My Data East Star Trek has been missbehaving over the last six months... and at TPF'09... and again a while preparing all of my machines for another United Way charity drive at work.
The machine has been randomly resetting... burning laser kick coils... letting the magic smoke out of power transistors... and being an all around gremlin. Lately its been giving me wacked out soundeffects which didn't match gameplay... attract sounds were playing instead of turbo slingshot sounds... It was like the CPU was off in the weeds pulling the wrong sound addresses. Scoreing was off too.. sometimes getting me to unbeliveable scores in a short period of time.
Since the other 3 machines are at work right now; I've been able to spend some ?quality? time with the wacked out problem child.
Usually what happens is the resets are random. and mostly doing no obvious harm.
This last time I replaced both predrivers and the power driver TIP36C as well as the coil diode when I replace the burnt coil.
Last weekend; I left it on for about 3-4 hrs while I hung Halloween decorations outside. I happend to be in the garage when I heard the game reset. This time It didn't come back to life.
I notice the machine had the kicker coil energized causing me to immediately fipped-off the machine. No- not the finger... using the switch. Although; I think I gave it the bird after it was off IIRC.
Turning it back on and the laser kick coil re-enegized. So I know the power transistor was toast again.
Posting the problem report on R.G.P gave me some ideas... but I had already started looking at Marvin's fixit site for inspiration while waiting for the experts on usenet to offer their advice.
Here's my thought process to solution - I had pulled the PSU board from the head to look at the DB1 bridge rectifier looking for cold solder joints per Marvin's fixit site:
http://www.pinrepair.com/de/index2.htm#resetTR5 (2N6057) is a big T03 transistor on the power supply board with that big ash heatsink. TR5 is responsible for regulating 5V to the machine and more importantly the cpu board.
Well; I thought to myself:
"self; what if the heatsink grease on that transistor/heatsink is dried out.... maybe that is the cause of heat related resets"
So I proceeded to remove the transistor noticed it didn't have any grease ... just an insulator. The transistor mounts to a socket under the heatsink
When putting the board back in the pin the damn pin wouldn't run... .no 5V
so... wiggled the transistor:
"zap" 5v comes on... as does the pin but power goes back off.
Push on the socket from under the heatsink and "snap" the socket realigns and 5V comes online!
Out comes the board... and I disassemble the heatsink to get to the socket the socket "wipers" are looking kinda wide... not touching the B,E pins of the transistor. A pair of needle nose fixes that; then I reassemble and torque down the mounting screws reinstall - and whala ... resets don't come back.
Best I can figure is that the transistor wasn't torqued down by the previous owner. and it wiggled loose while it was destructed - I mean shipped - by NAVL.
Ofcourse I need some guys to come over and play the machine to see if it's really fixed - seems like a job for those darn AustinModders.... only time and constant use will tell me for sure.
:fingers crossed:
