48G Destructive Teardown - EEVblog

[Dave Frederickson]

Fast-forward to 9:40.



"That's not a knife."

[d b]

Dave's in like Flynn. Winner Winner, chicken dinner!

[Han]

There are much less destructive ways to open an HP 48 and leave it still quite usable.

[cruff]

(05-22-2017 05:51 PM)Han Wrote:  There are much less destructive ways to open an HP 48 and leave it still quite usable.

Unless Dave is trying to repair something, he doesn't take a lot of pains to keep the disassembly reversible. The 48 he took apart was one he was sent in a non-working state, as he couldn't bear to open up the previous one he received which was in nice shape.

[Han]

The other oddity about that calculator was the jumper between ROM and RAM chip. The calculator presumably got upgraded to 128KB, but such an upgrade never required anything more than a RAM chip replacement.

[Paul Berger (Canada)]

(05-23-2017 01:52 AM)Han Wrote:  The other oddity about that calculator was the jumper between ROM and RAM chip. The calculator presumably got upgraded to 128KB, but such an upgrade never required anything more than a RAM chip replacement.

That jumper is on one of the address lines which would suggest a broken land on the board probably from removal of the original chip, but I think a shorter wire could have been used.

Paul.

[TomC]

The labelling on the ROM is unlike any I've seen.

TomC

[Eric Rechlin]

(05-23-2017 01:52 AM)Han Wrote:  The other oddity about that calculator was the jumper between ROM and RAM chip. The calculator presumably got upgraded to 128KB, but such an upgrade never required anything more than a RAM chip replacement.

In the video he said that the original owner damaged a pad when doing the upgrade, so that's probably why there's a jumper wire. I also got the impression that the upgrader didn't know what he was doing 20 years ago when he did the upgrade, which is why it looks like a complete mess during the teardown (just look at the faceplate).