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COLECO RGB VER 4

3 years ago 880
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Description

SMOL

Documents

COLECO RGB copy

HOTDOG_WATER 2

TEST

MD-80SN (8-Pin Mini Din)

BOM

ID Name Designator Footprint Quantity
1 220u C39,C38,C8,C31,C30,C32 C1411 6
2 Header-Male-2.54_1x1 Y,+5V,GND,B-Y,R-Y HDR-1X1/2.54 5
3 10uf C15 C0805 1
4 0.01uf C16 0603 1
5 5VO 5V2 LABLED SOLDER PAD 55X100 MIL 1
6 GND2 GNDO LABLED SOLDER PAD 55X100 MIL 1
7 10uf C13,C7,C6 0603 3
8 GND1 GNDO1 LABLED SOLDER PAD 55X100 MIL 1
9 75 R33,R29,R27,R26,R25,R20,R3 0603 7
10 2.7k+ R16 0603 1
11 1.5k R12,R32,R9,R6,R7,R8 0603 6
12 12k+ R31 0603 1
13 2.2k+ R18,R13 0603 2
14 THS7316DG4 U1 SOIC-8 1
15 0.01U C1,C3 0603 2
16 0.01u C5 0603 1
17 0.1uf C29 0603 1
18 0.1U C2,C4 0603 2
19 B P3 LABLED SOLDER PAD 55X100 MIL 1
20 B-Y0 P10 LABLED SOLDER PAD 55X100 MIL 1
21 Y20 P9 LABLED SOLDER PAD 55X100 MIL 1
22 R-Y0 P8 LABLED SOLDER PAD 55X100 MIL 1
23 G P2 LABLED SOLDER PAD 55X100 MIL 1
24 CS P4 LABLED SOLDER PAD 55X100 MIL 1
25 R P1 LABLED SOLDER PAD 55X100 MIL 1
26 100 R15,R28,R11 0603 3
27 15k R35,R34 0603 2
28 560 R1 0603 1
29 680 R2 0603 1
30 3k R4 0603 1
31 7.5k R5 0603 1
32 3.9k R21 0603 1
33 5M R36,R37,R38 0603 3
34 1k R39,R40,R41,R42,R43,R44 0603 6
35 3.9K R14,R10 0603 2
36 LM359MX U2,U3 SOIC14N 2

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Comments (8)

Cory Miller Reply

The schematic makes reference that you are unsure of this, can you elaborate?


Also, this does not appear to need 3 trace layers, is there some particular reason for it?

hotdog6394 Reply

@wolvenar half of this is a copy of an old schematic for baby pac man (or something I forget). Someone is making their own version(s) on atari age but I don't think they are sharing the PCB design as open source. The ypbpr to RGB conversion part of this schematic is fine (since it should be the same as the schematic. The ypbpr amplifier schematic is what I have specific doubts about; its just taking whatever voltage the input signal is doubling it (then setting it as 75 ohm impedance) which is then divided by the 75r > 75r resistor divider network between the amp and the TV. I dont know what that voltage is specifically. It works and looks great on my TV I never bothered to measure it. There are however jailbars on my TV from component I don't think this has anything to do with the voltage or anything, as far as i remember jail-bars are a sign of a clock signal sneaking its way into video. If you removed the clock from the RF modulator then maybe it would go away idk. If you know of a better way to incorporate component let me know.


Here is a pic of the baby pac schematic
https://i.imgur.com/JjFw2jH.png


When I originally made the PCB design I made it freaking upside down. I corrected this in hotdog_water_2 (my names lol). I dont remember if I finished this board. The PCB is meant to sit flush below the PPU of the coleco (on the underside of the coleco motherboard). If you are unable to finish the PCB i could do it for you.

hotdog6394 Reply

@wolvenar So you can see on the schematic that a few resistors have + on them like a value and then the plus sign. the value is the minimum resistance.
So you need to proto a board and add a potentiometer in series with whatever that value is. There are only so many colors on the coleco but all you need to do is balance off of white.
So if you have an o-scope you find a screen that has pure white, or else a screen with a spot of pure white. That will be your peak voltage for the RGB values. max white is also max red, green, and blue.
So if you have your potentiometer crank it up till your peak voltage is 0.714V p-p (or 1v but 0.714 is standard i think) after the resistor divider for all three colors. Then measure your potentiometers resistance and add it to the resistance to get the total R value then you have the value you would need for the spots with resistors that say + on them. Red and blue should have the same total R value (i think) green will be its own thing. C sync needs the same treatment i usually set it as 1v p-p but as long as there is a 300mv shift it never seems to matter on my end.


The atari age RGB board was still using pots in a final design last i saw (bah i say). Pots are leaky and you can get rid of them by doing the above.
I can go way more into detail, I didn't know if you wanted to try to finish this or wait for me to get around to it.

hotdog6394 Reply

@wolvenar damn it last thing i swear. If there is a sync signal in the RGB signal which is possible then your max RGB voltage should be 0.714v above it.
Sync being typically -300mv to 0v so then your max voltage for RGB is 0.714v however if you have sync that is 0v to .3V then you want your RGB to be 0.714v above that (1.014v). I could be misremembering stuff but like i said I can go into more detail.

Cory Miller Reply

@hotdog6394 I am slowly working on a colecovision mainboard replacement that is mostly OEM, but with different ram to remove the multi voltage troubles, and also a modular output in place of the normal RF box.   I was thinking I could tweak this to be  a plug in style modular board. This would leave it so you could add whatever output you want, even planning a new modular RF output maybe. Still deciding on if I want to follow the exact pcb layout, or redo it with whatever works best, but still uses original parts.
I plan to open source it when it gets far enough along to be at least a workable system if it were made. So still a LONG way to go, basically just starting. This was a result of I have quite a few systems sitting around with corroded mainboards, and wanting to restore them. It might be of use to others when done.

Cory Miller Reply

My typonese in that last one.. OUCH!!!

hotdog6394 Reply

@wolvenar We could work together on it. As you can see I open source everything anyway. Really got nothing better to do most of the time. I'd do both a OEM replacement and a miniaturized version. I would replace every part/item i could from the original coleco, Everything SMD and go ahead and apply the RAM mods and any other fixes (there are more). Not sure what to do with unused floating power inputs though. Also don't include RF since it noisy af. You can convert RGB to anything pretty easily, and you already have ypbpr (that may need something different from what ive done btw), much better to mix composite and s-video with a different encoder than using existing mods, so use RGB into the BH7236AF encoder for both of those. Something like this : https://easyeda.com/hotdog6394/bh7236af-rgb-rgb-s-vid-and-cv
What I am getting at is since you already need RGB to get decent S-video/composite then you might as well have all 3.
I am not sure of the specs of the ypbpr signal but I've tried a LMH1251 and had poor results making me think he ypbpr on the coleco is non standard.


Ill port some of the out there schematics and see how far i get before i get bored.

Cory Miller Reply

@hotdog6394
The reason for the RF, partly, is some addons like the Atari "adapter". Also in part is it is intended for those who still DO want it to be RF.
Though maybe not the original rf parts, they SUCKED vs anything even close to more modern could do.
The point of this particular build is to replicate the original device in as many of the parts as feasible and sane from an otherwise non usable or hard to fix board, yet have the RF change option as it only makes sense for most.   This is mainly so a person can use the majority of what they have in a corroded mainboard, or one with bad ram etc. It may be an easier fix to just pull the unique chips and drop into a new mainboard. I would entertain going on to other more updated builds after that. Right now there are a few already on the market, but the main difference is it would be planned  to be open sourced schematic where anyone could just order a board.
These are not cheap as a low order volume prototype however so I might look into a larger run and offer them cheaper than you could have made as low volume.
As I am sitting right now I took a break after some of the track routing on this seriously kicked my butt for some reason.
The schematics available for the Colecovision leave plenty of room to complain if not just troubleshooting, making it a bit more of a challenge.
I also recently failed BIG TIME on a couple rather simple protoypes of other projects.
I scoured the layout of those projects many times over and had others look them over for obvious troubles.
Yet somehow got +5v wrong to a hex inverter chip, and misrouted another line from a switch to an incorrect input.
This wouldn't be so bad but they were SO simple of circuits even compared to the Colecovision
Stuff like that makes a person start to doubt their abilities. Makes me wonder how much skill have I really lost as I have aged.
As summer comes around though less of my time is available, as has been the case recently. Family really can eat up time in a huge way.

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