Retro Arcades Latest posts
Could be a useful site
Looks like it got some good info in all types of processors:
http://www.cpu-world.com/
http://www.visual6502.org/
Mortal kombat 2 pcb repair Missing Green signal.
The in game green signal was a muddy dark green instead of the usual bright green on characters like reptile etc.
Got the logic probe on the Jamma edge RGB outputs and all three signals were active & toggling as they should be so switched to the digital scope to get a better look at the three signals coming from the board.
The scope showed that the green signal seemed seriously diminished compared to the red and blue signals so checking the manual schematics it revealed a SN7407N buffer/line driver UA4 that drives all three signals, compared the green input(pin 5) and output(pin 6) to the red and blue input/outputs on the SN7407N and the signal was much weaker from the green output.Removed UA4 and a quick out of circuit test with the Boardman 4000 confirmed the faulty SN7407N.
Replaced UA4 and now the board is fully working
Hantarex mtc 9000 dead with smoking R105 resistor
Monitor Flickered and died and could smell a burning from the back of cab.
Removed the Hantarex mtc 9000 and got it on the test bench, on power up i was getting no neck glow and the large white resistor on the side was getting very hot and burning up.
Checked and replaced the TR 15 and TR 20 transistors with bu508a's and tested.Monitor now worked but could not stabilise the picture with horizontal Freq without the power cutting out.
Ordered a Capkit and changed all the capacitors but problem still the same.
Checked the poly caps at c36 and c40 with my cap tested and these were both dead.Replaced and now the monitor is fully working.
Repair log Missile Command sound but no video fault
On boot up gettiing no display but can hear the game running, suspect display output circuit.
Traced RGB signals back from edge connector to the colour RAM at L7 n82s25n inputs looked ok with the logic probe but seems that the outputs were being sent to the dm74175 latch were dead.
Replaced L7 with an equivalent N82S25 ram and now getting a display but with missing red signal.
Got the logic pulser, and put it on pin 3 of L7 (COLRAM select) with each pulse the colours were randomly changing so changed the 7442 at E8 and now the game is fully working.
Jon Stoodley achieves Perfect Game Game.
32 years in the making, UK player Jon Stoodley finally achieves a live perfect score on Pac-Man!
A perfect Pac-Man game occurs when the player achieves the maximum possible score on the first 255 levels (by eating every possible dot, power pellet, fruit, and enemy) without losing a single life, and using all extra lives to score as many points as possible on Level 256. The first person to achieve this score was Billy Mitchell of Hollywood, Florida, who performed the feat in about six hours. Since then, six other players have attained the maximum score in increasingly faster times.
Read more about it here:
[url:2yu9yps9]http://www.twingalaxies.com/entry.php/200-Pac-Man-Achieving-The-Perfect-Game-Jon-Stoodley[/url:2yu9yps9]