The AL-80B? does not use real deal plate block caps, but a pair of disc caps.? ?The disc caps are not RF rated either.? ? Any plate block cap needs to have enough pf? so it's reactance (XC)? is 5% ( or less) at 1.8 mhz.? There is barely any RF current flowing through a plate blocker on 160m...... but the current through em progressively increases as freq increases.

As a reminder: I just had to replace all three of the 2200 pF/6 kV disc plate blocking caps on my Alpha 8410:

But there was no smell when these blew; they just shorted the high voltage, causing a plate current fault which, fortunately, shut down my amp before any catastrophic damage occurred. These caps apparently shorted out one by one, cracking independently as each broke down from the high power and voltage (plate voltage in my 8410 is just under 2900VDC). The total capacitance was originally 3 x 2200 pF = 6600 pF; I replaced them with a set of six 1000 pF/10 kV discs I bought a few years back, but unfortunately, I didn't think to take a pic of the installation. However, note that the way the caps are arranged above, the "outside" of one cap is directly adjacent to the "inside" of another, which means you have the full plate voltage between the capacitors. To make certain there would be no flashover between capacitors, I therefore spread the replacement caps out evenly but kept the leads all twisted together as shown above and as short as possible so as to minimize any additional inductance. So far, so good, on my Alpha 8410, which has a pair of 4CX1000As in parallel, far more than what a pair of 3-500s will do.

>Correct component would be a pair of HEC? 500 pf HT-50/58,? 7.5 kv? ceramic doorknob caps in parallel .?

> You can buy those cheap, directly from mfj / Ameritron.? That's what's used in the Ameritron?

>AL-1500 / AL-1200 / AL-82.

If I was not in a hurry to get my Alpha back on the air before I missed out on another pileup, I would have ordered HECs instead of using the disc ceramic caps. In the olden days, pre-COVID and pre-Ukraine, you could buy doorknobs of all sizes and voltages from Russia or even ND2X at dirt-cheap prices and receive them within several weeks (with all sorts of strange and exotic Russian stamps on the boxes). Nowadays, that's neither so easy nor cheap? 8-(

..... all 30 of em test to 15 kv? ( which is the limit of my hi-pot tester that I bought last year from CTR engineering).

High voltage hi-potters are very easy to make and relatively-cheap to boot; just search epay for 10+ kV variable power supplies, perhaps using search terms such as "neon sign power supply", "Tesla coil power supply", or the like. No longer do you need to spend el mucho buxos for shipping a heavy, old, surplus neon sign transformer; now, the Chinese are selling small, adjustable high voltage power supplies, completely self-contained on a single PC board. I bought one, which consists of a small PC board with the circuit on it and an onboard transformer, for about $40 a couple years ago; it operates from 12 volts DC. I tested and evaluated the board, then designed and built my own hi-potter. It's fully adjustable from a few hundred volts to over 10 kV, and my hi-potter includes both a voltmeter as well as a leakage current meter, both mounted on and behind plexiglass to prevent me from touching them while in operation. It actually goes to at least 11 kV and will provide a few tens of microamperes current, which is as much as you want to have arcing around within a leaking tube, and far more than enough to tell whether it's good or not. It's such a small and cute little gadget that it's difficult to remember that it's more than capable of killing me if I'm not careful with it!

73,

Steve K0XP