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Pioneer SX-535 distortion in left channel

Akprocess

Akprocess

New Member
hi, i like the blue lights so thought a 1970s Pioneer would be my next project. Recapped everything but found i could not align the power amplifier on page 12 of the instruction manual TP1 and VR1 only have a range of .6 to 1.2 mv whereas the right channel can be perfectly aligned to 15mv and sounds much better. the potentimeter has a variable range from 1 to 82 ohms like the right side, so i believe it is ok.

the left channel is kind of like an "off channel" radio station - not quite. this is the same for all devices AUX,Phono and FM.

looking at other threads i replaced Q1, Q3, Q5 and Q7 - each one while checking VR1 but no improvement on distortion.

For now i ordered more transistors matching the Equalizer and power amp. Any ideas - generally these problems are something other than replacing transistors. the small caps could be bad but the resistors seem to be in range. thanks for any help, Rich
 
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followed a great thread :
https://audiokarma.org/forums/index.php?threads/pioneer-sx-535-noisy-transistors.809085/

which lists all the components and their comparable replacements. Since I'm still tracking down the distortion i decided to try and replace the Q1-4 SC1344 transistors in the the Equalizer even though it's phono oriented. i found a few KSC1845FTA's on the internet (paid the price) so i tried them and found no audio for either channel. Then i restored the 2SC1344 on the right channel and it worked so tomorrow i'll restore the left too.

I wonder why the KSC1845 didn't work. the Cheap transistor tester find some of the new KSC1845 defective so i only used what tested well. FM performs pretty descent as does AUX - but all could improve especially the left channel that does not align properly.
 
You nailed it - followed your direction and it works great.

got the phono back but still working on the distortion - on to SW & control board.
 
you are correct, thanks!

I found a trimmer at the local PC store - 100 ohms and a little difficult to calibrate but at least i have the ability to control the left channel to 15 mv like the right channel.

there is still distortion on FM/phono/tuner so not done yet. Q1 & Q2 2SC1344 were replaced with KSC1845FTA so eliminated that possibility.
 
ok, aux and FM is working great both channels.
Phono - replaced the 4 transistors and works great both channels with MONO but only left channel with stereo.
on stereo, the right channel has EXTREMELY low volume - all turned up it's there.

i have deoxited all switches and connections and resoldered any point that i can see.

took off the faceplate and resoldered and deoxited the switches until they're dripping.

there is some component that i have missed and i don't know what it could be. Maybe i've checked it so many times i am overlooking now.

if it's works on MONO and loudness also functions - am i still at the equilizer? i have the BIAS set on both - at 15mv.

any ideas at this point would be helpful - i don't know what to "redo" what i haven't already done twice (and more).

thanks
Rich


any help
 
ok - i know it's the equilizer board. The right channel is very faint for phono.

i ohm'd the difference between the right and left channels down thru the sw board. At first it seemed like the board was the issue but since FM and Aux worked fine for both channels that couldn't be true.

It is difficult to measure exact ohms of resistors inline within the equilizer and some of the exact replacement values would need to be bought specifically for this purpose.

so i clipped (not advised) the left channel post from the equilizer to the right channel on the phono rotary switch to override the right channel. The audio was loud and clear proving everything beyond the switch was working fine on the right as well left.

Proving this, i took a chance and bought an SX-535 equilizer parts board. I will replace the capacitors and transistors then try the new board. if i can't piece together a good equilizer board then i will order the exact resistor replacements and fix it that way...

i will report back if my fix works.
 
I replaced the equilizer board and have the same issue on the right channel. it is the phono rca connection. the twisted on wire looks ok and ohms to the equilizer right channel but is very finicky for connecting properly. I thought soldering it would seal the connection but it doesn't - have to look into this further.
 
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