31 Oct
2016
31 Oct
'16
12:48 p.m.
On 31/10/2016 20:51, "tony duell" <ard at p850ug1.demon.co.uk> wrote:
My earlier google-fu was hampered by getting the IC number wrong and taking
a macro photo of it has shown my error, it's actually a Plessey MR9735
Teletext/Viewdata chip that 'drives a 625 line Colour Television Receiver to
display the contents of the Page Store'
http://www.datasheetarchive.com/dlmain/4d6e79fdc0fb675d8dd857876f8d6bdd195f5
7/M/MR9735
http://www.binarydinosaurs.co.uk/STCExecutelAnalogueBoard2.jpg
Before I replaced the failed potentiometer (new one seen top left) the
display looked like its horizonal hold had gone so I reasoned that's what
the pot controlled. I can *nearly* get a steady picture but the brightness
is out as well, despite there being working pots for that and contrast. The
brightness seemed more constant before I replaced the radial cap with the
PET one which is why I wondered if the choice was wrong.
My recent Executel addition has a 5" screen
with associated analogue board
that seems to be powered from a display chip I can't find any info on, and
Well, it won't be _powered_ from that IC. My guess is that said IC provides
the HSync and VSync signals, the video comes from other devices on the
main PCB. But that is a guess without seeing the machine/ Hence the
question - am I wasting my time without a schematic for this
analogue board?
You haven't told us what the problem is. 
Do you get anything on the screen? Is the CRT heater
glowing? Have you
measured the CRT pin voltages?
There's a recognisable picture, yes.
I can see one IC on that 'analogue board'.
Looks to have metal heatsink
tabs so I am going to make a wild guess that it's a TDA1170 vertical
deflection IC Are there any other ICs on the board? My guess is that
the 'analogue board' could be reverse-engineered without too much
work.
It is indeed a TDA1170, there's also a TDA1180P.
Here's the machine in all its glory:
http://www.binarydinosaurs.co.uk/STCExecutel01.jpg
Board:
http://www.binarydinosaurs.co.uk/STCExecutelBoard.jpg
Cheers!
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
