On 31/10/2016 20:51, "tony duell" <a...@p850ug1.demon.co.uk> wrote:
> >> 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/ 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 >> Hence the question - am I wasting my time without a schematic for this >> analogue board? > > You haven't told us what the problem is. 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. > 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?
