Model III/4 to composite video
Christian Lesage
I guess it's been asked before, but does anybody know of a simple
circuit to convert the Model III/4 video signal to composite video?
Thank you,
Christian
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Mark McDougall
> I guess it's been asked before, but does anybody know of a simple
> circuit to convert the Model III/4 video signal to composite video?
Umm...
TRS-80 video <--------------------------> composite video
Regards,
--
| Mark McDougall | "Electrical Engineers do it
| <http://members.iinet.net.au/~msmcdoug> | with less resistance!"
Christian Lesage
> Christian Lesage wrote:
>
>> I guess it's been asked before, but does anybody know of a simple
>> circuit to convert the Model III/4 video signal to composite video?
>
> Umm...
>
> TRS-80 video <--------------------------> composite video
>
> Regards,
>
I'm not sure if you meant that TRS-80 video is indeed composite video.
While this is true as regards the Model I, the model III and 4 have
separate VSYNC, HSYNC and luminance signals, that I need to combine into
a single composite signal. Model III and 4 video could be described as
NTSC video, but not as composite video, since none of the signals are
combined.
Cheers,
Mark McDougall
> I'm not sure if you meant that TRS-80 video is indeed composite video.
> While this is true as regards the Model I, the model III and 4 have
> separate VSYNC, HSYNC and luminance signals,
Oops, don't know why I was thinking Model I, not 3/4... :(
RedskullDC
"Christian Lesage" <us...@domain.invalid> wrote in message
news:hpb4hg$1hre$1...@adenine.netfront.net...
> Hi all,
>
> I guess it's been asked before, but does anybody know of a simple circuit
> to convert the Model III/4 video signal to composite video?
>
> Thank you,
>
> Christian
You could easily use the circuit from the Model-1 to create a composite
output.
If you don't have a copy, they are online at :
http://www.incolor.inetnebr.com/bill_r/trs80_schematics.htm
You may find some of the transistors difficult to find though, depending on
where you are.
The Australian MicroBEE had a much simpler circuit, which basically does the
same thing.
Checkout:
http://microbee.no-ip.com/uploads/Hardware/Schematics/mboard_1248-6-06.jpg
Video section is in the lower right hand corner.
Cheers,
Red
turnkit
the sync signals as described in the Model III tech reference manual
and connected them to a DB9 (?) connector and connected a mono chrome
monitor I had. Actually if I remember correctly I connected on a
couple of monitors. Most did not work -- some sync problem. But I
had one green-screen monitor that sunk just fine.
This probably doesn't help much as it wasn't exactly your question but
I thought it interesting.
Also a product like this might work if you attach the right lines
(?)... I suppose luminance would just go to one or more of the RGB
lines:
http://www.monoprice.com/products/product.asp?c_id=101&cp_id=10114&cs_id=1011407&p_id=4724&seq=1&format=2
Christian Lesage
> After high school I worked at a computer store, around '87. I took
> the sync signals as described in the Model III tech reference manual
> and connected them to a DB9 (?) connector and connected a mono chrome
> monitor I had. Actually if I remember correctly I connected on a
> couple of monitors. Most did not work -- some sync problem. But I
> had one green-screen monitor that sunk just fine.
I think some monitors needed positive sync signals while others needed
negative sync signals. Some would accept any kind of sync signal.
Anyway, I don't own a TTL monochrome monitor, so I need an adapter.
> Also a product like this might work if you attach the right lines
> (?)... I suppose luminance would just go to one or more of the RGB
> lines:
> http://www.monoprice.com/products/product.asp?c_id=101&cp_id=10114&cs_id=1011407&p_id=4724&seq=1&format=2
I could be wrong, but I doubt those devices can handle a horizontal
frequency of 15.7 kHz as regards the input signal. (I would be happy if
somebody could prove me wrong.) Standard VGA uses a frequency that is
twice as high (31 kHz).
In addition, I'm afraid those devices introduce a small delay since they
digitize the input signal as part of the conversion process.
I think I will brew my own adapter using inspiration from the schematics
provided by RedskullDC. This is a $5 project. I just need time!
