8 Jan
2017
8 Jan
'17
11:05 a.m.
On 08/01/2017 18:20, "Tony Duell" <ard.p850ug1 at gmail.com> wrote:
Yep. I'm pleased we found that mod in the other unit because I made my own
bridgeboard and hooked the display up to a Microvitec CUB, I got exactly the
same picture (in colour) on that as I did in mono on the 5" TV so I knew the
analogue board and TV were OK.
No, in trying to trace some of the lines along the bottom of the board I
took the monitor cable off and traced the pins. They are:
1 - 5V
2 - NC
3 - looped to 5
4 - Sync out
5 - looped to 3
6 - emitter of V326 via R336
7 - GREEN
8 - RED
9 - Inverse sync (which also goes via R332 to the base of V333)
10 - BLUE
11 - GND
12 - GND
13 - 12V
14 - 12V
OK.. My dislike of 2114s is legendary, but probably not the problem here....
They're OK too, surprisingly. I took them off the board and put them in a
PET8032 as video RAM.
4116-2 wired as 2 banks of 8.
Yeah, 8085A. Thanks to list members I have some spares to try.
I've only got a cheap-ish Saleae compatible 16 channel analyser. Watching
code is a bit above my current level of self-paced learning :)
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
However, two
of us bought units at the same time and the other one has a
little bridgeboard containing a 74LS244 that sends the RGB signals to a DIN
socket on the back of the case for an external monitor. I also can't see a
And in a sense there was... luminance line
on the connection to the TV board on mine, just
red-green-blue with sync and inverse sync which go to the horizontal driver
Do you mean that the common cathode connection of those diodes goes to
the monitor connector but nowhere then on the monitor PCB? Is the MR9735 doing anything? Is it accessing memory,
for example?
I still wonder if it has to be initialised (say to vewdata rather than
teletext mode) and if this is not occuring.
Its address and data buses are active as is the pair of 2114s that are
acting as a page store. There's a 74LS240 buffering the data bus and that's
active. You could be
right though, I'm not convinced the unit is actually running
any code yet despite the ROMCS lines working and I can see activity in all
16 RAM chips. Data bus and address bus at CPU and ROM chips looks happy from
What are the RAMs? If they're more 2114s I wonder if they have problems
that are confusing the CPU (perhaps corrupting the stack?) a 'doing
something' point of view. All the control lines on the CPU are
pulsing with the exception of IO/M but if all the IO the chip is doing is to
memory then that's to be expected.
What's the CPU? 8085? I've had those fail in odd ways. I've
disassembled the ROM code so I'll have a look through that for an init
routine, also the datasheet should tell me what its expecting at powerup.
Personally, I'd stick a logic analyser on it and start tracing the code. See
if it is executing anything correctly.