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On Sat, May 18, 2024 at 11:52 AM, Joe - W7RKN wrote:

It appears I have a shorted 3-500Z tube in my AL-82 amplifier.

It also appears that right now the 3-500Z or ZG tubes are unobtainium.

...

3-500's are nowhere near the "unobtanium" status.? Getting expensive now? Yes... but still quite readily available. While the original Eimac's are getting harder & harder to find (and those that are available are quite old), the Chinese ones are fairly plentiful.

Not sure about the reliability/longevity of the Penta-brand tubes. They've been around a while, but the company itself is a bit checkered (their "facilities" in the greater LA area have changed locations many times in the last few years). The same "company" (location) also sells the "Machlett" brand (although they are also ChiCom).? I also now see the "Amperex" brand being sold (eBay), but they too are no longer a US-made tube... "assembled in China".

Henry Radio in Los Angeles sells a ChiCom version (a 3-500C) for a fair price, and it comes with a one-year "guarantee".? I've been running a pair of these in a couple different amps (swapping them between a Drake L-4B, and a Henry 2-KD Classic) for a couple of years, without any issues.

They can be ordered direct from Henry radio, HERE: https://henry-radio.myshopify.com/collections/amplifier-parts/products/new-greenstone-3-500c-glass-transmitting-tube-guaranteed

I have no affiliation nor interest with them, just a satisfied customer (I own a few Henry's!)

Good luck!

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73,