8640b Power Supply Repair
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8640b Power Supply Repair Filed in 8640b on Nov.02, 2016 Early in the repair cycle of the 8640b, when I had just finished the brass gearset installation, I ran into a problem during the first power up after reinstallation of the deviation and range module. When I powered up the unit, I saw a flash from under the main board, and the unit came up with no led frequency display. I suspected that I had lost one of the power supplies. After finding the manual for the generator, I saw that there were 3 power supply boards with led indicators on them to indicate the various voltages were being generated. 5v indicator I found that the 5v indicator was not lit. Looking at the schematic of the board, I tracked down that it should have some relatively high voltage DC coming in on pins 15 and 9 of the module ( or pins 1 & 2 of the rectifier module). It had nothing coming in. I saw in the schematic that it was fed from a rectifier board. Since this had easy access, I pulled t