Thursday, February 9, 2017


Last summer I borrowed my friends Poly 800 for a test ride and a cleanup. I read about the Moog Slayer mod from the website and I went ahead and did it. After plugging the thing in and jamming a bit with it, I was like, f........k me, I need one of those! It sounds very lofi, yet very interesting. It's got that sort of in between a Casio and a Poly 6 sound, very cool stuff. I asked him to sell it to me, but he didn't want to. So after a while I gave it back to him knowing I was going to find another one at some point. So, a couple of weeks ago I got a call from my crate-digger-friend Nico who was in a independent thrift shop in Montreal and was like: Hey man! There's a Poly 800 here for sale but it doesn't work. We tried to plug it in with a 9v adapter and nothing lights up?? Immediately I knew they we're plugging a different polarity into it so there was hope. Ether it was fried or perfectly working but not the right plug. She was asking 25$ for it. I told him to get it. Worst comes to worst I would of wasted 25$ and maybe make a bit of money selling the good parts.

20 minutes later he shows up at my house with the thing in his hands and it looked pretty good. The joystick and all the keys were still there. That's usually a good sign. He had bargained it for 15$. So, I plug it in with the proper adapter and the lights were on but no sound. It was dirty as hell so I thought that maybe if I give it a good clean up, maybe it would play something. The lights were on, thats good enough, it was not burnt out, my gut feelings were right about the polarity I guess. The next day I open it up and it looked like a shit storm in there.

I started by cleaning it up roughly just to see if it was worth the trouble to dismount it all and thoroughly clean up every part. I plugged it back in, went through the presets to see if anything was coming out. I could hear some noise coming out as I pressed the notes but most of the presets were gone. I could hear the oscillator of preset 14 and the modulation and all, but it was faded. I went through the parameters and I programmed a bit of a sound, so life was still in there!

I dismounted the whole thing, removed all the PCBs, buttons, etc. The main frame and the keyboard (all electronic components where removed obviously) had to soak for a few hours in the bathtub. There were signs of acid leakage from the batteries through various parts of the boards. I took alcohol and Q-tips to remove it. Luckily, no chips were affected by it. Notice on the first picture of the inside (top) that there is a circle on the main module board that looks like a place for those 3V batteries, only no signs of batteries? I remembered from my friends Poly that his had the batteries on it. So I knew the leak didn't come from there and I also figured that because of the absence of batteries there, the memory was probably wiped out, resulting the absence of sounds from the presets.

One of the ribbons was damaged. I don't know if it was related to the battery leak or something fried, or whatnot? One of the connectors was broken and it looked like the 2 first pins were burnt and cut out. So I cut the 2 affected wires and re-soldered them directly on the board.   


After endless hours of cleaning and troubleshooting, I reassembled the boards back and plugged it in. Now the whole thing seamed to work. The presets were still not there and some of the parameters were not working. Mainly the second DCO actually. None the less, it was working decently enough for a 15$ thing. I was willing to be in peace with a more than half working Poly 800 for that price. Now before I put the screws back on, the fun part was to be done. The classic Moog Slayer mod. There are other mods that can be done on it, but I tried a couple and it made it sound kind of bad. I'm not really into the lofi sounding circuit bent style engines for my personal music. Just the Moog Slayer mod is sufficient for my needs. If you research on it, you will find all kinds of fun stuff to do with it.

I'm not going to in details about the mod, because the guy at pretty much covers it all in details. I simply followed his instructions to do mine. I really recommend that you do it if you have the Poly 800, it truly changes the game. You can really make it sound great and it becomes more fun to play with. A little note on it, the cut off and resonance are still active in the programming. If you want the full effect, you have to put both of them at the highest settings to have the full range of the potentiometers. Seriously, beware of the resonance, it oscillates like crazy when you put it up at full speed!

PS, If you live around Montreal and you are not at ease with electronics, you could also pay me to mod yours! Write me a message and I'd be happy to mod it for ya!

At last, the mod was successfully done and all the screws were put back in. The synth looked almost brand new. Now it was time to put the factory settings back into it. I went to research how to do it and it was somewhat easy. I found a few videos on Youtube about it and I tried it and it was not working at first. You have to put the thing on TAPE mode and basically run an audio program through it. You can find the original wave file here. Some people recommend that you record it on tape and do it like in the old days which makes sense. However, I manage to do it directly from my computer. You might have to play a bit with the levels from your sound card. I have an SPL Crimson sound card and I played the sound from the headphone jack with the volume level set to 12 o'clock.

I went back to check the presets and they were all there! The second oscillator was also working. The synth works like a brand new one! I spent that evening programming all the settings as I pleased and adjusted all the cut off and resonance to fit the mod for each presets. I couldn't believe it, a lot of work plus 15$ got me a "very good" synth!

The next morning I fire up the thing and NO MORE SOUND! WHAT??? Then I remember the batteries missing on the PCB. Oh! right! No more memory again... All my programming was gone. I read about that problem too and sure enough, there is 2 versions of the Poly 800. The mk1 and the mk2. My friend had the mk2 which had the batteries but mine is the mk1, no batteries. The only way to have its memory was to put C batteries inside. I didn't want the C batteries, so for now I simply took the wires connecting to the battery compartment and installed a 9v square battery instead. I don't use it without the power adapter anyhow. It works for now. I will solder the 3v battery thing on the PCB at some point, but now it's time to jam with the thing!