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[Circuitbenders]

I've got a Korg Poly800 mk2 that refuses to do anything ither than produce filtered noise. I've been lead to believe that this is a fault with the firmware eprom.

I've taken a dump of the eprom in there which was labelled as an HN4827128G-25 and then erased it, and that worked fine. When i click 'blank test' on my willem programmer software it comes up that the device is blank and if i read it every entry is FF.

I've got a dump of a working Poly 800 mk2 .bin file off the net but thats labelled as being from a 27C128 eprom and won't write to the eprom i have. I don't know if this is because the one i have is damaged and can't be written to, or because its the wrong kind of eprom for that file.

Is the HN4827128G-25 actually compatible with a 27C128 .bin file or has the person who uploaded it just labelled it wrong? It seems unlikely there would be different eproms in different Poly 800 mk2's. If the eprom i have is actually damaged an can never be written to, should i be getting hold of a 27C128, trying to track down a HN4827128G-25, or looking for some eqivalent thats easier to get hold of?

If anyone has a Poly 800 mk2 and has faciliies to take eprom dumps could you do me a copy and send it to me?

[Gordonjcp]

The actual type of EPROM isn't important to the image.  You can use a 27C128 just fine.  What *is* important is that you select the correct type of EPROM when you're burning, because a 27C128 requires a different programming voltage from a 27128.

If the EPROM you have only reads back 0xFF then either it has been erased or it is knackered.

You can use any EPROM that is 128kbits or larger, but for a 27C256 (for example) you'd need to burn the image twice (low half and high half), or strap the extra address line low.

[Circuitbenders]

so in theory an image that appears to have been taken from a 27C128 should write fine to a 27128, which i'm assuming is what my HN4827128G-25 actually is, as long as i have 27128 selected when i write it?

I'm hoping that the eprom i have is reading FF because its erased. It did have a load of data on it until i erased it with my UV box but i can't seem to write to it for some reason, it does verify as OK but that doesn't seem to mean that much. Could trying to write to it as a 27C128 have damaged it in any respect or would it just not write?

Typically i have a few 27C256's but I think i'll have a hunt through some parts boxes for another 27128 before attempting to use one of those.

(EDIT)
I've just read on some wiki article that C eproms need 6V to write and non C ones need 5V but i've written plenty of 27C256's fine at 5V, in fact i only just noticed that my programmer has a jumper to select between 5V, 5.6V and 6V. Is it really that important?

[Gordonjcp]

Yes, extremely important.  Also the programming voltage applied to the Vpp pin must be right - for an oldskool 27128 EPROM it must be 21V, for a 27C128 or 27128A it must be 12.5V.  Too high a Vpp will zorch the chip, too low will leave it utterly nonplussed by your attempts to gain its attention.

[Circuitbenders]

for an oldskool 27128 EPROM it must be 21V.

Ahhhh, thats got it, i was trying to do it at 12.5v.

I've managed to rewrite the firmware to the eprom and stuck it back into the Poly800 and its made no difference whatsoever. I guess its either something else thats causing the problem or the eprom isn't working quite as it should, although i'm guessing i wouldn't actually be able to write to the eprom and it wouldn't work as far as it does if it was that knackered.

Back to the drawing board. 

[C M O S]

Hi
 I am in the middle of repairing a KORG POLY800 II at the present time. This one has died although all voltages are present on the main circuit board and the main cpu appears to be giving some activity with some signals lost. I have just ordered a MSM80C85 OKI uP and also the TIMER/MEMORY PIO chip 81C55 this should bring this thing back to life. My question is, where can you get the EPROM .bin file for the main eprom?? can anyone help??  Semi Company "LITTLE DIODE" Provided the uP and the PIO chips. I have a multi programmer called GALEP and  hopefully use this to burn the new software onto a replacement eprom.

[Gordonjcp]

You might want to look at the Poly 800 Yahoo! group.  The .bin files for the various flavours of Poly 800 are out there.

Are you sure it's the CPU and PIO that have failed?  They're normally pretty reliable.  How did you test them?

[Circuitbenders]

What are the exact symptoms of whats gone wrong? I've repaired a few Poly's now and the problems are almost always something in the power supply or some logic IC dying.

I've uploaded the poly800 mkII main eprom file here if you need it

http://www.mediafire.com/?ndjxebmmgmj

[C M O S]

Thankyou so much for the POLY 800II eprom bin!!!
I have two service manuals, POLY800 & POLY800II. For some reason the output waveforms are omitted from the poly800II manual. As the cpu section is almost identical i used the waveform data from the 800 manual. The 800II in question is giving no sound and no display. I was amazed at how complex the the power circuit is in this thing!!. I have tested every aspect of the power section and this appears to be ok. 5V Lines are present and also -5v line is present, nothing being pulled low. The +/- Supplies are also correct for the analogue sections. Using a 20Mhz scope i checked the communication between the cpu and pio and it would seem as though one of the timing lines is missing also one of the reset lines is missing. With the cpu removed reset line works. Most of the resets are generated by external circuits. I managed to get the pio and cpu very cheaply so i will try this. I will post and tell you how i get on.
THANKS AGAIN!!

[Circuitbenders]

I've had a problem with the timing clocks missing before, where one of the clocks for the M5232 was missing but in that case it did start up but neither DCO would make any sound.
The issue on mine was is with one of the logic IC's at IC16, IC17, or IC18 which generate the clock

One of the weird things i've had with a poly800mkII was with a version of the main board with EMI in the serial number which appeared to have both an analogue and a digital ground, unlike most versions. As far as i could make out the grounds were linked via the shielding under the board so if the board wasn't screwed into place with the shielding connected to the ground then the thing just wouldn't start up.

[C M O S]

You are correct, the shielding is also a earth bridge. I made sure that this was fitted correctly although you can get caught out by this. Sorry i am posting messages on the circuit benders forum regarding the repair of a poly800, there are probably other forums that can help. I am looking at adding some bells and whistles once this thing is repaired though.
THANKS!!!!!!!!!

[C M O S]

Managed to import the poly800II EPROM bin file to the GALEP programmer, have looked at the code and all is good!
Going to do a comparison of the original backup just to see if the code is the same. 27c128 EPROM i could not find in my workshop managed to purchase one on ebay £1.40!!! Going to cook and burn the chip monday.I will let you know if you like if there is life!!

[Gordonjcp]

If you have a 27C256 or 27C512 EPROM then you can use that by blowing the image either twice or four times, blowing it so it sits in the top 128kbits of the EPROM, or ensuring that the extra address lines are pulled low when you plug it into the Poly 800.

[C M O S]

I suppose i could have done that as i have a surplus of 256,512,1001 eprom variants. It is down to the sophistication of your programmer and software i suppose. I could have copied the data several times and pasted the data at certain areas within the chip. I did not think though that £1.40 was bad for a 27c128 . I am still waiting for the chip to be delivered, as soon as i see sight of it i will post the outcome. I know it has been said that the uP and PIO in the poy800 II are bomb proof but every test i have undertaken has proved that it cannot be anything else at fault. All resets and voltages are present including all the clocks. The outcome of the comparison was device mismatch at quite a few memory areas meaning that the bin file is an update or my original data is corrupt. There is a ref sticker over the eprom window, i will post this when i get home.

[C M O S]

Cleared the data from the eprom i bought from ebay, burned the poly 800II data to the chip ,installed in the synth and low and behold.......DEAD!.  Have not recieved the cpu or the pio as of yet, as soon as these are recieved i will post results. The original poly800 eprom's number was 851006. I have read many times on the web that the eproms in the poly become corrupt and lose data.. I do not think this is the case with this synth.