Palomar 300a RF Deck Swap

[kayej]

I have two Palomar 300A amps. One is for the lower voltage transformer and the other is for the higher voltage transformer. I have the lower voltage transformer and wondering if I can convert the higher voltage RF deck to run on the lower voltage transformer.

 

[nomadradio]

Yep. Only difference is the rectifier wiring. The high-voltage version tends to have a rectangular epoxy block with four wire leads, a "full wave bridge rectifier" device. The low-voltage version has two series pairs of 3-Amp rectifier diodes, typically 1N5405 or 1N5406. We use the 1000-Volt version 1N5408. In the forty-plus years since it was built this has become the generic device of this sort. The slightly-lower voltage versions were a bit cheaper than the 1000-Volt number decades ago. Now the 1000-Volt part is just, plain cheap. If you simply copy the layout and wire-jumper setup from the one unit to the other, this should keep you out of trouble. Just make sure you sever the foil traces that the factory cut through on the low-voltage version of that center circuit board and duplicate the bare-wire jumper layout.

73

 

[kayej]

Yep. Only difference is the rectifier wiring. The high-voltage version tends to have a rectangular epoxy block with four wire leads, a "full wave bridge rectifier" device. The low-voltage version has two series pairs of 3-Amp rectifier diodes, typically 1N5405 or 1N5406. We use the 1000-Volt version 1N5408. In the forty-plus years since it was built this has become the generic device of this sort. The slightly-lower voltage versions were a bit cheaper than the 1000-Volt number decades ago. Now the 1000-Volt part is just, plain cheap. If you simply copy the layout and wire-jumper setup from the one unit to the other, this should keep you out of trouble. Just make sure you sever the foil traces that the factory cut through on the low-voltage version of that center circuit board and duplicate the bare-wire jumper layout.

73

After removing both RF deck pc boards they are in fact identical. Same part number and foil layout. There were two jumper wires on the high voltage foil side (which I removed) and other than that the holes for the rectifier diodes were there and all other components remain pretty much the same. Re-routed the wire-jumper layout and will test for smoke soon. 73

 

[nomadradio]

Cool! Couldn't remember if the board was laid out for the bridge and modified for the doubler, or laid out for the doubler and modified for the bridge.

Either way, if you copy the setup correctly it will work, all other things being equal.

73