AL-572 Transformer Buck-Boost connections

[Naysayer]

Hello DX community,
I'm trying to set my Plate voltage on a homebrew 4cx300 amp. I'll take any voltage from 1.5 to 2kv but I'm also having a measurement issue. I'm getting higher voltage than expected post-V. Doubler. I'm feeding 920-30 AC into it and getting about 2.5 out, which is too high. I presume my meter is reading peaks? I should have about 875vac max, is that right?

Both my plastic VOM and RCA Voltohmyst w/ HV probe display the same values in & out. How can I adjust for load when measuring pre-completion (no tubes inserted)? Transformer is from an AL572 amp (w/ buck boost) but I don't have the jumper board pictured in the Ameritron paperwork/manual (instructions premised upon the wires being assigned letters A, B, etc). I can only judge by the color of the buck boost wires (Orange, Blue, Grey).
Currently the Blue is disconnected; AC fed to: 1.) Grey and; 2.) Striped Brown & Black wires together. The solid Brown & Black wires are tied to the Orange wire. This yeilds about 930vac which is better than the 1100v I got previously. I'm still about 75vac too high. Is this as low as I can get it given my 120vac input?

neil, NYC

 

[nomadradio]

Once upon a time I had a Peter Dahl diagram from a replacement he made back in the day. Showed the buck/boost winding in more detail. I'll see if I can turn it up next time I get to work.

73

 

[Naysayer]

Once upon a time I had a Peter Dahl diagram from a replacement he made back in the day. Showed the buck/boost winding in more detail. I'll see if I can turn it up next time I get to work.

73

Thanks, I've been going by process of elimination. I have 1500vdc post-doubler which is great for where I'm at now and the next few weeks. The next bump up that I know is correct is a bit over 2600 which is too high.
Thanks again
neil

 

[Naysayer]

Thanks, I've been going by process of elimination. I have 1500vdc post-doubler which is great for where I'm at now and the next few weeks. The next bump up that I know is correct is a bit over 2600 which is too high.
Thanks again
neil

 

[Naysayer]

I stumbled upon the transformer wiring diagram for the AL572 amp this morning. The Wingfoot Amp article includes a breakdown of the Buck Boost winding too. Found it at: https://www.frostburg.edu/personal/latta/ee/wing813amp/psschematic/813platescreenschematic.html
Transformer 406-1532 same color wires and it's Ameritron from decades past.

neil
n2eye

 

[BJ radionut]

Ameritron AL80B AL811H AL572 Amplifier Trouble Shooting

 

[Naysayer]

Cleaning I found receipt with diagram from Ameritron at time of purchase (September 2012). Tab was $142 plus $30 for shipping. Sure miss those prices. A hand-drawn wiring diagram was also included which I'm posting for anyone else who may want to see how Buck Boost winding is configured.

I'm a day or 2 away from applying RF to my 4cx300a HF amp build. Have all the test voltages on the Tetrode Boards from G3SEK. Any day now.
neil, NYC