Service manual

Wells-Garnder Color Vector Monitor Guide
Page 18 of 73
Neck Board
The neck board very seldom has problems. Occasional faults will be caused from mishandling
where someone has broken some of the pots that control the RGB drives. Check the pots if you
are missing a color. If you are blowing your 5A fuses and your other boards are OK, check C503
(33 uF @ 250V). If this is open, shorted or cold soldered, it will cause the 5A (or 6.25A
depending on your board) fuses to blow.
The wire marked GRY next to the tube socket on neck board is a grounding wire. The wire bolts
to the aluminum monitor frame between the HV cage and the deflection board.
HV Supply
Last is the HV supply. The HV transformer (or flyback) is fairly robust, and does not fail very
often. Normally, HV failures are due to a semiconductor or capacitor failure. Unfortunately,
replacement HV transformers are unavailable, although the Atari-designed Disco raster monitor
contains an identical HV transformer. The Disco monitors are very difficult to find as well.
You will frequently see HV units with the protective metal shield removed from the case and
discarded in attempt to keep it cooler. The shield reduces the EMF emissions and the picture
distortions that go along with it. If your picture is slightly distorted, this may be the cause. If you
upgrade the HV section as outlined in this document, your monitor should run much cooler and
removing the metal shield should be unnecessary. However, it is always a good idea to run your
games with the back door removed to allow for proper airflow.
Solder Joints
Also watch for broken solder joints at the base of the connector pins for all the major connectors.
You tend to rock the plugs back and forth when you pull the connectors off and this often cracks
the solder joints to the circuit boards, which were poorly soldered to begin with. You may also
want to check each pin for continuity with the next component on its trace line (and also with
adjacent pins), and remove and resolder any dubious connections. While you are at it, resolder
the three pins of the PTC thermistor (in the middle, along the left edge of the deflection board) as
they are almost always loose for some reason.