Midway Power Supply MCR Voltage question..

ZEN

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I have completely repaired a 90412 Power supply for a kickman I am restoring, in the manual is has test points for the +5v and the +12 voltage. On both of those I am reading double, 9.8 for the +5 and 24.9 for the +12, kind of strange that both would be almost exactly doubled, what part of the supply could cause this, what should I look for for a failure? everything looks pretty good as far as my work goes....anyhelp would be appreciated fellas.....thx....
 
I have completely repaired a 90412 Power supply for a kickman I am restoring, in the manual is has test points for the +5v and the +12 voltage. On both of those I am reading double, 9.8 for the +5 and 24.9 for the +12, kind of strange that both would be almost exactly doubled, what part of the supply could cause this, what should I look for for a failure? everything looks pretty good as far as my work goes....anyhelp would be appreciated fellas.....thx....

That is strange. Those two circuits arn't really related. I'm leaning towards your meter....do you have another to double check?
 
Does this power supply have a -5v supply? And if so, are you testing it with your black lead on that instead of Ground?

-Ian
 
Two meters, one digital and one analog both same readings...I was just going off of the troubleshooting manual, testing points A and B and C give you the V for +5 & + 12, I dont think the -5 circuit is on this board (supply # 90412, Tron, Kick, Kickman, etc)
 
Two meters, one digital and one analog both same readings...I was just going off of the troubleshooting manual, testing points A and B and C give you the V for +5 & + 12, I dont think the -5 circuit is on this board (supply # 90412, Tron, Kick, Kickman, etc)

You are correct, this supply doesn't have a -5VDC rail.

If you measure the voltage across C102....that's the 12VDC rail.
Voltage across C106 is the 5VDC rail.

Edward
 
Got back to this, pulled the board and replaced a diode in the 12v circuit, I am now getting 12v spot on, but I am getting 6.5v on the 5 volt side, not sure how to test the capacitors in circuit, is there a way to do that with a MM, I am close to getting this game to life, any ideas or things that are frequent failures to check?
 
I am getting 6.5v on the 5 volt side

Is this with the motherboard plugged in?....or unplugged?

The early version of the MCR power supply needed a load on the 5VDC rail for it to regulate. Without a load, it'll usually run around 6.5VDC. This could be your case.

Later board versions have an IC at U6.....a 555 timer. Early versions do not have this. At some point Midway started jumpering a 68 ohm 1/2 watt resistor across C106 to give the 5VDC rail a dummy load, thus...causing it to regulate. If you've got an early version...tie a resistor across the cap (or you could just plug it in to the board and see what happens). If you've got a later version (or an early version with the resistor), you definately have regulator problems.

Edward
 
Elutz, thanks sir, I tested voltage tonight with the boards plugged in and it was dead on 5.01 v!
And here is the kicker, the boards work!! I am rebuilding my G07 so I pulled my 13" test monitor to it, and vioila, I get kickman, and coin door lights and a ridiculously loud hum from audio, I think the amp is bad??? I have not replaced the interconnect cables yet from Bob Roberts. Man, a lot of work, but a $50 kickman that can take a repair from a guy like me, well, thats just fricken kewl. Anyone know how often the sound issues are the amp and not the SSIO sound board? I went from starting the cab on fire last night to end my misery to not far off froma damn nice kickman for $50...
 
Audio hum on MCRs is pretty common....and can be caused by a lot of stuff. First, they hum a bit to begin with.

Likely culprits.....the small amp board, power supply board caps, any of the three big caps on the transformer assembly, lighting ballasts (Kick has several), weak connectors, weak fuse block.....that should keep you busy for awhile :).

Edward
 
I have the same issue with a 90412 on a spy hunter machine. 12 volts coming out of the 5 volt line and 22.9 where there should be 12.

What diode did you replace to solve this problem?
 
Audio hum on MCRs is pretty common....and can be caused by a lot of stuff. First, they hum a bit to begin with.

Likely culprits.....the small amp board, power supply board caps, any of the three big caps on the transformer assembly, lighting ballasts (Kick has several), weak connectors, weak fuse block.....that should keep you busy for awhile :).

Edward

The two green tantalum caps on the audio amp PCB have been the source of loud hum for me on 3 different MCR games. Thanks Jon Exidy for that tip!!
 
Good info.
I was getting frustrated at these 90412's and couldn't figure out what was wrong.

Plugged it in and was able to get it into spec (was not going to plug in boards with voltage over 6V, but the loading it down seemed to do the trick) but even though the voltage was good (on a DMM) the boardset wouldn't boot (just garbage on screen).

Put in a switcher and WizzyV3 adapter and it boots fine. Tried it with the heavy-duty switcher and arcadeshop MCR adapter and it worked fine. Tried another spyhunter boardset and same thing...sooooo I'm thinking that the 90412's are putting out dirty voltage. Didn't hook up a scope. Sent an email to Bob Roberts to get a rebuild kit.

Either way, I have 4 of the MCR 3 dual-power amps.
#1 works great and I put in another SpyHunter that was just sold.
#2 Hisses
#3 loud hum
#4 Channels 4, 5, & 6 are really scratchy when doing sound test.

All of these were tested with the same boardset in the same cabinet. I tried switching out with the working 90412 that I had (it went bye-bye with the sold Spy Hunter) and there was no difference in the noise vs. switcher powered.

Will try to get some of the green tantalum caps and see if that helps. I replace the electrolytics on amp #3 and it didn't change things.

Any other ideas. I have done a lot of swapping out and am very sure that the differences have been isolated to being something on the Dual-Amp boards.
 
go to http://www.orderfrombob.com/

search (Ctrl-F) for "90412"

There are a couple entries. Hope that helps.

BTW, I sent an email on the 23rd and haven't heard back from him or his helpers yet. Hopefully just the holidays slowing things down.
 
Looks like a good time to be working on PS boards for Tron/Spy Hunter. I've got three I'm working on right now. I rebuilt one with a kit from Bob Roberts and its works fine in both games.

On to the second one - rebuilt and tested in Spy Hunter before hooking up the boards - had +5,+12, and -5 volts. When I hook it up to the game I got garbage on the screen. Tested in Tron and the game comes up and plays, but no sound (unregulated audio voltage is at 16V). Tested it again in Spy Hunter and the game came up - but also no sound. Then the game went to garbage. Now the +5V is at 3.3V and can't adjust with the pot. Anyone know what to check for the drop in +5V and also why no sound?

Will wait to rebuild board #3 until I figure this one out.
 
Bump - just curious if anyone has seen as issue with the Tron/Spy Hunter PS board that results in no sound being produced from the game.
 
No sound at all could be indicative of no 12V power to the board set and Cheap Squeak Deluxe (CSD).
 
Follow-up, replaced tantalum caps

Good info.
I was getting frustrated at these 90412's and couldn't figure out what was wrong.

Plugged it in and was able to get it into spec (was not going to plug in boards with voltage over 6V, but the loading it down seemed to do the trick) but even though the voltage was good (on a DMM) the boardset wouldn't boot (just garbage on screen).

Put in a switcher and WizzyV3 adapter and it boots fine. Tried it with the heavy-duty switcher and arcadeshop MCR adapter and it worked fine. Tried another spyhunter boardset and same thing...sooooo I'm thinking that the 90412's are putting out dirty voltage. Didn't hook up a scope. Sent an email to Bob Roberts to get a rebuild kit.

Either way, I have 4 of the MCR 3 dual-power amps.
#1 works great and I put in another SpyHunter that was just sold.
#2 Hisses
#3 loud hum
#4 Channels 4, 5, & 6 are really scratchy when doing sound test.

All of these were tested with the same boardset in the same cabinet. I tried switching out with the working 90412 that I had (it went bye-bye with the sold Spy Hunter) and there was no difference in the noise vs. switcher powered.

Will try to get some of the green tantalum caps and see if that helps. I replace the electrolytics on amp #3 and it didn't change things.

Any other ideas. I have done a lot of swapping out and am very sure that the differences have been isolated to being something on the Dual-Amp boards.

replaced all the tantalum caps on all 3 Dual-Power Amps and it didn't seem to make any difference. Only -after- I went to that trouble did I unplug the audio out from the CSD. Quiet as can be with perfect sounding game audio (no Peter Gunn theme, of course) and no hiss... so now I know it has something to do with the CSD. Interesting thing is that it didn't do that (that I remember) with the best Amp. Might have to ask the new owner if I can borrow it back for a little bit for troubleshooting.

Did a little research on CSD problems causing a humm, but haven't been able to try any of them yet.
 
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