Conic TVG 201-4
July 2019 – May 2020
Restoration of an old pong clone from Conic, which was in a pretty terrible state when I bought it, but the asking price was very low as a result and Flynn and I thought it would be a good thing to test our skills on…
Checking things over…
This is the machine as it arrived. We paid £5 for it in July 2019. The listing explained that it had severe battery leakage, and we can see the discolouration to the outer case, so we know it's going to be pretty bad...
Lifting up the top panel, where the paddles are stored we can see how dirty it is and how corroded the battery compartment screws are.
The paddles seem OK, if dirty and marked. Most importantly the knobs are present - we probably wouldn't have bought it if the knobs were missing. Or if anything else was actually missing, for that matter.
Inside the battery compartment…
First look inside the battery compartment and it's epically bad. Still, let's see how much of the hardware we can rescue. ..
The biggest issues are probably the screws that hold the case together. They look very far gone.
Pretty grim.
The spring on this side has gone completely!
There's what remains of a screw in there somewhere.
Disassembly & cleaning
Had no chance of removing the screw normally & couldn't drill it out either, so we've broken the plastic surround a little to get the case apart. Shame, but pretty small collateral damage given the state of things.
With all the battery hardware removed, we're now trying to save as much of the original metal as possible by soaking it in vinegar. Maybe that spring can be re-used? Or the screws at least? Some of the metal just disintegrated in our fingers, though.
Next thing is to get through those rusty screws to separate the main board from the case - how bad is it inside?
There we go, board is out. Switches are rusty, as is the box shield over the RF circuitry. Everything else is just dirt though. The labels and plastic button caps look pretty good.
Several hours of cleaning later, and with the two electrolytic capacitors replaced, the board is starting to look OK.
However, it doesn't work - we connected a 9V supply but the board makes no sound and there's no picture to tune in to. We'll have to come back to this to figure out what's wrong later.
Fixing the battery compartment
In the end we couldn't rescue any of the battery contacts, so we're going to cannibalise a cheap battery pack to replace them.
There we go, with all that corroded metal and acid cleaned out, and the replacement contacts in place, we're starting to get somewhere.
More cleaning…
Having de-oxidised the screws in vinegar for a week, and scrubbed the worst of the rust off them, all the small parts can go into the ultra-sonic cleaner for a few minutes.
It's time to take a closer look at the paddles and prepare them for retro-brighting along with the case.
We cleaned the marks off with a wet "magic sponge", squirted contact cleaner into the potentiometers and rubbed platen cleaner along the wire and the jack surround at the end, to treat all the soft plastic and prevent it from cracking.
Retrobrighting
We painted peroxide cream onto all the light-coloured plastic, covered it in cling film and put it outside in the sun for a few hours, turning it once an hour or so.
You can't see it very well here, but we also bound vinegar-soaked kitchen towel around the paddle jack ends to de-oxidise the metal pins, and wrapped them with gaffer tape.
We've found this method to work very well, and the plastic has all come up clean and even. And the paddle jacks came up nice and shiny after some scrubbing too. We're very pleased with how this is looking now.
The only thing that's suffered is the paper label on the top cover. We've tried to protect it, but it's not easy when it's undergoing so much cleaning.
Perhaps we should cover labels like this with clear plastic tape in future? We've done this on other machines where the label is damaged and we want to retain as much of it as possible, but plastic tape isn't the most durable of materials either, and it will yellow and perish one day, ruining the label for good.
Troubleshooting & fixing
Time to return our attention to the board and why it's not working. It was very quickly apparent that the AY chip was not getting the 9V on pin 4 that it should be. The switch is ok, so it must be something between the switch and the chip, and there are only three components it could be: the zener diode in the photo, the resister next to it and the transistor you can just see in the bottom right.
The diode looks like it has a chip missing, so that's the first thing to look at. We remove it from the board in order to test it with the component tester, but before we can do that one of the legs just falls out of the diode. Luckily we can see from the markings that it's a BZX 79C 6V8, so we order a replacement.
Meanwhile, we still need to find out whether the chip and the rest of the board work when pin 4 has it's requisite 9V supply. So we bypass the upstream circuit and patch the chip straight to the positive side of the power switch...
Sure enough, the board works perfectly! And the image is very stable, probably helped by those new capacitors. It does start to drift a little over time, as components heat up, but we'll see what we can do about that when that replacement diode is in place and the whole board is fully working.
One thing we do notice though, is that one of the paddles doesn't have nearly enough range any more and is only able to move the bats a few inches at the top of the screen.
We strip the potentiometer on the offending paddle, to see if there's anything obviously damaged and give it a thorough clean, but it doesn't help - the range is a fraction of what it should be when compared to the other paddle using the multimeter to measure their respective resistances.
So we order a replacement pot. 24mm base, 20mm shaft, Linear B 500kOhm - hopefully it will fit right into the paddle just like the old one.
Flynnie solders in the replacement Zener diode, but the board still doesn't work when we remove the patch lead.
(We were experimenting with using a Dremel gas iron. Turned out to not be a good idea at all, on another project…)
So we pop the transistor out and sure enough, this looks like it might be the culprit. Should probably have checked it in the first place!
Here it is. A bit of digging and I discover a data sheet for it - a standard 2N2222 should be a suitable replacement.
And sure enough, with a new transistor in it fires right up! Hooray!
Reassembly
Everything's now done on the main unit, so it's time to close up.
Have we remembered everything that needs to go in before we screw it all together...?
And the sheared screw is going to have to stay like that - 3 screws should be enough to hold it together, anyway.
I was really struggling to clean the plate, when I realised it still had the protective film on it!
If this console was rarer and in mint condition, I would definitely keep the film on, but in this case it's like finding an extra upgrade!
Looks much better.
I'm also leaving this plate loose, so we can easily remove it and move the slider down past the point that the cutout allows, to the hidden 'handicap' game modes.
All back together and time for a test. This is always the most nerve wracking one - worst than the first 'moment of truth'. So many times we've had a unit that just stops working at this point, after we've put it all back together. Luckily this time not only does it work perfectly, but the paddle with the broken potentiometer seems to have miraculously healed itself!
Maybe all that contact cleaner we used did work it's magic after all.
Finished!
All done!
Time for the beauty shots…
Pretty pleased with how clean the battery compartment turned out. And yes it does work with batteries in!
Epilogue
But hang on, I wonder if.... sure enough, the film is still on the main logo decal as well!
Beautiful!
