Dolly – she’s coming to life

The continuing saga of the Dolly Parton pinball machine…

I bought an Alltek MPU which arrived last week.  Immediately I swapped the old MPU out, and with fingers crossed I turned on the power… (baited breath inserted here)

The game scores, and plays – but the feature lights aren’t working… darn it! (something else inserted here).

After reaching out to GAPAS ( with requests for ideas, my friend Kenny came over to help with some testing. Unfortunately, we couldn’t quickly determine where the problem was. So, we took the boards (MPU and Lamp driver) over to his house and dropped them into his Six Million Dollar Man (painfully held breath) and  EVERYTHING worked!

This is great news!  I was afraid something was wrong with the Lamp driver board and I’d be having to purchase something new, or the new MPU itself was faulty.  But as they worked fine on his machines – I’m back to looking at the Dolly game itself.

Unfortunately, I left Wednesday for a vacation, and just returned home Sunday night [Well, not really unfortunately – it was a great time in Cancun].  I hope to have time tonight to put the boards back into the machine, and check the leads that Kenny sent me over the week and weekend.

I’m very excited to hopefully add Dolly back to the land of the living – she’s never been a good zombie and this half life living dead isn’t what I hope for her.

Dolly – why won’t your switches work for me? – aka the Bally Pinball switch matrix

MPU Pre-Cleaning
U8 image

U8 image

I have been trying to figure out how to address the Bally switch matrix.  I have found (as I have recorded on my issue tracker) that I have 8 switches that aren’t responding.  I looked up how to build the visual diagram of the switch matrix – a grid of 5 columns, and 8 rows.  The first column (0/zero) has switches 1-8, the second column (1/one) has switches 9-16 etc.

I have laid out all the switches based on the game manual and number allocation assigned to each switch – and have determined that 7 of the switches that are out are all on the same column (switches 17, 19-24 – switch 18 is unused), and then switch 34 for a 30point rebound is also out. If this was a Williams game I’d know better how to approach the problem, but Bally addresses the issue of switch management differently – particularly in relation to the matrix.  I know it is handled in one of the two PIA chips (U10 I believe).

I have determined that connector J2 Pin3 is the one that feeds the column.  Now what, not 100% sure :).  I’m guessing I need to make sure I’m getting continuity somewhere else – but haven’t determined that yet.  It is 1am, and I’ve been working on the game for 3+ hours at this point.

Hopefully, one of my great friends will have an idea of how to resolve this.

Dolly – It’s Alive (again)!

Dolly Parton Backglass

Dolly Parton Backglass
The other day I was thinking about the 20k resistor that I didn’t have – and got to thinking.  “Can’t you run resistors in series or parallel to adjust the net value?” I thought to myself.  So, I called my dad as I thought that if you put them in series you then added the ohm rated resistance values together.

I have an 18k, and I have some 1k’s – I need a 20k…  So, I soldered the selected ends together (after calling my dad to verify) and put them in. Hoping against hope – I put the board in the machine and gave it power.

I had the machine  where the LED (which indicates boot status success/failure) to be constantly on. I counted this as progress.

Tonight though I had some more time

So, I re-verified all the continuity points for my U8 IC on the MPU.  And of course found a number that needed to be updated.

If you are a follower/reader you know that I recently determined there was more corrosion damage than I had originally thought (in my haste). So, I spent the past few times that I’ve had free to remove that, and install a socket for the U7 chip.

After this process the LED got through the flicker and first flash.  YAY – there needs to be 7 successful flashes for the game to boot up as each one indicates a phase completed.

Energized with my success I realized that I had not verified continuity on the U7 socket that I had replaced. And remembered belated that there was a trace that had evaporated in the corrosion cleaning phase under U7.  I found one leg of the IC completely isolated from the game – figured what points it needed to connect to.  Verified each of the other 21 legs on the chip – and after 2 hours of testing and soldering I decided to hold my breath and plug it in again.

Watching the LED like a hawk – it flickered.  Then flashed… once..  after a bit of a pause it flashed again, and again, and again, and again, and again, and again – and then there was a sound sequence, and the scores lit up.


The game is now in the same playable state as it was when I received it – but it not longer has the battery leaking more corrosive gasses and destroying the game.  It now really looks like  a Frankenstein machine with trace wires crisscrossing all across the back.  It isn’t pretty, but it is working – and I didn’t have to spend $200 to replace it.  I can live with not so pretty when no one will see it unless they pull the board out of the game.

Now.. time to run down the switch problems…  (next post)

Dolly – Bally MPU U8 progress

With the help of my friends at GAPAS I was able to determine test points and continuity areas of my Bally MPU for the Dolly Parton pin so that I’ll be able to put in jumpers where necessary to resolve the problems with U8.

However, while testing I found that pin 8 and pin 22 were showing continuity. I was pretty sure this shouldn’t be the case, but as I have only this Bally pinball machine – I have no other MPU to test against.

Today I was able to get my friend Robby to help me – as he has a few.  He verified that there should not be continuity between 8 and 22 as I suspected.  But then there is the issue with – well why are they connecting when they shouldn’t.

I knew that pin 8 was supposed to be connected to ground for the power portion of the circuit.  And it looked like 22 should have been to a positive power source – and after checking pin22 did seem to test good to the little through hole solder junction on the board (with a + sign next to it).  Of course this wasn’t foolproof as I was testing continuity between that + and ground… which is a big obvious NO NO.

After having stared at the board so long while determining the pin out connections – I was thinking perhaps it was a bad capacitor.  C13 seemed to stand out to me – it is near the battery, and could have been damaged some way from the acid problem.  Or, perhaps, it was due to heat or some other from when removing the IC stand at U8.

I cut a lead off the capacitor – and like magic no more continuity between + and -.  Now, I’ve added a new 0.0uF Axial Ceramic capacitor to my shopping list for this week at the electronics component store..

Hooray for progress, and thanks again Robby.

Bally MPU Corrossion – Woes and Repair

U8 image

U8 image

I’ve cleaned up the corrosion on my Dolly Parton MPU (Bally) – BUT Some of the traces were really damaged and a few I can’t determine where they should connect, and others might not have continuity any longer.The only component apparently affected that I have had to replace and am concerned about is the U8 chip.Unfortunately I can’t read a schematic well enough to figure out where on the board I should be checking.

I’ve been looking online for a quick guide of what to check and where each pin should connect on all the normally damaged components as this is a REALLY common problem with Bally’s, BUT I haven’t found anything that will really help. Basically a trace diagram for the MPU would be awesome but alas I’ve not turned one up.  And I’ve not found high enough resolution images of the front and back to work from reliably.So, does anyone know off the top of their head where all 22 pins on the U8 should have continuity to?  🙂  If I need to add jumper wires it would be awesome to know where they should land.

I’ve been trying to map this out and here is what I have so far.  I know some of the legs should have continuity with other legs on the same chip – but not 100% sure which those might be, and if the pair also should have continuity to some other component.My notation is IC / or resistor/capacitor #.  e.g. U7.1 = Chip U7 Pin 1

1 – U7.20
2 – U7.21
3 – U6.6
4 – U7.23
5 – U7.18
6 – U7.17
7 –
8 – GND
9 –
10 – U11.29 (??Paired with 9?)
11 – U11.28 (pair12)
12 – U11.28 (pair11)
13 –
14 – U11.68 (??Paired with 13?)
15 – U11.26 (pair 16)
16 – U11.26 (pair 15)
17 – U18.6
18 – U17.8
19 – U17.6/ U10.23
20 – U18.7
21 – U6.4
22 – R12 left leg (also Big pad which I believe leads to Batter + terminal)

Do Pins 11 and 12 only link to the other? Should there be a connection anywhere else? As you can see I’m missing a couple which I’ve not been able to identify.


One of the GAPAS members (Ken) sent me the following based on his review of the schematic:

1 – (A3) U7.20 / U6.5
2 – (A2) U7.21 / U6.6
3 – (A1) U7.22 / U6.7
4 – (A0) U7.23 / U6.8
5 – (A5) U7.18 / U6.3
6 – (A6) U7.17 / U6.2
7 – (A7) U6.1
8 – GND
9 – (DI 0) U11.29 / U7.6 (pair 10)
10 – (DO 0) U11.29 /U7.6 (pair 9)
11 – (DI 1) U11.28 /U7.7 (pair 12)
12 – (DO 1) U11.28 /U7.7 (pair 11)
13 – (DI 2) U11.27/ U7.8 (pair 14)
14 – (DO 2) U11.27/ U7.8 (pair 13)
15 – (DI 3) U11.26 /U7.9 (pair 16)
16 – (DO 3)U11.26 / U7.9 (pair 15)
17 – (CE 2) U10.34 / U11.34
18 – (OD) U18.6
19 – (CE 1) U17.8
20 – (R/W) U18.7 / U10.21 / U11.21
21 – (A4) U7.19 / U6.4
22 – (VCC) R12 left leg (also Big pad which I believe leads to Batter + terminal)
The (A)ddress lines and (D)ata lines will go to multiple chips.

QUESTION: should I be getting continuity between 8 (gnd) and 22 (VCC) ? If not then I’m wondering if I need to replace C13

Dolly – There she is

Prior to any committed pinball machine repair I finished the first initial cleaning to get an idea of how the game will look.  The amount of grime that came off was pretty impressive.

I still need to decide if I want to do any touch-ups at this point cosmetically or not.  I’m inclined to just apply wax to it at this point and let it be, and come back to this in the future.  The cosmetic issues on the playfield are not as important as dealing with the switch and battery issues.


Hello Dolly

Dolly Parton Backglass

Today a friend sent me some information on a Dolly Parton pinball machine.  Of course I had to call and find out more about the opportunity.

It resulted in my purchasing the game.  I’ve started a dedicated page for Dolly Parton along with the associated Task List tracking for things that I need to do, and have accomplished.

Jeremy and I have an agreement to max the Pin collect at 8 machines as that fits comfortably in the space allocated.  With this change I now have 9 – must resolve the overage soon.