Pioneer VSX-527-K distorted audio after replacing parts

[tietoharrastelija]

Hi,
my friend asked to look at the amplifier. Amp model is Pioneer VSX-527-K.

First symptom was no power or standby.

Found few faulty components from AMP5 Assy: transistors Q404 (2SD2390), Q410 (2SB1560), resistors R430 (0R47), R431 (0R47) and R439 (100 ohm). All belongs to Front Left Channel.

Purchased transistors from eBay (from France). Soldered new components and reapplied thermal paste to heatsink. After it amplifier starts and can hear music ok from right speaker but left speaker has distorted and lower sound than right..

Checked all idle current adjustment points. FL (TP401) test point says 0 mV. Value won't change when turn VR401. Normal value should be 2 mV +0.2 mV. Can't find faulty resistors from circuit. I have only multimeter.

Anyone have any tips on what else to look for?

Video from issue on Youtube (first left channel, second right channel and, last left channel: https://www.youtube.com/watch?v=D5dxitiHdbU

Service manual for VSX-1022-K (AMP5 Assy Schematics is same for VSX-527-K):

PS. I have also oscilloscope (but it's so old and I don't know how to use it )

[alfatv]

Re: Pioneer VSX-527-K distorted audio after replacing parts

Check all transistors and diodes from your screenshot with multimeter (diode mode).
Collector to emitter shorts are typical.
If that doesn't help, measure voltages at all transistor pins and post it here.

[petehall347]

Re: Pioneer VSX-527-K distorted audio after replacing parts

q409 maybe bad .. also check the diodes .. what voltages at the outputs ? i expect bases to be plus minus 1.2v ish . emitters 0v . and collectors plus minus rail voltage .