Linear or Switching Power Supplies

D_Harris

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Does anyone have a list of games where the switch from linear to switching power supplies is not recommended?

I know that keeping the original power supplies in Williams games like Joust, StarGate, Robotron is preferable, but how many others?

What about the Atari raster games like the System 1, Millipede and Pole Position? Or vector games like Asteroids and StarWars?

In fact, what about MCR games like Satan's Hollow?

I'm not talking about longevity(where I think linear power supplies win out), but operational performance of the games.

Thanks.

Darren Harris
Staten Island, New York.
 
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Well, on MCR games, especially Spy Hunter, the switching power supply tends to produce a hum in the audio, so if possible, the original linear supply is probably best to retain.

On Atari games like Millipede, Dig Dug, Centipede, Kangaroo, etc - the power requirements are low, and the original linear power supply works very well here. These are reliable games as is, so I'd just keep the original supply because it's much easier to fix that than to wire in a switcher. Also, on games like Dig Dug and Star Wars, which use an EAROM for saving high scores, you need some unusual voltages that you're not going to be able to get from a switcher. In general, the ARII works pretty well, and in most cases, I'd fix it up and keep it with the original supply. The ARII is also the sound amplifier, so you either have to keep it in the game only for sound, or install another amplifier.

Pole Position... You should always replace this with a switcher. The original scheme of using two ARII boards is terrible, and the power supply in this game is a big reason for it's unreliability. That and power distribution at the boards themselves - you want to connect the power supply directly to the test points as well as the edge connector fingers (if there's even any power fingers left, they usually burn off). You need a big switcher though - most common cheapie little ones won't cut it. You need five volts, and lots of it. Last Pole Position I did I used a computer power supply.

System 1 games seem to have a lot of power supply problems, the ARIII doesn't seem nearly as reliable, and I know most people prefer switchers here. I don't have any System 1 games, so I'm not as well versed. I'd ask someone else about those...

Taito games should use a switcher. The orignial Taito power supplies were among the worst ever, and they run just fine from switching supplies.

If you have a Defender with the original supply, it should be replaced with something else. Either a switcher (can cause intermittent loss of scores/settings), or a later supply, from a Stargate or Robotron. The original Defender power supply has no overvoltage protection, and it can actually fail in such a way that causes RAM chips to catch fire.

-Ian
 
I know that keeping the original power supplies in Williams games like Joust, StarGate, Robotron is preferable, but how many others?

A notable exception is Moon Patrol, which is actually an Irem game. A switcher works great in it, and is arguably even preferable.
 
The original Defender power supply has no overvoltage protection, and it can actually fail in such a way that causes RAM chips to catch fire.

-Ian

I have heard of tuning for maximum smoke, like in radios, but that is ridiculous.

I knew there were bad power supplies but that one is down right harmful.
 
If you have a Defender with the original supply, it should be replaced with something else. Either a switcher (can cause intermittent loss of scores/settings), or a later supply, from a Stargate or Robotron. The original Defender power supply has no overvoltage protection, and it can actually fail in such a way that causes RAM chips to catch fire.

-Ian

They also put the overvoltage protection on a daughterboard that plugs in between the Defender PS board and the wiring harness. It is documented in the Stargate drawing set. I have only seen two of them in person. Most of them were tossed by operators that didn't know what they were and thought they were filters like Midway used on Galagas. Just another thing to break, so toss it.

Make Trax is also a non-Williams design and could easily be converted to a switcher.

With Williams games it comes down to:
(a) Does it have a 6809 or 6800 processor (including 6802, 6808 and 6810)
and
(b) Does it have CMOS to save settings/high scores.

If yes to both, then it is a candidate for rebuilding the linear. If no to either, then switch away.

ken
 
Ok.

For my Joust, StarGate, and Robotron games I'm sticking with the original power supply. As well as Satan's Hollow and Star Wars. (I haven't even tried to fire up my Asteroids game yet).

I am tempted to go with a switching power supply for my Millipede game since I can't get it working, but I'll change all the caps on my ARIIs and associated game boards first, and definitely go with a switching power supply for games like Choplifter, Elevator Action, Indiana Jones. (I'll rebuild the original Nintendo switching power supplies for Mario, DK, etc.). All my Pacs already have switchers.

My PCB Collection
**************
Asteroids (x3)
Astro Fighter (x2)
Astro Invaders
Arkanoid (x2)
Arkanoid: Revenge of Doh (x2)
Carnival
Centipede
Choplifter (x2)
Crystal Castles (x2)
Dig Dug
Donkey Kong (x4)
Elevator Action (x2)
Eagle
Frogger
Fatal Fury II
Gaplus
Galaga
Galaxian (x3)
Hogan's Alley
Indiana Jones
Jail Break
Jr. Pac-man
Joust
Missile Command
Moon Patrol
Mario Bros. (x2)
Mr. Do! (x2)
Millipede (x2)
Make Trax
Metal Slug
Metal Slug X
Ms. Pac-man (x2)
Nova 2001 (x2)
Pengo
Pooyan
Pleides
Phoenix
Pac-man
Pac-man Plus
Pole Position
Puzzle Bobble
Road Blasters (x2)
Robotron 2084
Rush n Attack
Scramble (x2)
Super Cobra (x2)
Star Trek (4 Boards)
Star Wars
Super-Pacman (x3)
StarGate
Satan's Hollow
Samurai Showdown II
Thief
Tempest (1 main board)
Tetris(x2)
Time Pilot'84
World Heroes II (x2)
Vs. Super Mario Bros. (x2)
-----------------------------------
MOTHERBOARDS
********************
Play Choice
Atari System 1 (x3)
Neo Geo MVS (x3)

Thanks.

Darren Harris
Staten Island, New York.
 
A notable exception is Moon Patrol, which is actually an Irem game. A switcher works great in it, and is arguably even preferable.


I've had Moon Patrol on a switcher from day 1 and had no issues yet. Been nice. Same with Bubbles actually.
 
What about a Pacman/Galaxian? Linear or Switcher?

Pac-man was the first game I converted to using a switching power supply.

I'd been interested in thoughts on whether this should also be done with Super Pac-man which is different hardware.

Darren Harris
Staten Island, New York.
 
Ok, I'll assume that Super Pac-man, like most, will be better with a switching power supply.

Does anyone have any info on what makes the ARIII power supply in a System 1 game unreliable?

Thanks.

Darren Harris
Staten Island, New York.
 
There was a thread about that and the ARII's. As I recall, it is the feedback logic that causes issues. Originally the feedback circuit was there to maintain the 5V power at 5V, but as corrosion and age affected the feedback, the power supply would up the voltage to compensate and it could raise the 5V to dangerous (to chips) levels.

ken
 
They also put the overvoltage protection on a daughterboard that plugs in between the Defender PS board and the wiring harness. It is documented in the Stargate drawing set. I have only seen two of them in person. Most of them were tossed by operators that didn't know what they were and thought they were filters like Midway used on Galagas. Just another thing to break, so toss it.

ken

Is that what that is? I have one or two of those mounted on a power supply in my "Box of Williams' Power Supplies"...
 
There was a thread about that and the ARII's. As I recall, it is the feedback logic that causes issues. Originally the feedback circuit was there to maintain the 5V power at 5V, but as corrosion and age affected the feedback, the power supply would up the voltage to compensate and it could raise the 5V to dangerous (to chips) levels.

ken

Yes, I know the thread. I wasn't referring to the ARII, but instead the ARIII used in a game like Indiana Jones.

Darren Harris
Staten Island, New York.
 
Is that what that is? I have one or two of those mounted on a power supply in my "Box of Williams' Power Supplies"...

If they look like this:

attachment.php


That is what you have. You will probably recognize most of the same components that are on the Joust & later PS boards. The two components in the heat sinks are the SCRs and in the center are the zener diodes that comprise the bulk of the overvoltage circuit that was added to the later PS board.

They don't have a lot of value, but they are rare.

ken
 

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I can understand not using a switcher if it doesn't meet the requirements of the system (e.g. it doesn't supply all the rails needed, or can't handle the load on certain individual rails). Is there some other technical reason beyond this for sticking with the original linear supply? I've seen mention of some games "not liking" switchers, losing high scores, etc - anyone got more details?

I'm all for keeping things as stock as possible btw, so this is just engineering curiosity.

LeChuck
 
I can understand not using a switcher if it doesn't meet the requirements of the system (e.g. it doesn't supply all the rails needed, or can't handle the load on certain individual rails). Is there some other technical reason beyond this for sticking with the original linear supply? I've seen mention of some games "not liking" switchers, losing high scores, etc - anyone got more details?

I'm all for keeping things as stock as possible btw, so this is just engineering curiosity.

LeChuck

Williams games (both video and pinball) and some other games that use 6800 series processors (including 6809s) have problems with power supplies that are not designed to provide a +5V that lasts slightly longer than the +12V supply.

From a previous thread:

Switchers can be problematic with Williams games. It is related to the 6809 CPUs they used. The 6800 series of processors has a glitch in that when they are powering down, they grab the address bus and dump random values all over the memory space. The Williams engineers knew about this (they learned the hard way when building pinballs) and came up with a clever hack. The big capacitor on the Williams power supplies will provide a few milliseconds of extra power when the machine is turned off. There is a circuit on the motherboard that monitors the 12V unregulated power. When the power is switched off the 12V goes to 0 instantly and a circuit on the MPU board senses this and turns off the CMOS memory's write enable. This protects the CMOS memory while the big cap powers the CPU for a little longer. Switchers don't have that. When a switcher turns off, both +5V and 12V go down at the same time, so the CMOS memory protect doesn't have a chance to kick in. It is just random chance whether the CMOS values get overwritten with garbage or not when the CPU goes down. That is why the recommendation to restore the Williams power supplies whenever possible. If not, you will just have CMOS trashing every so often.

ken
 
Thanks for the background, that's just what I was after. If anyone is keeping a list of linear vs switcher, I think it would be useful to document the "why" details like this as well.

On a side note - what thread did that quote come from? My searching of this forum only turned up this thread in response.

LeChuck
 
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