Service manual

Wells-Garnder Color Vector Monitor Guide
Page 71 of 73
HV Board Notes.
On the HV circuit board there are two diodes D901 and D902, which the Atari TM-183 manual
does not identify. They are just referred to as "silicon diodes". Apparently the replacement for
these is NTE558 – a 1500V general-purpose silicon rectifier in a DO41 package. Also be careful
installing the zener diode ZD902. Apparently some people mistakenly install this at D902 instead
of ZD902. The monitor will not work if you make this mistake!
Please be careful if you decide to replace R918 (25K potentiometer) in the HV unit. R918 needs
to start out adjusted to an in-circuit resistance of 5.5K when testing the upper two contacts of the
three. This is the average of the normal adjustment range, which is always between 5K and 6K.
If you have the potentiometer maxed out you will probably damage your unit when you turn it
on.
R915 on later revisions of the HV board is the same as R908 (1K Ohm, 1/4W resistor).
NECK BOARD
The Neck Board is the PCB attached to the neck of the monitor tube.
Zanen Neck Board Parts
Location Part Number
C503 33 mfd 250v axial capacitor