27 Jan
2011
27 Jan
'11
2:34 p.m.
Tony Duell wrote:
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
... 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 *think* what I've labelled as "VDU #1" is the standard 40-column board
(1KB
RAM isn't enough to do 80x25 text), and "VDU #2" is a hi-res board. From
memory, there's not a lot on the little rear-panel RGB output board; just a
few passives and transistors - I certainly don't remember it having a
modulator, so I don't think my machine does hi-res PAL output (if it does it'd
have to be via the UM1111 modulator on VDU #1)
Ditto.
Sadly, I've seen one at Bletchley in a very poor state, which I think had a
black bezel around the drives.
I do know of one other person who has an 8" setup in private hands; IIRC that
has an aluminium bezel around the drives (although the case tops and sides are
still "380Z black").
Are we talking X/Y-class filters here, or primary smoothing caps just
downstream of the bridge rectifier?
I've had many ones of the former fail, but I can't think of a single machine
I've worked on where I've needed to replace the latter. I've *seen* older
equipment - 60s and early 70s - where they've been replaced, but it's not
something I've had to do on the age of machine I normally work on.
I seem to recall a small tantalum capacitor somewhere in the PSUs of one of
the 380Zs that I've had letting go after a short while of use after being in
storage - big bang and a lot of smoke. That's the only time I've had that
happen to me, but it was a bit unnerving at the time :-)
On 25 January
2011 20:18, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Most of them have TV outputs, whether the PAL encoder is fitted or not.
The standard configruation (at least for 40 column machines, the 80
column video card is different, and I've never seen one), is that there's
a composite video output and a UHF TV output both fed from the text
system. If you add the hi-res card, the UHF output remains text-only,
the composite output carries text and hi-res suitably combined. There is
a header plug on the high-res board that carries the output of the CLUT
(8 bit), that's where the RGB board and I assume the PAL enocder are
connected. What I can't rememebr is if/how the text video output ends up
on those boards. > Folks,
>
> Picked up one of these wee beasts today at long last, Z80 CP/M and CP/N
> machine from ~1981, complete with not-oft-spotted hi-res colour PAL boar=
ds
The H-res board is not that rare. The PAL enocder
is, if you have that.
Yup, the machine has a TV-out as well as the standard
monitor. The PAL
board is marked as such and has a colour modulator on it. Is this the 5.25" floppy version or the 8"?
I thought the former normally
5.25". I've only ever heard talk of the
8" 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...
Yes, mains filters can and do blow. I've replaced a few -- well,
actually, most of the time I've replaced the capacitors only (seaprate
components on a PCB). If there's potted filter module, I guess you
replace the whole thing. A failed mains filter may blow the fuse, but I doubt
it'll do any more
damage to anything. I wonder if it's worth put a light bulb in series
with the mains live wire (that's a real light bulb, of course, not one of
those CFL things) and powering up the filter/transfoemr with the
secondary windings of the latter disconnected? It should catch
catastrophic failures with no further damage.
Yes... and if there's a chance of damp, it's probably worth stripping the
whole system and checking for corroded connectors, IC legs etc. and then
testing the PSU under a dummy load anyway.
cheers
Jules