Need 2kv regulated circuit for dead CRO

[oldtech2000]

Hi guys,The 2kv forward converter,which provides the EHT
in my CRO, has died.The ferrite EHT transformer has a shorted turn and spares are not avaliable.Fairly simple circuit with 3 transistors and some feedback from the secondary for regulation.Probably supplies about 4mA of current and runs around 25Khz.
Do not think i can rewind the transformer, so i am interested in any similar circuit,using an E core that i could adapt.Thought of using a circuit for a laser (from the net) but they appear to have little if any regulation and run over large voltage ranges depending on load.
All suggestions greatly appreciated...Regards...George

 

[ericgibbs]

Hi guys,The 2kv forward converter,which provides the EHT
in my CRO, has died.The ferrite EHT transformer has a shorted turn and spares are not avaliable.Fairly simple circuit with 3 transistors and some feedback from the secondary for regulation.Probably supplies about 4mA of current and runs around 25Khz.
Do not think i can rewind the transformer, so i am interested in any similar circuit,using an E core that i could adapt.Thought of using a circuit for a laser (from the net) but they appear to have little if any regulation and run over large voltage ranges depending on load.
All suggestions greatly appreciated...Regards...George

hi,
You could consider a voltage doupler/tripler using a small mains transformer.
With good smoothing and some regulation it will give the 2KV at 4mA.
If you go this route, keep the transformer itself away or screened from the CRT.

Try Google for, Mains Voltage Doublers, Triplers

**broken link removed**

Voltage multiplier:
http://www.rmcybernetics.com/science/high_voltage/voltage_mult.htm

 

[oldtech2000]

Hi Eric,Thought of using a mains transformer but the circuit actually uses a trippler,feed by the 2kv winding, to develop around 6Kv for the final anode.....this would need large capacitors at mains frequencies so i gave the idea up.Thanks for the reply...George