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SX-1010 Tracking Hiss - Always Present - Especially When Treble Increased

PTL-Pioneer

PTL-Pioneer

Super Member
Hi all

I have this problem with my pioneer SX1010 - Hiss through the speakers, does not matter which speakers i use, does not matter what room i move unit to, or what socket i use.
The noise increases whenever i engage tone controls and move treble higher, but it is present with tone control switch off also. Engaging the treble makes it really pronounced!
It is not normal hiss either, like just the noise floor of the receiver i have had a few receivers now and they have all been dead quiet.

Can you give me some guidance on how to isolate and fix this problem, i know they are the kind that are real headaches to track down.

I have read a few threads that people said they fixed this issues with a good deoxit of the controls etc.
I hope you can help me, thank you

The history of the unit is that it was fully recapped and gone through by AK's own Zebulon, so i hope he can provide some guidance also. Everything works perfectly it is juts the hissing that is loud enough to be intrusive during low level passages in music
 
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I would use the main-in/pre-outs to see if it’s in the preamp section or power amp. Other than that, I’d be interested to know if transistors were replaced when the caps were done (I suspect they were; Zebulon certainly has a solid reputation). You could be tracking transistor noise.
 
With the tone set to on, no inputs and with volume, you can hear this hiss?
What happens with volume?
You said speakers, so it's heard in both? You can use the balance to isolate.
Is it noticed more in one input than others? Like FM verse's AUX, Phono?
Do the filter switches make any difference?
Did this issue develop after you received it? :eek:
I sent you a PM.
 
Yes, hiss is present with nothing connected except speakers.
Both channels hiss left and right with balance knob.
If I put on the high filter, low filter or the - 20db switch hiss reduces.
With tone control to off, slightly less hiss.
Tone control on, any increase in treble make noise much more noticeable
 
So the hiss is only when the tone is on?
Or greatly reduced when tone is on?
 
Hiss is present all the time. Does not matter if tone control is on or off.
But, when tone control is on hiss is louder. When treble is increased it gets even louder.

Upping the volume increases the hiss volume also
 
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Mine has a hiss, but I can only hear it with ear up to the speaker, louder than the rest of my gear, but hardly a bother. Same thing if tone engaged, it gets a bit louder. Perhaps the nearly 50 year old design?? Just guessing, as I am no tech.

Zebulon's work on this unit is stupendous, no complaints. Hope you get yours where you need it, paultlaw.
 
I cannot stress enough that this is certainly not any fault of zebulon. I would really like that to be clear to everyone who reads this, i have the utmost respect and esteem of his knowledge and workmanship.
 
onwardjames said:
Mine has a hiss, but I can only hear it with ear up to the speaker, louder than the rest of my gear, but hardly a bother.
Click to expand...

I know that hiss you are talking about, have had multiple receivers come through my hands and they all have that bit of background hiss, this is different though, in my humble opinion anyway.
 
All I can contribute is wild assed guess.

Could the speaker relay be dirty/malfunctioning?
 
Thanks for the reply, relay is brand spanking new, no issues there.

My wild guesses are dirty switches, drifting resistor on tone amp, or even potentially diodes on power board. I am going to open it up and have a look at the board, maybe something will visually look off, I doubt it though
 
Ok so managed to get access to the tone control board - Has a pair of KSA992, and all other transistors are the original 2sc1312's.
Would i be better to replace them with KSC1845FTA?
 
I don’t know why I didn’t replace those but even with the tone off you still get some hiss.
:dunno:
I’m checking one here I completely rebuilt.
I’ll have a report tomorrow.
 
tone defeat appears to leave q1 q2 q3 q4 in play on the control board .
i might have missed if both or just one channel .
 
I replaced the 1312's for 1845fta, still the same. Faceplate and hood are off, bottom plate on. It's 3.20am here, time for bed, thank you all for the help, much appreciated!
 
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