6 Oct
2001
6 Oct
'01
11:30 p.m.
At 10:43 07/10/2001, Michael Schneider wrote:
Well, it's not that the transformer HAS to die....
Adrian should try to listen to the thing: If he clearly hears the
transformer
humming under load, throw it away.
No, there is no significant noise from it. There's quite a powerful hum
just as it starts up, but that only lasts 1/2 a second or so before it goes
as good as silent.
Or: place small magnetic objects very
close
to the transformers core. You need a considerably large magnetic field
on the
surface of the core to influence the electrons in the CRT's beam, which
are,
after all, still a few inches away. So, the "small objects" might
move...
OK, I did two tests. Firstly with a telescopic magnet-on-a-stick thing
(used for picking up screws & the like from dark corners where they
inevitably fall) - the transformer induces a noticable vibration in that.
Secondly, I put a small screwdriver bit on top of the transformer. When
switching on, it tried to twist around (it actually did twist, but was
thwarted by the plastic ridges on the transformer).
Conclusion: This transformer IS putting out a very strong magnetic field...
Oh, another idea: Adrian, have you tried to place the
transformer on the
table,
outside of the casing? I mean: leave as much as possible of the original
cabling
in place, just put the transformer out of the way? If this helps, you
know
what to do 8-)
This is actually something I was thinking about last night. I could easily
fabricate a connector in the back of the computer, then move the
transformer out into its own box. OK, it wouldn't be "authentic PET" any
more, but it would completely cure the wobble. This may end up being the
only solution for my 8032-SK, since the transformer is so close to the
monitor that there's nowhere to put any shielding. I can't put the
transformer outside as it is, since the internal wiring is not long enough.
The other possible problem I'll have with shielding is: It's going to be
trying to move about in the magnetic field, isn't it? Meaning I'll have to
bolt it down pretty firmly to prevent it making too much noise...
Another possibility is to build a very simple step-down box (2-1) so I can
use the American transformer (which originally came with the machine); I
may pursue this option anyway since I now have two US-sourced CBM disk
drives, both of which require 115vac.
Yet another option - I could try re-orientating the transformer so the
magnetic pollution is pointing towards the front & rear of the machine,
instead of up & down like it is now. To do that, however, I'll need to
fabricate some kind of mounting bracket, and I don't have the material or
tools to do that right now. Also, I'm not sure how effective that'll be...
--
Cheers, Ade.
Be where it's at, B-Racing!
http://b-racing.co.uk