On Tue, Jul 3, 2018 at 12:12 am, Roger Evans wrote:
There is a jumper on the A28 board for 525/625 operation of the composite
video but it should affect the 7000 plugin readout (CPU generated) and the
read gun scanning consistently. There are multiple jumpers for normal or fast
scan and these need to be consistent. Pages 4-9 onwards of service manual 2
give all the jumper settings.
If the 7912AD is a 525-line model and you set the jumper on the A28 board for 625 lines, the readout gets repeated at the bottom of the TV display because the readout board's counters aren't set up to deal with the extra lines. There exists a modified readout board (I've got one here as a spare) which has a load of extra logic bodged on to it dead-bug style to handle the readout properly in 625 line mode.
If my memory is correct the digital display
does not show the readout from the plugins.
You mean the X-Y output or the 'digital' video output? I think the latter does show the readout, but the X-Y output certainly doesn't.
Chris
