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Started by BlueBMW, March 15, 2012, 01:00:41 pm
Quote from: panzeroceania on April 05, 2012, 12:06:41 pmwhat systems would these be used for? PC Engine mainly? I am interested, I want to support work like this. Any idea on price points?I need to buy/make an RGB amp for my Sega Mark III.I would buy one though as I need one for my NEC Supergrafx, I already have one for my Super CD2 but it would be nice to have something for the Supergrafx
Quote from: BlueBMW on March 15, 2012, 01:00:41 pmdoes anyone have any design change recommendations?
Quote from: viletim on April 11, 2012, 10:15:28 pmAbsolutely!
Quote1. Use a THS7314 instead of a THS7315. It has a gain of only 2 which makes it much better suited as a video driver.
Quote2. Remove the potentiometers from the circuit. They will cause a signal level mismatch between channels and add noise. The amplitude of the PCE video signal is constant. Measure it!
Quote3. The amplifier is missing a bias network. The video will swing below zero, outside the linear region and the signal will distort (clipping). In practice, the darker parts of the video will appear black as the details will be lost.
Quote4. The PCE will have a TTL sync signal available, so instead of the expensive LM1881M, you can use a cheap logic gate to buffer the sync signal.
Quote5. Your have silkscreen over your copper pads. Silkscreen will resist solder!
Quote6. You can significantly reduce the noise picked up and radiated by you PCB by filling all the unused space on the green layer with ground connected copper.
Quote from: BlueBMWI thought about making a way to bridge past the potentiometers if they are not desired in a specific setup. The idea with this board is to just install the components needed for a specific application. The pots may not be necessary on the PCE/TG16, but other applications may require them.
Quote from: BlueBMWI consulted the guy who's been helping with the design of this chip concerning this issue. He said he selected this particular chip because it is self biased and doesn't require a coupling cap.
Quote from: BlueBMW on April 11, 2012, 01:29:37 pmQuote from: panzeroceania on April 05, 2012, 12:06:41 pmwhat systems would these be used for? PC Engine mainly? I am interested, I want to support work like this. Any idea on price points?I need to buy/make an RGB amp for my Sega Mark III.I would buy one though as I need one for my NEC Supergrafx, I already have one for my Super CD2 but it would be nice to have something for the SupergrafxPrimarily I designed these with the NEC consoles in mind, though they could really be used anywhere a signal amplifier is needed. Aside from RGB, they can also be used on NEC consoles to amplify the S-Video signals that the HuC6260 chip generates (pin 40 for Y) and then strip the composite for nice clean S-Video without an external encoder.Price point isnt set yet... I'm really hoping to be as cheap as possible though. As it is, I'm looking at a parts cost of around $10 a board fully populated. So add in whatever assembly time is worth, shipping / packaging costs and whatever a fair profit is on these, that will be the final price.
Quote from: micro on November 09, 2012, 12:53:56 amI like the idea of having a little amp/buffer board for the PCE. But BlueBMW, I'm wondering why you did fall back on using single transistors?So I tried to design a little THS7314-based board, including the changes viletim suggested....With 3.6 MOhm pullup resistors the 7374's input pins should be biased at 0.91 V. The datasheet suggests to set the cutoff frequency of the input high pass filter at about 3 Hz, so that will give us a Cin of 82 nF.I still have to try out if that circuit really works...
Quote from: GUTS on November 09, 2012, 04:01:19 amThere was a guy over that PCEFX boards a couple years ago who had awesome little RGB/S-Video boards made for the Turbo Duo. I bought one off of him for about $25 and it was worth every penny, the picture is beautiful. They look fairly similar to your original design, and were very versatile. I could take a picture if you're interested in what they look like.
QuoteAny news on this lately?
Quote from: micro on May 17, 2013, 06:22:18 amI haven't tried out the THS7374 yet. It seems the 7374 is very similar to the 7314. But in case of the PC Engine / Turbo Duo you can use composite video for synchronisation and it doesn't have to be buffered because it's already available on the (Turbo Duo's) AV out.For which console, monitor or video input device do you need the sync signal amped or buffered?
Quote from: micro on June 05, 2013, 07:51:55 amThe PCB's have arrived:Heffa, have you already ordered the SMD parts? I need the SMD parts, too.I could order all neccesary parts except for the THS7314, which is hard to come by in Germany.Are you interested?