(Topic ID: 130808)

Williams WPC 5v Drop


By Crash

3 years ago



Topic Stats

  • 25 posts
  • 11 Pinsiders participating
  • Latest reply 3 years ago by PinballManiac40
  • Topic is favorited by 9 Pinsiders

You

Linked Games

Topic Gallery

There have been 3 images uploaded to this topic. (View topic image gallery).

fr_246.jpg
fr_245.jpg
schematic.png

#1 3 years ago

I've seen this issue on a couple of games lately. The 5v power supply is near or exceeds 5v in both cases. For whatever reason I'm getting a 200mv+ drop between the CPU board's 5v input connector and the game ROM.

Fish Tales
Driver board J114: 4.97v
CPU board J120: 4.97v
Game ROM: 4.76v
210mv drop

White Water
Driver board J114: 5.07v
CPU board J120: 5.06v
Game ROM: 4.83v
230mv drop

Both games are resetting frequently. I've never seen anything like this, usually it's at the driver board itself or the connectors going to the CPU board. The only cap I see measures 5.05v across and I also reseated the ROM with no improvement (WH20). Could the ROM socket possibly be the culprit? I am aware they cause all sorts of issues at times due to their design. Or could the issue be more difficult to track down/repair? If the latter is true then I will simply opt for the cheaper and more stable WPC 5v mod.

#2 3 years ago

I would just track the power from point to new see where you drop and then triage from there. Truly follow the schematic and measure from point to point across the circuit.

Marc

2 weeks later
#3 3 years ago

I replaced the CPU board in White Water with one of the same part number. The 5v supply has improved slightly and the resets are not as frequent, but I'm still seeing a large drop between J210 and the game ROM. There is no drop in the initial vcc section stemming from J210 in the schematics prior to the break in the drawing...

J210 5v rails (2x): 5.06v
Game ROM pin 32 (vcc): 4.85v

schematic.png

Following the schematic tracing backwards from the ROM...

W4: 5.05v
W5: 4.85v
W2: 4.85v

The above appear to be test points on one side of a zero-ohm jumper at each location. I tested these jumpers and there is no drop across them. I moved the game ROM and batteries over from the old board. Suspecting a battery problem, the VBATT side of W5 reads 4.11v when the game is off. The batteries need to be changed, but I don't see anything odd with those and the game is currently keeping memory.

However, I did notice something strange with the 1.5k resistor at R3. One side reads 5.04v, but the other reads 4.97v. For comparison I tested across R96 and R97 near the top of the board and got only a 10mv drop across them, even though they are both 1.5k as well. I am pointing to the low side of the resistor in the second photo. Is this normal?

fr_245.jpgfr_246.jpg

#4 3 years ago

How is the power foing to the games?

#5 3 years ago

I'm getting a steady 119v at the wall outlet. This is the only machine resetting, but it doesn't seem to be an issue apart from the CPU board as the voltage coming in at J210 is a healthy 5.06v. I'm also considering a possible issue with the game ROM... that's the only other thing I carried over from the old board.

#6 3 years ago

Any ideas? Do I just need to send it to Clive? I have two boards doing this and don't want to spend money having them both repaired if it's something simple.

#7 3 years ago

I usually come into threads like this hoping that I know something that can help the OP, but you've got me here.

Knowledgeable people never ask easy questions!

#8 3 years ago

Yeah I'm in the dark as much as you are here. Again, I'm thinking it may be a chip on that board dragging the voltage down but the game ROM is the only one I see with a vcc input. And if that's the case I will send it off anyway.

I will try the original board in another working machine and see if the problem follows.

#9 3 years ago

Rob Kahr's daughterboards (http://kahr.us/) have been my first go-to when I run into this type of reset. Both times I've run into random resets, the board solved it & it's only $28 and doesn't require any work other than unplugging a cable & plugging it into the daughterboard. Just a thought anyway, it's a small investment & can't hurt.

#10 3 years ago

Ok so I got some readings on two more games that do not have reset problems and the results are interesting...

TAF
J210: 4.97v
ROM: 4.77v

BSD
J210: 4.85v
ROM: 4.63v

So that 200mv drop to the ROM is normal. Next I'll be investigating the driver board. Thanks for the help.

#11 3 years ago

First, move the batteries off that CPU board.

Here's the reset problem determination procedure...
http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Game_resets
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

1 week later
#12 3 years ago
Quoted from boustrophedonic:

Rob Kahr's daughterboards (http://kahr.us/) have been my first go-to when I run into this type of reset. Both times I've run into random resets, the board solved it & it's only $28 and doesn't require any work other than unplugging a cable & plugging it into the daughterboard. Just a thought anyway, it's a small investment & can't hurt.

Since I have already replaced the caps and regulator on the driver board and the issue is not connections between boards (5.06v coming in) I opted for Kahr's board. Now I am getting 5.15v to the CPU and 4.91v at the game ROM. No more resets!

#13 3 years ago

Kahr's products are legit.

#14 3 years ago

The reset is caused by a watchdog circuit. The watchdog circuit is probably on the other side of the that resistor, so the voltage at the ROMs shouldnt be a major concern when finding a reset reason.

If you have good +5v on the input pin, but it still resets, there is something going on. Failing filter cap could not hold the charge during a current spike (flippers). Resistance on the connector plugs. Etc..(see Chris's link). Scope would let you watch the power when the flippers are going off.

Glad you fixed it with the Kahr board, but the tech inside me think that is a bandaid and your power supply still has problems. But if it works, it works! Hard to argue to mess with the board when you have it working.

#15 3 years ago

Well of course, that's the first approach I took. The first thing I did was replace key components and that worked great for a few years. Then it started acting up again, and it was just the MPU board resetting (which is the main drag on the 5v power supply). If it were my game I would go through the machine 100% but as operators we don't have the time. The game is a high location earner.

The funny thing is I tested voltages as low as 4.79 on another game and that one does not reset at all.

#16 3 years ago

Another thing, a lousy capacitor job at C5 on the driver board will provide good readings but will not stand up to gameplay. What I did after re-pouring solder joints on all that makes up the 5V digital it was still resetting. I try my best to not make jumpers on the back of a board but if I ruined the wells on C5 there was little choice so after jumpering the resets went away.

#17 3 years ago
Quoted from Crash:

Well of course, that's the first approach I took. The first thing I did was replace key components and that worked great for a few years. Then it started acting up again, and it was just the MPU board resetting (which is the main drag on the 5v power supply). If it were my game I would go through the machine 100% but as operators we don't have the time. The game is a high location earner.
The funny thing is I tested voltages as low as 4.79 on another game and that one does not reset at all.

While the 4.79 might be enough to keep the watchdog circuit happy. When the flippers go off you are depending on a capacitor to act as storage tank to keep the voltage up. If you deplete the capacitor in the time of a flipper pulse the voltage dips and the watchdog triggers a reset. This happens so quick, a DMM may not see the voltage drop.

Poor physical connections add resistance too.

#18 3 years ago

You Probably have a Bridge rectifier with an open leg. Instead of a full wave you are relying on a half wave rectifier. Having excellent capacitor will allow the game to power and play but will cause reset when under heavy load, Change the Bridge

#19 3 years ago
Quoted from gregfilek:

Change the Bridge

Test the bridge!

#20 3 years ago

I changed it already, as a lot of people suggest.

#21 3 years ago

You changed the bridge? Did you buzz for continuity on both sides of the board after replacement. Those traces on both sides of the board can be tricky.

#22 3 years ago

Yes. I had to run a jumper afterwards for C5.

#23 3 years ago

Sounds legit.

#24 3 years ago

Like he said, it's a location machine. It can't be down for 3 days to do what we'd like to do to fix it once and for all (20 more years)!

#25 3 years ago

I end up finding on a lot of games having either loose or burnt female pins on J101 being the most common to cause resets.

Promoted items from the Pinside Marketplace
$ 10.00
Cabinet - Sound/Speakers
Gweem's Mods
$ 29.99
Cabinet - Sound/Speakers
Lighted Pinball Mods
From: $ 29.00
Boards
KAHR.US Circuits
$ 229.99
Lighting - Other
Lighted Pinball Mods
€ 4.99
Flipper Parts
Multigame
$ 49.99
Playfield - Toys/Add-ons
Lighted Pinball Mods
$ 109.99
Wanted
Machine - Wanted
Branson, MO
$ 159.99
Lighting - Other
Lighted Pinball Mods
$ 369.00
Cabinet - Decals
Mircoplayfields
Wanted
Machine - Wanted
Mill Valley, CA
$ 9.95
$ 47.00
From: $ 5.00
Cabinet - Other
Rock Custom Pinball
$ 50.00
$ 49.99
Playfield - Toys/Add-ons
Lighted Pinball Mods
$ 229.99
Lighting - Other
Lighted Pinball Mods
$ 21.00
From: $ 80.00
Lighting - Interactive
Pinball Z
From: $ 40.00
Cabinet - Other
Rock Custom Pinball
€ 3.70
Wanted
Machine - Wanted
Hackettstown, NJ
$ 36.00
Playfield - Toys/Add-ons
MONSTERFISH MODS
Hey modders!
Your shop name here

Hey there! Got a moment?

Great to see you're enjoying Pinside! Did you know Pinside is able to run thanks to donations from our visitors? Please donate to Pinside, support the site and get anext to your username to show for it! Donate to Pinside