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TECHNICS SU-8600 Balance Issue

surfshaun

surfshaun

New Member
Hello everyone! Audiokarma rocks!

Sweet looking unit I just nabbed.
Perfect cosmetically and looks clean to the untrained eye.
The balance knob feels very scratchy tho, almost like a grinding is happening inside of it.
Lil bit of corrosion on the pot inside. When hooked up to speakers it will play very strongly out of the right channel, though kinda scratchy, but very faint out of the left channel. I can turn it all the way left but still very faint. Right pops and crackles while adjusting the balance. Fuses are clean.

Input would be much appreciated!

Please & Thanks
 
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Hello. Welcome to AK !

I see your unit uses the "2SA798" double transistors. Those parts are faulty, they always fail. After a good cleaning at the controls and switches, I'd start replacing those with a pair of low noise transistors. There is a whole thread here at AK about "2SA798 is there a replacement?"

Those transistors starting to fail usually do pop and crackling noises, sometimes very loud, sometimes like a background "wind" noise full of scratchy noise.

Make sure to clean the "pre out" "main in" connection. You could even swap the conectors, or swap premp channels connecting R from pre out to L on the MAIN IN (use any RCA interconnect cable), to confirm if you have a problem at the preamp or at the power amp.

Service manual here. I'm talking about TR401 and 402 at the power amplifier section, page 10 of the PDF file.
http://www.hifiengine.com/manual_library/technics/su-8600.shtml
 
Thanks for your input, it is very much appreciated and needed!
Will refer to the service manual to get a better understanding.
What does the "pre out" "main in" connections look like?
 
at the back of the unit, you have 2 jumpers, connecting the preamplifier output to the power amplifier input. So you could use that preamplifier OUT and send the signal to a different power amplifier, or take the signal from another preamplifier and connect it to your power amplifier.

An "integrated amplifier" is a preamplifier and a power amplifier in the same case.
 
Ok I see what your talking about now. Just got the deoxit and have been doing a little spraying. Seems to have smoothed out the balance pot.
Had the can set to medium and it got somewhat soggy quick, gunna give it a few hours to dry before testing.
Should I be able to test the sound with headphones? or is it necessary to set up speakers to test?
 
For this pourpose headphones are Ok. Actually you will perceive the balance better with headphones.
 
Sounding Epic! Couldn't be more happier, everything is working fine!
Just another question regarding crossover of bass and treble?
Should i set it to 500hrz or 250hrz for the bass and 2.5hrz or 5hrz for the treble.
Not really sure of what the difference is.
 
Good news!

I can't tell you about the "crossover" setting. The crossover ffequency is the transition frequency , a hig-pass filter letting only high freqs to pass, or a low pass filter, cutting high freqs and letting low freqs to pass.

I don't know the function of that setting in your unit. I'll check the user manual and post back.
 
It's not a "crossover", it's "turnover" setting.

It changes the frequency in which the tone controls work. The bass, set at 250Hz, will affect only the deeper bass. Set at 500 Hz, it will affect a bit higher bass. More noticeable change with smaller speakers that can't reproduce very low freqs.

The same with the treble control. Set to 2.5KHz will affect the mid range, and setting to 5KHZ it will move the higher freqs only, without affecting the mids too much.

I'd set it to 250 and 5KHz, to leave the mid-range unaffected. But adjust it to your taste, or change it on some recordings that need it.

User manual here:
http://www.hifiengine.com/manual_library/technics/su-8600.shtml
 
Thanks for your detailed input!
Very much appreciated.
Yeah regarding cleaning the amp everything sounds great. What I did learn in the process tho is that the major lack of my left channel is coming from my phono input from my turntable. I came to this conclusion because my aux is fine. Tested from my iPhone to the headphones and balance to the right then left worked great no problem at all and no popping. When turntable connected to either phono 1 or 2 input balance issues occur through. Right is good left is dim and quiet. So I think it's from the turntable. Cleaning that now.
 
If you swap left and right cables connected to the phono input, and the problem stays on the same channel, the problem is at the amplifier. The "phono" inputs go to a "phono preamp" that raises the signal level and apply a RIAA eq., before going to the tone preamp. You could have a problem in that phono preamp, or at the function selector (dirty)
 
Yeah I switched the left/right cables and the problem went to the other channel. I also tried the phono 2 input and same thing, so I'm pretty sure its coming from my turntable. Now that I think about it I was having the same problem with my last amp hooked up which is why I got the new Technics SU-8600. I took apart the turntable (Technics SL-Q2) and cleaned it with deoxit, but same problem.
 
Just went back and cleaned the stylus and where it connects into the arm and kabam, it works perfect!!! Crazy how just a lil bit of oxidization can affect these old electronics so much.
 
:thumbsup:

I fixed a couple of turntables with one channel "dead" in a similar way... loosen connectors at the cartridge, or loosen solder inside the chasis.
 
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