Dr Who mini pf not working

[robm]

Hi All,

Have a Dr Who with Mini PF not working at all during mini pf test or gameplay.  Things i have done:

Completely stripped and cleaned mini pf

Use 12V battery, mini pf works fine when connected to this, moves smoothly

Swapped CPU with known 100% working one - same issue, Mini pf does not work

Swapped Power Driver board with known working one - same issue, Mini pf does not work

Swapped Motor driver board with known working one - same issue, Mini pf does not work

Triple checked connector plugs to and from motor driver board

Continuity from motor to motor driver board is fine (although i when i put one lead on red motor wire, it gets continuity to both red and black on motor driver board)

Fuses all test good (tested out of machine)

Home opto on mini pf works fine in switch edges

Playfield glass switch is fine, and i push this down during testing

All other functions of mini pf work (kickers and flasher)

This was a machine left in storage for many years, so i have also cleaned the whole machine down - it did actually work a couple of times when i first put it all back together.

Only other strange one i could think of was maybe a dodgy ROM?

Any ideas as i seem to exhausted all possibilities....

Thanks

Rob

[Strangeways]

Stupid question time - Have you shorted the playfield glass switch (top LHS corner). The mini PF will not work at all during any mode, but you will hear audible warnings.

[robm]

No i haven't Nino, just tested it works in switch edges.  Are you suggesting i should or shouldn't?

Also, i have 20v going into the motor driver board

[Strangeways]

No i haven't Nino, just tested it works in switch edges.  Are you suggesting i should or shouldn't?

Also, i have 20v going into the motor driver board

The mini playfield won't work at all unless the switch is closed. From memory, it won't work during test mode. Power is cut to the motor board, as you could easily lose fingers when that mini pf lowers.

[joele]

The mini playfield won't work at all unless the switch is closed. From memory, it won't work during test mode. Power is cut to the motor board, as you could easily lose fingers when that mini pf lowers.

100% correct, close the switch and see if it moves...

[Homepin]

From the OPs message:

"Playfield glass switch is fine, and i push this down during testing"

[robm]

I suspect you guys are onto something.  While it works every time in switch edges AND I connected the wires together before the plug it still plays up. After I shorted these switch wires together it moved up about 1/4 of the way and stopped. Now it won't work again. In game play it says warning warning keep hands away - even with the switch showing closed in the switch edges matrix!

I guess I will look at switches up and down from it in the matrix?

I put new connectors on all the plugs at bottom of mpu as there was some corrosion.  But if this was an issue I would have thought it would take out a whole row or column - not just one switch?

[Homepin]

Maybe this is a direct switch due to its importance?

[robm]

Just had a look at the matrix - its in column 8 (82), all others in that column are not used except Mini pf door right (88).

Might have to do some continuity testing as there may be a dodgy connection somewhere in that column wire...

Too cold now; 12 degrees in North Qld is ridiculous!!

[Pintoxicated]

Have you had a thorough look at the playfield glass switch to make sure no wires are loose and/or diode (I think it has a diode) as well as making sure that the switch arm is adjusted correctly?  If that warning is sounding it isn't recognising that playfield glass switch as being closed.

What do you mean too cold, I think 12 degrees would have been out op temp today.  The car was saying 1 degree when I took the young bloke to footy this morning, we had our first good frost as well.

[robm]

I've twisted the wires together that go to the glass switch, so i am certain it is always closed.

Yeah - i've turned soft, i'm originally from Orange in NSW and moving right up north was the best thing i ever did.  Mum sent me a photo of snow in Orange the other day - in the middle of the day up here its warm enough to go waterskiing in later July.

[Strangeways]

I've twisted the wires together that go to the glass switch, so i am certain it is always closed.

Yeah - i've turned soft, i'm originally from Orange in NSW and moving right up north was the best thing i ever did.  Mum sent me a photo of snow in Orange the other day - in the middle of the day up here its warm enough to go waterskiing in later July.

But does the switch register during the switch test ? You can close the switch but that does not mean it is working. The two wires that go to the switch are often crushed or stretched from the head being folded. I say this because the switch SEEMS to work during the edge test but not during normal mode (intermittent). Does the audible warning message also occur when the door is open ? I can't remember. But if it does, you should be able to go the mini playfield test with the glass on and obviously the front door open.

The fact it worked for a short time is interesting. I know the mini playfield assembly can be fickle, but I've not heard of it being this unpredictable.

[robm]

OK - in switch edges and single switch test, 82 (playfield glass) works fine. I left it on single switch and lifted the playfield, wriggled wires, and it always stayed closed.

The unused switch above it (81) says it is open, however the noise it made sounded like it should be closed.  When you moved to a switch that is closed, or close a switch, the machine makes a different noise - and it makes this every time i got to 81, although the matrix display shows it as open.  Both 81 and 82 have an "(A)" displayed in the single switch test as well - i did not see that in any other switches in the column - does this mean anything???

I also noticed that when i press 88 (mini pf right door exit), that it actuates 78 (lite lock button on mini pf).

[Strangeways]

This is a really strange problem. Boards are ruled out and there are funky switch matrix issues.

There seems to be an issue related to the switch matrix and that switch 88. I was wondering what would happen if you removed those three switches from the switch matrix, which are mounted on the subway ramp. Just pull the connector.

When doing the testing, is the mini playfield in "home position ? Can you connect the 12VDC supply to the motor and set it to the highest point of travel and then re connect to the game and observe ?

I had a similar issue AFTER installing the two cliffy's where the front of the mini playfield jammed against the playfield and simply never moved up or down. I had to loosen the assembly and move it back and it worked fine proving the problem was physical. I know you mentioned in your original post that you have connected a 12V source and it does work, but was it while the mini playfield was in the game or on your bench ?

[robm]

OK, finally had a chance to get a look again at this today. To answer your question Nino - yes i have tested mini pf movement with it installed in the machine - no areas of binding.

Taking a look from the beginning again, i tested continuity from the motor driver board to J122 on the power driver board - all good, and motor driver board light is on.  The voltage is around 9V at the motor driver board - is this a bit low?
 The thing that confuses me is that the manual and the tech chart show different wire colours for J122 - ie: manual in section 3 states pin3 is blue vellow, but tech chart shows blue yellow as pin 4!!! I swapped these around, no difference though.

BUT i am trying to get the motor to drive by grounding the transistor. I assume from this http://www.pinballrebel.com/pinball/cards/Tech_Charts/Bally_Doctor_Who_Tech_Chart.pdf that Q22 is the correct one?  When i ground it, nothing happens. Also, i am not sure of the function of Q20 (mini pf on/off) - do both need to be grounded together?  Q20 grounding by itself does nothing as well.

Thanks in advance