Neo Geo repair help

BulletMag

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I am currently restoring a MVS M1T board,
I have what looks like corrosion on the 4990A chip so i have removed it with the intention of replacing it...

Unfortunately i seem to be having trouble sourcing a replacement at a reasonable price, i have found a vendor here in the UK selling new old stock at £15 with free shipping but this seems a little to much in my opinion (they appear to be the only people selling here in the UK)

Is there a suitable alternative to the 4990A or does anyone have a supplier at a reasonable price ? (if not is £15 the going price for this chip?)

should i not be able to source a replacement how likely is this chip to be dead ? is a known victim of failure on these boards ?

thanks for your help
 
Can you show a picture of the chip ? In some cases I've gently passed sand paper on the legs. (High grit) removed the corrosion from the legs and its been able to come back from the dead.
 
I'm currently at work so i can't provide a picture until i get home but thats what i have done (hit the legs with a fibreglass pen)
They do require tinning to prevent oxidisation but all in all the chip appears ok.

ill post a pic tonight
 
That chip is very resilient. Most times when you get calendar errors it's because of a bad crystal, caps connected to the crystal, or a failure in the traces/components delivering power to pin 14 of the D4990.

I have some NOS spares somewhere that I brought home from Japan last August... but they aren't cheap. $12 each. I'm not exactly sure where I put them though.

Raymond
 
Glad to hear that, i have changed the crystals and have the 20pf and 30pf ceramic capacitors on their way (the crystal shell was very green)

You saying that you got your chips for $12 shows that really £15 quid is about the correct going rate for that chip then... ill bear that in mind.

I'm having trouble with the Coolermaster ATX PSU I'm using at the moment turning off when I power on the board, this is only on the 5v line though the PSU stays on if only the 12v line is attached.
I can get 5v to the board from an old external HDD PSU but this is only 2amp so isn't ideal, ill try and connect that this weekend and see if i get power to pin 14, if so then ill throw the original chip back in.
 
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