Ameritron AL-80B

most icoms do not drive well. the automatic swr saftey circuit makes it throttle back. with a eimac tube he should see 1000w to 1200w wired for 220v. now if it has the 3500zg good luck getting 700w out. they are very hard to drive to full output. i sugest he wire the amp for 220v and drive with 100w. that is what the amp and tube is designed to do.

Carey

AL-80B

3-500Z 5.0 14.6 130 0.5 20 4.0 0.4 3.0 0.4 0.74 14.0 110 TUBE SPECS.From RF Parts.

The AL80B needs at least 80 watts drive for specified output.
The Plate/Load controls are not correctly adjusted/the band input coil/s need to
be adjusted,maybee the alc control is set to full ,very high swr,this amp
will not operate well into a swr of 3:1:1 or higher-the risk of arching/burnig up
the band switch is very high if not loaded correctly.

Paul

'Eimac' hasn't made a 'glass' tube in something like 15 years. Know what the shelf-life is for the average 'glass' tube? (I really doubt if I'd buy a 3-500 with 'Eimac's name on it now.) I can remember when 'Eimac' announced they were dropping the 'glass' lines, there were rushes to get them, the retail prices did NOT stay the same. How many people do you think hoarded warehouses full of 'Eimac's?
- 'Doc


(And if you ever saw 1200 watts out of a single 3-500, it definitely was not driven to 'spec'. Or for very long.)

W5LZ said:

(And if you ever saw 1200 watts out of a single 3-500, it definitely was not driven to 'spec'. Or for very long.)

Click to expand...

3-500z or 3-500zg?

...either.

1,100 maybe 1,200 is doable from a 3-500zg

'Do-able', but not likely at all with commercially made equipment. The primary reason being that the power supply just isn't 'big' enough. I know of one commercially made (fairly common) 2 tube amplifier using 3-500's that may get close to that per tube. It definitely is not cheap. The AL-80(A or B) won't do it without modification.
- 'Doc

I gotcha, you're not questioning the tube, but the amp.

... not quite, 'got', yet.

I am questioning the amplifier, but only because it isn't normally capable of providing the necessary requirements to make that tube produce as described. The one amplifier that I think would furnish the required voltage/current, and which is a commercially produced amplifier, would have to be operated with only half of it's normal tube compliment, which in effect, means the amplifier has been modified. Not drastically, but still not operated as it was designed to do, which also means that the tube wasn't being pushed beyond it's specification.
Of course, if you are willing to trade reliability for 'higher' performance, are only interested in 'bigger numbers' instead of usefulness, then 'pushing' a 3-500(Z or ZG) is certainly one way of doing it. But then you are also going to be working that tube out of it's usable/practical operating ranges for maybe a gain of roughly 20%, which won't even be noticeable except in loss of quality of signal. If that suits you, then have at it! I think I'd also start a 'nest egg' to help pay for that tube's replacement, and probably other things in that amplifier.
- 'Doc

(Ask me how I know about that and what it has to do with an AL-80A or AL-80B. I've have/had both of those amplifiers for quite some time. Did almost every 'trick' for more output from a single 3-500 tube I've ever heard of, and some of them actually do work. But most of them that 'stress' the amplifier/tube are just not worth the trouble and expense. You can 'push' anything, but is it really worth it? It's much better to 'loaf' along than run it at 'max'. Ain't getting as much as you wanted/expected? Get a bigger one! Which is the point of this thread, I think.)