Radar CRT anode voltage booster, 100 Vac 800 Hz

[Paolo Cravero]

Hello.
I am trying to revive a radar display unit from early 1970's that mounts a 7ABP7A CRT. The filament tests good. I've sorted out all voltages and I need to provide 100VAC to generate the required 7kV on the anode (5kV minimum). Thing is ... it's 100 VAC at 800 Hz, because boats back then used 800 Hz. I think they settled to 400 Hz afterwards and I have no idea what they run off now.

I attach the diagram of the voltage booster inside the display.

Considering the totem of voltages I need to feed to the unit, I will have -150, +10, +20, +80-100, +350 VDC readily available as a source for 100 VAC 800 Hz.

I am looking for a simple circuit arrangment to produce the required AC (or alike) and I hope neonixie wizards can help.

Thank you!
Paolo

PS: if everything works, the next challenge will be 80Vac at 30Hz for the deflection coil motor assembly.

[bogdan paduraru]

Paolo

For an ad hoc solution  I recomand to use my setup for the EL displays

A Chinese TDA2030 power amplifier, its output conected to a secondary of power transformer ( primary 220VAC / 4 to 8 /10VAC secondary) 

Input of tda amplifier conected to a signal generator 

If need more details, contact me privately 

Bogdan 

On 3 Mar 2026, at 11:46, Paolo Cravero <paolo....@gmail.com> wrote:



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[Paolo Cravero]

Hello Bodgan.

I followed your path and I bought a TDA2030A module. I was surprised to measure that AC transformers do not become too lossy at 800 Hz, at least unloaded.

In order to get 100Vac @800 Hz I had to feed 12W input to the poor TDA2030. It got really hot, but I noticed that at 8W input the whole setup would work too and stay within an acceptable temperature. 

In the attached picture, heavily underexposed, I am moving the "center" knob to create the persistent trace on the CRT.

I am now moving forward to get the radial deflection to work, then to display something meaningful. But first I need to build a CRT power supply to free up those in the lab.

Thank you for the tip!

Paolo