John's Arcade Forum - Classic Arcade and Pinball Collecting and Restoring Discussion Forum - RETRO MAME - Nintendo Vs Forum

Hi all-

Noob here. After watching some of John's tech videos I decided to buy a couple troubled games and try to fix them myself.  I have some experience fixing older pinball machines, mostly parts replacement and some light work on PCBs replacing parts and reflowing soldering.

When I bought Pole Position, everything seemed to be working fine except that cars and signs in the distance were appearing as blocks.  However, shortly after I brought it home it started having a garbled screen and the sound was going bonkers.

The test screen says that both RAM and ROM are okay. 

Here is a photo album of suspect things I've found in the cabinet with descriptions --- some cut hanging wires, wires soldered to the PCB, a disconnected fan, a bunch of unattached ground wires: http://imgur.com/a/lYd9V

I haven't pulled out the boards because some of the wires are soldered directly to the PCB and I didn't want to start messing with it until someone can suggest a solid plan of action for getting this machine working again. 

I'm comfortable with testing voltages and replacing parts on the PCB, but my knowledge about where to test voltages and what to change out is pretty much zilch.

Thanks in advance for any suggestions.

fix the harness up. Get all of the soldered mess out of there and start working through the wire harness making sure everything is fine.

You have a long road ahead of you.

Build up some cables with .250 spade connectors to connect to the test points on the board, you will have to figure out how to splice them into the power lines on the harness. Its possible the board just isn't getting enough power. Pole position needs at least 4.5V, sometimes you can get  lucky and it will run down to 4V but that is rare.

Once you get the harness sorted out we can talk about PCB repairs if that is still required.

The soldered wires might be jumpered wires for the voltage mods like I showed in my Pole Position bullet proof video.

Someone on KLOV directed me to your Bullet Proofing video. Once I watched it I understood that (as you say here), the soldered wires were bypassing the harness to the edge connector, which had been retinned on Pin A on the first board and Pin A & B on the second board. I desoldered them, cleaned them up and and jumped them to test points on the board.

I tried the bullet proofing as per the video-- was very meticulous about it, triple checked my work. Before I did the bullet proofing, the game would at least play, it just had a screen that was looking pretty crazy.

When I plugged it in after the bullet proof mod it went straight to a stuck garbled screen. I unplugged it immediately, double checked again, I feel like I did the right thing as described. In the video you had the wires going to all the appropriate test points on the board, which is how I did it-- but to make sure I hadn't made an error I removed all of the bullet proofing wiring and tried only tapping into one test point for the 5v and one for the ground for each board. This did not change anything, I still had a frozen garbled screen.

I used the ground wires going to the A pin on the edge connector each board and bypassed them to a ground test point, and the 5v wires going to the B pin and wired them to the 5v test point. On the pinout I did notice that there is a second 5V at pins R  on one board and Y on the other- should I be diverting those as well?

I pulled up and reseated all the chips as well.

Iankellog- I tested the 5V wires and am getting a solid 5V on each  are you suggesting I bypass the entire harness with all the wires to various test points on the board? I know how to test for voltage--  but most of these are ground wires-- how do you test a ground wire exactly? Forgive my ignorance.

If you are getting around 5V measured at the PCB then you are fine. just make sure both PCBs are getting 5V as they don't share the same power supply.


It sounds like you did that though and your next step should be getting the board out of the cabinet and prepare for board repair.

Get the board out, inspect it, take photos and post them here. I see that pattern often when the z80 sound processor is dead or the 52XX custom chip is dead/damaged/missing


Check around the battery, make sure its GONE and there isnt any battery acid damage. That is a very common failure and it usually takes out the z80 as well as the reset circuit.

Iankellog-

Thanks for helping me troubleshoot this.  To clarify, I tested 5v wires before they touched the board. Should I be testing directly on the board when connected/plugged in? There is no corrosion of the battery that I can see, but if I remove the battery, do I need to bridge the gap it leaves with wire?

I inspected the boards and found a few suspect areas. I posted another album-- this is as high a res as I could get w/ my phone but I could potentially use a better camera.  Suspect areas are circled in red: http://imgur.com/a/pkwzV

Remove the battery and do not out anything back into it.  If you want high score saving we can talk but for now just get that battery out of there.

You need to be checking the voltage at the board while it's running.

By no means am I an expert - but I am a fellow Pole Position Owner.
It sounds and looks (by your Pictures) that we bought the exact same problem!

Ian made some suggestions to me and I actually got my board working - for a time!

Here is what I did.

1st - unhook your PCB edge connector and test the voltages on the PS - make sure your +5 is as close to 5 as you can get.
After you turn it off and re-hook up the edge connector Power it up and THEN check the voltages at the boards (the jumpers that are soldered to the board) Mine had quite a bit of power loss in the line... So I had to have my brand new power supply quite a bit higher to get the full 5 to the board.

That solved my jumbled screen (for a time).

I also pilled every single chip and cleaned the contacts with a damp magic eraser - keeping in mind I can't replace most of these chips easily so if you do - be careful. 
My board was FILTHY.

My battery was OLD and not working but fine... Others suggest you pull it - do so!

Also - here is an easy and satisfying one!
Take that fan out - peel off the sticker in the center - pull the 3 screws and give the exposed berrings a shot of WD-40 or something.
it will run SILENT after that!  and give you that "ahhh I fixed something satisfaction"  :)

I have had mine up and running for a few hours but it is presently giving me a Blue Screen an a ran error that I can't fix.
Good luck!