26 Nov
2017
26 Nov
'17
7:02 a.m.
On 26 Nov 2017, at 06:15, Tony Duell <ard.p850ug1
at gmail.com> wrote:
On Sat, Nov 25, 2017 at 11:02 PM, Adrian Graham via cctalk
<cctalk at classiccmp.org> wrote:
Yep, it runs from 0-11.82V.
Evening!
Can you get it down to 0V? OK... Firstly, measure the voltage on pin 8 of
the monitor PCB. Can you get
it to swing from 0 to around 12V?
Yes, it tops out at 11.82V. Scope the video output from the CPU board (on pin
2 of the monitor PCB). Is
it a good TTL level
signal?
Yes. Given that it?s TTL and a 3-wire connection (composite plus H&V sync) I should be able
to feed that into a PET monitor shouldn?t I? Wish I hadn?t given
away my ?big? TRS80 Model 4 :/
I have no idea if the sync polarities are right, but you can try it with a Pet
monitor. A TRS80 Model 3 has the same monitor as the Model 4 of course. (And I wish I could find a 4P over here?.)
Perhaps embarrassingly I can?t remember where mine came from but given I?ve had it since
the early noughties that?s not surprising. It may even have been from a car boot sale.
What happens if C101 is removed? Also try running it with TR101
removed (or at least the emitter lead of that transistor disconnected).
Nothing happens, in that the picture is the same as it is with both those components
fitted.
Cheers
A