I’ve been lucky and was able to buy 27 used, untested ZM1550’s. So I’ve made a test setup to get them all sorted out as fast as possible once they arrive.
This is just a little test print on which I soldered three 5 pin connectors and one 4 pin connector and then connect all the segments of both digits together (a with a, b with b, etc.). Then I soldered some wires to connect them to the CN3 connector on the pinball display driver. The shield is connected to pin 1 of CN1 and the decimal points and both anodes are connected to the appropriate pins on CN2 in the same way.
Fortunately, the first ZM1550 module I put in worked, so I know the setup was good.
Unfortunately, not all the modules I put in worked 🙁
Well, the playfield is almost done!
I’ve cleaned out the cabinet and head.
I’ve installed the new microswitch (#52) that let’s the machine know the ball is on the 2nd level playfield.
I’m still missing a few rubbers, but they are in the mail.
The 20A fuse on the transformer box burned out while I was working on the playfield. I stuck a new one in and that burned out too. So I removed all the lights and measured the wiring to look for shorts. There were none. I stuck the lamps back in one by one and now everything works… Weird.
The guy I bought the ZM1550 display modules from mailed me to say he is abroad for work and will send them next week.
I still have the CPU board problem though… I’m going to swap out IC’s 8, 19, 31 and 37 for good measure. The way the CPU reacts to the DIP switch 4 position looks like it’s unable to read the settings once PROGR is off. When I put the switch back in PROGR mode, I can read all the settings, which to me means the RAM is good.
I’m also writing a extensive memory test program that will write alternative 0x55 and 0xAA’s to every memory position between 0x1800 and 0x1BFF. When a test fails it will show which test failed in which nibble at which location on the Player 1 display. This way I should be sure if the memory is good and I can test with both positions of DIP switch 4.
I’ll keep you updated.
The mailwoman came with goodies this morning; four 3081 chips! So I put them in the CPU board and ran Leon’s test EPROM again. Victory!
So I mounted the board back into the pinball machine, connected everything and switched it on. Not so good… The sound was weird, only a few cracks and screeches would come out of the speaker.
I disconnected the sound board from the CPU board and ran the test and all went well, so clearly there was a problem with the communication between the CPU board and the sound board. I checked the schematics and the only thing that could be wrong was the entry stage behind CN7.
Using my multimeter I immediately found that all the data lines where shorted to the +5V. So only the resistor array ICR6 or the 74LS244 could be the cause. So I started with desoldering the resistor array, but that wasn’t the problem. So I desoldered the 244 and found the culprit!
Off to the store I went. Bought a couple of BF422’s and a 4042 as well for the two display driver boards that needed them and even went round to the hardware store to get some screws, there’s a lot of screws missing in the cabinet and head.
Back home, I put all the components where they should be and succes! I have sound!
The two display driver boards got their components too and now I have 4 working displays.
Next week my ZM1550’s should arive and then I can fix the last display.
And that’s it for the electronics… OR IS IT???
The game still won’t start. No flickering lights, no sound, no highscore showing, nothing… just all 0’s on the displays and that’s it.
When I put DIP switch 4 in PRGM mode, the soundboard now makes the annoying warning sound and I can do all the tests, reset the accounting and set all the options. So I set the options, resetting the ones that already had a good value, clear the accounting and do the tests. All tests are fine. The displays do their thing, the lights go on and off, the solenoids scare me and the sounds are played in order. But then there’s the button test (test #2) that just shows 18. And whatever button I press, it doesn’t change. I guess I’ll have to go through the wire harness and measure what signals I do get.
Guess that’s my queue to end this article and get back to work!
Guess what I’ve been doing yesterday… correct! Fixing displays…
As you might remember from a previous post, I had two working displays and three that needed work.
Well, after a days work, I have three working displays, and components ordered to make that five (5) working displays!
I had three 4×2 digit display boards with faulty ZM modules. So after some soldering magic, I now have two more working 4×2 digit display boards and one with two (possibly three) faulty ZM modules. Luckily I found a fellow enthousiast who has a few Valvo ZM1550 modules to spare, so there should be four of them coming my way soon! YAY!
Three of the display driver boards were faulty. After some testing, I found one board with a faulty IC2 (4042) and two boards with a faulty BF422’s. From the two boards with the faulty BF422’s, I made one working one. With the BF422 transistors and the 4042 chip on order, the display driver boards should be ready.
Pinball life is good!