Coleco Telstar Arcade (6071) Composite Video Mod

[UnkieRobbie]

I have been fortunate to get my hands on a Coleco Telstar Arcade Model 6071 (the triangular one). The RF modulator has deteriorated and I need to convert this system to composite video. This is where I need help. It looks like it would be pretty simple to do, but I'm a newbie and I don't completely understand the chips and pins and I don't want to risk destroying the console by experimenting.

 

I'm attaching some pics for reference. There is a single coax cable connecting the board to the RF converter. I would assume that this cable is carrying all of the video information. Can I just take this signal and convert to composite? Does anyone have instructions or pictures that are specific to the Model 6071?

 

I would greatly appreciate any assistance anyone could provide.

[chas10e]

There is a tuning pot in that RF box. this video helped me:

 

 

I don't have the expertise to figger-out a composite mod but there are some that hang out here that might

[TheProgrammerIncarnate]

If the modulator has an RCA jack going in and another going out, you should be able to unplug the output cable from the modulator, and the input cable from the motherboard, then directly connect the output cable to the motherboard. That may do it, unless it needs amplification.

 

Oh, and while you have it open, could you take good pictures of the front/back the accessible PCBs? I'm going to (eventually) emulate the 7600-series chips (which are in the carts) and need to know what the inside of the console looks like and what glue logic ICs it uses.

[UnkieRobbie]

Thanks, Programmer. I had wondered if it might be that easy. I tried bypassing the RF (connecting directly to the board), but my TV doesnt indicate a signal. Im guessing it needs amplification. Do you know of a simple amplifier that would work in this application?

 

Im in the process of cleaning the electronics as we speak and will take some pictures while I have everything apart.

[UnkieRobbie]

Here are the pictures that Programmer requested. I'm not happy with the way they turned out, but maybe they will be of some help. Also, I'm new to the retro gaming world and I don't have a lot of experience, but I'm happy to help in any way that I can.

 

Honestly, there aren't a lot of IC's in this console. Everything I have read said that the bulk of the IC's were contained in the game cart. I can get pics of the cart insides of it will help you. If I can help clarify anything, please let me know.

 

 

[TheProgrammerIncarnate]

Quote

Honestly, there aren't a lot of IC's in this console.  Everything I have read said that the bulk of the IC's were contained in the game cart.

The ICs in the console should just be small/medium scale integration glue logic chips, while the cart contains a (single) much more complex chip. One of these has been decapped here.

 

Quote

I can get pics of the cart insides of it will help you.  If I can help clarify anything, please let me know.

 

I need to know are how the pins of the chip inside the cart are connected to the internal circuitry, so pictures of both sides of the cart's PCB would be helpful.

 

Ok, now for the mod, it's a good idea to experiment with alligator clips & a breadboard until you know exactly what circuitry it needs. Clip wires to the trace going into the connector (the one on the mainboard that leads to the modulator), as well as to ground and voltage source (the battery compartment's terminals are the easiest spots to connect to.) For amplification, all you should need is a NPN transistor with the collector connected to +X volts (through a resistor in the 100-1K range which throttles it.) The base should be connected to the video signal from the console, and the emitter should be connected to the TV through a composite cable. The cable's ground also needs to be connected to the console's ground.

 

This is a "quick and dirty" mod as it may need biasing & impedance matching to get a better picture (hence using jumper wires before doing anything permanent.) I did a similar mod recently with the Telstar Combat, and it looked great on a cheap digital TV, though somewhat lacking on my old analog tube, so a TV's electronics may be able to compensate. If it looks bad on the TV you use, or you want to use it on multiple TVs, then you may want to improve it.

 

Anyway thanks for the pictures, they should be good enough to figure out the internal workings, at least when the pictures re-appear. The forum update made them vanish ;(

[SoundGammon]

A friend of mine wants me to put a video mod in his Coleco Combat unit.

 

Anyone have any info on this?

 

[ChrisM]

Resurrecting an old thread here, as I got my hands on a really nice Telstar Arcade unit but had video quality issues.

 

I cleaned the hell out of the RCA output contacts and tried multiple external RF modulator solutions but none resolved the problem.  So I opened it up and attempted the tuning pot fix.  BIG MISTAKE!

 

I didn't realize I was torquing it too much and the entire tuning pot piece snapped clean off - which means a totally dead signal.  Ugh.  I wish I had tried just plugging a new cable into the internal modulator box FIRST to see the result before I started messing with the tuning pot.  That RCA output is readily accessible and easy to unplug/plug.  That would at least tell you if it's just a bad output cable.

 

At this point I think I'm going to look into a composite output mod but lack the skills to try it myself.  Will probably try to loop in a vintage repair shop to see if anyone is willing to give it a try.  Will report back if I have any success!