Beschreibung

Williams System 3 thru System 11C High Voltage Parts Kit.

This kit includes the following components:
1N4730A -- Zener Diode, 3.9V - ZR1 and ZR3
1N4763A -- Zener Diode, 91V - ZR2 and ZR4
1N4764A -- Zener Diode, 100V -- Alternate for ZR2 and ZR4 (See Notes below)
1N4004 -- 400V, 1Amp Rectifier - D3 and D4
MJE15030 -- Transistor, NPN - Q1 (SDS-201 Alternate, See Notes)
2N5401 -- Transistor, PNP (MPSD52 Alternate) - Q2
MJE15031 -- Transistor, NPN - Q3 (SDS-202 Alternate, See Notes)
2N5551 -- Transistor, NPN (MPSD02 Alternate) - Q4
RMOS2-39K -- Resistor, 39K ohm, 2 watt (Alternate for 39K 1/2 watt and 39K 1 watt) - R1 and R4
RCF1/2-1.2K -- Resistor, 1.2K ohm, 1/2 watt (Alternate for 680, 1/2 watt) - R2 and R5
RCF1/2-330K -- Resistor, 330K ohm, 1/2 watt - R3 and R6
CCD-0.1uF-500V -- Ceramic disc capacitor, 0.1uF, 500 volt -- C8 and C12 for Systems 3 through 6, C2 and C4 for Systems 7 through 11c

Notes --

There are no current replacements for the obsolete SDS-201 and SDS-202 transistors.
MJE15030 and MJE15031 transistors can be used to replace these but due to different pin outs
the transistor legs MUST be crossed as shown in the link below.
This note does not apply to later System 11b and 11c boards.

Use of 1N4763A's in place of 1N4764A's reduces the output voltage by 9 volts.
This lowers the voltage to the displays and display drivers to approximately 91 volts.
Although there is a minimal reduction in display brightness,
the advantage to this voltage reduction is a longer lifespan in both
displays and display drivers. Some displays will not work with the reduced voltage.
If your display is excessively dim,
strobes or doesn't work after rebuilding the supply -
install 1N4764A's in place of ZR2 and ZR4.

For improved heat dissipation, 2 watt resistors should be installed with a
slight air gap between resistor body and printed circuit board surface.