2SD313 TRANSISTOR, CASSETTE MOTOR DRIVER.Replace the PLA (906114-01) still doesn’t work?Īnother problem can be your power supply, here’s how you can test your power supply:Īnother video with a black screen repair:Ĭassette motor will not turn when FF/REW or PLAY is pressed.Replace the VIC chip still doesn’t work?.If you see a flash on power-on, first try to remove the SID still doesn’t work?.Do you see a flash? No, replace the clock generator 8701 (small chip next to the VIC chip).Note: do this at your own risk btw □ Black screen? This method has been done many times in the Arcade scene / repairs. If the fault changes/improves, you have a good chance of pin pointing the faulty chip without soldering. Just push a known good memory chip over the chip to be tested. The piggy back method gives you an educated guess identifying the faulty IC. After that was fixed, both dead test and normal boot worked fine again. In this case it turned out to be a short between pins 7 (A1) and 8 (Vcc) below RAM chip U10. U26 pin 11 also connects to the RAS pins on the RAM chips (pin 4 for older boards with 8 chips, pin 5 for newer boards with 2 chips), so a similar problem might appear if the same break was between the RAM and U26. The cause of the problem was a worn or broken trace in the RAS line between U26 pin 11 (74LS373) and the VIC pin 18. The symptoms with a cartridge were vertical bars with colors and patterns varying depending on the cartridge installed, and sometimes included patches of random pixels around the screen, and the computer was otherwise frozen up. The display shown in this picture is with the 586220 diagnostic cartridge installed without cartridges produced only a blank black screen at power up. – Bad socket contact on U1 (CIA) – bottom pin(s)Ī bad trace on the board (broken or causing short circuit) can be the cause of all sorts of problems. Blank screen if chip is shorted (remove to check) and chip may get hot to the touch. Partial failure: some keys or joystick positions don’t work, one character appears ahead of startup cursor or random characters appear at startup. No keyboard or control port access but cartridge works. Though in this case the problems were simply caused by a bad connection between the CIA1 chip and its socket, similar symptoms can likely be caused by a failing CIA chip. The computer seemed unresponsive on every boot. On one boot, screen was filled with white garbage characters (third picture). Sometimes the characters kept switching between upper and lower case. ![]() After about 10 seconds of waiting, most of the normal startup text appeared along with some garbage characters, and in some cases automatically typed load/run commands (second picture). The most common outcome was an empty blue screen with borders (first picture). Caused various abnormal startup screens, including a simple black screen on a couple of boots.
0 Comments
Leave a Reply. |