SY35 output problem

Covering the SY22 to SY55 and TG Modules.

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wolft
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SY35 output problem

Unread post by wolft » Sat Oct 27, 2007 11:18 pm

Hi all
I hope someone can help. The output of my SY35 has gone completly dead (L/Mono and R). The Headphone output is fine.
Any help is much appriciated.

Thanks
Wolfgang

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Clyde
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Unread post by Clyde » Sat Oct 27, 2007 11:40 pm

Hi Wolfgang,
Welcome to the Forums! Could be a loose connection at the output jacks (or a bad output cord, try one you know is working), but I think that unlikely as it's both of them. I would suspect the output section board that connects to the outputs, broken solder lead, bad capacitor, or something similar. If you are a handy, electronics repair oriented person I would say open it up and see what you find. If you don't feel comfortable with doing so, then perhaps it's time for an authorized Yamaha service center to take a look.
Clyde

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wolft
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SY35 output problem

Unread post by wolft » Wed Nov 14, 2007 8:49 am

Hi all
First thanks to Clyde. I did take your advice and opened the synthesizer. As the main circuit board is double layer I found it very hard to follow the circuit, so I ordered the service manual. With that in hand it took only 5 min. to find the fault. The line outputs getting switched delayed through a relay when the synthesizer gets powered up. A simple circuit made of a capacitor and a transistor powers the relay. In my case the transistor was faulty and quickly replaced.
The SY35 is as good as new.
If anyone requires the service manual or parts of it please contact me (the schematics is a bit tricky to scan as there are three A3 pages).

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lava77
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Unread post by lava77 » Wed Nov 14, 2007 2:54 pm

I have exactly the same both output problem with my sy22. I wonder if they are the same internally for that section. Anyone know?

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Clyde
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Re: SY35 output problem

Unread post by Clyde » Thu Nov 15, 2007 4:11 am

wolft wrote:Hi all
First thanks to Clyde. I did take your advice and opened the synthesizer. As the main circuit board is double layer I found it very hard to follow the circuit, so I ordered the service manual. With that in hand it took only 5 min. to find the fault. The line outputs getting switched delayed through a relay when the synthesizer gets powered up. A simple circuit made of a capacitor and a transistor powers the relay. In my case the transistor was faulty and quickly replaced.
The SY35 is as good as new.
If anyone requires the service manual or parts of it please contact me (the schematics is a bit tricky to scan as there are three A3 pages).
Glad you found the problem and were able to repair it without major hassle. If you would, please PM (private message) me on this site as there is an issue I'd like your input on. Thanks!
Clyde

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Unread post by Clyde » Thu Nov 15, 2007 4:16 am

lava77 wrote:I have exactly the same both output problem with my sy22. I wonder if they are the same internally for that section. Anyone know?
As the SY22/35 are from the same era (within a couple of years) and of such similar design, I would think that they would have very much the same/similar design in that area, but I can't state this as fact, only a guess on my part.
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wolft
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Unread post by wolft » Thu Nov 15, 2007 6:22 am

lava77 wrote:I have exactly the same both output problem with my sy22. I wonder if they are the same internally for that section. Anyone know?
Hi Lava77

Have a look at the following picture.

Image


The signal (left and right channel) comes out of the VCA (IC31) and goes into the P. AMP (IC32) for the phones. It also branches off further down to the L/mono an right output. The later gets activated by a relais (RY1)
When the synthesiser gets turned on, IC35 and the transistor TR4 switches the relais on with a little delay. In my case TR4 was faulty.

If your phones are still work and the circuit of the SY22 is similar to this it should be easy to locate and fix the fault.

A word of warning though. If you not confident and have some experience to work with electronics get someone to look at it for you as you could do easily more damage to your SY22.
Hope that will help you.

Wolfgang

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Clyde
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Unread post by Clyde » Thu Nov 15, 2007 2:40 pm

Excellent advice Wolfgang! I try to always warn people to not attempt repairs if they are not experienced with repair for those very reasons (doing more damage). I will do minor repairs on my own gear, but if it gets a little complex I'm more than willing to pay my excellent tech friend to do repairs for me, he will get it right the first time and it is money well spent in my opinion.
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Re: SY35 output problem

Unread post by Push-Pull » Tue Dec 14, 2010 7:41 am

Thank's everyone for the advices on this topic !! Image Image Image
It help me to give again the life to a dumb SY22.

Again the TR4, remplaced in my case by a simple BC547. 8)

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Re: SY35 output problem

Unread post by mscott » Tue Jul 17, 2012 4:53 pm

An old thread yes, :-)
my SY35 had an identical problem, must be a common fault.
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Re: SY35 output problem

Unread post by musicgearvideos909 » Fri Nov 02, 2012 11:38 pm

Hi, I agree with the common fault problem. My TG33 which I just bought has no sound on the outputs. Haven't opened it up yet but yeah probably a loose connection.

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Robespierre
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Re: SY35 output problem

Unread post by Robespierre » Sun Jan 11, 2015 11:07 pm

Hi, just for more reference: I bought a used SY-22 on eBay whose headphone outputs worked but whose main outputs didn't work.

Per this thread, I replaced TR4, but the relay RY1 still wouldn't switch.

So, I just cut the connection between the 2.2k resistors and ground coming off the relay, and soldered wire to short from the relay to the 680 ohm resistors that lead to the main outputs.

Problem solved! Outputs work perfectly. I guess either the relay on mine is burned out, or I didn't install the new transistor properly.

Either way, my method is a gross kludgy hack, but it works. Based on the description, the circuit I bypassed is like a soft start circuit? So I'll just be sure to keep all levels turned down when powering on and off or making and breaking connections.

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Re: SY35 output problem

Unread post by AudioSaucer » Sat Jan 17, 2015 2:55 pm

It actually makes sense to bypass the relay :)
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Re: SY35 output problem

Unread post by SiriusHardware » Mon Sep 14, 2015 7:19 pm

Hi Folks - just bumping a recent thread because I have a related problem - I think it makes for a better reference resource if it's all kept in the same place?

My problem is slightly different to the OP's problem, my L+R line outputs work but while I was listening to a MIDI sequence through the headphone output on my SY22 the other night, in the space of one second one channel faded away to nothing and never returned. It's not physically intermittent and the headphones in question are OK with everything else. It's not the headphone socket or the headphone socket solder joints either - I have checked, both visually and with a meter. I've scoped the audio at the headphone socket solder joints on the track side of the PCB - the audio is there on one channel, missing on the other. I haven't made any serious attempt to trace further back because I don't have a track layout diagram.

Surfing onto this useful thread and, bearing in mind the likely similarity between the SY22 and the slightly later SY35, looking at the SY35 diagram I see that the most likely cause of the problem is that one channel of the headphone audio amplifier IC has died, although there is an outside chance that it could be one of the small components between the IC and the Headphone socket.

Can anyone point me to a circuit / schematic diagram for this section of the SY22 specifically?

Failing that, does anyone know what sort of IC the headphone amplifer IC is? If I'm going to start stripping bits out I would prefer to have a replacement IC to hand so I can do the job and put it back together all in one go.

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Re: SY35 output problem

Unread post by SiriusHardware » Mon Sep 14, 2015 8:06 pm

Update: I decided to delve in.

The audio power amplifier for the headphones (IC32) is an an AN7148.

At this time, I still don't know whether IC32 has died, but what I have noticed, on inspection, is that the three 100uF capacitors lined up alongside the IC have all been leaking a lot of electrolyte, a lot of which is still pooled around them on the PCB. It's also started to eat away at the tracks in the surrounding area although so far I think it's just the green top coating which is affected. I've mopped up what I can but it needs to be washed thoroughly with IPA to get rid of the rest - not something I can do here.

No other capacitors on the main board have done this, but all three identical 100uF / 16V capacitors have, so this was obviously a bad / weak batch of the particular type / manufacturer of the 100uF capacitor used in my SY22 - unfortunately, maybe in yours too? 8O

If you have your SY22 / SY35 apart for any reason, I strongly suggest you inspect these capacitors, as yours will be more or less the same age as mine.

The capacitors in question are those whose positive pins go to pins 3, 8 and 11 of IC32 on the SY35 diagram.

I'm going to take the board to work tomorrow, take off the failed capacitors, clean up and if necessary repair the corroded tracks before replacing the capacitors with new. If I'm lucky the power amplifier IC itself may not actually be blown.

The funny thing is that the last few times I've had the SY22 on I've been thinking that the headphone volume was getting quieter and quieter even with the volume wound up to maximum, and then just putting it down to my rapidly dying middle aged hearing. In fact, the problem was real and was caused by these capacitors deteriorating.

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