Lady Bug

Ran through self test OK, came up with chequer board screen and then reset most of the time. Occasionally would start game, but with credit noise continually playing and credits rapidly counting upwards. This is caused by CPU 4 (E5) not running properly. checked the eprom and ram (C5,D5 and E5) and ram was faulty….

Missing Chip. This was a converted moon cresta board. The IC at 1.2S (shoehorned in sideways between rows 1 and 2 by the sprite ram) was missing. This was not featured on any schematics I had, so I traced the connections to see what it could be. It basically takes the output from the sprite…

Capacitor burnt. (game board), particularly at C37 the capacitor was showing signs of extreme heat. Replaced them all with 22uF 25V axial electrolytics. No Speech / Some SFX missing. (game board) Output from speech chip SC01 was OK, as was output from IO Custom (X3). checked transistors in output stage and 2N4401 was faulty. (Q2)…

Carnival on a Gremlin / Sega Vic Dual PCB. Just had blue bars on screen, although probing the Z80 showed it was trying to run code. Using a logic probe I discovered that the /WRITE signal of the ram chips was always high. This signal comes from a 74LS10 at U77. Checked this chip and…

No picture, Hole blown through LOPT. Had problems tracking down replacement – little tip given to me by Hantarex engineer – you can use the LOPT from an MTC9000 as long as you cut pin 2 off. (If you leave it connected, you will get a direct short to GND)

Totally dead, no screen display (blank white screen).  For this I used the Fluke Z80-S2650 adapter to check out the ram and rom, and located two errors. The rom mapping was incorrect, with a large range of locations returning random values. Examining the board (since I have no schematics), all of the chip select lines meet up…