ATK memory test erros: faulty ICS A501 6C and Cabletronic RAM exp.

[luigi75]

Hi, I have got problems with my two Exp card A501_rev_6c https://drive.google.com/open?id=1PK...4zYbbG_9NmcJI0 and a Cabletronic https://drive.google.com/open?id=1-v...JT5irvlLSxNSbi.
I tested them with Amiga Test Kit 1.7 using the exp address, because both cards were not detected by the system, and I got these results:

for the cabletronic: https://drive.google.com/open?id=1m5...2H-sGM_LcHwtU0

for the A501: https://drive.google.com/open?id=1eR...x_9-Bi8dWa94Xq

I can guess some ICs are faulty, but which one?
Can somebody explain me how to interpret those errors?
Thanks

[luigi75]

I managed to find out the faulty chip on the A501: it was the U1.
I installed a new working chip on top of it and got no errors.
GadgetUK calls this technique 'piggybacking'.

[Jope]

I hope you didn't leave it like that? Piggybacking is used to find the broken chip, then you remove the broken chip and install the working one in its place.

[luigi75]

Of course I didn't!

[Hewitson]

Originally Posted by Jope

I hope you didn't leave it like that? Piggybacking is used to find the broken chip, then you remove the broken chip and install the working one in its place.

That's the correct way to do it, yes. I've seen countless arcade PCB's with the chip literally soldered on top of the other one.

[Jope]

Originally Posted by Hewitson

That's the correct way to do it, yes. I've seen countless arcade PCB's with the chip literally soldered on top of the other one.

You're giving operators way too much credit for doing the right thing. They were there with varying expertise just trying to get the game back to making money ASAP. :-)