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Discussion Starter #1
Hello,

I recently fixed my Pioneer VSX-1015TX. Prior to the fix and still post, the Left channel has low levels at initial startup and crackling /distortion at higher frequencies most notably until it warms up. Distortion disappears once warm but volume is still lower seemingly. This happens from the speakers and I first noticed it with some Sennheiser headphones. What is the likely culprit of this distortion and level I discrepancy? Caps perhaps? I do notice also, audible differences beyond the left and right channels in multichannel mode, leading me to believe its main caps on the amp itself, two 330uF 100v. Both test a bit lower but certainly not out of a 10% spec.

Should I be focusing more on the power delivery to the Sap mosfets (?) or maybe it's (what I believe to be) caps around the preamps? PA9010A (I'm still learning)

Thank you for your time.
 

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Discussion Starter #2
To add, would increasing the cap sizes around the preamp and mosfets while also upgrading to some Silmics, boost performance? Again, still learning.

Note, main caps, 15k uF, test around 13.5k and are near equal. I cant push high volumes (apartment 馃檨馃檨馃檨馃檨/forum/images/smilies/wink.gif so I'm assuming upgrading these isn't really worthwhile?
 

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Could be a semiconductor device.

Just to rule out a dirty volume control, is there any effect like noise or scratchy sounds when you turn the volume control back and forth?
 

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Discussion Starter #4
Volume knob does not function correctly, coincidentally I'm fixing it now hopefully with some contact cleaner. It's a digital knob so I don't think those effects would occur
 

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Any idea what semiconductors I should be investigating?

Could be any, but perhaps the amplifier output transistors since they're under the most thermal stress.

You could troubleshoot by getting a can of coolant spray and squirting each device starting from the output and working your way back, on the assumption that that will bring the distortion back.

The amp might actually be an IC chip.

You could also get a used replacement for about $100

https://www.ebay.com/sch/i.html?_from=R40&_nkw=Pioneer+VSX-1015TX&_sacat=0&rt=nc&LH_Sold=1&LH_Complete=1

unclick the "Sold" filter to see ones still for sale.
 

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Discussion Starter #8
I, was wrong and jumped the gun. Seemingly, the distortion has disappeared. I threw on some headphones to double check. This perplexes me. Now I did clean the contacts of the speaker terminals which were somewhat dirty. I don't understand how that or even the volume knob would influence the behavior.

On a related note, now when I switch inputs from the buttons on the same pcb of the volume, sends a pop noise through my subs.

What's happening here? Maybe it's a cap on the main control board or bad path to ground? 馃

I used deoxit fyi
 
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