Problem Atari power supply help

[Body pop]

I checked at the power supply (big connector plug unplugged )
I never actually checked with that plugged In as couldn’t get multimeter in there
So I would need to follow those points you showed me to somewhere I can get the multimeter on it then

 

[Ace`]

You can check at the power supply with the plug plugged in and power off to see if the resistance is very low, you will then know you have a short or not. You just don't know what's causing it this way but it's a start.

 

[Body pop]

So checking at the power supply it’s showing 0 .
At the power supply with big plug plugged in
That’s in dc mode
On smart it shows this

 

[Ace`]

With the machine OFF and the meter set to this setting (ohms) what reading do you get?

 

[Body pop]

Thanks 🙏
Below I took readings
First is with all connectors off pcbs
Machine turned off and big plug attached

next reading pic -with one (bottom)power connector removed from pcb

Last pic is reading with all connectors off pcbs

Is there any clues there ?

 

[Body pop]

Does any of those readings mean anything ?

 

[Ace`]

Sorry forgot to reply, those look normal no short it seems. Without schematics or wiring diagrams its going to be very hard to help any further.

 

[Body pop]

Sorry forgot to reply, those look normal no short it seems. Without schematics or wiring diagrams its going to be very hard to help any further.

Thanks mate ,you went above and beyond as usual.
Very much appreciated 👍

 

[Body pop]

Has anyone any experience of running one of these on a switcher ?

 

[Bods]

The paperboy I had was fitted with Jamma PSU for 5v but I didn't wire it up, if I could get to my cabs I'd try and help as it's much easier with cab to look at what your doing but that's always my issue
Would have thought a few others here would know a fair bit on 720/Paperboy cabs to advise, not worked on them that much myself so far, mainly sorting PSU/Transformer for Toobin but not sure how that compares to these

 

[Body pop]

Interesting ,as the bottom board in my cab is championship sprint
So I would imagine that would be the same
Would love to get this going again
Its giving nothin on screen at all now ,monitor comes on but its just blank basically
There’s also the 15 v situation,id need to find where it goes and check its getting that too
There’s always the mame option I suppose


Getting to the back of cabs is the enemy of having them

 

[Ace`]

You'd have to check to confirm before doing it but I think it's a case of cutting the ground and +5v wires I labelled (on the big plug) and connecting them to a switcher and leaving everything else as it is. I don't know what the +15v (AC?) is used for but if you leave everything else and it's working you wouldn't have to worry about it.

 

[karlcdoe]

Interesting, that looks *nothing* like the setup from my genuine Atari Ireland 720 degrees that came out of an arcade in Grat YArmouth in the mid 90's.

 

[karlcdoe]

The images posted above of the schematics appear unreadable on my pc however I made a very nasty test loom for Paperboy/720 from a scrap paperboy loom ages ago and most of it runs on +5v but you do need +15v to drive the video amp (I think) and/or hit the reset circuit over the head or you just get a black screen. I think it might also be used to tell the nvram to write the high score tabe before the 5v collapses on power down.

On the very faded masking tape wrapped around the loom it looks like the extra voltage needs to go to a pin on J15 on the cpu pcb and that looks to be a yellow/white wire one pin away from the edge on the end furthest from the 'key' pin and it is also conected to the power connector on the video pcb as shown in the pic above.

I suspect I might have got away with wiring it up to +12v on a switcher before I upgraded to a bench power suppply but time passes and recollection without revision has faded into that past

Obviously wiring +15v to any incorrect pins will result in terminal magic smoke escape so be very careful.

 

[Body pop]

Great info today guys
Gives me some hope
Yeah those schematics are unreadable ,I didn’t even realise I’d posted them as I was the middle of writing a post
Worked out well though as some good advice here

The terminal magic smoke worries me
I’ll most likely try finding that 15 v and making sure its there
Then doing what ace says and putting the 5 v and grounds on a switcher
Can I safely use a separate mains plug for it for now ?

I think I came across a few of your posts in another thread while searching karlcdoe
Have you still got the 720

 

[Bods]

Interesting ,as the bottom board in my cab is championship sprint
So I would imagine that would be the same
Would love to get this going again
Its giving nothin on screen at all now ,monitor comes on but its just blank basically
There’s also the 15 v situation,id need to find where it goes and check its getting that too
There’s always the mame option I suppose


Getting to the back of cabs is the enemy of having them

Champ Sprint is same boards but they used newer power supply stuff than the Paperboy cabs, question is was 720 same as Paperboy or Champ Sprint, that I can't remember, all require same voltages though