No v-logic?

[Doomguy42]

Hi there, I like repairing 90's coin-op and arcade boards. I've got one that's proving difficult as I haven't got this far with my learning yet.

There's some Led's to establish activity on the main mpu. On this board a "V-logic" led doesn't illuminate. I'm trying to establish what that means. Google tells me a high or low logic state? Does that mean 5v all around the board... if so I buzz 5v round from the input rail to the IC's and it's there... so could it mean something else?

I don't know if it means 5v or board with the clock signal being active, I've swapped out the crystal resonator and it made no difference. It could even be related to the processor not being awake?

Im struggling to narrow this down so can anyone please help? I'm missing to many pieces of the jigsaw still.

 

[rjenkinsgb]

What board is it - what game?

A photo or three would be good!

 

[Doomguy42]

It's called Epoch it's a popular type of old fruit machine board pretty rare when working. I've repaired battery damage to the left of the dips. These are pretty difficult I've fixed 2 so far but this is a new problem. The damage wasn't too bad just trying to work out if something elsewhere is faulty. I'm stuck currently.

 

[narkeleptk]

Shot in the dark here but it looks to indicate if the lower voltage supply is working. Probably used to power those mcu's. Either 5V or 3V depending on what the board uses. I have not looked at your board in the pictures much but maybe check for bad vr's or see if the mcu's have proper supply.

 

[Pommie]

My guess would be that V-logic is the supply for the logic chips. Normally 5V. Have you metered it?

Mike.

 

[rjenkinsgb]

I've found an online copy of the manual, though the board schematic is illegible.
**broken link removed**

The section about diagnostics implies that the VLOGIC LED is simply across the 5V power on the board (with a resistor) so if you have 5V measurable on the board itself, the most likely thing is that the LED has failed.

(See chapter 6 - fault diagnosis).


When you said "arcade boards" I was expecting something like a Space Invader or Galaxians type... I've got quite a bit of experience with those & and still some kicking around.
That one is relatively modern by comparison and being surface mount, probably quite a bit trickier to repair.