30 Jan
2011
30 Jan
'11
8:57 a.m.
Tony Duell wrote:
Actually yes, that would likely make sense, if the video's all running via the
connector on the CPU board - the system bus therefore wouldn't be hooked to
anything and so might not need termination.
Odd,
I always assumed it was a standard part of hi-res functionality. Any
chance of some board photos of the VDU boards sometime?
The 16 wire cable is part of the hi-res system, and the machine can't run
properly without it. I wonder if the OP was refering to the RGB output
module -- it's quite possible to have a hi-res machine without that fitted.
Yes, that was my assumption, that Adrian just doesn't have the RGB board. I
thought that all machines with hi-res had that output board too, but that's
just from observation of surviving machines, and RML seemed very good at
churning out systems tailored to the customer's individual needs. (I actually
run my machine without the RGB output board plugged in because it has a short
somewhere and I've never got the tuits together to fix it)
I am pretty sure my 380Z (and all the ones I used at school) has the
voltage reguatlors mounted internally (on the metal cover over the PSU
area) and a fan.
Yes, those are by far the most common. Someone popped up on the RML mailing
list a few weeks back with a system with internal regs that appeared to have
never had a chassis fan fitted, though (maybe it's possible to get away with
that with a minimal-config, cassette-only system).
I suppose we're only a day away from Adrian being able to get the correct fuse
now, so maybe he can handle waiting :-)
cheers
Jules
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)
I am a little puzzled. AFAIK you can make a minimal system with no bus
cable or termiantor atall -- just the CPU board linked ot the 40 column
VDU. Video output comes from the VDU card. Do you have any idea waht sort of components could be
fitted on the
terminator bord? Are there spaces for (DIL) ICs, or jsut discretes?
For the video portion: modulator, "video in" and "video out" sockets
(two
ground pins on each and one for signal), and then a handful of discretes.
For the termination portion: 4 capacitors, 1 resistor, 3 diodes, a 16-pin IC
that's likely a resistor network, and two 18-pin ICs that have had their
markings ground off (bastards!).
It actually says "Black and white modulator / bus terminator board" and then
"BWM 1/1" on the PCB which for RML is unusual - I don't think any of their
other boards list their purpose like that. Copyright date is 1981, so it's not
like it's a very early board or anything. (the PCB itself is a pale green and
quite transparent - in my photo I can see PCB traces for the reverse side -
which is different to all the other RML boards that I've seen, too)
I wonder if it hints at there being another variant of the 40x25 video board
around which doesn't have the modulator on-board? Or maybe the terminator
board that I have was a low production run for some bespoke RML client, and
they had some existing video equipment that wouldn't work with the stock setup?
... 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. 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. There are at least 2 versions ofthe 5.25"
machine. One has a pair
offull-heigfht drives fitted horizotnally, the otehr has a pair of 2/3
height (!) drives mounted vertically. The latter seems more common.
That's interesting. Mine has the horizontal drives, and I always thought of
those as being the most common :-) I think I did a detailed inventory of the
systems at Bletchley and emailed it to someone many moons ago - I'll have to
see if I can dig that out. Of the five or six systems they had, I don't think
any two were quite alike.
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)
I am pretty sure the PSU will draw less than 750mA with no load. I don't
know about the switch-on surge though a 750mA anti-surge fuse would
probably be OL< a quick blow one may not be.