MCR power chassis/brick and supply overview

jacklick

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Donor 9 years: 2013, 2016-2021, 2023-2024
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I know I get a lot of benefit from watching other's videos so figured I would try to put one together. I liked Dokert's Atari power brick overview and didn't see one for testing MCR and since I am putting one back together for a spy hunter might as well try to share a bit.

I am not trying to be a youtuber so no need to subscribe but happy to hear comments for improvements to make future ones better.

Oh and sorry for the dirty fingers, was sanding and painting arcade parts earlier in the day and forgive use of incorrect terminology etc...it is mostly for jacklicks like myself in this hobby not the experts :) Hope it helps someone.

 
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Very nice video! Thanks for doing this.
 
Very nice video! Thanks for doing this.

Thanks. I found your printout of the J4/J5 connectors on PS board which is helping me on next phase of testing. Did you do that in excel or other? Was thinking of augmenting it.

Anyway, I am puzzled (might do another thread) on why the filter capacitors are generally and partially associated with creating the audio hum. On both my Tron and Spy hunter the power amp is getting fed the unregulated isolated 12v which doesn't even touch those filter caps.
 
Hah, that wasn't my chart. That was a reference that I used when troubleshooting voltage issues with my Spy Hunter.

And then a couple of years ago it disappeared off the web and I spent some time reconstructing the info from archive sites until it was back together again. I just posted it here so that other people could use it because it's pretty handy.
 
jacklick said:
Anyway, I am puzzled (might do another thread) on why the filter capacitors are generally and partially associated with creating the audio hum.
Because the regulated 12v is fed into the ssio - the lm3900 and 3403 amps in the pre-amp portion of the sound circuit.

jacklick said:
On both my Tron and Spy hunter the power amp is getting fed the unregulated isolated 12v which doesn't even touch those filter caps.
The unregulated 12v (usually betwen 14 and 15v) is filtered through the big 4700uF cap on the 90412. Only the coin door lights and counters aren't filtered.
 
Because the regulated 12v is fed into the ssio - the lm3900 and 3403 amps in the pre-amp portion of the sound circuit.


The unregulated 12v (usually betwen 14 and 15v) is filtered through the big 4700uF cap on the 90412. Only the coin door lights and counters aren't filtered.

Got it. Thanks for the info. I know you have been in the weeds on this system for a long time.

Has anyone ever tried messing with jumper jw1 or jw3 or even jw4? In my thread searches I haven't seen them mentioned related to experimenting with eliminating hum.
 
good job on the video

my two cents added to all this is that they sell that silver capacitor at Grainger real cheap like 4 bucks but that was a while ago since i bought one but who knows how much it is now
 
good job on the video

my two cents added to all this is that they sell that silver capacitor at Grainger real cheap like 4 bucks but that was a while ago since i bought one but who knows how much it is now

Thanks. I have new respect for others that can make these videos...I am tripping all over my words, using incorrect terms in addition to umming, ahhing and weird lip smacking (wth is up w/ that).

Despite all this, I tried again and revisited the power chassis to include measuring AC ripple voltage and putting these large caps on an ESR meter. Feel free to offer technical corrections and input.

 
Is your DMM true RMS?

I was told recently that the checks for the AC ripple that you did (and that I've done in the past) are only valid on true RMS DMMs but I'm not 100% sure of that.
 
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Is your DMM true RMS?

I was told recently that the checks for the AC ripple that you did (and that I've done in the past) are only valid on true RMS DMMs but I'm not 100% sure of that.

Good question and info as I was/am not aware of that caveat. Below is from the manual for the BM235. I am a complete layman so have no idea what most of it means but will assume the meter is sufficient until someone educates me otherwise :)

I do have an oscilloscope that I am happy to leverage to test these larges caps with as well, if someone tells me how.

Source EEVBLOG BM235 User's Manual
True RMS
RMS (Root-Mean-Square) is a term used to describe the effective or equivalent
DC value of an AC signal. True RMS is the term which identifies a DMM that responds
accurately to the effective RMS value regardless of the waveforms such as: square,
sawtooth, triangle, pulse trains, spikes, as well as distorted waveforms with the
presence of harmonics. Harmonics may cause :
1) Overheated transformers, generators and motors to burn out faster than normal
2) Circuit breakers to trip prematurely
3) Fuses to blow
4) Neutrals to overheat due to the triplen harmonics present on the neutral
5) Bus bars and electrical panels to vibrate
Dave's Note: Whilst this is a True RMS multimeter (that's good), like most lower
end multimeters it does not use a separate True RMS converter chip. It relies
upon the internal multimeter chipset capability. This gives the meter a low True
RMS frequency response of only a few hundred Hz (check the specs), and is
typical of other meters in this class. Don't be fooled thinking that "True RMS"
automatically means "high frequency range measurement".
 
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Thanks. I found your printout of the J4/J5 connectors on PS board which is helping me on next phase of testing. Did you do that in excel or other? Was thinking of augmenting it.

Anyway, I am puzzled (might do another thread) on why the filter capacitors are generally and partially associated with creating the audio hum. On both my Tron and Spy hunter the power amp is getting fed the unregulated isolated 12v which doesn't even touch those filter caps.

Well not sure if it's truly augmented but I did put this drawing together for a prop in my next video.

The black dots represent pins that are used in my Spy Hunter.
Dotted circles link common pins.
Red is for positive on +5 reg
Green is for positive on +12 reg

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Hate to spam my own thread but was curious about the sense line on these MCR power boards. Maybe cdjump can jump in again.

I can't figure out if the sense lines or ckt are even used on these games. The -sense line is tied to gnd, via jumpers jw1 and jw3, on the power board. I believe is similar to doing "the sense mod" on Atari AR power supplies. Additionally, my spy hunter doesn't have the sense lines wired to the game boards anyway.
 
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Video of the power supply board. Again, I know I likely have some stuff wrong so feel free to correct. I will say that by making the video it forces me to try and read/learn/understand a bit more which is ultimately benefiting me...I think/hope.

 
Quick one on replacing the battery with coin cell. Note the game doesn't require a battery to boot. I thought I read that somewhere but it boots fine w/ or w/o battery.

 
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MCR Spyhunter HUM issue solved!

and the reason I even started down this MCR discovery path. MCR Hum issue solved. Might do at least one more, in the future, on a different power supply that has a reset ckt issue.

 
That's pretty cool; glad you found the issue!

It's kind of odd; those caps weren't reading that far off from the new ones you used...
 
That's pretty cool; glad you found the issue!

It's kind of odd; those caps weren't reading that far off from the new ones you used...

I know I was surprised. I guess, in theory, plugging and unplugging and plugging back in the power boards and cheap squeak multiple times could have helped but that sounds more improbable.

Also the ESR spec could be different on the new caps vs the old. They were measuring out of typical values but could have been even more from their original specific spec or maybe the cheap squeak was just more susceptible to whatever noise they were causing. Guessing a bit....a lot.

So in conclusion, for my Hum issue at least, no need to replace the big chassis caps or even the isolated 12v 4700uf audio ckt cap.
 
Was searching Mid-Atlantic Arcade group on facebook and found this which is 1000 times better than my description of the components in the video. I briefly reviewed and the only thing that I think is incorrect is the Gray sync ckt reference. That is actually the "pump charger" which feeds the "one shot", both of which are part of the reset ckt....based on my understanding.

Not sure how the AC sync ckt truly works but only U4 &R202 are involved in the below diagram. U4 feeds the rest of the AC sync components (u6, c207, r219, etc) which are not shown.

<<edit>> Also will mention, for those that don't watch the video :), that the fuse F1 is actually part of the +5 regulation ckt. U2 and Q105 get their power from the unreg +12 straight from game transformer. here is where I discover that https://youtu.be/OpBOEqojOJY?t=3m48s

Anyway still nice little diagram.

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Is there a higher resolution version of that picture available? A direct link maybe?
 
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