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 Forum index » DIY Hardware and Software » Video synthesis and manipulation
Using the MC1377 to generate video
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urbanscallywag



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PostPosted: Sun Oct 12, 2008 4:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

I think your clips are amazing! Shocked

That looks like lots of fun.
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creatorlars



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PostPosted: Mon Oct 13, 2008 8:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, beautiful!! Thanks for posting.
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rubendelacosta



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PostPosted: Tue Oct 14, 2008 5:59 am    Post subject: Reply with quote  Mark this post and the followings unread

would it be possible to hack a scart cable and make a simple passive processor? something like this:

http://img72.imageshack.us/my.php?image=sacrthackon6.jpg

and instead of potentiometers it could be used vactrols for cv control

sorry, no paint skills...
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jnuaury



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PostPosted: Tue Oct 14, 2008 6:56 am    Post subject: Reply with quote  Mark this post and the followings unread

rubendelacosta wrote:
would it be possible to hack a scart cable and make a simple passive processor?


yes you can also do the same thing to VGA cables
theres a few other passive things you can do too
like swapping the RGB channels or tossing an audio signal on to one of the RGB channels making a passive highpass or lowpass filters is also fun


for the video addition to my modular i was thinking about using the VGA output from my laptop to supply sync and treat the RGB channels as three separate B/W signals.... theoretically easy but im expecting to hit a few bumps in the process of converting them to synth voltages

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creatorlars



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PostPosted: Mon Dec 15, 2008 8:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Time to revive this thread! Smile

I finally built a MC1377 RGB-to-Composite+LM1881 Sync Seperator circuit based on the schematics I posted earlier in this thread, and -- it works! By this I mean that I was able to pass a video signal into both chips, generate sync, and view a stable video signal at the MC1377's composite output. I haven't had a chance to test it further than this or with VCO's yet, but it's definitely the first step.

I'm looking into setting up a small monitor+vcr+camera input+oscilloscope rig for the purpose of further experiments/circuit design soon, and I'll report back with my progress. If anyone's still interested in help with designing/improving this circuit, or helping me come up with a cheap Sync Generator solution, that would be awesome! I've got 8 samples of the LT1251 Video Mixer chip in now, too... I think these will be key to building any sort of mixing/keying or Sandin IP module clones.
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BananaPlug



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PostPosted: Mon Dec 15, 2008 9:53 am    Post subject: Reply with quote  Mark this post and the followings unread

I've heard of people programming a PIC chip to generate all the necessary sync signals. Don't have code or anything but it seems like a good way to go since those chips have all the necessary timing capabilities, I/O pins, low price, user base, etc. Worth doing some searches anyway.
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BOB-SNARE



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PostPosted: Wed Dec 17, 2008 5:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

creatorlars wrote:
Time to revive this thread! Smile

I finally built a MC1377 RGB-to-Composite+LM1881 Sync Seperator circuit based on the schematics I posted earlier in this thread, and -- it works! By this I mean that I was able to pass a video signal into both chips, generate sync, and view a stable video signal at the MC1377's composite output. I haven't had a chance to test it further than this or with VCO's yet, but it's definitely the first step.


I have been using this RGB-CVBS board
http://www.arcademvs.com/ARCADE_ACESSERIOR.htm
with an AVR to generate the Sync and blanking/clamping.
but I seemed to have a problem with black level. I have breadboarded an XR2206 VCO with some V and Hsync options too.
This is mainly because the 8038 seem to be twice as expensive!

So I thought I'd try the MC1377 RGB encoder to see if there is any difference with the black level. I have it working with DC,
but I have noticed it is really sensitive to supply ripple.
This is also due to the fact I'm trying to use a switching regulator that has 100mV ripple!
Anyway, what chroma filter circuit did you use R-C or the 2nd-order with delay-line and xformer?
Did you use the oscillator circuit from
http://www.preromanbritain.com/gwem/martbean/ataridiy/conv.htm
?
That doesn't look right to me. I used the built-in Colpitts osc as per the datasheet.

Quote:

I'm looking into setting up a small monitor+vcr+camera input+oscilloscope rig for the purpose of further experiments/circuit design soon, and I'll report back with my progress.

Scanimate style?

Quote:

If anyone's still interested in help with designing/improving this circuit, or helping me come up with a cheap Sync Generator solution, that would be awesome! I've got 8 samples of the LT1251 Video Mixer chip in now, too... I think these will be key to building any sort of mixing/keying or Sandin IP module clones.



Has anybody had a look at Processing.org?
It seems like a handy tool for modelling video effects before you build them.
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creatorlars



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PostPosted: Wed Dec 17, 2008 9:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

I think I recall seeing that arcade accessories board before, but it had slipped my mind. $23 is a steal compared to any alternative I've seen! I'll have to order one of those to play with.

I built the circuit exactly like that Atari DIY schematic you mentioned, with the R-C chroma filter and the oscillator as shown. It seems to work, but like I said -- really need to get some sort of setup to make testing easier. I don't know enough about the transformer/delay line to even start buying parts. I am learning as I go.

Can you explain more about the AVR sync generator?

The XR-VCO with V and H sync options sounds great. I have built six of these so far and it would be an easy build for doing some dedicated R G & B source oscillators.

So how do the outputs look with your setup? Are you getting usable oscillator-driven visuals yet? With an internal sync generator, are we going to need to genlock or timebase correct external sources like cameras or VCRs? I'm using an LM1881 for now, so I'm forced to try to sync the oscillators using a sync from an external source anyway.
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creatorlars



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PostPosted: Fri Dec 19, 2008 1:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

I pulled out my MC1377+LM1881 circuit again last night and tried to drive the Red input with my XR-VCO synced to the VSync generated by a dummy signal sent by a VCR to the LM1881. It definitely worked, and while I wasn't sure exactly how well, I was able to view the VCO and see different waveform outputs. While I was expecting pure red video, I'm guessing it's not that simple, as the output was more blue. Maybe I need to ground the Blue and Green inputs or make sure they're getting that black level signal.

I definitely had to attenuate the VCO's output quite heavily in order to get it in the right voltage range. Also, I'm not sure how well the VSync signal was sync'ing the VCO, I might have to boost the gain on it.

Anyway, very exciting stuff. I found some good links for microcontroller sync generation also -- but I want to get the RGB Encoder solution refined enough for a primitive prototype before I come up with a better sync solution. Plus, without genlocking or time base correction, I have to use the sync stripped from the external source to use an external video source at all -- that's as far as I understand it, though. Any ideas on how we're going to handle time base correction or genlocking for multiple input sources?? That's another battle... and maybe best left for external gear.

I think I'm going to order an AD724 -- they are $11 from DigiKey but look vastly superior to the MC1377 -- no need for external chroma filter or delay line, or and only 2-3 external components at all. Guess I'm going to have to learn how to surface-mount solder and use those adapter boards.

Please keep the discussion going. Smile Hopefully I'll have some videos soon.
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jnuaury



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PostPosted: Fri Dec 19, 2008 2:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

creatorlars wrote:
While I was expecting pure red video, I'm guessing it's not that simple, as the output was more blue.


yeah from working with the IP or even little experiments with plugging sources into various inputs of a VGA cable, color is a little strange to get a hang of and definitely not as intuitive as mixing paint or something. its tough to get a color you have in your head, but once you start plugging things in to 2 or 3 inputs some beautiful unplanned color schemes can emerge.



creatorlars wrote:
I think I'm going to order an AD724 -- they are $11 from DigiKey but look vastly superior to the MC1377


From a discussion with Kyle of LoVid http://www.lovid.org/ (i should have posted this link much earlier...) they go with the AD724 and say its much simpler and easy to use than the AD725

and you can get free AD724 samples from analog devices... youll have it within a week and wont pay a penny (the catch is you need to register with an email address from a business or .edu email)




and just for fun heres some IP stills...
http://flickr.com/photos/25517350@N04/tags/ip/

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creatorlars



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PostPosted: Fri Dec 19, 2008 2:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Very cool. I ordered a couple AD724s from DigiKey and look forward to playing with them.

Can you elaborate more on what the Sandin IP patch was like (modules used, points connected, etc) just for simple VCO-driven RGB visuals?
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jnuaury



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PostPosted: Fri Dec 19, 2008 2:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

creatorlars wrote:
Can you elaborate more on what the Sandin IP patch was like (modules used, points connected, etc) just for simple VCO-driven RGB visuals?


those 5 stills cam from the same patch. i had a camera heavily modulating two VCO's which were usually a little above audio (but ended up with sidebands all across the audio range). i think i had two mixers (the adder/multiplier) set up with three inputs each VCO and then the camera. one mixer went to one of the RGB inputs and the other went to the other two. the camera was just in the room point at a chair or an empty wall most of the time but every now and then i pick it up and swirl it around... zoom in and out, etc.

the IP uses cameras (i think surveillance cameras) that are switchable between an internal or external sync. you of course need to drive them with the same sync as the RGB encoder if you want a stable image. sometimes i switch the sync to external which will result in the camera signal sliding and if you listen to it its a detuned drone. the horizontal bar in some of those stills are from the misaligned sync of the camera

oh and the IP has a preamp type module for taking cameras into the system where you can adjust gain and bias of the incoming signal. i love leaving the gain way too high or low and throwing the bias off a bit sometimes. it can take whatever the camera is pointed at and leave a more abstract image.
and the clipping helps establish shapes if you are modulating a VCO with it and not using the actual camera as an image

i probably used a separate preamp for each vco too

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ringer



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PostPosted: Mon Dec 22, 2008 8:00 pm    Post subject:
Subject description: CA3126E
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Hi Lars,

I am interested in your quest, I don't have the chops for this video stuff, but I will try out the circuits once they are ready.

I saw this lot on Ebay, 100PC LOT CA3126E -16PIN DIP TV CHROMA PROCESSOR-NOS, Item number: 400019451481

I saw them and thought they might be helpful, good luck with your development.

Regards,
Ringer
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BOB-SNARE



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PostPosted: Tue Dec 23, 2008 3:44 am    Post subject: Reply with quote  Mark this post and the followings unread

creatorlars wrote:
I pulled out my MC1377+LM1881 circuit again last night and tried to drive the Red input with my XR-VCO synced to the VSync generated by a dummy signal sent by a VCR to the LM1881. It definitely worked, and while I wasn't sure exactly how well, I was able to view the VCO and see different waveform outputs. While I was expecting pure red video, I'm guessing it's not that simple, as the output was more blue. Maybe I need to ground the Blue and Green inputs or make sure they're getting that black level signal.


I'm using non-interlaced PAL (i'm asusming you're using NTSC?) based on the timing from
http://www.retroleum.co.uk/PALTVtimingandvoltages.html
you may need to blank the RGB signals to GND during sync and colour burst. Some timing for this is at
http://elm-chan.org/works/yuv2rgb/report.html


Quote:

I definitely had to attenuate the VCO's output quite heavily in order to get it in the right voltage range. Also, I'm not sure how well the VSync signal was sync'ing the VCO, I might have to boost the gain on it.


The inputs to the MC1377 are expecting 0.7Vpp
Also, the XR-VCO does not do true hard sync. The problem syncing triangle core VCOs, it requires the
state (up or down) to be reset and the integrating cap to be discharged. Also, it's only up to
15KHz which is around line frequency? Replacing the timing cap with a smaller one will work.

I'm assuming you were seeing scrolling horizontal lines?

Quote:

Please keep the discussion going. Smile Hopefully I'll have some videos soon.

cool!
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creatorlars



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PostPosted: Mon Jan 05, 2009 12:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
you may need to blank the RGB signals to GND during sync and colour burst. Some timing for this is at


is this the function of the blanking & pedistal board found in the Sandin between the RGB input jacks and the color encoder board? any hints on how to achieve this with the 1377?

i'm a little confused about all the sync signal components and how they may need to process to the input signals before insertion into the RGB board. what should I do to an input signal besides passively attenuating it? should I be using some sort of op-amp buffer between the oscillator's output and the RGB encoder inputs?

i would try cloning the Sandin circuits directly, but they all use the obsolete MC1445.
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BOB-SNARE



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PostPosted: Mon Jan 05, 2009 8:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

creatorlars wrote:

is this the function of the blanking & pedistal board found in the Sandin
between the RGB input jacks and the color encoder board?
any hints on how to achieve this with the 1377?


Quoted from MC1377 datasheet:-
Quote:

it is essential that the portion of each input which
occurs during the sync interval represent black for that input
since that level will be clamped to reference black in the color
modulators and output stage.


So assuming you are using bipolar outputs from the XR-VCO (+/-0.5V as per Sandin IP)
and AC coupling (15uF), during the sync interval you need to drive -0.5V
if that is your lowest (i.e. blackest) level on to each of the RGB inputs.
I modified the XR-VCO design to be unipolar (0 to 5V with an attenuator
so it generates 0-0.7V) and that way black is 0V and much easier to switch through
analog switches (like a 4053) for blanking.
Simply, with AC coupling there is no black level reference, so during the sync timing pulse,
each side of the cap is clamped to a black level,
to create a reference.

Quote:

i'm a little confused about all the sync signal components and how they may need to process to the input signals before insertion into the RGB board. what should I do to an input signal besides passively attenuating it? should I be using some sort of op-amp buffer between the oscillator's output and the RGB encoder inputs?

The MC1377 RGB inputs have a 10k input impedance. I think the XR-VCO has buffered outputs doesn't it maybe with a 1K?

Quote:

i would try cloning the Sandin circuits directly, but they all use the obsolete MC1445.

The MC1445 in the RGB encoder is be used as essentially an analog switch, use a 4053 just like the circuit described in
http://elm-chan.org/works/yuv2rgb/report.html
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creatorlars



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PostPosted: Tue Jan 06, 2009 8:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Aha... that makes sense. Thanks for explaining it to me.

This explains why using the sync stripper circuit and an external signal from my VCR, mixed with a V-Sync'ed VCO, was producing more interesting output than just the VCO's directly using my rackmount sync generator.

So, I assume the two different attenuation knobs on the Sandin and the "pedistal" trimmers on the Blanking & Pedistal board are all related to finding the right black level and calibrating the encoder to the right voltage ranges on each of the RGB inputs? As I understand it, if you attenuate the signal level down, you're then going to have to adjust the black level for that input accordingly, assuming an AC signal?

My goal is to have a module that will accept any standard voltage from my modular synth -- does this mean I'd ideally have separate DC and AC inputs? Or maybe multi-input voltage mixers at the RGB inputs?

I really need to dig out my beginner electronics books and do some refreshing/studying.

You said you were having trouble with black level on your adapter board circuit -- what do you think was the cause there?

How is your output looking/working with the modified XR-VCO and encoder circuits you've tried? I'd love to see some screenshots. Smile

In other news, I received a packet of documentation and schematics last week from Jeffrey Siedler (who designed the Supernova 12 video synthesizer and was also a member of the excellent Severed Heads). There are schematics for an 8038-based Video VCO... there were 12 of these in the SuperNova 12, as well as some custom FX and RGB input circuitry (the rest; sync generator, video mixer, RGB encoder, etc were consumer devices.) He's given me permission to repost all of it, so expect some PDFs here soon!
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jnuaury



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PostPosted: Tue Jan 06, 2009 11:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

creatorlars wrote:

In other news, I received a packet of documentation and schematics last week from Jeffrey Siedler (who designed the Supernova 12 video synthesizer and was also a member of the excellent Severed Heads). There are schematics for an 8038-based Video VCO... there were 12 of these in the SuperNova 12, as well as some custom FX and RGB input circuitry (the rest; sync generator, video mixer, RGB encoder, etc were consumer devices.) He's given me permission to repost all of it, so expect some PDFs here soon!


wowzas!

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loss1234



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PostPosted: Fri Jan 09, 2009 11:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

wow
this thread is pulling me in!

i would love to see those pdf's!!!

thanks

what do i need (BARE MINIMUM) as far as chips and equipment to get into this?

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creatorlars



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PostPosted: Thu Jan 15, 2009 1:29 am    Post subject: Reply with quote  Mark this post and the followings unread

I think I may have found an easy solution to an integrated gain control and blanking/clamp level circuit, the TLS1233 RGB Preamplifier chip, which is available from Mouser. This coupled with the MC1377 would make a compact circuit for sure!

Please check out the datasheet and let me know if you think this could work:
http://focus.ti.com/lit/ds/symlink/tls1233.pdf
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creatorlars



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PostPosted: Thu Jan 15, 2009 9:38 am    Post subject: Reply with quote  Mark this post and the followings unread

After further review I've realized that the LM1203 is another similar chip that could work. I have a handful of those I bought from Futurlec. It requires many more external components but may offer a little more control over adjustments? There is an application circuit in the datasheet for this one using an LM1881 to generate the blanking pulse that looks good. In addition to providing input buffers and taking care of the black level clamp/blanking circuit, it looks like we'd have handy overall Brightness and Contrast adjustments as well.

My main questions at this point are 1) Will this take care of all the blanking/black level needs?, and 2) Will the R, G & B outputs of the LM1203 feed directly into the MC1377 circuit?

Another general dumbass question I have is how to handle signal attenuation -- if I need to scale down the output/input voltages to the right ranges between these circuits, do I just add a voltage divider with one resistors in the signal path and one to ground?

Also, if I wanted Gain & Offset controls on each of the RGB inputs, could this be handled in the LM1203 circuit or should I add another set of op-amp buffers beforehand?

What is a good general purpose op-amp that I could use for wideband/video purposes? The Supernova 12 schematics I have use EL2444s all over the place, but those are out of production.

I realize I may just be talking to myself here, but the purpose of this thread is to document these attempts. Smile Please comment if you have any suggestions.

I'll be uploading the Supernova 12 related documentation soon. I have complete schematics for the FX modules, the Video VCO, and a little info on the RGB Blanking circuit.

I should have one of those Y PLUS encoder boards coming in the mail soon, but I'm still dedicated to coming up with a complete DIY solution.
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dar303



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PostPosted: Thu Jan 15, 2009 12:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

I have a Sh!tload of Elantec EL2120's ( http://www.datasheetcatalog.org/datasheet/intersil/fn7044.pdf ) if you need.

It is a "wideband current feedback amplifier optimized for video performance" " Being a current feedback design, bandwidth is a relatively
constant 100MHz over the ±1 to ±10 gain range."

"Applications
• Video gain block
• Residue amplifier
• Multiplexer
• Current to voltage converter
• Coax cable driver with gain of 2
• ADC driver"

It also has a digital "disable" input!


They are in managable size SMD, I can send you as many as you want.
These used to cost about 15USD/ a piece but a friend gave me a full reel because his company had to obey the mighty ROHS!
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PostPosted: Thu Jan 15, 2009 3:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

dar303 wrote:
I have a Sh!tload of Elantec EL2120's ( http://www.datasheetcatalog.org/datasheet/intersil/fn7044.pdf ) if you need.

It is a "wideband current feedback amplifier optimized for video performance" " Being a current feedback design, bandwidth is a relatively
constant 100MHz over the ±1 to ±10 gain range."


EL2444 is a voltage feedback op-amp.
Current feedback op-amps like the EL2120 are OK for buffers and amps, but usually can't handle any reactive components in the feedback path (i.e. like a cap in an integrator).

creatorlars wrote:

After further review I've realized that the LM1203 is another similar chip that could work. I have a handful of those I bought from Futurlec.

The LM1203 or LM1205 could make an RGB fader with voltage controllable contrast pin.

A 4053 will also handle your blanking.

In the supernova12 design docs, what voltage range are the VCO outputs?
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PostPosted: Thu Jan 15, 2009 3:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm going to try it out with the 4053 this weekend and see what I can get. Do you think I could use the BURST/BACK PORCH output of the LM1881 to generate the blanking pulse? From the description, it sounds like this would work... and the LM1203 datasheet illustrates something similar using the LM1881.

Bob -- Is having separate Blanking & Clamping signals neccesary, as shown in the schematic you posted a link to above? Or should I be fine with just a single 4053 and the blanking signal switching the outputs to ground? I'm unsure about the function of the second 4053. Perhaps I'm confusing my terms as far as the differences between black level, clamping, and blanking.

It looks like the LM1205 includes blanking at the output -- does that mean the LM1203 wouldn't?

The Supernova VCO schematics don't reference output level... but I will try to get that and the RGB Blanking schematic uploaded.
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creatorlars



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PostPosted: Sun Jan 18, 2009 8:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well after a day of tweaking, I have color output! I made a basic mixer at the signal input with offset and gain controls (as per Ken Stone's DC Mixer schematic.) I don't have any widerange op-amps right now so I'm just using a TL072. This goes to a blanking circuit using a LM339 comparator and the CD4053 to switch signals to ground -- this is based on the Supernova 12 documentation. The output of that is going to the Y-Plus RGB encoder board that I got in on Saturday. Composite Sync and Horiz/Vert Drive signals (to sync the VCO) are coming from my rackmount Tektronix NTSC Sync Generator.

I seem to be getting a stable output (for example with a square wave sync'ed to Vert Drive I am getting red horizontal bars that do not scroll) -- the number of bars increases with higher frequency and the width can be changed via my MFOS VCO's pulse-width control. My MFOS VCO only goes up to 40KHz, and I'm not sure if that's fast enough to generate what I am supposed (?) to be seeing.

The strange thing is that the effect of the Blanking circuit appears to be non-existent... I have checked to make sure the CD4053's control inputs are receiving the right frequency from the comparator circuit, and everything is good there. I am sending it Composite Blanking from my sync generator -- but the video does not appear to react differently even if it's unplugged.

I am seeing pure black between the red bars just fine.

In any case, I need to increase the frequency range on my VCO to see what I can get out of higher frequency signals. The MFOS VCO seems to do fine with syncing to vert and horiz drive signals.

...almost there...
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