SY35 output problem

Covering the SY22 to SY55 and TG Modules.

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SiriusHardware
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Re: SY35 output problem

Unread post by SiriusHardware » Tue Sep 15, 2015 10:52 pm

Update #2: Fixed.

Took the PCB to work (where I have better light, better soldering and desoldering gear, more space, etc) and removed the three 100uF 16V capacitors next to the headphone audio power amplifer IC (IC32, AN7148). The PCB was awash with leaked electrolyte in the general area around those three caps and unfortunately, due to my habit of storing this Synth on end up against a wall, the electrolyte had run a little further down the PCB as well.

I washed the top side of the PCB thoroughly, temporarily removing components (including IC32 itself) where necessary to gain unobstructed access to the PCB. Leaving any of the leaked electrolyte in place would be asking for trouble as it would continue to rot any PCB tracks and component legs it could get into contact with.

Board cleaned, I refitted all the components including three new 100uF 16V capacitors in place of the ones which had leaked.

I put it back together. Both headphone channels were back up to their original volume... for a short time. Then, the channel which had originally been faulty started to go randomly on and off again! :-)

Of course every time I got close to where the signal path was being interrupted the fault disappeared, but eventually I found what the problem was. The track taking the output signal from IC32 pin 11 to the 10uF 16V capacitor which follows it passes through a plated-through hole from one side of the PCB to the other in one of the areas which had been flooded by electrolyte. The inner conductive sleeve which lines the inside of the plated through hole had been 99% eaten away by the electrolyte. To fix it I cleaned the copper pads surrounding the upper and lower ends of the plated-through hole and passed a suitable piece of tinned wire through the hole - a leg snipped off a spare 1N4148 diode is just about the right thickness - then soldered it on both sides of the PCB to restore the lost connection between the tracks on the upper and lower sides of the PCB.

It's been running solidly for a while now.
Last edited by SiriusHardware on Wed Sep 16, 2015 12:43 am, edited 1 time in total.

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Miks
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Re: SY35 output problem

Unread post by Miks » Tue Sep 15, 2015 11:02 pm

WOW - a nice description of how you hunted that issue down... ((i)) - - could be of valuable help for other users with a similar issue.

Glad you (apparently) solved the problem (Y)
My (key related) gear (in alphabetical order):
Kawai: K1 II
Korg: M1 (up'd to EX, w/ 'Cool Blue'), M1REX (w/ 'Cool Blue'), Poly-800
Roland: D-50, D-110, D-550, PG-1000
Yamaha: AW1600, DX7IID (w/ 'Cool Blue'), EX5R, RM50, RX5, SY99 (w/ 'Cool Blue'), TG500, TX-802, YMM2
Sector101: SYEMB05 (5x), SYEMB06 (3x), EXFLM2 (1kit), MCD Sweet16 (1x), WaveBlade 8MB Card (1x) & 1x Programmer Unit for WaveBlade


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SiriusHardware
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Re: SY35 output problem

Unread post by SiriusHardware » Sun Sep 20, 2015 12:16 pm

It's still working.

While I had it apart I took a photo of the area around the headphone amplifier to illustrate / indicate which capacitors had failed and should probably be checked, maybe even just changed anyway on any other SY22 / SY35 main PCBs, whenever the instrument is apart for any other kind of maintenance, but I can't see any obvious way to upload a .jpg directly into a post (there's no 'attach' in the editor).

I don't have a personal website or an account on dropbox, photobucket, flickr or whatever - is there a way to directly attach an image to a post? I've resized the image to a sensible size but I anticipate that the forum s/w will resize it to whatever it considers to be the maximum acceptable size anyway.

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Miks
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Re: SY35 output problem

Unread post by Miks » Sun Sep 20, 2015 6:47 pm

is there a way to directly attach an image to a post?
Of course it is...
Att.jpg
A picture may not exceed 800 x 600 pixels (Width x Height). After your choosen image is uploaded you may place the cursor to where the image should be displayed, then press the [Place Inline] button... 8)

Use the [Preview] button to find out if you're fine with the result... then [Submit]...

Good to see your SY is still working btw... (Y)
My (key related) gear (in alphabetical order):
Kawai: K1 II
Korg: M1 (up'd to EX, w/ 'Cool Blue'), M1REX (w/ 'Cool Blue'), Poly-800
Roland: D-50, D-110, D-550, PG-1000
Yamaha: AW1600, DX7IID (w/ 'Cool Blue'), EX5R, RM50, RX5, SY99 (w/ 'Cool Blue'), TG500, TX-802, YMM2
Sector101: SYEMB05 (5x), SYEMB06 (3x), EXFLM2 (1kit), MCD Sweet16 (1x), WaveBlade 8MB Card (1x) & 1x Programmer Unit for WaveBlade


http://rescuer-uslar.de/
https://www.facebook.com/Rescuer.Uslar/

SiriusHardware
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Re: SY35 output problem

Unread post by SiriusHardware » Mon Sep 21, 2015 2:17 am

Aghh! Can't believe I didn't see the 'Attach' button - I was looking at all the other function/tool buttons along the top edge of the editor box, it never occurred to me that the 'Attach' button would be somewhere else.

OK, so here goes - this is the area around the headphone amplifier IC32, seen after the leaked electrolyte was removed and the guilty capacitors were replaced:

The pinkish brown / discoloured areas are copper track exposed when the electrolyte dissolved away the green coating and then started to eat the copper itself.

The damaged through-hole connection I mentioned is between the two smaller electrolytic capacitors on the right hand side of the picture - although these capacitors themselves did not leak, electrolyte from the larger ones ran down the board into this area and caused damage to the through-hole plating.
Attachments
sy22caps.jpg

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Miks
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Re: SY35 output problem

Unread post by Miks » Mon Sep 21, 2015 9:21 am

I had a similar issue with my Korg M1REX - the acid of a leaking capacitor had 'eaten up' a copper trace coming from the CR2032 coin cell to support the RAM while the synth is switched OFF - the synth lost its internal memory eyery time it had been switched OFF. 8O A good clean of the pcb and a short piece of wire sorted that issue - since then the unit is in good working order (Y)
My (key related) gear (in alphabetical order):
Kawai: K1 II
Korg: M1 (up'd to EX, w/ 'Cool Blue'), M1REX (w/ 'Cool Blue'), Poly-800
Roland: D-50, D-110, D-550, PG-1000
Yamaha: AW1600, DX7IID (w/ 'Cool Blue'), EX5R, RM50, RX5, SY99 (w/ 'Cool Blue'), TG500, TX-802, YMM2
Sector101: SYEMB05 (5x), SYEMB06 (3x), EXFLM2 (1kit), MCD Sweet16 (1x), WaveBlade 8MB Card (1x) & 1x Programmer Unit for WaveBlade


http://rescuer-uslar.de/
https://www.facebook.com/Rescuer.Uslar/

kjw
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Re: SY35 output problem

Unread post by kjw » Tue Apr 19, 2016 9:30 pm

I am in the process of fixing my SY-22 and Wolfgang's post was very useful to help ensure the diagnosis was correct. I have a broken TR4 transistor too. I verified that by carefully shorting the CE pins with a screw driver tip and heard the relay click and checked the outputs too just to be thorough. I'm about to replace it. I'd be interested in any tips on the best, long-life replacement?

The (dead) TR4 is marked by its type on the board, 2SC2603. For my particular transistor death the measured voltages were 7.6v and 7.8v, I forget which way around.
sy22-mainboard-top-tr4.jpg
sy22-mainboard-top-tr4.jpg (69 KiB) Viewed 792 times
And this is the position on the underside. The layout may vary between revisions but on mine with the connectors at top of image, the lower two bins are CE.
sy22-mainboard-underside-tr4.jpg
To get at the top of the board you have to desolder the short black grounding lead near top right. The rest of the connections can stay on if you are happy working on it at 90 degrees.

All of my electrolytics were leak and bulge free thankfully.

Sistrum
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Re: SY35 output problem

Unread post by Sistrum » Thu Aug 04, 2016 3:18 pm

I recently obtained an SY35 , great a synth but it had output problem - ordered a replacement transistor and fitted it today - all now good. thanks for advice..

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