We come across a lot of old electronic gear with a bad HV transformer or filter
choke. Invariably, this was caused by a shorted filter capacitor that overloaded the
transformer or choke before the rig's power line fuse could blow.
This damage could have been avoided by installing a fuse in the high voltage line. This is a standard operating procedure for us. In the event of a shorted HV line, this fuse will blow before the main power line fuse. Typically, we use a ¼ to ½ amp 3AG style fuse.
The easiest place to insert the fuse is the power transformer's high voltage winding center tap, which is typically at ground potential. We simply lift the ground, connect it to one side of the fuse holder, then ground the other side. By using hot melt glue to fasten the fuse holder, the modification is completely reversible with no modification to the equipment.
Note that this fuse is not a safety fuse. It's purpose is to save the transformer and/or choke from a HV short. It does not take the place of a properly spec'd power line fuse.
This damage could have been avoided by installing a fuse in the high voltage line. This is a standard operating procedure for us. In the event of a shorted HV line, this fuse will blow before the main power line fuse. Typically, we use a ¼ to ½ amp 3AG style fuse.
The easiest place to insert the fuse is the power transformer's high voltage winding center tap, which is typically at ground potential. We simply lift the ground, connect it to one side of the fuse holder, then ground the other side. By using hot melt glue to fasten the fuse holder, the modification is completely reversible with no modification to the equipment.
Note that this fuse is not a safety fuse. It's purpose is to save the transformer and/or choke from a HV short. It does not take the place of a properly spec'd power line fuse.
Click on any picture to enlarge it
HV fuse installed in the HRO-60
to protect the receiver's
transformer and filter choke.