(Topic ID: 202391)

Williams Reset Generator Mod


By tomm1963

2 years ago



Topic Stats

  • 18 posts
  • 4 Pinsiders participating
  • Latest reply 48 days ago by arolden
  • Topic is favorited by 11 Pinsiders

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    23ad3f21769e8a88ed1df99ef95b2086aca22396 (resized).jpeg
    Capture (resized).PNG
    System11MinumunResetSection (resized).jpg
    WMS_Sys11_Reset_Section (resized).JPG
    Sys11_Battery_Rot_Done (resized).JPG

    #1 2 years ago

    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

    Sys11_Battery_Rot_Done (resized).JPG

    WMS_Sys11_Reset_Section (resized).JPG

    System11MinumunResetSection (resized).jpg

    #2 2 years ago

    i use a similar part to reset my replacement bally MPU and the -51 sound board. Simple, cheap, and they work well.

    I'm not sure its worth doing it to a SYS11 MPU unless all those parts got puked on by the batteries.

    You could even just cut out the reset generator parts and whack it across the 6802 legs. Could probably even hide it under the CPU socket or on the back of the board. Reset gen just hooks up the gnd +5v and the /reset. P1, P7, and P40 of cpu

    #3 2 years ago

    No battery damage, actually have NVRAM installed. Just an awful sound at startup. Possibly from not having clean 5V from reset circuitry.

    #4 2 years ago

    i'm not sure where jokerz was at with moving the sound stuff to a separate board, but don't forget about the sound board. It has its own CPU and support parts, including reset.

    The hum buzzing you hear is probably from the capacitors taking time to charge up, but not sure about the digital noises. If everything else works and is stable, i'd probably leave it alone.

    I will say my F-14 is pretty silent until at power on. I put all new electrolytic caps in it maybe 6-8 years ago.

    #5 2 years ago

    The hum on Jokerz is a well known problem. Williams released a service bulletin on the issue. After watching the first vid I posted, those guys claim a lot of odd startup noises can come from the reset circuits not giving clean power. I am ordering a few things from Great Lakes Electronics and was thinking of adding the reset generator to the order and next time I pull the board maybe giving this a go. Appreciate the input.

    #6 2 years ago
    Quoted from tomm1963:

    The hum on Jokerz is a well known problem. Williams released a service bulletin on the issue. After watching the first vid I posted, those guys claim a lot of odd startup noises can come from the reset circuits not giving clean power. I am ordering a few things from Great Lakes Electronics and was thinking of adding the reset generator to the order and next time I pull the board maybe giving this a go. Appreciate the input.

    revisted the schematic in f-14 and it does show the /reset from the MPU going across the ribbon to the sound board. also triggered a memory that some of the early sys11 (plain / no letter?) that didnt have /reset hooked up right going to the sound board, but my mem is foggy. Which sys 11 MPU are you using?

    you can stick a logic probe on /reset past the sound ribbon and make sure it is making it to the sound board. Probably jumper W1 on the sound board is /RESET.

    2 years later
    #8 69 days ago

    I am about to do this mod on an Elvira board that was destroyed by battery corrosion. However, I cannot find the correct part. I can get an MCP120-450GI/TO easily enough (450GI instead of 460GI). Are these parts interchangeable or do I need the 460GI?

    #9 69 days ago
    Quoted from arolden:

    I am about to do this mod on an Elvira board that was destroyed by battery corrosion. However, I cannot find the correct part. I can get an MCP120-450GI/TO easily enough (450GI instead of 460GI). Are these parts interchangeable or do I need the 460GI?

    450 should be a fine replacement. the final three numbers indicates the voltage trip point where it puts the processor into reset. 450 = 4.5v0dc max and 460 = 4.60vdc max. The GI or DI letters indicate the pin out arrangement. TO indicates package type (i think). See the datasheet for pin out.

    My go to reset part is MCP130-460DI/TO They are usually in stock at Arrow and other places.

    #10 69 days ago

    Great fix for a whole lot of extraneous crap that is no longer needed on these boards.

    The 450 gives a bit more of a hysteresis zone than the 460. Sometimes the low voltage dips are merely noise on the 5V line, more hysteresis will reduce triggering on noise. If you have a good, solid 5V line then either will work fine.

    Note that there is already a pullup on the reset line via resistor network pack SR19, pin 3. So for this one an MCP120 would be preferred. But if you were to use an MCP130 then that would work as well -- but the reset generator would need to pull down two load resistors (still an easy task).

    #11 68 days ago

    Thanks for the response, guys. A second question: the part I am looking at is DI/TO instead of GI/TO (https://au.rs-online.com/web/p/products/7240586/). Is the pinout the only difference with DI vs GI? Any other differences I need to think about?

    #12 68 days ago
    Quoted from arolden:

    Thanks for the response, guys. A second question: the part I am looking at is DI/TO instead of GI/TO (https://au.rs-online.com/web/p/products/7240586/). Is the pinout the only difference with DI vs GI? Any other differences I need to think about?

    just the pin out is different. two pins are rotated. they call it the die bond out i think if you check the datasheet.

    #13 68 days ago
    Quoted from arolden:

    Thanks for the response, guys. A second question: the part I am looking at is DI/TO instead of GI/TO (https://au.rs-online.com/web/p/products/7240586/). Is the pinout the only difference with DI vs GI? Any other differences I need to think about?

    Note that if you get the part with the different pinout - you need to modify the pinout arrangement as presented in the video to match.
    The "G" part versus the "D" pinout is a rather radical pinout change.

    #14 68 days ago

    Understood. You guys are right, the pins are totally different. I will install it opposite to the direction illustrated on Pinwiki to line up the reset pin with the top pin of Q39. Then I'll have to bend the other two pins so that negative (VSS) goes to the middle pin of Q39 and positive (VDD) goes to the bottom pin of Q39.
    Capture (resized).PNG

    2 weeks later
    #15 54 days ago

    Just installed the new reset generator. It's a bit fiddly rearranging the pins to match the pinout, but it works OK.

    23ad3f21769e8a88ed1df99ef95b2086aca22396 (resized).jpeg
    #16 49 days ago

    So, silly question, but is D2 still required when using the reset generator? It is not stuffed in this pic on Pinwiki which shows the minimum parts required when using a reset generator: https://www.pinwiki.com/wiki/index.php?title=File:Sys11_Battery_Rot_Done.JPG

    But it is still required for the batteries? I am getting an adjustment failure message but that might be because I did not stuff D2. But I didn't think anything of it because it was not on the parts list on Pinwiki.

    Thanks for any advice.

    #17 49 days ago

    If you are using batteries D2 must be installed or the batteries will not keep the RAM contents intact when the game is turned off.

    #18 48 days ago
    Quoted from barakandl:

    If you are using batteries D2 must be installed or the batteries will not keep the RAM contents intact when the game is turned off.

    I thought so! Thanks.

    Any other components necessary for the battery?

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