Anyone do this? Worthwhile? I have a Williams Jokerz that makes a lot of weird sounds during start up. Hoping this may solve it.
Pinwiki has some good info on how to.
An Alternative to Rebuilding the Reset Circuit / Using a Reset Generator (All versions of System 11)
There is an alternative to the stock reset circuit on all versions of the System 11 MPU boards. A reset generator can be installed. Since the reset section of all versions of the System 11 MPU board is susceptible to battery damage, this is a very easy, and minimalistic way to rebuild the reset section. To do so, 4 components will need to be removed and a jumper installed. The following work will have to be done.
Remove the Q39 transistor.
Remove the following resistors - (from top to bottom as installed on the board) R58, R60 (these two are just below the Q39 transistor), and R69.
Add reset generator MCP120-460GI/TO where Q39 was. Orient the reset generator in the same manner Q39 was oriented (pin 1 of reset generator will install in the bottom through hole). In other words, the "flat" side of the reset generator will face to the right.
Add a jumper between the right pad of R58 and the right pad of R60 (both resistors have been removed).
This a very simple, and in some cases, cheaper alternative to repairing the existing reset circuit. After this modification is performed, the MPU board will no longer need the +12v to successfully boot. However, +12v is still necessary for the sound section of the MPU on most boards, except the 11B and 11C variants. Likewise, any of the other components in the reset circuit can be removed if desired. Please consult the System 11 MPU board BOM and schematics to determine exactly what components can be removed. The MCP120-460GI/TO reset generator can be purchased from Great Plains Electronics. The MCP130 variant with an internal 4.7K ohm resistor can be used, but it is not necessary. This is because resistor network SR19 pin 3 is an external 4.7K ohm resistor used to pull up the /RESET line.
These components are in the area of the reset section, but are not part of the reset circuitry. They are actually related to the game RAM, enabling CMOS power to reach the RAM and to control pin 18, the chip enable pin of the RAM. Without these parts, the MPU will not successfully boot. Instead, there will be a single blink code from the diagnostic LED indicating a U25 RAM error (a "1" will display on boards with the 7-segment display). If the game display is connected to the MPU board, a "U25 RAM ERROR" message will be displayed.
D1 - 1N5817 diode
Q40 - 2N3904 transistor (a 2N4401 was used in this case)
R64 - 1 Kohm 1/4 watt resistor
R65 - 10 Kohm 1/4 watt resistor
R68 - 4.7 Kohm 1/4 watt resistor
for a System 11 (nothing) or a System 11A MPU, both of which have onboard amplifiers in the upper left corner and require 12VDC power, be sure to retain or replace the following parts:
L2 - 4.7uH inductor (or a simple jumper)
C27 - .001uf/50V ceramic capacitor
C28 - .001uf/50V ceramic capacitor
C29 - 100uf/25V electrolytic capacitor