My first EICO 751 came with the EICO 753, both were factory assembled items. When
the power supply got here, it had the distinct "Essence of ohm smell" indicating that the
unit had suffered a short of some type causing overheating of the resistors.

The schematic is here.

Opening the unit up revealed that both of the 15K 20 watt resistors were open, and
charred. Fortunately this didn't short, as that would have taken out the HV choke L1.
In the repair process I checked the filter caps C1 thru C4, found them to be leaky so
I replaced them with 4- 60uF at 450 VDC capacitors.

I also found R3 a 240 ohm 10 watt resistor, was open, after replacing it I was ready to
hook the unit to a variac and "bench test it, in stand alone mode. I checked the fuse, it
was a 10 amp 120 VAC type (wrong, and after putting in a 5 AMP slow blow type. I
plugged the unit into the bench variac and jumpered pins 1 and 8 to turn on the power
supply. Since this unit is all solid state I simply brought the input up slowly, while monitoring
the output HV line across pin 6 (HV+) and pin 4 (GND). Watching the meter rise with the
AC input increase up to 117 VAC.

Please note, here that the AC input specs for the unit is 117, there is no mention on the parts
list, so in that case I decided to always use a variac (10Amp Max) and set the loaded voltage
to 115 VAC. Also please note that if you are using this supply in the "Base Station" mode
That if you stress it, the case gets warm. This is not a problem if running in CW or SSB
mode, however AM mode and this supply will get warm if you are "Long-Winded".

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