29 Jan
2011
29 Jan
'11
12:17 p.m.
Adrian Graham wrote:
Odd, I always assumed it was a standard part of hi-res functionality. Any
chance of some board photos of the VDU boards sometime?
Does it have a case fan? What about voltage regulators mounted on the rear of
the case? The latter were early machines I think and quite uncommon. Typical
machines have the voltage regs internally and a chassis fan fitted, although I
know there's at least one machine out there with internal regs and no
forced-air cooling.
On 27/01/2011 22:34, "Jules Richardson"
<jules.richardson99 at gmail.com>
wrote:
Interesting - presumably the colour PAL board also does the bus termination
(my bus terminator card's also labelled as being for black and white video,
although components for that aspect aren't fitted - presumably it was used on
40x25 systems without the hi-res option)
Looking at photos of my system (physical hardware
is in storage), it has 6
boards:
32K CPU/ROM/RAM,
FDC/serial,
32K RAM,
VDU #1 (keyboard, modulator, composite out, 1KB RAM),
VDU #2 (composite out, 16KB RAM, 26-way header)
Bus terminator
Obviously the order isn't that important. Mine is (R to L):
32K cpu/rom/ram
VDU #1
32K RAM
VDU #2
FDC/serial
Colour PAL board - modulator goes to TV out and composite plugs into this
too instead of VDU #1 ... plus an
"RGB board" mounted on the back panel, which has RGBS BNC outputs
and hooks to the 26-way header on VDU #2. VDU #1 and VDU #2 are connected
together via 16-way DIL headers on the boards.
I don't have that. >> I
should be able to get a Megger at work. The reason I mention the
>> caps is because the last 3 or 4 machines I've had in have all blown
>> the mains filters.
> Right.. Those are not the capacitors that most people replace without
> testing on old machines...
And this machine doesn't have them anyway, it's a brick transformer. Done all that, the boards are in great condition as is
the PSU internals.
Good news!
Problem is the glass fuse has blown and I don't
have a spare at home, bah.
It needs 250V/1A and all I have easy access to are PETs which are 250V/.75A.
I'm not sure how close to the limit the systems typically run - .75A might
work I suppose, just for testing (and at least for soak-testing the PSU under
a dummy load, if you decide to do that)
cheers
Jules