Yamaha sy77 booting fail

the 77 had external ROM cards
did you mean that, bet not.
I think you dismantled the case totally
and accessed the main PCB (removed above)
and the got the wild idea to remove chips
or sadly bought it like this a cannibalized PCB.
no photos of your PCB posted, so be like 1000x hard to guess the condition of card.

we can tell you what all chips do.. I can.
the below PCB I circled the EPROM bank those are not ROMS but are EPROM with stickers on top to block light from erasing EPROM cells below the quartz window by accident.
I use black tape on mine, 100% protected EPROM. (I used to test them in production)
Eproms can Uv light erased and re programmed.
the other big chip there are SRAM 256kbit. on side or eprom bank.

That is the total OS there, embedded Operating system if you remove one
the keyboard goes, dead.
or 1/2 dead all.
It would be best to have those old EPROM
backed up. to a hex file. (or bin)
(an eprom programmer device (tool) does that so easy)

Some makers of EPROM (not mine)the charged gates inside can leak down when old.
and fail. (we at Philips semi made some of these) our do not fail.(in time)

see that yellow battery there will be bad.!!
first thing to fix is ,new yellow battery.

did Dm1 catch fire, why in the world remove it.? the sticker hides the chip name.
remove cover and look.
put back cover but use black tape.


my guess 27C64, 8k x 8.
you buy one
erase it and
re-program the OS code for that bank.
but you do not have this code, and is a set for all 4 banks at once I bet,.
machine code = code.
in a factory of this device.
we run checksums on the 4 banks, if fail
we must erase them and re-program them back a new.


we made these,.... back then.1990

the 77 had external ROM cards did you mean that, bet not. I think you dismantled the case totally and accessed the main PCB (removed above) and the got the wild idea to remove chips or sadly bought it like this a cannibalized PCB. no photos of your PCB posted, so be like 1000x hard to guess the condition of card. we can tell you what all chips do.. I can. the below PCB I circled the EPROM bank those are not ROMS but are EPROM with stickers on top to block light from erasing EPROM cells below the quartz window by accident. I use black tape on mine, 100% protected EPROM. (I used to test them in production) Eproms can Uv light erased and re programmed. the other big chip there are SRAM 256kbit. on side or eprom bank. That is the total OS there, embedded Operating system if you remove one the keyboard goes, dead. or 1/2 dead all. It would be best to have those old EPROM backed up. to a hex file. (or bin) (an eprom programmer device (tool) does that so easy) Some makers of EPROM (not mine)the charged gates inside can leak down when old. and fail. (we at Philips semi made some of these) our do not fail.(in time) see that yellow battery there will be bad.!! first thing to fix is ,new yellow battery. did Dm1 catch fire, why in the world remove it.? the sticker hides the chip name. remove cover and look. put back cover but use black tape. my guess 27C64, 8k x 8. you buy one erase it and re-program the OS code for that bank. but you do not have this code, and is a set for all 4 banks at once I bet,. machine code = code. in a factory of this device. we run checksums on the 4 banks, if fail we must erase them and re-program them back a new. we made these,.... back then.1990

OP do you need advice on electronics repairs for sure relics, here is some
31 years old today:
1: those battery all of them are no good now.
2; the electrolytic caps are no good either,
called re-capping in the trade.
3: if the EPROM bank fails check-SUM tests. they must be erased and reprogrammed or buy the whole PCB or full bank of EPROM used off ebay . where else but ebay has relic parts?
i'd bet Yamaha does not support this now. yah.
4: make sure (test) all power supplies inside DC are at spec an no high ripple,.
and more no burned parts or traces PCB
no boric acid leaking out of caps wreck it all.(bad to the bone this)
no missing parts, is DM1, missing by magic, IDK.

what does
"removed"
mean,, add word to that word to make it meaningful, like
I lost the CHIP (EPROM)
I remove it.
Bought it like this missing key parts.
it burned up, chip in quarts window looks burned. or casing of IC locks burned or warped. (any thing is possible in real world)
I broke pins off the chip, by accident.
see, post what the story is so we can be on the same page.
or someone left the sticker off top of DM1.
and set the PCB on the window sill and mr SUN erased the EPROM sure will for sure.
have proof off all,
the chip is all CMOS floating gate EPROM cells.(mosfet) they must not lose charge,
or fails hard. ALL eproms, made. good ones do not. (on modern PC the life spec. is 100years. on FLASH, ) and no window on the to mess up the charge later in time. (bad actor)
FLASH is EEPROM. actual. 2 "E"s OP do you need advice on electronics repairs for sure relics, here is some
31 years old today:
1: those battery all of them are no good now.
2; the electrolytic caps are no good either,
called re-capping in the trade.
3: if the EPROM bank fails check-SUM tests. they must be erased and reprogrammed or buy the whole PCB or full bank of EPROM used off ebay . where else but ebay has relic parts?
i'd bet Yamaha does not support this now. yah.
4: make sure (test) all power supplies inside DC are at spec an no high ripple,.
and more no burned parts or traces PCB
no boric acid leaking out of caps wreck it all.(bad to the bone this)
no missing parts, is DM1, missing by magic, IDK.

what does
"removed"
mean,, add word to that word to make it meaningful, like
I lost the CHIP (EPROM)
I remove it.
Bought it like this missing key parts.
it burned up, chip in quarts window looks burned. or casing of IC locks burned or warped. (any thing is possible in real world)
I broke pins off the chip, by accident.
see, post what the story is so we can be on the same page.
or someone left the sticker off top of DM1.
and set the PCB on the window sill and mr SUN erased the EPROM sure will for sure.
have proof off all,
the chip is all CMOS floating gate EPROM cells.(mosfet) they must not lose charge,
or fails hard. ALL eproms, made. good ones do not. (on modern PC the life spec. is 100years. on FLASH, ) and no window on the to mess up the charge later in time. (bad actor)
FLASH is EEPROM. actual. 2 "E"s

we also made OTP , same chip no window
called one time programmable.
yours is the fancy package, ceramic + a quartz window.

DM1 is the PCB model number stamped on PCB. we also made OTP , same chip no window called one time programmable. yours is the fancy package, ceramic + a quartz window. DM1 is the PCB model number stamped on PCB.

off hand based on age
the EPROM code loads into that huge (then)
Toshiba SRAM bank and runs super fast there.
HX 123 you meant the sticker shows that.
I guess HX122 is the boot strap, eprom ,and main OS, and the 4 bank are voices or who knows what?
ahhhhhh some never versions same year
have totally different Eprom banks, less chips !
so I give up lacking 1 photo of yours.

here is a great page on restoringhttp://jvgavila.com/Yamaha_SY77_repair.h...

and are OTP (no erasing possible) no re use.
here is the newer PCB, not the same as Ver.0


off hand based on age the EPROM code loads into that huge (then) Toshiba SRAM bank and runs super fast there. HX 123 you meant the sticker shows that. I guess HX122 is the boot strap, eprom ,and main OS, and the 4 bank are voices or who knows what? ahhhhhh some never versions same year have totally different Eprom banks, less chips ! so I give up lacking 1 photo of yours. here is a great page on restoring http://jvgavila.com/Yamaha_SY77_repair.htm and are OTP (no erasing possible) no re use. here is the newer PCB, not the same as Ver.0

the had DM2 board to, with custom Yamahachips
there. but 2 versions of DM1. one with 4 chips and one with 2 chips in the EPROM bank.
seen above missing top right. the had DM2 board to, with custom Yamahachips there. but 2 versions of DM1. one with 4 chips and one with 2 chips in the EPROM bank. seen above missing top right.