# [SOLVED] Sansui g-4700 discharging large amounts of static through right channel



## Coastwizard (Dec 16, 2009)

I've owned a *SANSUI G-4700 *tuner/amplifier since 1979. It had always performed well until a couple of years ago. Then, I started noticing the following:


When I turned it on, there would be a *release of static discharge only to the right channel*, sometimes enough to kick off the speaker's reset fuse.

Pushing the reset usually restored the sound without further static, but lately I've had to press the reset button repeatedly (sometimes 50+ times) before the discharge will stop.

At the same time, I noticed the LED indicator for the right channel would disappear and only come back gradually as the static diminished.

*Tapping firmly on the top of the tuner *will often cause a large static discharge to the speaker, and occasionally gets it back to operating normally.

Switching the speaker wires only moves the discharge to the opposite speaker.

*Some additional information:*


The speakers connect with bare wires, not with plugs.

The wires are heavy duty and their polarity is correct.

The unit's grounding wire is attached to a grounded outlet.

I have tried switching the speaker wires, raising the humidity in the room, and blowing the dust out of the unit. 

I have tried using the tuner with different speakers with the same result.

Thanks in advance for your help!

Randy :sigh:


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## Done_Fishin (Oct 10, 2006)

*Re: Sansui g-4700 discharging large amounts of static through right channel*

it might be a bad switch or Volume contact. 
Try removing ac input power, open it up and spray an oil based switch cleaning fluid into the switches and Volume control, joggling them on off and rotating as seems fit.

DO NOT TOUCH ANY POTENTIOMETERS you find inside since you may well upset the way your tuner works for ever! Only try the external switches and Volume Control


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## Coastwizard (Dec 16, 2009)

*Re: Sansui g-4700 discharging large amounts of static through right channel*

Ok. Since I started this thread, the right speaker on my system (the one that kept popping with static and turning itself off) has stopped working completely. Pushing the reset button does nothing. I tested both speakers by touching the ends of their speaker wires to a 1.5v battery. I only get a response from the left speaker.

I opened up the tuner and sprayed all the switches and volume knobs with a good control/contact cleaner/lubricant, then worked them well, like you suggested. I reassembled the tuner and hooked it up to an old pair of speakers to test. As soon as I turned the power on, the right speaker made a loud "pop" accompanied by a smoke smell and blew out.

At this point, can anyone tell me what to do next? I know 30 years is more service than I should expect from a tuner, but it was a special gift from my brother and it's always worked fine up until now. :sigh:

Coastwizard (Randy)


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## Done_Fishin (Oct 10, 2006)

*Re: Sansui g-4700 discharging large amounts of static through right channel*

Well the bad news is that the speaker may have to be replaced or repaired. Personally I would never test a speaker using a battery .. I'd swap the speakers over so that I cold test out on the working channel.

1.5V / 8 Ohms will result in about 0,2A so it would hardly be expected to cause any damage, but if it was 4 Ohms or even 2 Ohms as used on some equipment then it could be a different story.

Where did the smoke come from? Amp or Speaker?

I would suspect that you had DC voltage on the amplifier output, which is known to destroy speakers, and why I don't like checking out with Batteries.

Most amplifiers these days have protection circuits and as soon as DC starts to show at the speaker connectors, shuts down the channel. your tuner may not have had that built in.


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## Coastwizard (Dec 16, 2009)

*Re: Sansui g-4700 discharging large amounts of static through right channel*

First of all, thanks so much for getting back to me so soon!! 

Ok, well the D-cell battery I used to test the large speakers only caused a small crackling in the left speaker, but made no sound in the right. Those two speakers each have a reset button that kicks off if the speaker is overloaded. The left channel worked fine (and always has), and both speakers worked when they were on the left channel.

The older speakers I used for the test don't have reset buttons (unless they have fuses inside, which I doubt). The left speaker worked fine, but the right one blew out. The smoke smell came from the speaker itself. When I switched the still-working speaker to the right side, it also blew out, again with the smoke smell.

Thanks!

Randy


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## Coastwizard (Dec 16, 2009)

*Re: Sansui g-4700 discharging large amounts of static through right channel*

Is there any way to discharge DC voltage on the amplifier output manually?


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## Done_Fishin (Oct 10, 2006)

*Re: Sansui g-4700 discharging large amounts of static through right channel*

Unfortunately none whatsoever .. you can protect yourself a little bit by placing capacitors in the feed but that will also limit your output somewhat.

The fact that you say you swapped speakers and the same happened to the other good speaker leads me to believe that the final amplifier has blown, giving a DC voltage straight to the speaker. even if you were to place capacitors in line here, you would get lousy response, if you got anything at all.

You'll need to find someone who knows his electronics .. it could be a simple small transistor that has failed or the final pair (output transistors). The final Pair are usually a matched set but again there was a tendancy to put hybrid circuits (Sanken) that took the place of the transistors. The hybrids are somewhat difficult to find although not impossible.


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## Coastwizard (Dec 16, 2009)

*Re: Sansui g-4700 discharging large amounts of static through right channel*

Ok! Thanks for all your help, my friend. I guess 31 years of service is pretty good! Just don't make 'em like they used to!:sigh:

Randy M.


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## Done_Fishin (Oct 10, 2006)

*Re: Sansui g-4700 discharging large amounts of static through right channel*

very true .. now they make them so that you need to buy another one just after the guarantee period runs out .. or they persuade the buyer that they need some new fangled gadget on it so they bin it to buy a new one .. 

:wave: Good luck with the repair if you go that way ..


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