Acom amps also use this valve and its bigger brother 1500. The circuits are downloadable.
There is a lot if protection built in.
If you find a willing volunteer, with said amp, you could try it in that.
I have one here, and would happily swap it over if you lived closer.
I have not seen valve testers, that take this series of valves.
If you have an Acom dealer near you, get in touch.
KR
Andrew
On January 3, 2026, at 16:46, Jim Shorney via groups.io <jimNU0C=gmail.com@groups.io> wrote:
Interesting. Full disclosure, I have no experience with this amp but I did peruse the schematics. I do have some experience with tetrodes (NCL-2000). There is a lot going in there. Are the proper voltages actually making it to the tube sockets in TX? Does the step-start function normally with no tubes installed? It is possible you have a high voltage fault in one of the tubes. It might be worthwhile to test each tube by itself in the amp with airflow from the open socket blocked off.There is an active Alpha group on Facebook that may be able to provide some guidance.On Sat, 03 Jan 2026 08:19:30 -0800"David Mitchell via groups.io" <wb2pjh=gmail.com@groups.io> wrote:Hi Jim,I've got a fair amount of technical experience and checked all the voltages at all the test points and all were FB. The Penta 4CX1000A subs that Alpha used were notorious for screen grids shorting out, but finding nothing when testing each tube with my VOM, need to find someone reputable who can test these tubes in a proper test fixture to see if they're failing under load.I neglected to add that the two 20 amp main fuses did NOT blow, only the 2A fuse that runs the control circuitry and CPU.Thanks,Dave WB2PJH--73-JimNU0C
