Fixing, Restoring and Modding a Korg Poly-800!

I was given this 1985-era Korg Poly-800, as it was not working - and was going to be thrown away! In this video, I look at the synth, diagnose and fix the problems, restore it to full operation - and then make it better than ever, by installing the "Moog Slayer" mod, as well as a switchable 12/24db filter. I then demonstrate how the synth sounds with these mods installed!
Every sound you hear in this video came from the Poly-800 shown in this video. You can hear the full backing track in this video: • Korg Poly-800 Backing ...
This is not a tutorial on how to install these mods - there are plenty of online tutorials telling you how to do them, such as this one: web.archive.org/web/202204271...
Thanks so much to MissParker for the very generous gift of this Poly-800. It will be put to good use!
I use Caig Deoxit contact cleaner: amzn.to/3nGXGyW
I also use a soldering station similar to this one: amzn.to/3bpsBtH
I was asked if I could share the links for the parts I used to fix the Poly-800, so here they are:
Power Jack: syntaur.com/Items.php?Item=3062
Left and right output, also footswitch: syntaur.com/Items.php?Item=4334
Headphone output: syntaur.com/Items.php?Item=3978
Tactile switches: www.alliedelec.com/product/pa...
Other source of tactile switches: www.digikey.com/en/products/d...
0:00 Introduction
1:13 Unboxing and Inspection
2:43 Testing
3:43 Disassembly
4:36 Replacing the Battery
5:51 Checking & Cleaning Jacks
6:33 Tactile Button Problems
7:15 Reassembly
7:43 Reloading Factory Presets
8:29 Test Playing
9:31 Replacing Tactile Buttons
12:24 Replacing Jacks
14:19 Installing Moogslayer Mod
16:06 Installing Filter Mod
18:48 Cleaning Pots
19:19 Test playing and Demoing Mods
#Korg #Poly800 #Moogslayer

[@giovaxx69]

Back in 1990 I reverse engineered its firmware and patched it to make the cutoff filter respond to dedicated MIDI CC messages in realtime. It improved a lot!

[@kelvindodd5577]

Thanks Scott. I just pulled my old Poly 800 out and will be refreshing it. Bought it new.

[@palmacbeth885]

thanks. i love the content and pace of this video. thanks for measuring up the buttons and posting the link to buy the replacements.

[@Asmuk]

One of the best videos I watched at KZbin for a long time. Quite useful, thank you so much.

[@paulr5610]

I love this. Why on earth would anyone downvote it?

[@ScottsSynthStuff]

Yeah, I know, and one of those downvotes was literally 15 seconds after the video was published, so they didn't even watch the thing. Who knows?!?

[@daveogarf]

@@ScottsSynthStuff - Just Jerkwads on Parade, trying to harsh internet buzzes.

[@rpjmullin7689]

My MK 2 Poly 800 now only makes Random noises unfortunately

[@miguelluizmartins799]

Nice work! Congrats!

[@hubbarao]

Love your channel man, thanks for sharing all this! I subscribed when I realized you've helped me several times (Cobalt 8 firmware upgrade and general care tips). I found this video on accident trying to figure out why I couldn't load patches from tape. Thanks for the reminder to do the Moog Slayer mod! I plan to tackle this soon. Couple notes: My patches load but I never got the "Good" message that I had when saving/loading/verifying with actual tape recorder instead of a smartphone. Seems to have loaded okay regardless (at least most patches). My tact switches are touchy but I just use the bank hold (only use this in the studio). Also, corroded audio jacks can often be fixed by rolling fine grit sandpaper and giving the inside of the jack a quick scrub. Just wanted to share, maybe it helps someone. Thanks again!

[@gohkawai8206]

Thank you for creating this video. I have a KORG Poly-800 that I purchased new in 1985. It powers on but generates no sound, just like the one you repaired. I will refer to your video in order to restore mine. Thanks!

[@jamesdefrancesco7765]

Great vid. I have the ex800 and replaced the soldered battery holder as well. The buttons are also a nuisance but will work. That single filter is good but paraphonic is a bummer. However, as I watching this vid I realized that my new Solina is also paraphonic. Time to midi them together and see what happens. That 6 stage envelope is fun.

[@sandymissparker]

There are no words...this is amazing. xo

[@daveogarf]

You are one very fortunate man, sir! I'd LOVE to have a Poly-800 after playing a friend's years ago. The quirkiness is kinda' fun, and the sounds are somewhat unique. Thanks for the vid!

[@ScottsSynthStuff]

Unfortunately the Poly 800 was not mine, and went to its owner after I fixed it! That said, there is a really good (and FREE) software emulation of the Poly 800 that you can use in your DAW to get the same sounds: www.fullbucket.de/music/fury800.html

[@daveogarf]

@@ScottsSynthStuff - Thank you, Scott! I'll look for it.

[@HipixOFFICIAL]

They are still decently "cheap" in terms if synthesizers. I got mine a year ago for $200 on reverb. Just needed a new battery.

[@jjdekay6969]

A great save! .......its always good to have the right tools nearby to get a job done ,........and the "cat scan" sure does help in diagnostics.

[@ScottsSynthStuff]

She helped a lot with the JD-800 restoration as well, but for whatever reason has completely ignored the Polysix!

[@jjdekay6969]

@@ScottsSynthStuff LOL!!!

[@mrbungledisco]

Awesome video, thank you for sharing. Subscribed!

[@box88]

I’m impressed!

[@juliprivate715]

oh my, I have a non working poly800 sitting in my basement... totally need to go through the same procedure 🙂thanks for reminding me

[@waskerbasket9601]

Diggin those mods

[@b-north]

hey i literally just got one for free and it’s super clean physically but it don’t work , watching this definitely is helping me , i might contact you for more information if that’s ok with you

[@cassettedisco6954]

Amigo saludos desde México 🇲🇽 sabes tengo un Poly 800 pero no sé si sirva crees q podrías hacer un tutorial enseñando un poco del mantenimiento gracias ❤

[@valleyken]

Awesome.

[@JayKaufman]

You got super lucky with that battery not eating away at traces. These and a decent number of Korg synths from the same era (Poly 61, Poly 6, etc.) are quite well known for the batteries leaking over time and absolutely tearing the boards to shreds thanks to the acid. A few years ago these weren't even worth repairing because of it, but thanks to everything synth that's old being worth more money now, they're worthwhile repairing.

[@ScottsSynthStuff]

Agreed. I had a Polysix that I bought in the late 1980s, and over the next 10 years or so, the NiCd battery leaked in it and destroyed a bunch of traces on the circuit board. I restored it in around 2003 or so, replaced all the tactile button switches, and repaired all the corroded traces. It was a LOT of work.

[@jhtzlx]

This is incredible timing for me as I'm restoring a Poly 800 II too! Amazing video. Did you notice any difference on the buttons once the foam was removed?

[@ScottsSynthStuff]

Nope, no difference at all. I'm not sure what the original function of that foam was, but whatever it was, it certainly wasn't doing it anymore. Maybe it was to act as a seal/barrier for any dust and dirt that got through the buttons on top? I can't say for sure.

[@jhtzlx]

@@ScottsSynthStuff thanks getting back to me. What I found is that the foam just helps the longer buttons sit more uniformly. Without the foam they wobble a bit, but honestly it's barely noticeable.

[@WilsonPhotography1]

Thank you for this video. 😎 I didn’t quite catch how you was getting the audio file from your phone to the synth. If you could explain that would be awesome.

[@ScottsSynthStuff]

A cable. I plugged one end of the cable into the headset jack on the phone (which I admit most newer phones don't have) and the other end directly into the synth. I had to drag out an older cell phone with a headset jack in it to do this.

[@WilsonPhotography1]

Thank you. 😎

[@deanbr6ndo70]

Would look really nice with a volume knob the same as the res and cut off.well done.

[@ScottsSynthStuff]

Your probably right - but I only had two, and have no recollection where they came from! :)

[@mattisopen]

Superb presentation and clear description of how to restore this great little synth. Like some of your other commentators, I’ve had one of these instruments from new and 40 years on have two different problems that you weren’t able to cover as my model is one of the first and does not have back up battery, but relies on the type C batteries to back up the sounds, and when these expire, one loses the programmes. I’ve bought a CR2032 holder and the appropriate battery, but how do I wire it in and let it take over from the C batteries? Second issue: on turning the machine upside down I’ve upset the joystick, which has now gone limp. How do I fix this? It’s not broken as such, just limp and won’t stand up. You can still get modulation, but not pitch bend? PS: Although there’s a space on the board where the battery would go (in the future models) there are no terminals to wire the same onto the board, hence my fundamental problem.

[@ScottsSynthStuff]

Just tack-solder your battery holder to those terminals on the board and you should be good to go. If it doesn't quite fit, you can extend it using short wires (like I did) and tack-solder those to the board. As for the joystick, it uses little leaf-spring type springs - I would perhaps disassemble and see if one of the springs has broken? It could also just be dirty and preventing a spring from pushing against the stick end.

[@slavetothesquarewave]

You’re a god damn genius!

[@littlebritain64]

Exactly what I was looking for, many thanks!!👍 I am wondering if a ring modulation mod could be done as well!!

[@ScottsSynthStuff]

Ring modulation normally works on two oscillators and multiplies the oscillators together to get the ring modulation effect. The poly-800 has only the one oscillator per voice, so it's probably not something you could do.

[@littlebritain64]

@@ScottsSynthStuff Thanks for answering!! Yes, just after posting I was in a doubt about the Poly800 having one oscillator instead of two! You confirmed this!👍

[@richardelam3371]

great video....i have a poly800II that needs some components replaced due to dampness issue. do you or could you help me identify which resisters need to be replaced. thanks...would love to get it working again

[@ScottsSynthStuff]

If components were damaged because of inappropriate voltages because of dampness, you are (potentially) going to need some very complex diagnostic skills.

[@traditionaltools5080]

Excelent video. I wonder, is it possible to use a power supply when changing the battery so you dont loose the patches?

[@ScottsSynthStuff]

Plug it in and turn it on, remove the old battery, install the new one, it will keep the memory.

[@traditionaltools5080]

@@ScottsSynthStuff thanks!

[@FallenTape]

Awesome job..! Do you have the ref of the jack for the headphone and mono out ? I need to repair my poly 800 to. :) Thx a lot

[@FallenTape]

It is much too expensive for a shipment to Europe via Syntaur :(

[@ScottsSynthStuff]

I didn't even bother to look at the specs of it, or research it - once I saw that Syntaur had them, I just bought theirs. Usually, I will measure pins and sizes to find a component at an electronics supplier, like I did for the tactile switches.

[@FallenTape]

@@ScottsSynthStuff Okey Thanks a lot, i find it on Mouser, ref : SJ-63063B :)

[@clauscombat418]

Best video on the subject, thanks! Unfortunitely there are no true videos on how to do the mod on yt. All i found were short demonstrations. The somewhat cumbersome read of the original slayer mod webpage doesn't help either. Can anyone tell me why the pots need to be logarithmic, not linear?

[@ScottsSynthStuff]

Because audio is logarithmic, that's why it's measured in decibels. Anytime you're controlling audio levels with a pot, you need it to be audio/log taper, not linear. If you use a linear pot in an audio application, you get 95% of the pot's travel that does virtually nothing at all, and the last 5% travel goes from nearly zero to full.

[@clauscombat418]

@@ScottsSynthStuff Ok, thanks. I was just thinking about it from a mathematician's pov 🙃

[@tavil1296]

I have that output jack issue with my Korg x50

[@ScottsSynthStuff]

It's very common in many older synths.

[@MattPopOfficial]

The volume dial on my Korg Poly-800 half works, in that it raise the volume on the left channel only, unless I apply a little pressure (push it down) which makes the right channel join in. Is there an easy way to fix this?

[@ScottsSynthStuff]

It sounds like someone maybe at some point gave that knob a whack, and potentially broke one of the solder joints that connects the volume pot to its board? I would open it up and re-solder each of those connections from the pot to its board, see if that fixes it.

[@MattPopOfficial]

@@ScottsSynthStuff Thank you! Will give that a go.

[@MattPopOfficial]

@@ScottsSynthStuff I didn't need to solder in the end. Removed the plastic dial and gave the volume turning parts a dose of Deoxit and that seems to have done the trick.

[@nevets68]

Cute kitty!

[@ScottsSynthStuff]

She agrees. :)

[@BrooseWayniac]

what was the Job of the Trimpots before desoldering? And how it comes that you can still use the Poly 800 like before desoldering the Trimpots... as the new Potentiometer dont get saved with a patch aint the cpu misses the desoldered trimpots at anytime? Really confused here

[@ScottsSynthStuff]

The trimpots are used to calibrate the filter - cutoff and resonance. Once they are removed, the new potentiometers mounted into the top of the case take their place. So functionally they're still there - except now they are full-sized potentiometers. Now you can adjust the filter cutoff and resonance manually with knobs on the case, instead of using the trimpots mounted on the PC board.

[@Kassatube]

Hello, Scott! Can you please send me the location where the wires from the pots are soldered, as the website mentioned in the description is no longer active... By the way, excellent video.

[@ScottsSynthStuff]

What a shame that site went down, there was a lot of good info there. Anytime a site like that disappears, you can usually still find the content in the web archive, and that's the case with this one. You can see it here: web.archive.org/web/20220427121311/synthmod.net/korg/moog_slayer/

[@Kassatube]

@@ScottsSynthStuff Thank you very much! I just have a question about soldering the red wire to the resistor: can I use the resistor we desoldered from the ground, or should I buy a new one with a value of 470-510 ohms? I don't have much knowledge about electronics, I'm just a synth enthusiast :)

[@ScottsSynthStuff]

@@Kassatube you can just reuse that resistor!

[@Kassatube]

@@ScottsSynthStuff Thank you for the quick responses, You're the best. I'm diving into the work right away!

[@sophiabel]

I wish I could bring you mine for fixing! you don't happen to be in montreal? lol

[@ScottsSynthStuff]

Sorry, no, Cleveland! They're not too hard to fix, I'm sure there are people in MTL who could do it for you!

[@rocketvale6485]

I got ripped off by reverb for a poly800 w fm800 and moog slayer mods,makes only noise and wierd sounds,the seller says i have to load the memory from tape for it to have any decent sounds. I tried to return but got stalled and missed the cutoff date to return. I made a video of the only and best sound i could get.to hear search for “ axe lighthouse korg poly800 issues. I tried to load from tape but didnt load.any ideas

[@ScottsSynthStuff]

It took me quite a few tries to get it to load the sounds. It is really picky about the volume level, and some of the recordings of the factory sounds just didn't work at all for me. I ended up playing a KZbin video containing the factory data on my phone, and with the volume up all the way, running that into the synth, and after 5-6 tries it finally worked.

[@joselarios2571]

I restored the mk2. Can't find a power supply for it.

[@MG53v8]

My dco 2 has gone off line on mine

[@danielortizdecaracas]

Greetings to all, someone who can help me with my korg poly 800, connect a charger, I think it has a lot of voltage and it turned off and does not turn on anymore, what happened? could it be the protective diode at the input? Would the internal card be burned because of that? any trick remedy or solution here?

[@ScottsSynthStuff]

The diode protects against a reverse polarity power input. As to what has been damaged, you'll have to do some board-level testing to find out, really.

[@HipixOFFICIAL]

Mine keeps fluttering in and out of tune and it's driving me crazy. Even replaced the internal battery.

[@ScottsSynthStuff]

Have a look at the pitch bender potentiometer. Also, an unstable power supply can cause this.

[@HipixOFFICIAL]

@@ScottsSynthStuff It may be more than that, the synth seems to no longer hold presets after turning it off and on again. Such a pain these things are!

[@johnbrodsky5374]

Scott… do you offer a repair service to the public? I have a Korg Poky 800 that needs attention to get it back into proper working order. Seriously.

[@ScottsSynthStuff]

No, this is just for fun with my own stuff - but Syntaur does this sort of thing all the time, that's who I got some of my parts from.

[@NTRSN-Archive]

A shame you modified this Poly800.