Henry RF AMPLIFIER

HV Transformer Short

 NE7X - 01/27/2012

Ned AA7A was on the EL2A VooDudes DX-Expedition in Liberia Africa where he was using an Alpha RF amplifier. During the operations the amplifier started blowing AC fuses. Ned shipped the amplifier back to his home in the USA, then after Ned's returned from the DX-Expedition he starting troubleshooting the issue.

 

The amplifier is an Alpha, however what Ned discovered applies to all RF amplifiers, even Henry amplifiers, so this is good information for everyone.

 

Having the amplifier on the workbench, every time it was powered on, "BANG" the AC main breaker would trip. To troubleshoot the issue the first thing Ned did was disconnect the +B HV connection to the RF deck from the power supply. When he powered on the amplifier again, "BANG" the AC main breaker would trip. Next Ned checked the HV diodes, good. He then removed the diodes out of the circuit, powered on the amplifier, "BANG" the AC main breaker would trip. Next Ned disconnected the secondary HV transformer wires from circuit, powered on the amplifier, nothing, the AC main breaker did not trip.

 

Ned then removed the HV transformer primary wires from the circuit and used an ohm meter to check resistance between the primary and secondary windings of the  transformer. What he found was 40 ohms between the two windings where there should be infinity ohms. The transformer had a primary to secondary short.

 

Ned found and purchased a replacement transformer, installed the transformer and now the Alpha is fully working again.

 

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