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Your Most Agressive Modification To A Retro System


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**I tried to search and see if this topic had been discussed before, but did not come across anything concrete, so here it goes...  If I have missed a prior discussion, please let me know.**

I always wondered to what lengths others have gone to keep their old friends alive and kicking.  Please share your story no matter how insignificant you think the

repair is/was.  I always love hearing how others have saved these gems from the past.  If you have a picture, please post it!

My contribution:

Back when I started looking for a TRS-80 CoCo 2 to buy, I knew early on the RF Modulator output was going to need to go.  So I did a bunch of research on how to

hack the MC1372 modulator circuit so I could get composite video out.  I found the answer on page 12 of the MC6847 Video Display Generator chip manual.  It depicts

exactly how to build the circuit.  So I ripped the guts out of the RF can, rewired it in place, added an audio amplifier circuit, and added an audio output jack on the back of the can under the video.

Happy Sunday!

Edited by evlthecat
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I never really got all that "aggressive" with modding my old systems back when I had them, I pretty much used them as is, except for the occasional recapping or part replacement. Most of the "modding" I did was in the electronics space, designing, modifying, or building items or "tools" I needed or wanted, attempting things I had heard about or seen printed somewhere. Some more obscure things such as lineman's phones, a "blue box", radio jamming or boosting devices, were on my list. Mostly I like to see what I could make with what I had, I built a lot of failed circuits, and also ended up making some neat little devices, but it was all learning experience.

No internet back then, there were bulletin board systems (BBS), but they are stone-age compared to what we have at our fingertips today, and you could really run up a killer phone bill if you were not careful. By "killer", I mean your parents killed you when they saw the bill. So you mostly learned from others, books, and/or trial and error. Honestly, I did more repairing than modding back then.

However, later in the 90's and early 2000's, I did do quite a bit of modding on PC's, trying to squeeze every bit of performance out of them I could (before it was cool!), getting them to outwardly look and operate just how I wanted them. I don't do much in terms of modding anymore, no real reason, you can buy just about all you need and most of the work is done in software.

A close friend and I also made a lot of "props", like you seen in the TV and films of the era. Often taking toys of said items and modding them to look more like the actual prop used on the shows. One of my favorites was a Star Trek TNG Tricorder toy from Playmates I had purchased, it had a few sounds and 2 lights inside, that was it, so a lot of empty space to add things. It looked neat, but I thought it could be better. So I ripped it apart, put some real LED's in it that flashed in a pattern to the sounds, added a "panic button" that made the "red alert" sound, and modified the little fake screen to have a more realistic backlight by using a diffuser and an LED light off to the side. I bought it for like $10 on clearance and ended up selling it for $75, nice profit for the 1990's. haha

These days, I am playing a lot with Raspberry Pi and Arduino, but not much outside of that. 🙂

Edited by Strider
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When I had a 128 with easier sound programming, I made a silver box. Basically just ordinary DTMF but with the ABCD tones as well. The program had the blue box MF functionality but by the time I got into it all the switches in my area had abandoned in-band signaling so blue boxes didn't work anymore.

As far as modding goes, never really did that... but I have made a couple of repairs to my two Apple ADB keyboards that had cracked solder joints where the ports were soldered to the PCB.

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When I was in high school, installed a second SID chip for stereo SID tunes on my C64 (like soldering the 2nd chip right on top of the first, with a few pins bent out and the components for a small circuit kind of just soldered together close by, was a bit kludgy, but it worked, no pcb needed 🙂.  And the standard 8/9 drive number switch on my 1541.

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I had a Colecovision as a kid and came across a set of 3 broken ones at a fleamarket, probably 2004 or '05 or so. 

Never did a lot with the hardware, but I researched online and taught myself enough to figure out that the weak spot was the 4116 RAM chips used for video memory.     They required +5, -5, AND 12 volts to operate.   And the Colecovision main switch was only a double pull which means, yep, the -5 was always supplied to the board when the power supply was plugged in, which made sense since the datasheet said -5v had to be powered first to polarize the substrate.    Colecovisions were already notorious for the power issues and a dirty power switch always caused problems.  

So after studying the pinouts, I made a rather drastic mod that it turns out lots of other people also independently figured out, and I would have earlier if I had looked at the arcade board enthusiasts.    I bought a bunch of tubes of 4164 drams for $2 at a local electronics wholesale place.  (I think I still have dozens of these somewhere on the bench).    These were the same as the 4116 in terms of most of their pins, except (a) instead of 16k x 1  they were 64K x 1; but more importantly, (b)they needed only +5 volts to operate -- no need for +12 or -5 volt rails.   So you could drop these in and all you needed to do was keep the +12 and -5 not connected, tie a little jumper to get +5v to the correct pin, and tie the extra address line low through a resistor.    Yes, HIGHLY wasteful in terms of only using 25% of the capacity, but it was close to a drop in solution and worked perfectly.    Also, the 4164s ran a LOT cooler.   Like very noticeably cooler, which was also a benefit. 

As I recall, you couldn't get rid of the 12 volt completely because it was used in the RF box, and you couldn't get rid of the -5v because Coleco did some wierd mumbo jumbo that needed it for their controllers, and at any rate I used the +12 for my transistor based A/V mode that added Composite audio/video out without disabling the RF box.  

That was a nice little mod, and I still have the Colecovision that was the best of those three (also modded the controllers with microswitches for the joystick inputs for reliability too), and its still going and going.   

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I have never done a modding job on retro systems. I plan to. But if I were to be inspired by any mod job in the past, it would be Ben Heck's c64 laptop project. If I were to mod it would be something like that.

I really hope he'll do a cx16 laptop project in the future.



Sent from my SM-T720 using Tapatalk

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ATARI 520 ST, back in the days around 1987: Piggybacking RAM chips on the existing ones to upgrade vom 512kB to 1024kB RAM. It was quite thrilling soldering all those chips and adding those wires to the MMU 😅...

And it worked 😀!

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