Brian E. Brzezicki
Version 1.10 08/29/2013
Version 1.09 01/25/2013
Use this at your OWN risk, do NOT sue me if it breaks your board... if your doing this your board is probably already broken though ;)
So many years ago I bought a spy hunter. It worked nicely, until one day the linear power supply went out. Being that I was young and in-experienced with soldering or anything electronic really... my attempts at rebuilding it failed miserably so I replaced it with the famous MCR switching power supply adaptor. The game worked great and I was happy with my success. After claiming victory I took a break and I didn't play it for a few months.
Months passed and I turned the game on to see a moving screen something like this
So I though... hmm that's odd, and I did some research on the Internet. What I found was a common theme "Spy Hunters and other MCR games are VERY picky about the input voltage" and they often are very picky with switchers. So I started adjusting the voltage on the switcher, and after 20 or so minutes the game started working, and I thought to myself "OK... well they ARE picky but I must have found the right voltage... great!"
Feeling victorious (again) I stopped playing the game and
a few more month pass. One day I look at my pretty spy hunter and think "I'd like to play a quick game!". I turn on the game... and again the same screen of moving "R"s and white blocks. I think to myself "come on...again? really?..." but I pull the game out and start adjusting the voltage again and after about 20 minutes later and random things tried the game started working again and I think to myself "OK I just found the problem (because the last thing I did was mess with my AC circuitry"... alright it was a problem with the AC power brick. Problem solved?!?
A few more months pass with the game unplayed... One day I'm feeling the craving for some Spy Hunter (which a twinge of fear to turn the game on and have the problem again), but I think "Hey I fixed the problem last time... it's good". Then I turn the game on and the same screen again... so after a few choice words aimed at nobody...I pull out game, adjust voltage for 20 or so minutes, and then game starts working randomly and I'm thinking to myself "Well maybe the resistance on the siwtcher adjustment POT changed ever so so much.. and man these MCR games SUCK SUCK SUCK about voltage". But for the life of my I could not understand why these TTL chips specifically on THESE boards are the only ones in the world to have this problem... still I'm fairly new to electronics so... my game works and I'm happy for now.
A few years pass of this exact cycle of not playing for a while then turning it on to the rolling screen, and adjusting for 20 minutes before the game magically starts working... and I notice a trend, if I play the game the next day or a few hours later, the game works instantly... but if I wait a month or so... no dice... I'm starting to get interested now because I have learned a bit in the last few years and this makes NO sense at all... still I have no idea why this is happening and honestly I'm afraid to turn on this game, I even think of getting rid of this wonderful machine.
Now time passes it's the year 2013...My spy hunter game is doing it again! ok I've been fixing atari boards successfully for a year now and I'm gaining confidense in my skills.. I take my spy hunter apart, and build a test rig. By now I also have about 4 spy hunter board sets because each magically breaks and I get upset and buy a new one on ebay or from someone on klov (or get KLOV user cdjump to fix mine) Anyway, I hook my board up to my test rig and I test my game... rolling Rs. OK.. pull out another game board... rolling Rs. Pull out another board.. it works right away.. hmm... that's odd.
I do some research and find out that people have had luck starting the game on a switcher by connecting +5 to the "v.batt" input on the game board.. ok I do that and both my boards start up as long as it's connected... that's wierd.. but OK. I think to myself. "Why though do only "certain" boards work like this?" I don't believe in random concidence that repeats itself consistantly and realibly... Anyway I read the schmatics to what this v.batt line does, and see that eventually it goes to pin 24 on the static RAMthat holds settings... the power pin!!! ok that makes sense, if the chip is not powered then it's not working and the game would probably crash. But then I notice that pin 24 is directly connected to +5V,... but if +5V is connected directly to the power pin on the chip... why do I have to connect +5 to V.batt.. something does NOT fit.
Then I start taking the board apart and notice the wire that connects +5V to pin 24 on the static RAM is CUT on both boards that "don't work on a switcher" (without the v.batt trick).
All the sudden things start to make sense... Why my games would not work after sitting turned off for a while, and why it magically started workign when I adjusted the voltage for 20+ minutes! Since the +5V was not connected the power it was geting was from the battery on the Midway switcher adapter, after being off so long it lost it's ability to get the the power pin on the static RAM high enough for the game to work.. and the reason it started working after 20 minutes is NOT that I magically found the "correct voltage" that this game needed, but that the battery had charged enough to power the chip.
Note: The reason I'm guessing that the jumper was cut is I'm assuming these boards were hacked by the operators or whomever, to replace the on board battery with a lithium or other non-chargeable battery.