Hankin display problem

[Mr Pinbologist]

Hi Guys, I've been working on AP member howzat's, Hankin Howzat pin. Got it just about all sorted now except for the problem with the displays pictured below. For want of a better deskription of the fault, it has 'ghosting' on the digits which should be blank.. when the display should show just 00, the other digits are just on, glowing dimly. Also when the game has been played and its displaying scores, they are a bit hard to read as a result of this. Apart from this fault the rest of the game works normally.

The fault is on ALL displays, i have eliminated the displays themselves as being the fault by running each display one at at time with the others disconnected, (i originally thought one display may have been affecting the others). So im guessing it may be an MPU board fault 

Any ideas anyone????  i'd like to sort this one out if i can.

Cheers...Mitch

[dj10555]

Unusual fault! Have you tried swapping the 6821 on the MPU around? Might also be in the connector which runs from the MPU to displays. Is the connector anywhere near an acid damaged section of the board?

regards Derek

[Mr Pinbologist]

Hi Derek, yes i tried the 6821, fitted a brand new one as well as swapping it with the other one on the board. I also replaced the 470pF ceramic caps on the digit select outputs from the 6821 ic, to no avail. The connector seemed to be ok, havent looked at it in great detail as yet, and there is no acid damage on the board at all to speak of.

I DID also change a couple of the other ICs the 4502 which fixed the lamp problems it had and a couple of others, cant remember the board reference numbers, and the pdf copy of the schematic i have here is hard to read the component values  Ian has the full manual for his game which has come in handy so far for sorting the other issues it had.

[Skybeaux]

I had the same kind of problem with one , except that it was only ghosting on 1 of the displays and the others were fine.
It turned out to be one of the smaller chips on the MPU board but i can't say from memory which one.
I'm sure it was one of the 4011's or 4049 but i'm unsure.

[Mr Pinbologist]

I had the same kind of problem with one , except that it was only ghosting on 1 of the displays and the others were fine.
It turned out to be one of the smaller chips on the MPU board but i can't say from memory which one.
I'm sure it was one of the 4011's or 4049 but i'm unsure.

Thanks Ken. I know i replaced a 4011 on the board, there is also a 4049 that is part of the blanking circuit which i dont think i've changed, will try that next time i'm at Ians house.

[deep six]

Hi Mitch

I have the same machine sitting here waiting to get fixed, if you like you can borrow something from my machine if you need to swap over something to troubleshoot it.
Ian helped me out with a wiring diagram for mine so only too happy to help if I can.

Cheers

Ric

[benpin]

Had a problem, just very close to your issues. Pay a very close attention to the wiring loom that serve the displays,
Where in come in at the bottom of the display board and daisy chain the displays.
Have a very close look there and see if the wires are pitching or shorting that causing wacky displays issues
This issues sent me a wild  and nightmare chase, try everything from replacing the MPU and the display driver chips,
only end being wiring being shorted.

Hope this solve your problems and Good luck. 

[The pinballist formally known as Dean Morgan]

Connector on cpu maybe?

[Mr Pinbologist]

Hi Mitch

I have the same machine sitting here waiting to get fixed, if you like you can borrow something from my machine if you need to swap over something to troubleshoot it.
Ian helped me out with a wiring diagram for mine so only too happy to help if I can.

Cheers

Ric

Thanks Ric thats a really cool offer  I might just take you up on that offer if the other suggestions offered dont help. I'll try a few of the other suggestions first (thanks for the suggestions guys) 

from what i could tell the connectors looked fine when i had initially checked them.. ie no corrosion or anything like that, i havent been back to Ians to do any more work on the game (been busy house/job hunting). soon as i get settled in the new house i'll get back onto it. But i WILL have another real good look at the connector that runs the displays before doing anymore mpu board work.

Thanks again, Cheers.. Mitch

[Mr Pinbologist]

PROBLEM SOLVED  

This little issue with this game had me scratching my head for a LONG time  

Well today while doing some work on this game, i decided to have another look after Daniel (ddstoys) had sent a PM some time ago about a Hankin he was working on that had the same issue, and he had swapped power supply boards and that fixed the display ghosting problem.

Anyway to cut a long story short, after checking voltages, i found that the +8v offset voltage that goes back to the display filament winding on the transformer was missing.. turned out that zener diode Z1 was shorted. After a quick drive to Jaycar, and a few minutes to fit the replacement.. success at last  

Just thought i'd share what i found for anyone else with a Hankin with display ghosting issues, and may be of assistance to them!

I have attached some before and after pics.. sorry the 'after' pics arent that great, only had my mobile phone to take them but you get the idea.

Cheers...Mitch