Improving signal strength on Superboard II
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Improving signal strength on Superboard II
Hi all, the ntsc video signal from my superboard II is not strong enough for these lcd displays. I’ve tried two and the picture keeps dropping in and out. It is ok on an analog crt but not these LCDs. Any suggestion on how I get boost the signal?
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Re: Improving signal strength on Superboard II
A little more into I’ve tried both a video amplifier and an ntsc to hdmi converter and no luck. The signal just won’t lock onto a sync. It keeps dropping in and only. On both my 10” and my 5” lcd monitors I’ve tried. Hopefully someone can help I was planning on making the superboard two into a luggable laptop. But with no LCD it kind of kills the idea.
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Re: Improving signal strength on Superboard II
I know what you mean regarding the signal strength, I have a Klyball remake, and the only thing I can drive reliably is a small 5" CRT TV.
I can get a picture on my LCD display that has a direct composite input and works with both PAL and NTSC (I'm in the UK, so PAL, but my replica uses 60Hz) but the picture is very grey and rather fuzzy. On my 5" CRT I get screen wrap which isn't ideal either.
I've tried an NTSC to PAL adapter and a composite to VGA adapter, but they simply don't pic up the signal. If you have any luck with finding a way to boost the signal I'd be interested.
I can get a picture on my LCD display that has a direct composite input and works with both PAL and NTSC (I'm in the UK, so PAL, but my replica uses 60Hz) but the picture is very grey and rather fuzzy. On my 5" CRT I get screen wrap which isn't ideal either.
I've tried an NTSC to PAL adapter and a composite to VGA adapter, but they simply don't pic up the signal. If you have any luck with finding a way to boost the signal I'd be interested.
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Re: Improving signal strength on Superboard II
Well I tried a booster already. One that’s adjustable and has 8 outputs. I turned all but one down and when it locks onto a signal it looks bright and crisp but then dropped out of sync and back so I’m not sure what the issue is.
The monitor I’m using has ntsc composite, hdmi, vga, and BNC inputs. It uses 12v input. Standard cheap displays you can find on Amazon.
Have you tried adjusting the POT next to pin 12 ofJ2 ? That adjustments brightness.
The monitor I’m using has ntsc composite, hdmi, vga, and BNC inputs. It uses 12v input. Standard cheap displays you can find on Amazon.
Have you tried adjusting the POT next to pin 12 ofJ2 ? That adjustments brightness.
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Re: Improving signal strength on Superboard II
Why do you think the signal strength is the problem? Since the video amplifier doesn't help, I suspect that it isn't. LCD monitors are more picky about what signals they will display than CRT monitors are. If the frequencies or waveform are too far off from what is expected, the screens will blank. I've heard that some early models that didn't have such protection could be permanently damaged if fed an incorrect signal. OSI video signals don't adhere that closely to the NTSC standard in the first place, having a horizontal-to-vertical frequency ratio of just 256. Possibly, the modifications done to your board make it differ even more from the standard. Do you have, or have access to, an oscilloscope so that you could take pictures of the video waveform(s)? Or a frequency counter, to see what the vertical and horizontal frequencies are? What is the frequency marked on the crystal that provides timing for the board?
No current OSI hardware
Former programmer for Dwo Quong Fok Lok Sow and Orion Software Associates
Former owner of C1P MF (original version) and C2-8P DF (502-based)
Former programmer for Dwo Quong Fok Lok Sow and Orion Software Associates
Former owner of C1P MF (original version) and C2-8P DF (502-based)
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Re: Improving signal strength on Superboard II
Right I don’t think it is a signal strength problem either after I hooked the booster up. I should have clarified that in my second post. So I have been trying to figure out if there’s a way to correct the signal / sync.
I found this on marks page just now “ One-shot U65 generates a horizontal sync pulse at the end of each line (C7, at 15.375KHz) and a vertical sync pulse at the end of each frame (C15, at 60.0 Hz)”
Yes I have both analog and digital oscilloscopes. I wil try and take some photos today.
** I don’t know much about NTSC. Time to learn I suppose. From what I found, the horizontal sync is supposed to be 15.734 kHz and apparently the superboard is 15.375 kHz. Could this be the problem and how can I adjust it? Another crystal?
Could it being B&W with no color subcarrier be causing the issue as well?
I will checks all the frequencies next.
I found this on marks page just now “ One-shot U65 generates a horizontal sync pulse at the end of each line (C7, at 15.375KHz) and a vertical sync pulse at the end of each frame (C15, at 60.0 Hz)”
Yes I have both analog and digital oscilloscopes. I wil try and take some photos today.
** I don’t know much about NTSC. Time to learn I suppose. From what I found, the horizontal sync is supposed to be 15.734 kHz and apparently the superboard is 15.375 kHz. Could this be the problem and how can I adjust it? Another crystal?
Could it being B&W with no color subcarrier be causing the issue as well?
I will checks all the frequencies next.
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- Joined: Thu Apr 16, 2015 2:27 pm
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Re: Improving signal strength on Superboard II
I think the standard Superboard can display its output on most LCD screens, but I'm not 100% sure. I made up this chart a while ago showing the horizontal and vertical frequencies of a C1P/Superboard II with several choices of crystal frequency, along with the deviations from both the color and black-and-white versions of the NTSC spec, and the serial port baud rate and its errors as well. It relates specifically to the unmodified 600 board, I don't know if yours needs a crystal that is double the frequency of what the unmodified board would use, or if it uses the same clock-doubling trick that the 600D uses, or something else altogether. I won't be of much help in interpreting the actual waveforms, though others here may be. But if your board uses the original 3,932,160 Hz crystal, you might try replacing it with a standard 4.00 MHz crystal, as I think the horizontal frequency may be more critical than the vertical. Likewise, if the crystal frequency is around 7.9 MHz, you could try an even 8.0.
Code: Select all
Crystal Clock VSync Vsync VSync Hsync Hsync Hsync Bit Bit rate
frequency frequency freq. error error freq. error error rate error
rel. to rel. to rel. to rel. to
color B&W color B&W
spec spec spec spec
3,932,160 983,040 60 +0.1% 0 15,360 -2.38% -2.48% 295.38 -1.54%
3,993,600 998,400 60.9375 +1.66% +1.56% 15,600 -0.85% -0.95% 300 0
4,000,000 1,000,000 61.0352 +1.83% +1.73% 15,625 -0.69% -0.79% 300.48 +0.16%
No current OSI hardware
Former programmer for Dwo Quong Fok Lok Sow and Orion Software Associates
Former owner of C1P MF (original version) and C2-8P DF (502-based)
Former programmer for Dwo Quong Fok Lok Sow and Orion Software Associates
Former owner of C1P MF (original version) and C2-8P DF (502-based)
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- Posts: 163
- Joined: Thu Dec 14, 2023 2:17 pm
Re: Improving signal strength on Superboard II
Yes, I've adjusted multiple times in both directions, but it just ends up looking like a weak TV signal. I am wondering if the OSI is the full issue since I have a TRS-80 CoCo 1 with a composite mod and the picture on the same display varies from crisp to very fuzzy.Sideburn wrote: ↑Tue Mar 26, 2024 11:29 am Well I tried a booster already. One that’s adjustable and has 8 outputs. I turned all but one down and when it locks onto a signal it looks bright and crisp but then dropped out of sync and back so I’m not sure what the issue is.
The monitor I’m using has ntsc composite, hdmi, vga, and BNC inputs. It uses 12v input. Standard cheap displays you can find on Amazon.
Have you tried adjusting the POT next to pin 12 ofJ2 ? That adjustments brightness.
I did try fitting a 100uF capacitor inline in a similar manner to how the simple composite mod is done on the Sinclair spectrum, but it didn't really make much difference.
Looking at the signal on my oscilloscope, it seems almost like the sync drops off occaisonally.
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- Posts: 163
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Re: Improving signal strength on Superboard II
I have a 4Mhz crystal in mine and the hsync and vsync values you have there match mine. I haven't tried any other crystals.bxdanny wrote: ↑Tue Mar 26, 2024 1:46 pm I think the standard Superboard can display its output on most LCD screens, but I'm not 100% sure. I made up this chart a while ago showing the horizontal and vertical frequencies of a C1P/Superboard II with several choices of crystal frequency, along with the deviations from both the color and black-and-white versions of the NTSC spec, and the serial port baud rate and its errors as well. It relates specifically to the unmodified 600 board, I don't know if yours needs a crystal that is double the frequency of what the unmodified board would use, or if it uses the same clock-doubling trick that the 600D uses, or something else altogether. I won't be of much help in interpreting the actual waveforms, though others here may be. But if your board uses the original 3,932,160 Hz crystal, you might try replacing it with a standard 4.00 MHz crystal, as I think the horizontal frequency may be more critical than the vertical. Likewise, if the crystal frequency is around 7.9 MHz, you could try an even 8.0.
Code: Select all
Crystal Clock VSync Vsync VSync Hsync Hsync Hsync Bit Bit rate frequency frequency freq. error error freq. error error rate error rel. to rel. to rel. to rel. to color B&W color B&W spec spec spec spec 3,932,160 983,040 60 +0.1% 0 15,360 -2.38% -2.48% 295.38 -1.54% 3,993,600 998,400 60.9375 +1.66% +1.56% 15,600 -0.85% -0.95% 300 0 4,000,000 1,000,000 61.0352 +1.83% +1.73% 15,625 -0.69% -0.79% 300.48 +0.16%
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- Posts: 132
- Joined: Sat Feb 03, 2024 10:59 pm
Re: Improving signal strength on Superboard II
Is the character generator creating the ntsc timing timings and everything else other than the two sync frequencies?
I wonder if converting to rf and then using an lcd tv on channel 3 would make a difference.
I wonder if converting to rf and then using an lcd tv on channel 3 would make a difference.