The AM Forum

Check this out:

http://www.electronics-lab.com/projects/tubes/007/index.html

The design is garbage. It is the wirte up that is scary.

note in the write up, "Don't exceed the power limit. The limit is the place what begins a small arching  on  tube'g1. And you may hear a small ugly sound. Don't wait, decrease the power immediately."

really poor design ... disgusting!

A real Rocket Surgeon.

WARNING!  DON'T BUILT THIS DEVICE, IF YOU ARE NOT AUTHORIZED,  OR QUALIFIED PERSON,  ALL DANGERS

mo-ron engineering co. love that gain control

Now if it were done properly, is the 4x150a any good at all run in GG?

you may hear a small ugly sound..

The 4x150 can be used in GG with screen and control grounded and drive applied to the cathode as shown, but the grids can't take any power so they blow up frequently, and therefore it is not usually done. The control grid is rated 2 watts, screen 12 watts. If I were going to attempt it, I'd connect the little control grid to the cathode (or to the screen via a 10K 5W non inductive resistor) and ground the screen, and meter the screen current. Even so, with the grid and cathode grounded, it needs 300V or so on the screen to make the high plate current at least according to the datasheets, but the screen current is very slight. Therefore any mismatch or mis-tuning could cause too much drive to be dissipated in the screen grid and burn it up, causing a short from anode to screen. That's when the ugly sound is made. If you have the original 4X150 with the glass, you might get to see the sparks fly inside till the HV fuse blows!

The tube can be run GG AB1 with the normal screen and bias voltages applied, and drive to the cathode (which is at negative voltage). That is what Eimac reccommends.

with respect to the write up, the guy is Scandinavian (swedish?) and english is probably wobbly for him as it's not his primary language. So he should get a pass on that.

the cb lin-yar is still junk.  ::)

Which is a good reason for this NOT to be posted in the Technical section! ;D

I'm with Huz ... that's all we need Chicken Band junk and somebody gets the shitchz shocked out of em.

Not good...

That was a hint... save the derision of CBers for the QSO section.

I have no issues with the language, an arc in a nice tube like that is an ugly sound and the language use was correct. My points were technical regarding the use of the tube, or attempted to be so. No problem with the range over which the amp can be tuned either. I think the comments here have shown that the prevailing opinions, of those respected members who work with the kind of tube in various applications, consider the circuit to be ill-advised. That's a valid point and should be made when such a circuit is presented for review. 8-)