RE: Williams P.S. Boards - Upgrade / Repair Questions

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I recommend replacing the +5, -5 and +12 supplies with a computer switching
supply. If the Williams supply fails it can SMOKE your board or the RAM,
computer supplies tend to fail more gracefully and never go high on the
output voltage...they just shutdown on failure. We have modified these
switchers for use in Williams games, it is an easy mod.

John :-#)#

At 06:00 AM 10/30/00, Chris Loggans wrote:
>Steve,
>
> I was just working on one of these last night as a matter of fact. Which
>readings are low and what are they? Your best place to start
>troubleshooting is with a set of schematics. The set I have gives the
>expected voltages at different points along the circuit so you can find
>where things start to go bad. If you don't have these, let me know and I
>can scan the appropriate images in and send them to you.
>
>Thanks,
>-Chris
>
>-----Original Message-----
>From: Steven Winslow
>To: rasterlist@synthcom.com
>Sent: 10/29/00 12:18 PM
>Subject: RASTER: Williams P.S. Boards - Upgrade / Repair Questions
>
>Hello All !
>
>I've begun to install Bob Roberts' Williams PS repair kits (parts &
>connectors). I've managed to make a working board (works but resets my
>Joust after 10 minutes or so) non-working. Replaced all the caps, the
>7905
>& 732 regs, the 2N6057 & 2N3055 (not shorted).
>
>All the LEDs come on. Game won't even boot up now. I've taken voltage
>measurements but don't have the numbers available to put into this
>e-mail -
>they were all present but low. I could give the exact measurements
>later
>if this helps. Here's my questions:
>
>1. Are there any other commonly failing parts on these boards I
>should
>consider replacing?
>
>2. Do R14, R15 & R6 (The 5W resistors) usually need replacing too?
>They
>all seem to be way out of (5%) tolerance. In the circuit the 2 ohm
>measures out at 3 ohms. The .12 ohm measures out at 10.8 ohms and the
>.27
>ohm measures out at 11.9 ohms.
>
>3. Is there a good FAQ or other document(s) regarding Williams
>power supply
>problems, symptoms and diagnostics procedures somewhere you can point me
>to ?
>
>4. I've got probably 20 or so 4116 RAMs in a tube somewhere, do you
>think
>they've really blown or is the RAM errors from the low TTL voltage from
>the
>power supply ?
>
>Another PS board in my Defender made it through the upgrading and worked
>fine for a few days of playing. It now gives me a RAM error in both
>Joust
>(locks up with RAM error screen) and Defender (plays but with garbage on
>the screen, resets shortly after).
>
>I really want to be able to keep my Williams games original and I'm not
>interested in installing new switching power supplys. I do however,
>have
>one of Bob Roberts' new switching power supplys that haven't been
>installed
>in any game yet. Maybe I'll use it for testing purposes to ensure that
>the
>RAMs are OK. I have a Joust 2 that seems to have a good working power
>supply in it. Maybe I should use it for testing purposes.
>
>Whadda ya think ? Am I way out of line here ? Any suggestions or
>guidance
>would be much appreciated because I still have a couple cocktail tables
>& a
>couple more uprights to do this upgrading work to.
>
>Thanks !
>
>Steve Winslow
>
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  John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
  Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
  http://www.flippers.com
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Received on Sun Oct 29 21:03:08 2000