At 02:17 28/09/2001, Bill Dawson wrote:
>-> Since I left the big cap in place, it can only be the transformer
>-> which is causing the wobble - can't it?
>->
>-> I genuinely don't know. That's the only part I've swapped in the
>-> new 8032.
>-> Could a flakey transformer be making the screen wobble? How do
>-> transformers go flakey anyway, if indeed they *can* co flakey?
>
>Well, actually I think the transformer is the cause of the problem, but not
>in the way you are thinking. You may have an problem with the magnetic
>field of the transformer being coupled to the monitor, either via the yoke
>or directly to the CRT. Does the problem lessen as the distance between the
>transformer and the monitor is increased?
I don't know - to try that I'd have to disassemble the whole thing again :(
The earth wires are a bit too short to make testing that easy.
>See the photos of the Commodore Educator 64, Model 4064 at
>http://www.swtpc.com/commodor.htm . I remember the general position of the
>power transformer is similar to the Pets. Note the shielding of the
>transformer in the photos. This was used to prevent the problem which you
>are describing, and if this shielding is removed the wobble will occur. Try
>placing a shaded pole motor or large transformer anywhere near the sides or
>back of a modern monitor and you'll see the same wobbling effect.
Interestingly, the US transformer is of a different design to the UK one;
I'm assuming the primary windings are inside the secondary, and there's a
broad metal band strapped around the whole thing. The UK transformer has
the primary & secondary windings next to each other, and there's no
shielding at all. If I fabricate a box, I assume it'll have to be earthed,
and surround the whole transformer? Also, will any metal do, or does it
need to be ferric?
--
Cheers, Ade.
Be where it's at, B-Racing!
http://b-racing.co.uk
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Received on Fri Sep 28 2001 - 05:01:23 BST