8 Jan
2002
8 Jan
'02
4:06 a.m.
From: ard(a)p850ug1.demon.co.uk (Tony Duell)
Subject: Re: Ceramic capacitor question
To: classiccmp(a)classiccmp.org
Date: Tue, 8 Jan 2002 19:40:48 +0000 (GMT)
Reply-to: classiccmp(a)classiccmp.org
> The Compukit UK101 has several ceramic
capacitors, all marked 104Z 25V,
Why do you suspect they're faulty (or why do you want to replace them).
Most of the time, ceramic capacitors are used for supply decoupling in
these machines, which is not a particularly critical application. And
ceramic caps tend to last quite a long time anyway.
Yes, they can fail, but unless you have a supply line short or something,
I'd not suspect them.
Feel free to suspect or not but I fixed a mysterious problem on a
custom machine. Alldata used to sell whole machines for data pull up
on vehicle info/parts/TSBs) machine based around peecee board (to be
on topic I also repaired much eariler alldata machine around a atari
ST1040,. 1MB, 68000 I think). Both use CD as medium for data pull
up.
Back to this peecee board, this one made rapid "reboots" or resets
or like voltages going on/off every second. PSU design is kinda
pulled off the shelf w/ HUGE external passive heatsink, noticed it
has no PG signal except a small board wart bolted to PSU external
casing. That little board has one 8pin IC. That IC is readily
available and at power up, outputs comes up after certain time set
internally by that IC and small components countable with one hand.
Nothing else. Cause: small yellow coated ceramic capacitor looks
good till unsoldered it off that little board, one leg fell off
leaving a hole in the dipped package. BINGO!
Cannot put in regular peecee PSU, this case is designed to be
fanless and ventless to prevent dirt, shop's dirty stuff getting in.
Requires 24V for thermal printer (like a fax printer) so repair
that PSU is necessary.
Cheers,
Wizard