Korg Poly800/EX800 Users

If the Poly 800 works in every way except for sound then I don't think it is the RAM chip.
Let's try some more detailed questions first.

Are you able to program patches manually?Do the parameters in the patches stay saved if you select another patch and come back to that saved patch?
Do all buttons work?Do you see MIDI OUT note on and note off events when you press keys?Do you see MIDI OUT program change messages when you change patches on Poly?Do you see MIDI OUT CC messages when you move the joystick up and down, left and right?With your best detailed description, what sound comes out of the Poly when you press a key AND what happens to the sound after you release the note?After you release the note, do you hear a 'hiss' go away almost completely after some time passes?
Do you get a "Good" message when you reload patches from tape?Are you able to program the step sequencer?
/Mike


      From: "temsed7@... [korgpolyex]" <korgpolyex@yahoogroups.com>
 To: korgpolyex@yahoogroups.com 
 Sent: Sunday, December 11, 2016 7:49 AM
 Subject: [korgpolyex] Re: Poly 800 seems to works, no sound or strange sounds at very low volume
   
    Dear Steve,
I do thank you for your answer! I have spent my whole morning looking for that component, and actually, it seems this comes from Hitachi... However, 4 different chips could be the one you are talking about.These are:
HD-U050 BP HD-14051 BP HD-14053BP HD-63B50P

I found this in the service manual, but I don't know which one is the right one to replace... I suppose it's the HD14053BP as it's closer to the midi implementation. Moreover, there is one more mistery... On the chip inside my synth, something is written right under the name of the chip (HD1 4053BP) : 5K4T. I do not know what that means and this is quite annoying, indeed, because on some new 4053BP chips I can buy on the net, all of those hav different marks from this one! There are a lot of those, but no sign of the "5K4T" mark... This is strange.
Would you mind telling me what to do?
Thank you in advance,
Gloubi  #yiv4928982827 #yiv4928982827 -- #yiv4928982827ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv4928982827 #yiv4928982827ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv4928982827 #yiv4928982827ygrp-mkp #yiv4928982827hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv4928982827 #yiv4928982827ygrp-mkp #yiv4928982827ads {margin-bottom:10px;}#yiv4928982827 #yiv4928982827ygrp-mkp .yiv4928982827ad {padding:0 0;}#yiv4928982827 #yiv4928982827ygrp-mkp .yiv4928982827ad p {margin:0;}#yiv4928982827 #yiv4928982827ygrp-mkp .yiv4928982827ad a {color:#0000ff;text-decoration:none;}#yiv4928982827 #yiv4928982827ygrp-sponsor #yiv4928982827ygrp-lc {font-family:Arial;}#yiv4928982827 #yiv4928982827ygrp-sponsor #yiv4928982827ygrp-lc #yiv4928982827hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv4928982827 #yiv4928982827ygrp-sponsor #yiv4928982827ygrp-lc .yiv4928982827ad {margin-bottom:10px;padding:0 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