28 Feb
2008
28 Feb
'08
3:37 p.m.
(catching up on the list after being away for two weeks)
On 20/02/2008 18:07, M H Stein wrote:
On Wed, Feb 20, 2008 at 02:07:53PM +0100, Ade Vickers
wrote:
I agreed with Ade, though. The PET in the particular eBay auction was
one of the early ones with MOS Technology 6550 RAMs and 6540 ROMs.
They're not like the 2114 SRAMs and 2332/2532-compatible ROMs used in
slightly later ones, and spare RAM chips are unobtanium. It's not even
easy to substitute later RAM or ROM chips. For example, the 6550 RAM
chips are 0.4" wide rather than 0.3", they have four chip selects (2
active high and 2 active low) and the circuit relies on that for partial
address decoding. The common adapters I've seen won't fit.
When two of the RAMs in mine went (and that's the common fault) I was
extremely fortunate to get a replacement from another listmember,
otherwise I'd have had a 4K PET.
--
Pete Peter Turnbull
Network Manager
University of York
A nice-looking CBM Pet 2001 with chicklet
keyboard (Item #300199788685),
described as:
"The computer powers up fine as you can see from the pictures, but it is
only half way through the booting up process.... a simple problem to fix...
Don't forget the "from what I've seen on the net" part...
Erm, yes. Very simple to fix, if you happen to
have a spare of the part (or
parts) that have failed. Otherwise, a complete bastard (pardon my Francais)
of a job.... and well beyond your average ePayer, I'd warrant.
-------------
Boy, tough crowd...
Repairing a PET is often as simple as reseating a memory chip; worst case is
probably a bad ROM in which case you just replace all the RAM/ROM chips
with one of the modern 64K RAM/ROM adapters and sell the working old ones.