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judgeboz
6th March 2013, 09:31 AM
just got myself a red LAI cab (mk style) with a intermittent issue - the game come on ok 1 in 10 tries when I switch the thing on and off several times. I've checked all the wiring, unplugged and plugged in each connection again.

I get the following readings from the power supply +5v reads as 3v, +12v reads as 10v and -5v reads as -3v. This this within the acceptable range of does my power supply or does it need replacing?

DisQo
6th March 2013, 09:39 AM
I have always been told try to get it as close to 5 12 etc as you can get.

So if the power supply isnt doing its job, best replace it.

Danny helped me with the powersupply in my cab a while ago. He had em in stock.

Crafty
6th March 2013, 10:33 AM
I would suggest replacement John. Although some power supplies do have adjustment on them to turn the voltages up or down.
They are around 25 bucks if I remember correctly.

arcadus
6th March 2013, 10:38 AM
Power supply is definitely too low. It will cause the problems as described.

NMD
6th March 2013, 10:41 AM
Maybe try adjusting the PSU before replacing it?

Also check if the cab has one of these little monsters;
http://www.aussiearcade.com/showthread.php/56646-Resetting-LAI-25-quot-Lowboy-II?highlight=

Womble
6th March 2013, 10:41 AM
Are you sure you are measuring it correctly, you say the game will boot about 1 in 10 tries, if the voltage really was at 3v it would never ever boot.

In terms of voltages, the 5V is critical, it needs to be no lower than 4.8 anywhere on the board, so measure at the edge connector and at the back of the board on a chip of your choice. Over voltage at the input upto 5.2v to get decent levels at the back of the board is fine.

The -5v is not critcial, its usually only for negative baising the opamps in the audio section.

The 12v only powers the amplifier chip, it will be happy with anything from 9v to 20v ish.

All voltages are affected by the 5V tweak but you only need to worry about what the 5V is doing, ignore the others.

DisQo
6th March 2013, 11:00 AM
Are you sure you are measuring it correctly, you say the game will boot about 1 in 10 tries, if the voltage really was at 3v it would never ever boot.

In terms of voltages, the 5V is critical, it needs to be no lower than 4.8 anywhere on the board, so measure at the edge connector and at the back of the board on a chip of your choice. Over voltage at the input upto 5.2v to get decent levels at the back of the board is fine.

The -5v is not critcial, its usually only for negative baising the opamps in the audio section.

The 12v only powers the amplifier chip, it will be happy with anything from 9v to 20v ish.

All voltages are affected by the 5V tweak but you only need to worry about what the 5V is doing, ignore the others.

Perhaps its fluctuating the power? So sometimes it may be at the level to boot it up.

Womble
6th March 2013, 11:03 AM
Unlikely, psus don't die like that. Its either a bad PSU or the wiring on the harness is too thin on the power/ground lines. If the cab wiring is original (ie the cab has worked in the past) the PSU is the chief suspect, if the measurements were correct.

amutechservices
6th March 2013, 12:16 PM
hey john,call in and grab a power supply to try,at least it may give you a clue fairly quickly,