Bally/Midway MCR PS questions

joemagiera

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I own 4 Bally/Midway MCR games, Tron, Domino Man, Journey and Wacko and the upright versions all share the same power supply board: A082-90412-x000. I note upright because while reviewing the schematics today, at least one game listed a different version for the cocktail, A084 (probably was a typo). I also used a small "x" as I believe this is just signifying a revision in the power supply.

As for my questions, I have several different versions of this supply, -A000, -B000, -C000, -D000 & -E000. Are they all completely interchangable with each other? If so, what are the actual differences between them? It seems logical that the latest version (-E000) would be the best version, but who knows?

So you repair guru's, what do you think? What knowledge can you share? Do you feel these are good supplies (once recapped and such)? Or would you just get rid of them and throw in a switcher?
 
Do you feel these are good supplies (once recapped and such)? Or would you just get rid of them and throw in a switcher?
I don't know about the different revisions, but I can jump in on this one. They're as good as anything else of the era. The most common problem is that the cmos battery leaks and destroys a bunch of traces.

MCR games have +5v logic, +12v logic, cmos battery, and +12v audio. However the +12v audio is isolated to minimize noise: separate transformer tap, audio ground, etc. This is a fairly complex system and it's easy to end-up with a ground loop and 60hz hum. That's separate from the unavoidable flutter / digital noise at mid-volume (caused by a poorly designed volume-control circuit). Audio sucks on these games and can be very difficult to diagnose.

The arcade shop adapter should be "no different" because it uses the 3-pin plug, from the separate transformer tap, to generate a separate +12v unregulated audio power supply. I'd cautiously recommend it, but the grounding scheme of this game is so touchy that it's difficult to promise any change will not result in a ground loop. You'll find a lot of people who may not understand the underlying problem but hear the symptom which is 60hz hum.
 
I'm going with Joey, here.......though, he forgot to add....a reset circuit.

Some people believe a certain revision needs to go with a certain game/motherboard.....this is wrong. Any MCR power supply revision will work with any MCR game. One main difference I've found is fuse size.....most games call for the on board fuse to be a 3/8 amp slo-blo.....some (power hungry) games upped the fuse value to 1/2 amp slo-blo (Spy Hunter comes to mind, but I'm sure there's others).

Regarding the different revisions (besides the above fuse)....there's not a big difference. Early revisions didn't have the designations/componet locations screened on the boards. Also early revisions had a resistor (68 ohms 1/2 watt) tied across capacitor C106. Early schematics lists this as R300. Without this resistor, the 5VDC line WILL NOT regulate with out a load. With the motherboard unplugged, you'll generally see around 6.5VDC at the 5VDC line. I'd guess very early power supplies shipped without this resistor....thus causing techs to freak out and flood Midway's service department with calls.....trying to fix a faulty 5VDC circuit.....that was actually working properly. Obviously, a lot of techs are scared to plug a motherboard into a power supply that's outputting 6.5 volts on a 5 volt line. Midway's fix....tie a resistor across the 5VDC filtering cap. Later revisions included this resistor properly loaded into the circuit board and labeled as resistor R118. Confused yet?? Even later revisions of this power supply have screened markings for additional componets, but these conponets are not populated. And even later revisions HAVE these componets populated. It's IC chip U4, resistor R218, and capacitors C207 and C208. These componets make an additional circuit Midway called AC syncronization. I have no idea of the purpose of this circuit. I have NEVER seen a MCR game use this circuit.....it's not connected at the harness connectors. I have not been inside all MCR games, but I've been in a lot.....who knows, maybe one uses this circuit. I honestly assume this was for some project they aborted....I dont know.

Edward
 
I don't own a Discs of Tron, but I think they used it on that game for the fluorescent light strobe.

Ah-ha....I've never been inside one of those. Good to know!

Edward

Edit: I just pulled the schematics....Joey's correct. The AC sync circuit is used in the environmental Disc of Tron....So, an older revision power supply board wouldn't work in this machine.
 
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I'm going with Joey, here.......though, he forgot to add....a reset circuit.

Some people believe a certain revision needs to go with a certain game/motherboard.....this is wrong. Any MCR power supply revision will work with any MCR game. One main difference I've found is fuse size.....most games call for the on board fuse to be a 3/8 amp slo-blo.....some (power hungry) games upped the fuse value to 1/2 amp slo-blo (Spy Hunter comes to mind, but I'm sure there's others).

Regarding the different revisions (besides the above fuse)....there's not a big difference. Early revisions didn't have the designations/componet locations screened on the boards. Also early revisions had a resistor (68 ohms 1/2 watt) tied across capacitor C106. Early schematics lists this as R300. Without this resistor, the 5VDC line WILL NOT regulate with out a load. With the motherboard unplugged, you'll generally see around 6.5VDC at the 5VDC line. I'd guess very early power supplies shipped without this resistor....thus causing techs to freak out and flood Midway's service department with calls.....trying to fix a faulty 5VDC circuit.....that was actually working properly. Obviously, a lot of techs are scared to plug a motherboard into a power supply that's outputting 6.5 volts on a 5 volt line. Midway's fix....tie a resistor across the 5VDC filtering cap. Later revisions included this resistor properly loaded into the circuit board and labeled as resistor R118. Confused yet?? Even later revisions of this power supply have screened markings for additional componets, but these conponets are not populated. And even later revisions HAVE these componets populated. It's IC chip U4, resistor R218, and capacitors C207 and C208. These componets make an additional circuit Midway called AC syncronization. I have no idea of the purpose of this circuit. I have NEVER seen a MCR game use this circuit.....it's not connected at the harness connectors. I have not been inside all MCR games, but I've been in a lot.....who knows, maybe one uses this circuit. I honestly assume this was for some project they aborted....I dont know.

Edward

bumping as I am investigating some 90412 boards and wanted to somewhat guess / clarify part of the above, which definitely helped me. I have revC w/ R300 and revD w/o R300 as mentioned above.

Slight corrections.
- it is IC u6 for AC sync line
- educated guess....it is the components of the rev.D included AC sync line r218 and likely U6 needing reg +5 is what creates the load on the +5 line. This load negates the need for r300
- r118 is present on both boards and is part of the isolated unregulated 12v
 
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