emmanuelf

Going to user programmable (which is great) complicate things fast. Going from initial ATF150X, you need to add a sram and a microcontroller. You could perhaps collapse the microcontroller and the CPLD with a microchip or atmel µC with sufficient CLC cells. Or try to go single chip with a PSoC 5200. Next is the FPGA way ...

Hello, Interesting. I had exactly the same idea. As ramdacs are all obsolete and as I don't want to base a design on "new old stock" or refurbished ebay/aliexpress parts, my plan was to use a small CPLD or FPGA and a still active video dac like ADV7125/3. As I want the design to be fully open even at the toolchain, I go for FPGA, a Lattice iCE40 (LP8K) and protyping with a TinyFPGA BX. A MachXO with 5v tolerant pin and integrated Flash is more appropriate but is a no go for me. It seems a little overkill as a first though, as it complicate things (level adaptation etc ...) but could be a generic base for many converters. The stocks of music ramdac used in Tim 2600 RGB board will not be avaible eternally. I had targeted the Intellivision first, but I will use the extras in the FPGA for my "universal 2600" project which will drive programmable clock, button rewiring etc... with a soft core or with the help of a little µC. For the intv, the pll could help to regenerate and tune a clean hsync from scratch. But as I am very slow at completing my projects, you definitively will have something working before me 😊

XRGB 8 pin mini-din is the de-facto standard for RGB modded retro hardware. Starting to put more video standards on it is I think a bad idea. There is already well established standards for that with on the shelf cables : RCA and 4pin mini din. The only exception I would made it to put mono audio signal on the 8 pin mini din as the scart has audio input too on the same cable.

Or replace it by a ferrite bead.

Be careful with overshoot: Most of the time it is measuring artifacts, you must take the ground as close as possible as the measuring point.

ok

There is the soon to be retired, but widely available BH7236AF from Rohm. Less than 6$ by one from trusted sources like Mouser, 60 cents from Aliexpress. It is used in the RGB board for the 2600 from Tim Worthington. Higher pin count but near zero external component need (and no external clock). Correction, it need the color subcarrier too. Add: It could serve as a proper 75ohm driver for all the outputs including RGB and CSYNC and clamp RGB out on sync. But does not have the LPF of the THS7374. Could be tried in another revision to cut down the cost and adding composite and s-video.

You should be able to put the divider before the aop without disturbing mux transitions if you choose a high to ground value. For the rest, ok I understand your use-case. On my side I'm only interested in pure standard connection. These sega cables are pure hack I don't like, proper driver/buffering is the base. These special purpose driver are immune to short circuit, to esd, specialy designed to drive 75ohm imputs etc... All other things could/are working, but are not as clean/robust and able to face all the diversity of real conditions. But this is a personal point of view that I understand some will disagree with, especially from a DIY/Hobby/Hacking perspective.

Not good. You need the same buffering for CSYNC as for R/G/B. THS7374 give you a complete coherent interfacing with the display device RGB/Scart interface. CSYNC is subject to the same double 75ohm impedance matching (150ohm) see p26 of THS7374 data-sheet. Without, in real condition you will go into trouble with CSYNC at one time or another. Otherwise, good job! PS: why using followers and dividers instead of proper gain on each channel ? Ac coupling and "high"/not low impedance output on the coupling is not ideal.

Don't forget that you are dealing with signals considered very very high speed for protoboards. On a properly routed PCB, you will get even better results with or without the (to be enabled anyway in this use case) LPF.

Yes, but proper routing and mechanical design is an art too, it is a valuable part of the final result. As this is a pure disinterested unfinished work giveaway, I assume that the original attribution and credit is a simple unintentional omission. For the missing capacitor and labeling value error, the design was clearly marked as "Untested, use at own risk". To be complete and for the record, don't miss the R25 BoM value error: R25 must be 680R and not 680K. With a little bit of shifting/rerouting to add a THS7374 at the output, and some values tuning, this is the best price/quality compromise. LMH1251 is very costly, a pain to integrate with most pin unused and really overkill for the limited colorspace of the TMS.

You forgot the citrus3000psi ColecoRGB PAL And for XR8052, you have plenty of possible replacements : From AD you have AD8052, AD8042, ADA4891-2, AD8062 I don't see why is is "passable". All these suffer proper video output buffering. But you discovered these recently with the magic of THS7374 and his integrated LPF

Is there any plan for a re-edition ?

Which is close to the standard 40 IRE black level.

Yes I think. Off the shell standard video buffer (6db gain) have a 300mV output bias ( Ti THS73xx line).

Yes 0.7Vpp with up to 2V of bias. The complete specification transposed from the original CENEL/European standard (non public document) into British standard (public document): http://fr.meric.free.fr/Articles/articlesba/stsurtvplat/Scart/BS_EN_50049-1 Peritelevision connector.pdf

For scart, you could and should have a DC offset for proper operation. Up to 2V.

Better use the PAL version to completely remove the color burst. I bet that your are seeing is the result of the different summing of R-Y/B-Y/Y color burst. Only the Y signal color burst must be keep to not be affected by summing and be subtracted via Vref. The original TI circuit is only valid for 100% compliant TV witch should refer to the back-porch level ant not to the minus of colorburst/back-porch but if the discrimination of the distorted colorburst fail, back-porch level referencing may fail depending of the implementation.

Hook up the ground to your Video and Audio RCA connectors.

These pull-down should already be present onboard for proper operation of the console.

J3-7 is 0v referenced, J3-6 is -5v referenced. The later could be omitted and considered as a test point. The -5v referencing is need because of the ac coupling at the input needed for the -5v/12v used for the AOP and the command of the 4066.

For a refreshed circuit, don't forget about the hugely improved LMH1981, more pins but worth it in all other aspects.

Forget what I said. During blanking, RGB signal should be very low, normally at black level but near 0v with some equipments to get them working. All of these will for me to put mine under the scope Need a little bit of motivation and some time and space. Will try to arrange that.

Ok, I miss the ac coupling via C147. Yes that is my understanding too.

Yes, LM1881 based sync separator/stripper. But it was a false track. @ChildOfCv RGB signal blanking is not overkill in a pure RGB input ? Ok it work on an analogue TV, but could perhaps disturb the analogue front end of the OSSC (which is not a TV front end). Did you not miss a junction between the base of Q22 and the output of U29B ?