Korg Poly-800 Mk1 – Replacing Battery & Restoring Presets

This Korg Poly-800 Mk1 had suddenly started to behave oddly. If it made any sounds at all they were inconsistent and random. This would indicate that the memory is corrupt due to a bad battery. As I understand it there was no internal battery mounted in all of the Kort Poly-800 Mk1, they required batteries to me munted in the battery compartment on the bottom. In this machine the internal battery does not look original and one trace has been cut so I seems to have been modded at some point.

After the battery has been replaced the RAM memory has to be restored from a factory preset tape load file. This can be found in many placed; but here is one source:


Update 2020-06-15: If you want to perform the full modification (which I didn’t do here) on a Poly-800 mk1 you will need to do the following:

“Open the Poly-800 by removing ALL screws at the bottom. Note that those in the front are shorter than the rest.Locate the processor board. This is the large circuit board next to the battery compartment.
At the middle of the board you find two square solder lands, you mount the lithium battery (CR2032 or larger), or battery holder, here. The upper land is positive.
Remove C87, C88, D23.
Cut the trace to the left of the plus lane as shown. Short between trace and trace and D15 as shown. (D15 can be removed)
(quoted from http://yazawatamio.hatenablog.com/entry/20131211/1386760646)

You can see on the photos below that these components have been removed and that the trace in question has been cut (albeit in a messy manner)

The old battery and the cut trace
New battery installed

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4 thoughts on “Korg Poly-800 Mk1 – Replacing Battery & Restoring Presets

  1. Daniel Baught

    Would you consider doing this for me. i would gladly pay for sn h. and your time.

    1. Laban

      Hi Daniel, I am located in Gothenburg, Sweden. I believe you are located somewhere in the USA, right? So I think the transportation costs would be a bit too high 🙂

  2. Clint Milby

    Nice work and thanks for posting. I attempted to do this without soldering by taping a CR2032 but it still didn’t hold the programming. I’ll either have to learn to solder or take it to someone who can.

    Another question: my Middle F key dead. Have you ever repaired a dead key before or specifically on the Poly 800? If so can you talk about what you had to do? Thanks in advance!!!!

    1. Laban

      Taping the battery will not work very well I’m afraid, you’ll get very poor contact

      Regarding the keys I think (but I am not 100% certain) the keyboard in the Poly-800 is of the same type that is in the Polysix and Poly-61. Under each key there is a small rubber dome which the key pushes down on which makes contact a part on the circuit board. It is very common that these age or get dirty so they do not make proper contact. It is very common on the Polysix and Poly-61 that some keys stop working due to this. This can usually be resolved by cleaning all of the membranes. See the following video for how this is done on the Poly-61 : https://youtu.be/i0GAr-eXa5E

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