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Author Topic: 3-500Z TUBE-Which Brand Most Reliable  (Read 1255 times)
K4VDH
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Posts: 23




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« on: October 05, 2007, 08:38:17 PM »

Here I am again! I have an Ameritron AL-80B. I need to purchase a spare tube. There are so many different manufacturers! And so many different prices. Help me out here to make a wise choice! And, is there any difference between a 3-500Z and a 3-500ZG?? Thanks,
Jerry   KF4UJA  
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AB5Q
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Posts: 202




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« Reply #1 on: October 05, 2007, 10:36:10 PM »

I had good luck using RF Parts Co. 3-500ZG vacuum tubes. Carefully evaluate the need to keep a spare.  This vacuum tube is quite robust as long as you don't handle it improperly or routinely exceed its operating limits.

The difference between the Z and ZG is the (anode) plate material of construction. The 3-500Z has a tantalum plate and 3-500ZG has a graphite (amorphous carbon) plate.  Manufacturer's claim that the ZG has a slightly higher plate dissipation rating than the Z.
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N2AXZ
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Posts: 90




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« Reply #2 on: October 06, 2007, 08:00:32 AM »

I use a pair of 3-500ZGs in my homebrew linear, and they are great tubes.  I bought them from RF Parts.  However --- it is unwise to purchase a spare tube, as the 3-500ZG does not age well on the shelf.  These tubes need to be used regularly to prevent them from becoming gassy.  The getter material on the anodes needs to be heated to a bright red color every so often to scavenge any residual gas inside the tube. It is highly likely that a 3-500ZG that is kept on the shelf for a number of months without use will experience a flashover when it is placed into service.

So long as you exercise the tube periodically by making sure the anodes show color when they are being used, and don't abuse the tubes, they should function well for many years.

Good luck!

David, N2AXZ
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SSB
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Posts: 1




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« Reply #3 on: October 06, 2007, 03:22:28 PM »

If you are looking for an emergency spare then try on ebay for a low time tube for a decent price.  Then buy a new one.  I don't like to buy a new tube and let it sit for years as a spare.  I would rather buy a new one when a permanent tube is needed.  

If any 3-500z/zg is made to Eimac's original specs, then the z/zg have exactly the same electrical and mechanical characteristics.  

There is no 3-600.. tube.

Alex....
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K6AER
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Posts: 3520




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« Reply #4 on: October 07, 2007, 10:51:51 AM »

I believe all the variations of the 3-500 tubes Z’s and ZG’s are made in China. Pick a distributor who has a solid warranty policy. I have had excellent results with Penta Labs, RF Parts and Taylor tubes. All replaced bad tubes with infant mortality problems.
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K4VDH
Member

Posts: 23




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« Reply #5 on: October 26, 2007, 06:44:22 AM »

I sincerely appreciate all of your input on this subject. As always, there are so many of you out there who share your knowledge, experience, and expertise so very graciously!!! Again, thank you,          73
Jerry
KF4UJA
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