Troubleshooting guide

Cinematronics Vector Monitor Repair Guide v.1.0
Page 28 of 53
RECOMMENDED MONITOR UPGRADES
It is often suggested that the very first thing one does when repairing a Cinematronics monitor is to
remove and replace all the tantalum capacitors without question. There is some validity to this.
As power supply filter caps, tantalums are generally superior to electrolytics. They are generally
smaller for a given capacitance. They are often manufactured using a porous slug as opposed to the
layers of aluminum foil used in regular electrolytics. Therefore, ESR and inductance in tantalums is
generally minimized. That is almost always a very good thing.
However, tantalum capacitors are relatively expensive and two out of a thousand will fail without
provocation even in a perfectly designed circuit. The number one failure in these monitors, failures
that cause the breakers to blow, damage the DACs and or LF13331 analog switch and burn-out of
the output transistors are those damned tantalum capacitors. If they get reverse voltage for just a
microsecond, they become wires. When they fail, they usually short out, dragging the power supply
down close to ground. That is almost always a very a bad thing.
The following is a list of recommended Cinematronics monitor upgrades:
• You will want to replace the tantalum capacitors with something that has a low ESR. That
being said, you should replace them with an electrolytic -- 33uF @ 50V is a perfect
replacement value. Spend the extra money and get the smallest capacitor with the highest
ESR rating you can find. Your monitor will thank you for it. The only other thing to
remember when replacing these capacitors is to pay close attention to the polarity. You may
leave the tantalum capacitors C12, C13, C15, and C16 as they are at the output of the +/-
15V voltage regulators (IC4 and IC6). You can also leave C25 and C26 as they are at the
+5V regulator (IC8).
• Replace resistors R118, R119 R218 and R219 with 47 Ohm, 5W resistors. To do this, place
them on the underside of the PCB where there is more room.
• Replace al 1N4003 diodes with 1N4004 or higher rating, which includes D105-115/205-
215. There are 31 diodes on the monitor board.
• Replace the deflection transistors with the 2N3716/2N3792 pairs that are used in all the
Wells-Gardner 6100 vector monitors. These transistors are rated at higher specs than the
originals and are most likely easier to source. Just make sure that you replace BOTH
transistors on the heat sink even if you only need to replace one. These transistors must be
replaced in pairs.
• There is a required update that all the older monitors should have installed. A single diode
that prevents the LF13331 from being back driven if the +/- power supplies do not startup
or shutdown at the same time. The newer monitors have this diode already installed. In the
older monitors that do not work, death of the LF13331 is the number one reason.