Gottlieb system 1 display problems

[Mxzmark]

Hi all! I am in need of some System 1 experts to help me figure out some display issues on my 1980 Buck Rogers. The problem is the credit/ball display is not working ( stays blank) all other displays are on. This is a project machine so at the moment only the power supply and the displays are connected to the cpu. The power supply is new and is putting out the correct voltages. Also I have done all the ground mods to the boards and jumpered out the slam switch on the cpu. All the main displays come on with zeros after 5 seconds so it seems the cpu is booting. I moved the credit display to another system 1 game I have and the display works fine. I also tried my niwumph board in the buck rogers ( removed from my other game) and all the displays work. So as far as I can tell the problem is in the original cpu. I have tested all the ttl chips related to the displays as stated from pinrepair.com and all seem fine. (Used a DMM on diode setting). Is it still possible I have a bad ttl? Is there a better way to test it? Also is there a way to test the U6 spider chip that controls the displays? The info I have gathered is very vague on what ttl chips actually control the credit display. Please help I'm at a loss here.
Thanks!

 

[luch]

did you repin the connector ?

 

[spiroagnew]

If I were a betting man, I'd put money on a connector issue. I had this problem with my Totem recently. I wiggled the connector wires at the CPU board and sure enough, the credit display worked again. I re-pinned that connector, and had no problems since. Re-seating the connector when you switched over to the new board may have temporarily solved the issue for you, or you may have an intermittent connection at the terminal on the old board.

Just my two cents. Keep us updated.

 

[Mxzmark]

If I were a betting man, I'd put money on a connector issue. I had this problem with my Totem recently. I wiggled the connector wires at the CPU board and sure enough, the credit display worked again. I re-pinned that connector, and had no problems since. Re-seating the connector when you switched over to the new board may have temporarily solved the issue for you, or you may have an intermittent connection at the terminal on the old board.

Just my two cents. Keep us updated.

This is my next step. I have some connectors on order. Will keep you posted.

 

[REVOLUTION]

Also try your buck rogers board in a different game to eliminate a board problem.

 

[Mxzmark]

This is my next step. I have some connectors on order. Will keep you posted.

Ok guys I have all the displays working now. Re pinned all the connectors - no fix. I replaced the original battery on the cpu with a remote battery holder with fresh batteries and cleared all the memory ( after I fixed the broken wire I found on the audits switch lol) And just like that all the displays are now on and working great. Now to my next and final issue with this machine. It boots up and works fine and coins up as it should. When I press the start button to play a game most of the cpu controlled coils start to fire and then release and then fire again as well as some of the scoring chimes and just keeps going like that until I shut it off. Looks like a problem in the switch matrix but I don't know where? If I disconnect the switch matrix connector at the cpu A1-J7 and start a game no coils fire. When I run the audits coil test (test 13) all the coils fire 1 by 1 as they should. I did notice that someone has replaced a few of the switch matrix blocking diodes on the diode board with the wrong type. Should be 1n270 and they have 1n4004 installed. Could this be the issue?

 

[Menace]

I did notice that someone has replaced a few of the switch matrix blocking diodes on the diode board with the wrong type. Should be 1n270 and they have 1n4004 installed. Could this be the issue?

Get those 1n4004 diodes out of the switch section, they are rectifier diodes not switching diodes and as a result will not behave correctly. Don't bother tracking down 1n270, just use 1n4148 diodes.

This may not solve your issue, but it's a good place to start.

D

 

[Mxzmark]

Thanks I'm going to get a few of those diodes and replace the incorrect ones. Man,whoever worked on this pin before I got it was an idiot. It's a miracle I have got it working at all after all the messes up repairs I have fixed. Lol

 

[Mxzmark]

Diodes replaced and and shorting out hole switch replaced and the machine is fully working.

 

[spiroagnew]

What a beautiful machine. Would love to have a Buck Rogers some day.

 

[Menace]

Diodes replaced and and shorting out hole switch replaced and the machine is fully working.

Glad to hear you got it all sorted.

D

 

[Allan]

Thing with Germanium diodes when they fail they tend to open rather than short so if you get some nasty coil voltage heading to the mpu they tend to open before they burn the board up. Pretty much any diode will work in its place the strobe rate is only 400 cycles per second but a rectifier will short rather than open and you could get a nasty burn.