Logged
WB4SPT
Member

Posts: 138




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« Reply #7 on: September 07, 2013, 06:16:44 AM »

I have a pair of 3-500Z tubes that are of the 3-500C variety.  Today I cracked the glass at the anode cap of one of the tubes.  It makes sense to replace the tubes as a matched set.  So, what do I do with the old tube?  It is suppose to have low hours.  The tubes came in my recently purchased Henry 2KD Classic amp.  Do I keep it as a spare?  What might be a reasonable price to sell it used?  Do I mount it with a 5 volt 15 amp filament transformer & use it as a space heater/night light?  (That's the only humor I can find for now.)
Thanks for your comments
Joe KA8WEP

Sell it.  there are folks with single tube amps.
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K4RVN
Member

Posts: 760




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« Reply #8 on: September 07, 2013, 08:52:19 AM »

I have been running a 3-500C for several years now in my AL 80A. It is a graphite 3-500 made in China and has been a great tube. I bought mine from ESRC in Florida and it had a one year guarantee. It was satisfactory in every respect putting out expected power. New ones are less than 170 bucks. I would sell it as rotating tubes in an amp is trouble and could be hazardous.
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WB6WSQ
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Posts: 16




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« Reply #9 on: September 07, 2013, 10:07:40 AM »

If the one tube left is in good working condition, I would be possibly be interested in buying it.  Please contact me if you decide to do so and give me a price.  Thank you.
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G3RZP
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Posts: 4447




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« Reply #10 on: September 07, 2013, 10:48:59 AM »

Why is rotating tubes hazardous if you take due precautions regarding voltage, breaking etc?
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VE1IDX
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Posts: 144




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« Reply #11 on: September 07, 2013, 07:56:04 PM »

I would say if the glass is cracked the tube is NFG!!!!!  It is good for a ornament and that is about it.

He was asking what to do with the OTHER tube that is still good.
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W1QJ
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Posts: 1444




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« Reply #12 on: September 08, 2013, 02:49:22 AM »

I would say if the glass is cracked the tube is NFG!!!!!  It is good for a ornament and that is about it.

He was asking what to do with the OTHER tube that is still good.

Now why did I think he was talking about the broken tube?  DUH......
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K4RVN
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Posts: 760




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« Reply #13 on: September 09, 2013, 01:52:27 PM »

 To G3RZP. To err is human. Did not say it is hazardous, said it could be. Are you saying it cannot be?  I agree with you, taking the proper precautions , it should not be. I would still advise the thread starter to sell the tube, forget rotating the two matched tubes. Just my opinion from experience with 3-500 tubes that have lasted more than 15 years.
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G3RZP
Member

Posts: 4447




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« Reply #14 on: September 10, 2013, 12:57:43 AM »

If you never learn the proper procedure to change tubes and use it, it can be even more hazardous. Tubes left on the shelf do leak and sometimes, too much to be recoverable. Classic examples are wartime 826, 829B and 832 tubes. They were likely not to have a long life anyway, and most of them are extremely soft by now. People are finding that problem with 3-500Z that have been on the shelf for a long time.
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