Ebay grrrr #743

Pete Turnbull pete at dunnington.plus.com
Thu Feb 28 17:37:18 CST 2008

(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:
>> 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. 

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

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