Toshiba MK2555GSX PCB HELP!

[michael chiklis]

I would try to read the chip with something like this :

http://www.hddoracle.com/viewtopic.php?f=117&t=865

At least then you would know if the chip was killed or not. Then you could start looking for what to do next, depending on if you have valid ROM or not.

Rom chip was killed.
It's impossible to read anything via eprom

[jermy]

if the problem is the GND pin, the metal pad area on the bottom center is also GND

[michael chiklis]

No, it's not ground!

[digisupport]

Have read out many ROM chips that was killed by bad soldiering like this one.
There are still hopes, but its hard work to connect to these bounding wires again.
If heat has not killed the chip - it can still be read.

[jermy]

No, it's not ground!

you're probably right, but for some reason - i don't know why - the datasheet says otherwise

here is what it says on an ST chip that has been used on PCB MK2555GSX G002439-0A

and here is another chip from winbond that it's been used on another toshiba PCB (note no. 4)

but there is no point to argue with you, because as i have written on the beginning you're probably right and it's not GND, and the manufacturers don't know what they are talking

[michael chiklis]

There is a simple way to find out this, that's what i did!
Get a good working rom that has metal pad underside the plastic package and do a continuity test with a multimiter between metal pad and pin 4.
You will find out that there isn't any continuity!

[LarrySabo]

Rom chip was killed.
It's impossible to read anything via eprom

I'm not surprised--given the heat damage and now I see from your recent post, physical damage. Geez, what a gorilla they have in that repair shop, to do that to a ROM chip!

I always worry about damaging a ROM when I have to unsolder it, so I heat up the circuit board instead of the chip itself, but it still makes me nervous. I unsoldered one yesterday and almost had a heart attack when, at first glance, I could no longer find the key dimple. I had the chip upside down. Hahaha. That ROM doesn't have a heat sink on the bottom but did seem to have some lettering. ROM was read by the programmer without problem.

[fzabkar]

The word "pulled" does not mean the same as "connected". Usually a pin is pulled high or low via a pullup or pulldown resistor. This resistance could easily be in the 10K+ range. Could this explain the apparent disagreement between measurement and datasheet?