View Full Version : Sanyo 31C426 RGB input pinout


ituba
05-08-2017, 01:37 AM
I am new to videokarma and I know little about the internals of TVs. I have recently picked up a Sanyo 31C426 (chassis no A2G-42600) TV/monitor from a video production company, which was moving. It has an input port labeled RGB, which is actually the reason I picked it up. I'd like to use it with an old computer (an Amiga 500 actually), which outputs a 15.5 kHz NTSC RGB signal. Does anybody know the pinout of this RGB port? Is it--as I hope--an analog 15.5 kHz port? I can't find any info on this on the www. Thank you,

Imre

Titan1a
05-08-2017, 07:30 AM
I don't think so. Probably either digital RGB or 30Khz scan rate. The Amiga sends a 15 Khz signal unless you have a scan doubler.

dr.ido
05-08-2017, 09:06 AM
It's probably analog RGB - From memory the Sanyo MBC550 computer had an analog RGB output.

I've used other monitors that had this connector on an Amiga, though not all monitors using this connector for RGB were analog. If it is a TTL RGB input you'll get a picture with incorrect colors (if it locks at all, from memory the sync is also different).

Electronic M
05-08-2017, 10:05 AM
That looks like an EIAJ A/V connector. I've never seen one used for RGB video before. They were originally used for 2-way composite video + monophonic audio connection between a TV/monitor and an early tuner-less VTR/VCR back in the late 60's-70's. It made for a nice single wire connection so the TV could play the VTR's signal, and the VTR could record from the TV tuner....It is a shame they did not add 4 more pins for stereo to the original spec...If they had it probably would have lasted to the end of analog.

ituba
05-08-2017, 05:02 PM
Thank you Titan1a, dr.ido, and Electronic M for weighing in.

Titan1a: It may well be a digital RGB input, but I doubt it's 30 kHz. For one, this is a TV, so it can certainly handle a standard 15 kHz signal, and although my understand of Tv electronics is limited, I understand it would require little (or essentially no) additional circuitry to have an RGB input at 15.5 kHz, since that it is what a composite signal is converted to anyway before it's fed to the picture tube. In fact, such a thing is quite standard on TVs in Europe, which often have a SCART connector that can accept an RGB signal. Now, to have additional circuitry to accept a 30 kHz RGB signal is certainly possible, but I wonder what it would have been used for in 1985, when this TV was made. VGA was introduced in 1987.

dr.ido: You said you used other monitors with this kind of connector with an Amiga. Do you still know what the correct pinout is?

Electronic M: Yes, the connector does look identical to an 8-pin EIAJ jack, but it is labeled RGB and the TV does in fact have a mode switch in the front, and one of the modes is RGB. I found a picture on the WWW of a Toshiba TV (CX2084C) with the same kind of connector labeled RGB, but could not find any additional info on that TV either.

Titan1a
05-09-2017, 01:21 AM
This looks very similar to a monitor input I use on a Commodore 128 computer. Digital RGB.

dr.ido
05-09-2017, 07:39 AM
I've had Taxan, Roland, NEC and Hitachi monitors that used these connectors for RGB. The Taxan and Roland monitors were switchable between analog and TTL RGB - "Apple" mode was analog, IBM mode was TTL. I used the Roland and Taxan monitors on my Amiga. The NEC monitor was TTL only.

It is an 8 pin EIAJ jack. When I was making cables for these monitors I'd cut an old stock VTR cable in half to make 2 monitor cables. Sorry, I don't remember the pinout.

This link here has a pinout for a taxan monitor:
http://wouter.bbcmicro.net/hardware/monitors/index.html

Zenith26kc20
05-09-2017, 04:38 PM
Some early Proton brand TV sets used those. You may look for their manuals on line. I do remember vertical sync was a problem.

Findm-Keepm
05-09-2017, 09:58 PM
Germane, perhaps:

http://wouter.bbcmicro.net/hardware/monitors/taxan_3.jpg

https://i.warosu.org/data/vr/img/0010/91/1379889452751.jpg

It's either:

An 8-pin EIAJ jack, used for older analog (composite video) for VTR to TV interface.

==== OR ====

An 8-pin EIAJ jack, used for RGB input - R - G - B (TTL) and sync inputs.

Yours seems to be the latter. Byte magazine used to review combo TV/monitor sets in the 80s - it may be a good source for data, as American Radio History has scans.

ituba
05-10-2017, 12:13 AM
Thanks Titan1a, dr.ido, Zenith26kc20, and Findm-Keepm for your help.

I could not find any info on old Proton TVs, but I think Findm-Keepm has the correct answer and it is a digital RGB input. I pulled the rear cover and took pictures of the circuit board the RGB input is connected to. My understanding of electronics is limited, but it seems to me that the RGB input connects to the two ICs on the front of the board, and these appear to be digital gates.

So, Titan1a, this would work well with your Commodore 128.

colorfixer
05-12-2017, 10:59 AM
All might not be lost. See if you can get a schematic for this beast. You may be able to simply remove the gates that are in the video stream, or apply your RGB video to the output of this daughterboard directly. This monitor looks a lot like the original 20EZV arcade monitors which had cabinets rather than metal open-frame chassis.

Thanks Titan1a, dr.ido, Zenith26kc20, and Findm-Keepm for your help.

I could not find any info on old Proton TVs, but I think Findm-Keepm has the correct answer and it is a digital RGB input. I pulled the rear cover and took pictures of the circuit board the RGB input is connected to. My understanding of electronics is limited, but it seems to me that the RGB input connects to the two ICs on the front of the board, and these appear to be digital gates.

So, Titan1a, this would work well with your Commodore 128.

ituba
05-15-2017, 11:21 PM
All might not be lost. See if you can get a schematic for this beast. You may be able to simply remove the gates that are in the video stream, or apply your RGB video to the output of this daughterboard directly. This monitor looks a lot like the original 20EZV arcade monitors which had cabinets rather than metal open-frame chassis.

Thanks for the tip. That thought has crossed my mind too after I read a post online by someone who tapped into the input lines of the jungle IC of an older CRT to create an analog RGB input. But there are a few challenges. For one, I can't even find an owner's manual for this TV, let alone a service manual. I've looked up the Sanyo 20-EZV and found its circuit diagram, but that does not seem to have a digital RGB input. so it does not give me any hints on how the input daughterboard works in my TV. Although I can certainly manage soldering a few wires to contact points on the circuit boards, I really don't understand enough electronics to be able to trace the lines on the input daughterboard to figure out where the digital RGB signal is converted to analog. Even if I did find the proper points to tap into, how would I know if the signal voltage corresponds to the signal voltage of a standard analog RGB signal? Or is there some reason to believe that it should?

Electronic M
05-16-2017, 10:06 AM
Got an oscilloscope? you can compare video level of your source to points on the schematics and or chip data sheets.

You may be able to get somewhere by looking at the chip data sheets on the daughter board, following the traces to chips on the mother board and looking up the data sheets/schematic info for those.

ituba
05-16-2017, 09:49 PM
Got an oscilloscope? you can compare video level of your source to points on the schematics and or chip data sheets.

Unfortunately, I don't have a scope. My electronics expertise is definitely not enough to warrant owning such a tool. Of course, I'd love to have one anyway.

You may be able to get somewhere by looking at the chip data sheets on the daughter board, following the traces to chips on the mother board and looking up the data sheets/schematic info for those.

I'll give that a try, but somewhat doubt my ability to decipher this from the circuit boards. If I had the circuit diagrams, I'd have a fighting chance.