Or...
WHY THE F*** DO PEOPLE DO WHAT THEY SHOULD NOT...???
In the auction before last I bought several boxes of parts boards and in those were two Neo Geo MV4 bottom boards. I thought, hey... I need some bottom boards to use for advance replacements. Should be an easy fix.
WRONG.
Board 1: BIOS has been replaced with an EPROM. Someone replaced a surface mount chip and did a terrible job of soldering. It's missing a pad on pin 15 and has an extra pad on pin 2???
Board 2: Missing the BIOS chip. They pulled the chip from this one and here's where pin 2 is missing it's solder pad. The also pulled pin 28's pad but it's still attached to the heavy power trace. They tried replacing the Z80 and damaged 2 traces - one on each end of the chip - by trying to twist a large screwdriver under it to lift the chip. Sigh. Then they tried to patch the traces and used machine pin SIP sockets to seat a replacement Z80. Yuck.
Both boards look like a ham fisted monkey tried to solder on them. Since I need some advance replacement boards I dive in and see if these boards can be saved.
So... for starters... resoldered the SRAM chip on Board 1. OOPS. They didn't clean the pins on the SRAM before trying to reuse it. The chip is about 1 to 2 mm off the board surface. Sigh. Fixed the soldering issues. Removed the extra pad. Place 1 jumper wire to fix the missing pad. Now it fires up and has a UniBIOS in it (nice touch!), but has a Backup RAM Error. Replace the backup RAM. It works, but needs an audio cap kit.
Board 2... Install a BIOS chip. Clean up the pads, straighten out the pad for pin 28, install a new SRAM, and jumper the busted pad with some 30ga Kynar. Test the board and get a (GASP!) Z80 Error. Remove the kludgey socket and jumpers. Trace out all connections from the Z80. Install a new socket and use 30ga Kynar to jumper the 2 busted traces.
Still a Z80 Error. Replace the SM1 ROM and the board fires up but has no audio. Look closely. They desoldered the audio amp chip but left it on the board! Sigh. Resoldered the audio chip and tried again. No audio. Check the YM3016 DAC with the logic probe and hear the audio signals making it to the analog section from the digital. Crank the volume and put my ear next to the speaker and barely hear the audio. Time for a cap kit.
I'm about to fit a top board on these and test 'em with carts before jumping in with doing the cap kit.
It's EASY to do surface mount soldering with a minimum of tools. The next repair party I have I'll set some scrap boards on the benches and let folks play after showing some tidbits. Key items: Don't pull pads (duh!), you CAN reuse chips, but damnit... you need to prep the pins on them AND prep the pads by cleaning them and laying down some liquid rosin flux so that A) the chips are physically sitting on the board and B) you get a good, stable solder connection.
Chips can be pulled by using solder, chipquik, special tweezer irons, hot air, small diagonal cutters, razor knives, or other techiques. Putting them down requires just some liquid rosin flux and a hot iron. Oh, and a steady hand.
Ham fisted monkies need not apply.
WHY THE F*** DO PEOPLE DO WHAT THEY SHOULD NOT...???
In the auction before last I bought several boxes of parts boards and in those were two Neo Geo MV4 bottom boards. I thought, hey... I need some bottom boards to use for advance replacements. Should be an easy fix.
WRONG.
Board 1: BIOS has been replaced with an EPROM. Someone replaced a surface mount chip and did a terrible job of soldering. It's missing a pad on pin 15 and has an extra pad on pin 2???
Board 2: Missing the BIOS chip. They pulled the chip from this one and here's where pin 2 is missing it's solder pad. The also pulled pin 28's pad but it's still attached to the heavy power trace. They tried replacing the Z80 and damaged 2 traces - one on each end of the chip - by trying to twist a large screwdriver under it to lift the chip. Sigh. Then they tried to patch the traces and used machine pin SIP sockets to seat a replacement Z80. Yuck.
Both boards look like a ham fisted monkey tried to solder on them. Since I need some advance replacement boards I dive in and see if these boards can be saved.
So... for starters... resoldered the SRAM chip on Board 1. OOPS. They didn't clean the pins on the SRAM before trying to reuse it. The chip is about 1 to 2 mm off the board surface. Sigh. Fixed the soldering issues. Removed the extra pad. Place 1 jumper wire to fix the missing pad. Now it fires up and has a UniBIOS in it (nice touch!), but has a Backup RAM Error. Replace the backup RAM. It works, but needs an audio cap kit.
Board 2... Install a BIOS chip. Clean up the pads, straighten out the pad for pin 28, install a new SRAM, and jumper the busted pad with some 30ga Kynar. Test the board and get a (GASP!) Z80 Error. Remove the kludgey socket and jumpers. Trace out all connections from the Z80. Install a new socket and use 30ga Kynar to jumper the 2 busted traces.
Still a Z80 Error. Replace the SM1 ROM and the board fires up but has no audio. Look closely. They desoldered the audio amp chip but left it on the board! Sigh. Resoldered the audio chip and tried again. No audio. Check the YM3016 DAC with the logic probe and hear the audio signals making it to the analog section from the digital. Crank the volume and put my ear next to the speaker and barely hear the audio. Time for a cap kit.
I'm about to fit a top board on these and test 'em with carts before jumping in with doing the cap kit.
It's EASY to do surface mount soldering with a minimum of tools. The next repair party I have I'll set some scrap boards on the benches and let folks play after showing some tidbits. Key items: Don't pull pads (duh!), you CAN reuse chips, but damnit... you need to prep the pins on them AND prep the pads by cleaning them and laying down some liquid rosin flux so that A) the chips are physically sitting on the board and B) you get a good, stable solder connection.
Chips can be pulled by using solder, chipquik, special tweezer irons, hot air, small diagonal cutters, razor knives, or other techiques. Putting them down requires just some liquid rosin flux and a hot iron. Oh, and a steady hand.
Ham fisted monkies need not apply.



