SY77 booting in a loop

Yamaha SY77 is a 16 voice multitimbral music workstation first produced by Yamaha Corporation in 1989. The SY77 is a synthesizer whose architecture combines AFM (Advanced Frequency Modulation) synthesis, AWM2 (Advanced Wave Memory 2) for ROM-borne sample-based synthesis, and the combination of these two methods christened Realtime Convolution and Modulation Synthesis (RCM).

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Re: SY77 booting in a loop

Unread post by Rara » Thu Dec 13, 2018 7:44 am

Thanks for the tip :-)
I'll make an order for those after I find out what switchs my CZ's/FZ need.

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Re: SY77 booting in a loop

Unread post by Rara » Fri Dec 14, 2018 9:45 am

I contacted the seller/auction about the dm1 board, it was posted a month ago nearly.
I've asked about the tracking number, no telling where it is at the moment.

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Re: SY77 booting in a loop

Unread post by Rara » Tue Dec 18, 2018 1:53 pm

My replacement DM1 board has arrived and after I read about corrosion on Horizonsounds board
I got the magnifiers out and had a look at mine. Date code December 89 (previous board Jan 90)

I found corrosion on all of the resistors adjacent the floppy connector CN104
and also on some pins of IC132 and IC134, also found on C223 and R119 next to IC123

It seems corrosion is limited to those areas only.

I noticed a black wire going from pin 2 of CN107 to R153, I am not familiar with this.
IIRC this was not on my current DM1 board. Is this one of Yamaha's revisions during production?

IMG_0389a.jpg

I also found what looks like burnt tape under these two components (I forget the name of at the moment)
which are immediately adjacent the CPU

IMG_0395a.jpg

I wont know for a while yet if this board works. touch wood it does.

one amusing thing I did find, was cat hair. how it managed to find its way under some IC's is beyond me. :eusa-think:
It looks to be a short hair tabby or a tortoise shell. :animals-cat: :)

Rara 0-)
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Re: SY77 booting in a loop

Unread post by EB5AGV » Tue Dec 18, 2018 2:37 pm

The damage is caused by leaking electrolyte from capacitors, I would replace them.

The components are quartz crystals and that should be isolating/dampening material.

Jose
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Re: SY77 booting in a loop

Unread post by Horizonsound » Thu Dec 20, 2018 1:39 am

That black wire looks like it comes off the header for the keyboard. Bit of a hack if you ask me.
It's probably a cracked trace below the header, or possibly corrosion.


Still no luck with either DM1 board for me. I have a mouser order coming in tomorrow which has all parts to rebuild the power supply and replace all caps on both DM1 boards I have.

Anthony.
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Re: SY77 booting in a loop

Unread post by Rara » Thu Dec 20, 2018 2:33 am

Makes sense now you mention it. could even be a broken or bent pin on the header,
I've seen that a few time before on various gear.
I wont be holding my breath for this to be fixed anytime soon.
I had a thought, I'm not a programmer, could you read the firmware code if you had it
to see what could lead to that "lets see that again" (second image in OP ) screen and
possibly trace a fault that way?

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Re: SY77 booting in a loop

Unread post by Horizonsound » Fri Dec 21, 2018 10:54 am

OK... so I have rebuilt my power supply. New caps, rectifier, regulators, and my original the DM1 appears no good. Caps on the DM1 all replaced too. All joints reflowed on headers as well.
I’ve noted that it runs for a little while and outputs sound, but then freezes. If a notes is being held, that locks and continues. All front panel functions freeze as well.
Of interest, I note that the longer it is left off, the longer it operates before freezing. Thus, it does appear like an overheating kind of problem.
IRQ M3 error still is present.

The replacement DM1 from Vintage Synth Shop is totally dead. Does not even show the SY77 start up screen.

Am I just completely out of luck here??

Anthony.
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Re: SY77 booting in a loop

Unread post by Rara » Fri Dec 21, 2018 11:21 am

Some off what you describe is exactly what happened to mine while it was booting in a loop.

I was lucky enough to wiggle a few buttons on the front panel during start up and it came good,
i was able to do a brief system check and check rams and roms. no error so i exit test mode.
I started to play. when I played a few notes mine did exactly as you described. before going back to a loop
then dying right there. My existing DM1 (or dm2 who knows) is totally dead, no boot at all not even front panel leds.

Out of luck, I 'm starting to think that way, my tech has had my SY77 since April, he's authorized Yamaha tech .....

may be treat it like a pc and disconnect various other parts like keyboard, front panel,pitch bender, floppy drive
etc and see if its not another part causing the fault.

if nothing external to the DM boards, if any chips have failed, I'll guess propriety chips or a fault in the cpu itself
and H8/532's are getting very expensive now.

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Re: SY77 booting in a loop

Unread post by Horizonsound » Fri Dec 21, 2018 12:15 pm

You can pull nearly every peripheral. The only connectors the DM1 needs to run is the power CN119, CN103 to the DM2, and the two keyboard connectors. The DM2 needs it’s power and the digital output. With only these connected, my same symptoms remain.
I am suspecting RAM (IC127, 128, 129, 130). Might pull these and socket them. You can get four replacements of these for USD $10.
Unless someone wants to convince me otherwise.

Anthony.
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Re: SY77 booting in a loop

Unread post by Rara » Fri Dec 21, 2018 1:14 pm

Socketed ram why not, that makes perfect sense. I wont convince you otherwise.
In fact i might mention that to my tech.

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Re: SY77 booting in a loop

Unread post by EB5AGV » Fri Dec 21, 2018 4:29 pm

Horizonsound wrote:
Fri Dec 21, 2018 12:15 pm
You can pull nearly every peripheral. The only connectors the DM1 needs to run is the power CN119, CN103 to the DM2, and the two keyboard connectors. The DM2 needs it’s power and the digital output. With only these connected, my same symptoms remain.
I am suspecting RAM (IC127, 128, 129, 130). Might pull these and socket them. You can get four replacements of these for USD $10.
Unless someone wants to convince me otherwise.

Anthony.
Yes, it seems like a wise decision. On my 35 years or so fixing electronic gear, which includes computers and microcontroller systems, as the one used on the SY77, after capacitors, RAMs are one of the primary suspects. Just a couple weeks ago I had a pesky intermittent trouble on my music PC (which I have connected to the Genos) which finally was due to a faulty DIMM.

But don't forget ROMs. The EPROMs have a tendency to fail. If they are socketed, copy them. Sometimes the EPROM programmer reads them fine even if they are failing on the circuit.

I have also a second SY77 waiting to be fixed, it is a Winter project but someday I will take care of it!

Jose
Jose Gavila

Yamaha DX7, TX81Z, DX11, 4x SY77, TG77, SPX990, SY85, A3000, EX5R, EX7, MOTIF RACK XS, DGX660, PSR-EW410, Genos

Akai S5000
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Casio CT-X5000
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Modartt Pianoteq 6
NI Komplete 12
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Steinberg Cubase Pro 10, The Grand 3
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Re: SY77 booting in a loop

Unread post by Horizonsound » Fri Dec 21, 2018 10:03 pm

I've found a source for RAM chips, and have ordered a set and sockets.

The schematic calls up Hitachi HM62256LP-10 however what is physically installed on the board are Toshiba TC55257BPL-10. I have bought a set of both.

There are two sets of RAM. 4 x 32K for the main, and 2 x 32K for the sequencer. A while back I read a thread where someones sequencer was freezing up after a while, and needed a hard reset. Could be related to mine, but the mine being the main RAM.

Should be here in about a week, then the joys of desoldering DIP28 double sided boards with plated through holes.

I don't mind spending a bit of time and money on this, as I picked up my SY77 for only $5.

Anthony.
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Re: SY77 booting in a loop

Unread post by EB5AGV » Fri Dec 21, 2018 10:26 pm

Wow, great price!

If you want to keep the PCB stress to a minimum AND you don't mind destroying the old ICs, you can cut the pins close to the IC body and then remove them one by one, clean the holes and install the new socketed ICs

Jose
Jose Gavila

Yamaha DX7, TX81Z, DX11, 4x SY77, TG77, SPX990, SY85, A3000, EX5R, EX7, MOTIF RACK XS, DGX660, PSR-EW410, Genos

Akai S5000
Arturia Keylab 61 MkII, Pigments, Analog Lab 3, Piano V-2
Casio CT-X5000
Kawai K1, K1-II
Korg M1, Wavestation, X3, Triton Rack, Triton Le 76
Modartt Pianoteq 6
NI Komplete 12
Roland D-50, JV-1080, XV-3080
Steinberg Cubase Pro 10, The Grand 3
StudioLogic SL88 Studio
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Re: SY77 booting in a loop

Unread post by Horizonsound » Sat Dec 22, 2018 1:40 am

Thanks Jose. I normally don't do that but in this case I think I will, given i'll have two full sets of RAM to work with now.

Has anyone else used utsource.net for components? I have once or twice before, but they seem to have improved their business model and wanting to take on mouser vs element14, but only selling ICs. They also have the H8/532 (HD6475328CP) microprocessor available for US$14.19

Anyone experienced in pulling the source code and programming these? I suspect they have the CSM and can't be read though.

Anthony.
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Re: SY77 booting in a loop

Unread post by Rara » Sat Dec 22, 2018 4:55 am

$5 :o :o :o a new record low ((i)) I thought mine was a steal at $270.
source for the CPU is on this forum somewhere in the SY77 section, I downloaded it a while ago, I cant remember the thread it was in.
If you cant find it let me know.
H8 is cheaper than I was led to believe, that's handy to know.

Rara 0-)
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