2 Jan
2016
2 Jan
'16
3:18 p.m.
Going through and testing the collection over this Xmas period also prods
me into doing mods I've procrastinated about. A very simple mod but here
is a write up for anyone who is interested...
http://www.classic-computers.org.nz/blog/2016-01-03-composite-video-for-zx8…
Terry (Tez)
2 Jan
2 Jan
3:48 p.m.
Which type of transistor did you use for the mod? I don't see that in the
writeup.. though I could well be missing it.
Linked article says only "simple NPN"
On Sat, Jan 2, 2016 at 5:18 PM, Terry Stewart <terry at webweavers.co.nz>
wrote:
Going through and testing the collection over this
Xmas period also prods
me into doing mods I've procrastinated about. A very simple mod but here
is a write up for anyone who is interested...
http://www.classic-computers.org.nz/blog/2016-01-03-composite-video-for-zx8…
Terry (Tez)
4:43 p.m.
NPN is used for simple video amps... so 2n3904 or equivalent.
-Pete Rittwage
Which type of transistor did you use for the mod? I
don't see that in the
writeup.. though I could well be missing it.
Linked article says only "simple NPN"
On Sat, Jan 2, 2016 at 5:18 PM, Terry Stewart <terry at webweavers.co.nz>
wrote:
Going through and testing the collection over
this Xmas period also
prods
me into doing mods I've procrastinated about. A very simple mod but
here
is a write up for anyone who is interested...
http://www.classic-computers.org.nz/blog/2016-01-03-composite-video-for-zx8…
Terry (Tez)
4:46 p.m.
On 3/01/2016 12:48 pm, "drlegendre ." <drlegendre at gmail.com> wrote:
Which type of transistor did you use for the mod? I don't see that in the
writeup.. though I could well be missing it.
Linked article says only "simple NPN"
Good point. I'll have to mention it. It was just a common old 2n3904.
Terry (Tez)
5:50 p.m.
Thanks Terry, fair enough. =)
Has it been done with the ubiquitous 2N2222A? That one is probably in
everybody's kit.. it might be even more common than the 3904
Wondering.. is there a way to re-purpose that Chan. 3/4 switch as an RF /
Composite switch? That way you'd still have a correct (local) RF output, as
well as the Composite video.
On Sat, Jan 2, 2016 at 6:46 PM, Terry Stewart <terry at webweavers.co.nz>
wrote:
On 3/01/2016 12:48 pm, "drlegendre ."
<drlegendre at gmail.com> wrote:
Which type of transistor did you use for the mod? I don't see that in the
writeup.. though I could well be missing it.
Linked article says only "simple NPN"
Good point. I'll have to mention it. It was just a common old 2n3904.
Terry (Tez)
6:06 p.m.
On 3/01/2016 2:50 pm, "drlegendre ." <drlegendre at gmail.com> wrote:
Thanks Terry, fair enough. =)
Has it been done with the ubiquitous 2N2222A? That one is probably in
everybody's kit.. it might be even more common than the 3904
Wondering.. is there a way to re-purpose that Chan. 3/4 switch as an RF /
Composite switch? That way you'd still have a correct (local) RF output,
as
well as the Composite video.
Actually you probably could if you wanted to keep RF. You'd have to make
sure it's hardwired to the right RF channel of course but yea..
It's interesting that none of my present TVs would tune properly to the RF
of the ZX81 but they will with some of the other RF only computers like the
Coco 1 and Atari 400? More circuitry in the latter perhaps...
Terry ( Tez )
6:22 p.m.
"It's interesting that none of my present TVs would tune properly to the RF
of the ZX81 but they will with some of the other RF only computers like the
Coco 1 and Atari 400? More circuitry in the latter perhaps..."
I'd have no idea about that one, other than I can verify that there was a
lot of variability in the video quality of early game & home computer
systems.
My first machine was a (NTSC) VIC-20 which I ran on a 12" B&W RCA TV set
from the late 1970s. It was not all that bad, really -
quite legible with
those massive characters, but not so great for games or anything
requiring
color recognition. I was very happy to receive a "proper" S-Video monitor
with my C-64, which arrived some two years later.
On Sat, Jan 2, 2016 at 8:06 PM, Terry Stewart <terry.stewart296a at gmail.com>
wrote:
On 3/01/2016 2:50 pm, "drlegendre ."
<drlegendre at gmail.com> wrote:
Thanks Terry, fair enough. =)
Has it been done with the ubiquitous 2N2222A? That one is probably in
everybody's kit.. it might be even more common than the 3904
Wondering.. is there a way to re-purpose that Chan. 3/4 switch as an RF /
Composite switch? That way you'd still have a correct (local) RF output,
as
well as the Composite video.
Actually you probably could if you wanted to keep RF. You'd have to make
sure it's hardwired to the right RF channel of course but yea..
It's interesting that none of my present TVs would tune properly to the RF
of the ZX81 but they will with some of the other RF only computers like the
Coco 1 and Atari 400? More circuitry in the latter perhaps...
Terry ( Tez )
3 Jan
3 Jan
4:34 a.m.
On 03/01/2016 02:06, "Terry Stewart" <terry.stewart296a at gmail.com>
wrote:
It's interesting that none of my present TVs would
tune properly to the RF
of the ZX81 but they will with some of the other RF only computers like the
Coco 1 and Atari 400? More circuitry in the latter perhaps...
Going from an old, old memory from when TVs became auto-tune rather than
dial-in or 'press-a-button-and-hold-until-something-happens' I recall it was
to do with the 'black level' from the ZX81 in that it was too great and
caused the autotune mechanism to skip it altogether as it wasn't seen as a
useable signal.
Hopefully someone else can elaborate on that.
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
10:32 a.m.
On Sun, Jan 03, 2016, Adrian Graham wrote:
On 03/01/2016 02:06, "Terry Stewart"
<terry.stewart296a at gmail.com> wrote:
What's this about holding a button?
It's interesting that none of my present TVs
would tune properly to the RF
of the ZX81 but they will with some of the other RF only computers like the
Coco 1 and Atari 400? More circuitry in the latter perhaps...
Going from an old, old memory from when TVs became auto-tune rather than
dial-in or 'press-a-button-and-hold-until-something-happens' I recall it was
to do with the 'black level' from the ZX81 in that it was too great and
caused the autotune mechanism to skip it altogether as it wasn't seen as a
useable signal.
Hopefully someone else can elaborate on that.
--
Eric Christopherson
10:46 a.m.
On 03/01/2016 18:32, "Eric Christopherson" <echristopherson at gmail.com>
wrote:
On Sun, Jan 03, 2016, Adrian Graham wrote:
Modern technology :)
Going OT for a moment here (sorry Jay) over xmas I was talking VCRs with my
Missus and went off searching for the very first one I used back in '83-ish,
a Ferguson Videostar. I was surprised to re-learn that the channel tuners on
that were all the 'spinning wheel' type. There was one on fleabay for 10ukp
but I wasn't allowed to bid.
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
On 03/01/2016 02:06, "Terry Stewart"
<terry.stewart296a at gmail.com> wrote:
What's this about holding a button? It's interesting that none of my present TVs
would tune properly to the RF
of the ZX81 but they will with some of the other RF only computers like the
Coco 1 and Atari 400? More circuitry in the latter perhaps...
Going from an old, old memory from when TVs became auto-tune rather than
dial-in or 'press-a-button-and-hold-until-something-happens' 
4 Jan
4 Jan
3:36 a.m.
On 03/01/2016 18:32, Eric Christopherson wrote:
On Sun, Jan 03, 2016, Adrian Graham wrote:
I dont know abourt the ZX but when I worked on VDUs and wanted a quick
comp output.
I seem to remember you could connect a 560R to positive going TTL video
and a 390R
to negative going TTL mixed sync and you would get 1v comp into 75R.
Rod
On 03/01/2016 02:06, "Terry Stewart"
<terry.stewart296a at gmail.com> wrote:
What's
this about holding a button?
> I recall it was
> to do with the 'black level' from the ZX81 in that it was too great and
> caused the autotune mechanism to skip it altogether as it wasn't seen as a
> useable signal.
>
> Hopefully someone else can elaborate on that. It's interesting that none of my present TVs
would tune properly to the RF
of the ZX81 but they will with some of the other RF only computers like the
Coco 1 and Atari 400? More circuitry in the latter perhaps...
Going from an old,
old memory from when TVs became auto-tune rather than
dial-in or 'press-a-button-and-hold-until-something-happens'
3227
days inactive
3229
days old
10 comments
7 participants
participants (7)
-
drlegendre＠gmail.com -
echristopherson＠gmail.com -
peter＠rittwage.com -
rodsmallwood52＠btinternet.com -
terry.stewart296a＠gmail.com -
terry＠webweavers.co.nz -
witchy＠binarydinosaurs.co.uk