Defender RAM Failure

[jammatt]

Ciao, after some days without touring on my cab, i got a RAM failure.
I know that often its because socket and because of this im gonna change it with new one, but i would like to understand RAM fails message on ROM board.
In my case 2nd and 4th leds are tourned on, i was looking at the manual "Setup Booklet" and indicates:

x=Bank, y=Chip No

Bank Indicated:
= 1
= 2
= 3

Chip Indicated:
= 1
= 2
= 3
= 4
= 5
= 6
= 7
= 8

Does anybody can help me for understand?
Thanks

 

[bomjac]

The manual will show you exactly which ram it is. There are 3 banks of ram horizontally, each with 8 chips vertically (numbered 1 to 8).

Try a reseat of the ribbon cable first and also of the ram in question. Once the dodgy chip is identified, you could swap it with the one before it to check that the fault indicator moves to follow the chip. That would allow you to positively ID the chip as faulty.

 

[jammatt]

Thanks, ok in my case the leds indicate 5, so i should change 4P 5P 6P

 

[bomjac]

It's telling you 5P is faulty, so swap 5P with 5O - reason being is that it has already tested the rom at 5O as being ok. However, you could swap the rom out anywhere as you suggest.

If the fault moves to 5O on boot then the ram chip you swapped is the dodgy one. If it stays on 5OP then could be the rom socket at fault.

IIRC defenders tests first bank 3, but I forget which bank it tests next.

Edit: you need to to watch for the led which lights before the -x-x that indicates the bad rom. That will tell you which of the 3 banks it is in. The above was written assuming that it was bank 2 the problem was. However your theory of swapping around 4P, 5P, 6P will work. Swap 5P with 6P in this case, as 6P has already passed the test being in bank 3bomjac2018-05-29 09:45:36

 

[jammatt]

As i know, ram test always go row 3 then row 1 and then 2.
So first blink is for Bank, and second one (im
my case 2nd and 4th led) is for Chip?

Hope i understood
Thanks so much for helping me

 

[chadsarcade]

Are you getting nothing on screen? Using the advance button inside the coin door will get you to the ram test and display the ram at fault in numbers on screen if your board is working enough.

 

[jammatt]

I'll try and let you know.
Thanks

 

[jammatt]

Its say: RAM 32
i tried to change RAM 3S but nothing changed.
Also socket are new.
Can be the RAM before or after? Or its for sure thatone?
Thanks

 

[chadsarcade]

Not got the diagrams in front of me, but is row S not near the outer edge of the board? The RAM is counted from the centre of the board outwards, if it's RAM 32 you want the second one out from the middle of the board on bank 3.

 

[LawmanAUT]

Jammatt, im running the original pcb´s in my defender as well but I switched over to the highscore savekit online from Jochen. Big benefit ist that you dont need the original roms any longer. But im not sure if this is an option for you.

 

[bomjac]

The order of testing is as below afaik:

• 3-1, 3-2, 3-3, 3-4, 3-5, 3-6, 3-7, 3-8
• 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, 1-7, 1-8
• 2-1, 2-2, 2-3, 2-4, 2-5, 2-6, 2-7, 2-8

Why is this important?

The game tests the RAM in the sequence above. If it shows 3-2 as faulty, the swap the chip from 3-2 with 3-1. If 3-2 still shows as faulty then you know that the chip in 3-2 is good (because previously it was in 3-1 and tested ok).

So if 3-2 still shows faulty your issue is somewhere in the address line (either between the PCB's and the ribbon or in the address decoder chip.

• You can actually test each and every ram chip by removing all of them, then populating the board 1 by 1. This means that on RAM test 3-1 will initially show the fault.
• Insert a RAM chip too 3-1. Run a RAM test again. If the chip in 3-1 is good, then the fault will move to 3-2.
• Rinse and repeat all the way through to 3-8, then the same for 1-1 to 1-8 and 2-1 to 2-8.

Your information conflicts here to the original info. Originally you said the indication was -X-X in bank 2 meaning chip bank 2, chip 5, and then you later say it is bank 3, chip 2.

 

[jammatt]

Thanks so much guys and thanks so much for your explanation bomjac.
ROM board indication is still -X-X, but if i do RAM test its say RAM 32.
Image HERE

I'll try to do like you told me.
I think something happened when i soldered the new RAM socket, i should check all the connection with schematics

Matt

jammatt2018-06-04 23:31:03