Hey guys - just picked up my first Data East game; a Maverick with a few issues I am trying to work through.
I have some experience with Early SS Bally/Sterns but I'm getting stuck here. Just looking for some input/guidance to get this one working.

Let me give you a rundown of this project so far and the problems I'm trying to figure out.

When originally picked up the main issues as told was, the DMD was dead, as well as the flippers.

- So far, the DMD has been replaced and is working 100% as far as I can tell.
-power supply has +5 and 12, but -12 isnt there. reading .500~

-low volume on speakers, and very loud hum/buzz from speakers(louder than the usual DE hum) volume pot inside coindoor does nothing. I’m guessing this is due to the missing -12V

- It came with a Rottendog flipper board and new coils, which are now for the post part working.
Originally they only seemed to work in the test menu, but they do work in game (somewhat). The ball lock coil isnt working so it has to be fired manually to eject the ball into the shooter lane. Once plunged the flippers have power. I assume this is working as intended?

I've gone through the test to track down some other coils/flashers that are not working and have highlighted the attached page from the manual.

I'm trying to get that ball lockout in the trough/shooter lane going first but suspect that a few of these issues are linked.

So far, the following has been done.

-confirmed power to the coil. reading 45v on both lugs
-confirmed the diode at coil is working, even replaced it with a new one, banded side to the power lug
-replaced q46 transistors
-shorted q46 to ground, coil fires
-confirmed continuity from connectors to coil on cpu/ppb
-reflowed all pins on both ppb and cpu

I am starting to suspect an issue farther up the line in the ICs but would like to exhaust my options prior to shotgunning ics as i currently dont have access to a logic probe.

Any help/input would be greatly appreciated! Maybe some of you DE guys see something I don't
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-12Vdc was missing when I picked up the game. I cannot for the life of me find any topics, guides, anything regarding a fix for this, so I’m not sure where to start with it.

It crossed my mind it would be effecting my coils but, no where to start with it.

As for coils, I’m setting my sights on getting the assembly lock out working. The pre transistor was replaced, tip122 replaced with a a tip102.
Continuity confirmed. fired the coil via shorting the transistor to ground. Tested and even changed the the diode on the lugs. And tested voltage to the lugs. 45vdc to both.

I have some 7408s arriving Wednesday, and may also have access to a logic prob then as well

Pulled the power supply. Tested the bridge rectifier at DB1. Tested .400-460 on both sides -/+. From what I’ve seen it should be between .400-.600, correct?

I reflowed all the header pins while I had it out.

Put it back in and tested voltages without the cpu hooked as it’s laying on my table.

+5vdc reads 5.06
+12Vdc was 16vdc and change
-12Vdc tested at .526 (same reading at the -12Vdc pin on the harness to the sound board.

Tested at the rest of the BRs on the back back box. All with in .400-.500

Poked around at CN1 feeding the power supply AC... and to my surprise... it looks like it’s wired it reversed?

I’m getting 9.23~- AC on pin 2-3 and a fluctuating reading on 1 which I assume it is the ground. From what I’ve read they’re supposed to be on pins 10-12. I forget the actual readings now for the other 3 pins(I believe 12, 23 and 1.12~), but it’s a newer 12 pin connector with a key pin.

Am I right thinking that would be a common burnt connection, that would need to be replace, and someone wired it backwards, or would I have a lot more issues /dead boards?

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Replaced C1 cap and DB1 just now.

-14VDC with no cpu installed. The speaker hum sounds “normal” now. Although I didn’t hear the Lauren Belle sound. Last night I’d still get it without the cpu.

I’ll put that chip I pulled out back in now as they arrived today and see what I get with everything back in the head
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Yeah...I totally missed that... ugh.

I've been multitasking, being a new dad, trying to work on this project. Probably rushing a bit. Which is bad news.
I did question the health of this meter last night though.

That -12VDC was actually jumping around from -/+35mv which is probably why I have NO sound now. I'll try to do a deeper dive on the psu tonight.

But a bit of good news is that 7804 I replaced restored my Left 5-bank drop target solenoid, and the Lauren Belle wheel, which is nice...I guess.

Ok checked the harness coming from the transformer. It seems all there. I spotted the grn-grey/solid grey connection that splits to the flipper board.

Measured the voltage at CN1 coming to the Power supply.

pin 1 purple 22VDC
Pin 2 orange 35VDC
Pin 3 orange 35VDC

Pin 10 grey-green 23VAC
Pin 11 solid grey 0.850VAC
Pin 12 grey white 11.68VAC

Also measured the BR at DB1 although I’ll be honest, I don’t now enough about them yet.

Top left corner 11.45VAC
Bottom Right corner 11.85VAC

Pulled all the fuses and checked the holders. I didn’t see any damage/cracked. They all feel strong

TBH I wasn’t sure what you meant about measuring AC ripple on C1.

I assume, set to AC and put leads on -/+, and same for DC?

On another note; I did some work on the mpu and got all those coils/flashers working now. I believe I have some insert flashers that are out but I’m fairly confident they’d work with a new bulb.

Also pulled off the rom and cleaned it up.

I was getting some intermittent switch troubles. They’re all test fine in diagnostics, but wouldn’t register in game. That seems to have cleared up.

So all that’s a nice little win. I’ll dive back in on that -12Vdc again when I get home this evening.

measured C1 voltage

12 VDC and 0.001 VAC

pulled the cap out, resoldered. checked continunity to -12 TP4 and also from the DB1 lug that is on the same trace (topside) to C1 as well as CN6 2

still gettinng between -12 to 30mv at TP4 and CN2 on soundboard.\

No sound

I'm stumped.

Sorry to clarify

C1 measured +12VDC and 0.001VAC
TP4 was still measuring in mv (-12mv +30mv)

I even desoldered the 1000uf25v cap at c1 to double check its polarity silkscreen on the pcb and check the schematics. Negative/ Andes leg to the out side of the board or down if you’re looking at the pcb mounted in the Backbox.

I have not seen -12V anywhere yet, on or leaving the board. (TP4, C1 or at CN6)

Also he’s the measurements I took from DB1 looking straight at the psu installed in the box. With CN6 connector and C1 left of the drawing.

Is the lug reading 11.81VAC supposed to have continuity to the large pad that it sits in? Looks like a ground plain but I does not have continuity to any leads I have tested on that pad.

D782F85E-CC75-4BDD-A4F8-6825059AC03F (resized).jpeg

Also confirmed continuity from CN6 pin 2 (psu) to the -12Vdc pin on CN2 to the sound board. Which also has continuity to FB3 and that row as well as the tab of VR1.

Ok so this is all over the place.

Just tuned it on.

I’m getting .955VDC at TP4

Tested at CN6-2 -16.15VDC
Same at CN2-3 -16.15VDC
As well as FB3

So now I’m missing +12VDC to pin 3 & 6 of CN6

TP3 is testing fine though

Ok traced the issue back to the lug of DB1 on the top side of of the board. Reflowed and bam! Sound is back, volume knob works. We’re in business!

Thanks so much wayout440 for sticking with me on this!

So obviously still have some quirks to work out.

Ball trough coil kicks 2+ balls out at the start of the game. Put 4 new rollover switches and diodes in. Same thing.
Sometimes in switch test it registers the balllock as 6 ball instead of four. Starting that two non used switches are active.

Tested the switches at the board and they check out fine, so I don’t think it’s a short on the board itself.

Clearing a set of drop target banks starts firing different coils
Ie. dropping all of the 5 van special DTs will start cause the VUK coil to fire 3 times, pause, repeat etc.
Four bank will cause the the ball lock coil to fire

Did a bit of testing with that method yesterday and ruled out it being on the board.

Took a closer look at things today...

I believe a previous owner put a 5 bank DT in which had a lose white-brown wire dangling by one of the switches and touching everything. Reattached that. Also the connector to the playfield harness was still pinned for whatever game that DT came out of. So I swapped the wiring around to match the harness. Also whoever had it before me must have been trying to track things down as the white-red wire on CN10 at the board had been pulled out and then soldered to the connector. Fixed that up and everything seems good except for that mangled DT bank.

The reset bar is completely reamed out and missing e-clips where the two rods hold it to the body and so it’s mechanically fuckered.
I don’t think the stop adjustment bolt was right and it also has a Williams coil and plunger link which binds up because everything is so twisted.

I found a full replacement bank and a knocker coil assy as that was missing as well. Hopefully they arrive sooner than later as I want to clean this up and start playing the hell out of it.

As far as I can tell everything is playing as it should.

I have to sort out the cabinet speaker, it’s not working, and the back box speakers sound very tinny. I assume it’s the amp. Just some GI connector replacement at the psu, take a look at the optos and some tidy work and I think it’s good to good

Yeah this is exactly what I had wanted as a project. 99% of the game is there, parts wise. I wouldn’t say it’s working 100% mechanically or electronically, -pretty close- but it’s in much better shape than it was a week ago when I first picked it up.

I was pretty intimidated working on a more modern system at first; my first pin was a Spy Hunter that I picked up less than a year ago. I got pretty comfortable with the old Bally systems as that game had me mauling the whole cabinet and all the boards with every issue you could think of.

Either way there’s definitely some light at the end of the tunnel for this game that no one wanted to fix.

Again, I appreciate the guidance! I’m sure I’ll have more questions once I begin to dial everything in a bit more.