Date   : Tue, 11 Apr 2006 04:02:40 +0200
From   : "W.Scholten" <whs@...>
Subject: More on fault stats

See the previous post for faults I found in the micro's themselves, 
there were more but they give you an idea. Micro's do of course have a 
higher probability of being defective than add-on hardware (exercise for 
the reader why this is so), so here are some stats of BBC add-ons I've seen:

  - Joysticks: One in ca. 5 had a broken connection in one of the wires 
(near the joystick base), so needed to replace the whole cable or chuck 
it away. I chose the latter. Another I used briefly then the spring (to 
centre it) broke. I don't have the right spring to put in it, so had to 
chuck it (I'm not going to keep them for spares, my house is too full 
already).

  - Diskdrives: 3 defective/unreliable ones in ca. 17 drives.

  - ROM boards: I think I've seen about 5, 1 or 2 had broken pins on the 
bottom (file flat surface, drill hole with miniature drill, solder in a 
bit of wire of the right thickness to fix this), 2 had wires cut off. 
They all worked after fixing these mechanical problems. Not everyone can 
do the hole drilling, as you need a miniature drill. For the wires you 
need a soldering iron.
    Another board was damaged by battery acid. ICs were damaged and 
needed replacing. See also my Atom repair page for an extreme case.

  - Solidisk 4MHz boards: I have 2 versions, the 256K had a bad RAM chip 
(I substituted a slower one, seems to work ok), and broken off wires. 
The 32K one had broken off wires.

  - Eprom programmers: I've seen a couple. On my Morley, the ZIF socket 
came loose, had to epoxy it. This one also has a bad cable, need to keep 
it in a specific way or it won't work. I didn't feel like fixing the 
cable yet.

  - EPROMs: A couple of bad ones out of maybe 100

  - Tube ULA: one dead in ca. 5

So "95% works" isn't true for most of the expansions/add-ons for me. 
There are often mechanical problems, and although not difficult to solve 
for me, problems (timewasters) nonetheless. The ICs are usually ok, but 
note that those that get hot such as the Tube ULA and RAM have a much 
higher probability of being dead. Discounting broken off wires which are 
quite easy to fix, that still gets me far away from 95% with add-ons.

-- 
Wouter
---
BBC micro | Calculators | Classic PC games: http://www.xs4all.nl/~swhs/whs/