NLG Users Repair Logs and Other Ramblings. Request your very own topic. Just ask any site staff. > Channelmaniac's Arcadecomponents' Old School Repair Logs

Repair and Recovery Techniques

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channelmaniac:
If you need to replace a 23C1000 mask ROM you can use a 27C100, 27C301, 27C1000, or a Toshiba 571001 - basically any EPROM that is a non-JEDEC pinout type of EPROM. The problem is that the mask ROM is 28 pin and the EPROM is a 32 pin device.

If the board has the extra pins on the socket or has holes to where you can mount a 32 pin socket then it's a direct replacement. If there is only a 28 pin socket and no room for adding more pins then you can simply use 2 jumper wires on the EPROM to make it work in the 28 pin socket. Solder a jumper from pin 2 (an enable pin) to pin 16 which is ground to enable the outputs of the EPROM. The other jumper goes between pin 30 (NC, or No Connection) and 32 (Vcc, a.k.a. +5v) so the EPROM has power. Use 30ga Kynar wire wrap wire when you do this and solder the wire on the shoulder, close to the body of the chip.

Enjoy!

channelmaniac:
Here's how to determine the pin out of the edge connector on a game:

1. Find +5 and ground using continuity checks to your 5v logic.
2. Find speaker outputs by following the traces from the audio section to the edge connector (data sheets help for this)
3. Find +12v by following the traces to the audio amplifier or DRAM (4116 and 4027 use +12v, again, data sheets)
4. Find -5v by following the traces to the OpAmp chips or DRAM (4116 and 4027 use -5v and again, data sheets help with this)
5. Find video outputs using your logic probe. Having a probe with audio will help you ferret out the sync line quickly.
6. Find the control inputs using your logic probe. They will be tied high, but NOT have continuity to the +5v lines. Momentarily ground each to find the coin inputs then the starts and then the player controls.

Enjoy!

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