The Bally AS2518-17, the AS2518-35, the Stern 100 and Stern 200 MPU and finally the Bally A080-91638-D000 MPU (6802 MPU) have a LED to indicate mistakes during the boot status of the board. It is placed in the lower middle. If the LED is always on, you might have serious problems to repair it. Please do not try to fix your board yourself, if you have not done anything like this before. In 99% of all cases, you damage more than you repair. Sorry to say, but that is my experience...

B) messure the important voltages - LED always on or off:

You can skip this step, if you get more than one flash or at least a short flicker. Check 5V at TP5 and 12V at TP2. If the LED is always off, change either Q2, the LED or the 1/2W 470R resistor. Make sure, that all chips are in their right places and no pin is broken. Once you have taken all chips out of their socket, put them in again. It helps in 2 of 100 cases.

C) LED always on, voltages are OK:

Bad thing, because there are plenty of possible faults. Check, if your MPU is jumpered for the right Prom/Eprom combination. You can find an overview (jumper-information) on this website. Next check, if you have +5V at U9 (6800), Pin 40. If not, or your MPU starts booting by shorting Pin40 and Pin39 together, remove Q5 and order some reset ICs. You can find them in section Sandra. Next remove all ICs in sockets, except U9, U11 and U6. LED still on? Change U11, change U6, change U9. LED still on? Messure +2,40V at pin 3 and + 2,38V at pin 36 and pin 37 / U9. If the voltage is to high or too low, change 9602 (U16) and 74AC00 (U15). LED still on? Might be a defect socket - check for bad socket pins, start with U11 and U9. LED still on? Might be one of the ICs on the left or a broken trace.

D) 1st short flicker:

OK, that is a good sign. U9, U11 and U6 are OK, change U1, U2, U3 and U4. Note: In most cases, there is only one prom placed in U2 or two proms in U2 and U1. One of these ICs has a fault. Sometimes even a bad U6 can cause problems. you can see the proms in sockets U1-U2 on the left (MPU with Future Spa Proms)

E) 1st flash:

Change U7, a 6810 static ram. Usually, these don´t go bad, so you might have other defects like shorted or open data lines etc.....

F) 2nd flash:

Change U8, the 5101. Do not replace it with a 2101 or 5101 again, use the EEpromadapter and also remove that stupid battery. You can find this adapter in section Sandra. Sometimes it is the 6800. If your MPU starts without a working 5101, it is the 4011.

G) 3rd flash:

Replace the PIA at U10. Replace the 4049. There might be also a bad socket or a bad capacitor or resistor at an outgoing port PA or PB (messure voltages and compare them!). If not, you have a broken or shorted trace.

H) 4th flash:

Replace the PIA at U11. Replace the 4049.

I) 5th flash:

Replace C16, then the NE555.

J) 6th flash:

Might be a broken F4 fuse. Messure 21V at TP3. Change U10. Change U14 (4049). Change R30. Change R113 (2K). Change R17 (150K).

K) other fixes:

Games with chime unit: If the bumpers and slingshots are energized instead of the chime unit, you have a bad J4 / MPU connector.

X) NTOAQ (not that often asked questions):

Q: Why do some repair facilities do not repair MPUs with Augat and brown sockets? A: I do not know. From my point of view, especially the Augat sockets are quite the best ever used ones, however the brown sockets with the plastic cap placed on top of the socket indeed cause problems..

Q: Why does my Stern200 MPU sometimes boots, sometimes not? A: It is usually a problem of the sockets. Be careful, you can easily bend the IC legs if you remove a chip.

Q: The 4 displays have a very strange behaviour. What´s up? A: That is usually the 5101.

Q: I would like to buy original Bally or Stern Motorola ICs with Bally / Stern part numbers. Where can I get them? A: Just ask for them, they are in stock.

Q: I have 7 flashes, but the game makes still trouble. A: Change the connectors. Although some of them might look OK, the often cause problems and messuring won´t help that much.

Q: The MPU continues blinking after the 7th flash. A: That is either U7 or R24.

Q: The LED of my MPU is placed on the right and not on the lower middle A: Please turn your MPU 90 degrees.

© 2005 Nicole. Please report mistakes!

Please do not ask questions, that are already answered in the text:)