I have used thousands of 3-500zg penta tubes in customers pa’s. Not once have I had an issue or have any customers reported an issue.
But I was putting new tubes into pa’s that I had gone through and made right. You can’t just plug tubes into a pa that could have any issue.
The 572b tubes have issues now and then, but that’s a factory issue. Penta does an excellent job pre testing, but sometimes the 572b tube can still have an issue.
Why I have the customer drop ship the tubes to me to test in their amp prior to shipping to them. Rather it happen here and not at their qth.
If you have a problem with a penta tube they just replace it. Unless obvious abuse. They do t make you Jim through hoops.
73
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On 2024-05-18 13:40, Jim VE7RF wrote:
On Sat, May 18, 2024 at 09:11 PM, W7WRX wrote:
The best appears to be from CTR engineering. There are two plants
that make 3-500 tubes in china. These are the best of the two. They
are fully Hi pot tested and guaranteed. Mine have been rock solid.
811A 572B 3-500Z Vacuum Tubes For Sale - CTR Engineering, Inc
(ctrengineeringinc.com) [1]
I have had very bad luck with Penta. Over and over failed or gassy
tubes out of the box. I ended up just getting a refund, They were
nice to deal with, no trouble. I was told they likely just got a
bad batch. Maybe they are better now. This was a year or two ago.
CTR gets his 3-500Z's from the exact same chinese factory as
Pentalabs....and also RF parts. These are the ones with the white
bases. Factory #2 is junk, with a 70% failure rate....and those all
have brown bases.
Even tubes from the good factory all just 1 kv hi-pot test between
grid and cathode. (Eimac's are typ 5 kv from grid to cathode...and 16
kv from anode to grid). The good chinese tubes have higher grid to
cathode C vs eimac. It appears the chinese tubes have spaced the
grid closer to the cathode vs eimac.
A month ago, everybody and their dog got a severe bad batch of chinese
572B's..... like the entire production was screwed up...... but the
572B is another, all together scenario.
Links:
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[1]
[2] /g/ham-amplifiers/message/40384
[3] /mt/106173952/8135091
[4] /g/ham-amplifiers/post
[5] /g/ham-amplifiers/editsub/8135091
[6] /g/ham-amplifiers/leave/12941173/8135091/773995006/xyzzy
