Hi, I had to remove the head, disconnect all cables and put it together again.

I guess I just blew my board ...with a "pop" and "buzz" sound. Looks like its was "C1" and "C3", whatever its for.

I named the plugs but there must be obviously a error.

Could somebody please send me photos from the head?

I mean from all plugs inside the head and plugged ones on board?

Thank you so much.

IMG_20171003_142557 (resized).jpg

IMG_20171003_142629 (resized).jpg

I didn't know that. Thank you. I will check and change the caps.

To be sure that I didn't had a black out while playing with the plugs, I still need photos.

Anyone out there with a Truck Stop?

... oh boy ... thank you for help!

I disconnect the the power supply board

IMG_20171003_193619 (resized).jpg

.... and guess what... I buzzed again. Pretty strange without power

IMG_20171003_194003 (resized).jpg

Now the transistor Q5 was blown up.

You are right, normally its hard to get the plugs wrong connected, but this two plugs fits well between themselves:

IMG_20171003_194253 (resized).jpg

Thats the bill, for working in a dark garage and didn't double check the wire colors

Now the lights on playfield are burnig an the displays are showing two letters, no LED on board blinking, no attract mode. Seems the board is dead. I'm new into pinball electronics, but I figured out to check some components.

IMG_20171003_212842 (resized).jpg

I done some measurements in the area above, shown on the photo:

D7 Glas-Diode shorted
Q5 Transistor shorted
R14 Resistor should be 82K OHM but its 33K
R15 Resistor should be 62K OHM but its 5,2K
R11 Resistor should be 47K OHM but its 31K

What will be the result, when a resistor does not have the right OHM-value? Does the board will still work somehow?

Anyway, what do you think. Its the board ruined, or should I try to change the components?

I need a beer

Thank you. I ordered the parts. I will come back. I may need your knowledge

Hi, i'm back again. I spend hours to try, test and learn. But in the end, I get no sign of life. I orded a new CPU, Game-ROM, Test-Rom, RAM PIA and PNP/NPN [...].

I used the pinball 6803 repair guide from pinrepair (Clay Harrell).

I tryed to get the test-rom running, but the board is still dead.

I checked/changed:

C1: 6.8 mfd (non-polarized)
Q2,Q6,Q4: 2n3984
Q3,Q5: 2n4403
D1: 1n958b (7.5 volts, 1/2 watt)
D3: 1n4148 or 1n914
D4,D5: 1n4606 (can substitute 1n4148 or 1n914)

So I took a closer look at the CPU:

There are U1 CPU chip (renewed) at pins 4,5 +5 volts. But pin 6 is only 2,82V (always) - power on = 2,82V...no up no down.

"Reset is fed from +12 volts through transistor Q2 and Q3" = there are no 12V....

Q2 = 0,71V/1,41V/0,70V (renewed) - measurements on legs
Q3 = 4,43V/3,82V/4,54V (renewed) - measurements on legs

"When capacitor C1 (6.8 mfd) is charged at boot up, this will launch Q4 (2n3984) and which opens Q5 (2n4483), thus bringing +5 volts to U1 pin 6 as the reset."

C1 gets only 2,81V and on the other end on C1 we have 0,73V (C1 renewed two times, same results)... guess that not enough to charge the capacitor?

On TP2 we have 4,54V (power supply direct connected the DMM we have 5,1V) and on TP3 12V

I tryed to read the electronic schematic, but its confusing for me. It all starts with 12V on D1 and we have 12V, then trough D1 we have 4,98V on the other side. R1 - starts with 12,10V and ends with 12,08V [...]

Any idea how to figure out, why the cpu dont want to work?

Help needed. Thanks.