Troubleshooting guide

Cinematronics Vector Monitor Repair Guide v.1.0
Page 21 of 53
Connecting the Electrohome supply to the Vectorbeam monitor is trivial. The drawback is that new
mounting holes will need to be drilled in the monitor's metal side panel. The new cable needed is
simple enough to show below. The only caution here is that the wire for the +400V connection
MUST have insulation rated for 600 Volts or greater.
Cinematronics Electrohome
Deflection board HV Power Supply
PCB connector Connector P900
+90V 1 <----------------------------<5
2 > [ not connected ]
+400V 3 >----------------------------<1
+25V 4 >----------------------------<8
GND 5 >----------------------------<7
6 > [ not connected ]
Chassis --------------------------------------<P901-9 Aquadag GND
Before connecting the new supply, check the voltage level of the +25V supply. The Electrohome
EHT supply was designed to operate over an input voltage range of +23VDC to +38VDC but it's
better to be sure. When you do power up the Hi-V supply you will probably need to adjust the
anode voltage. The FOCUS voltage will also need to be adjusted to +400VDC. Its adjustable limits
are -140V to +400V so definitely check it.
RESULTS:
The CATHODE output voltage (and the FIXED 400V, P900-3) track the adjustment potentiometer
so when you adjust the anode voltage, the 90V & 400V also change. This is why I chose to use the
variable FOCUS output. I have my supply set so that I get 116V, 400V and 15.4kV. If the anode
voltage is set lower than 15kV the picture expands past the edges of the tube due to the slower
electrons being deflected for a longer time than they should. The 116V is almost 30% higher than
what the intensity circuit normally expects but the 2N5550 transistors, which do the level
switching, can handle this without any problems.
I have my supply running at its maximum output but according to it's specs it should be able to
handle it. So far, I've only had the machine running for a few hours and it seems fine. Only time
will tell whether this replacement will hold up.