500+ 1MB Trapdoor Ram issue

[djos]

Hi All, I bought this 1MB Trapdoor Ram board for my 500+ from an AmiBay member recently:

But I've been noticing some weirdness ever since installing it - most obvious was small weird graphics corruption issues and most demos/games crashing almost immediately. So I decided to run MemTest 4.0 and almost immediately got these type of errors:

but if I take the 1mb board out everything is perfect and MemTest reports no issues.

It looks like the extra 1mb chip-ram is being allocated some place it shouldn't be or something weird - this is a Rev8a board, should I be modding anything to fix this?

PS, Im also running Kippers awesome 8mb auto-config ram board.

 

[Bryce]

I'd suggest cleaning the contacts first and testing everything again.

Bryce.

 

[djos]

I'd suggest cleaning the contacts first and testing everything again.

Bryce.

The contacts are about as pristine as they get, notice the errors from MemTest, it's not finding things where it expects to and the Test ultimately crashes but if I remove the 1mb board the test works flawlessly:

 

[kipper2k]

From symptoms posted it looks like you have a bad chip on the board. Try touching the top of all the ram chips and see if any of them are hot, if it is, then that would likely be the culprit.

 

[djos]

Thanks kipper, I'll give that a go.

 

[djos]

Ok so I fired up another 1mb trapdoor card I had access to and it tested perfectly so now I know it's 100% the card.

I also got out my multimeter and all the resistors etc all tested out close to specs. I then inspected the entire board with my magnifying glass and found something interesting - 1 chip is showing possible signs of heat stress on only 5 of the pins (they have noticeably lost their shine compared to all other chip pins):

 

[rkauer]

You found the culprit. Replace it and the board will live again.

The best way to replace the chip is with a SMD rework station, but you can snip the pins near the chip itself with a pair of cutting pliers and dessolder the leftover with an ordinary soldering iron.

 

[djos]

Thanks mate, I don't have an SMD station unfortunately so I think I'll just just put it in the future projects basket.