Pioneer VSX-520-K Protection problem

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

Maybe a reset at this point, it wouldn't hurt either.

Haha tried that already, still same with DC msg.

[rievax_60]

Re: Pioneer VSX-520-K Protection problem

Most amplifiers rely on a few certain screws to ground the input sockets to the rear panel.
If these screws don't provide a contact, the amp wont work properly.

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

Most amplifiers rely on a few certain screws to ground the input sockets to the rear panel.
If these screws don't provide a contact, the amp wont work properly.

Its all tight.

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

Can i get some assistance on CP107 on how to measure those pins? I believe B+ and B- should be 100V. But when measure B+ and AGND, there's reading about 50v, is that a leak of DC on main board?

[rievax_60]

Re: Pioneer VSX-520-K Protection problem

Measuring 100v between B+ and B- rails is normal if the rails measure +50v and -50v respectively to ground.

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

Most amplifiers rely on a few certain screws to ground the input sockets to the rear panel.
If these screws don't provide a contact, the amp wont work properly.

Measuring 100v between B+ and B- rails is normal if the rails measure +50v and -50v respectively to ground.

Ok i have measured the amp block thoroughly and there's no faulty components on it but when i plug it in to main board via CP107, then there's DC leak via CP203 on speaker assy. Almost all the legs has DC leaking. My friend said, if i pull out CP107 from amp to main, it will disconnect the amp but the receiver will turn on fine provided theres no shorts on main board to cause a dc protection. Looks like the DC is still present on speaker assy relays. Sighs

[rievax_60]

Re: Pioneer VSX-520-K Protection problem

What DC voltage reading are you seeing? And is it on all amplifier outputs?

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

I see dc around 47v on FR,FL,C,SR,SL connector that goes to speaker assy

[rievax_60]

Re: Pioneer VSX-520-K Protection problem

Look for something common to all amplifiers like the - rail that feeds the emitters of the voltage amplifier transistor via R227 10 ohm. And also the +12v rail that goes to the 7.5k resistors that connect to the input transistors' emitters.

[rievax_60]

Re: Pioneer VSX-520-K Protection problem

If you find nothing wrong then measure the voltage at both ends of the input capacitors, C206FL, C206FR.

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

Hey folks, im back after a long time due to work load. OK as for updates, i manage to fix the amp as on the power amp side, a couple of regulators seems faulty triggering the protection circuit. Now the amp powers up perfectly, all relays clicking fine.

BUT, I measured using DMM @ 200mV setting,

Left speaker output there's -31.3mV present while the right side -7mV dc offset present. What do i do now? Checked the big caps, they read just fine and measure as it should using a cap meter.

All the driver amp transistors seems to be fine as well as none blown or short.

Update : All surround speakers and center speakers, L&R speaker outputs are working perfectly fine with all under 10.0mV. Weird.

Could it be the big caps failing intermittently?

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

The amp at cold start, right channel has at least -30mV and left shows -0.00mV. After about 10 or 20 minutes, right channel resets back to 0.00mV. May i know why is this? Anyone can help?

[budm]

Re: Pioneer VSX-520-K Protection problem

30mV offset is not going to trip the speaker protection relay, the trip point is usually around a Volt or two to trip the protection circuit.

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

30mV offset is not going to trip the speaker protection relay, the trip point is usually around a Volt or two to trip the protection circuit.

But is it normal for -30mV to present @ speaker terminal? Ive seen + and above dc offset, but mine is minus offset. Thats the weird part. Sound wise no problem, still kicking good.

Minus 30mV present when volume at zero with no signal input and speakers unplugged. Ive let it run for couple of hours, still showing -30mV. Only the right channel. Left seems fine.

[kevwag]

Re: Pioneer VSX-520-K Protection problem

Most amplifiers rely on a few certain screws to ground the input sockets to the rear panel.
If these screws don't provide a contact, the amp wont work properly.

That's an interesting theory, but it would have to be a pretty bizarre set of circumstances for poor earthing on an input at the pre-amp end to cause DC on the output stage of the power amp!

That said, I just managed to cause DC on the INPUT of my VSX-520, taking out C206C with a loud bang! This is a good example why you should use the service manual, even when you're experienced and know what you're doing. I dived in without the manual, replaced the output transistors and also needed to replace the protection transistors as they were also dead-short. It has been well over a decade since I worked on electronic repair of this type and it seems things have moved a long way...

The protection trannies were marked C3200 and A992, which, back in my day you could have safely assumed would have meant 2SC3200 and 2SA992 but not now apparently! I should have used KTC3200BL and KSA992F - these codes didnt exist back when I did this for a living! I Feel a bit silly for not having checked - lesson learned the hard way!

I don't need the centre channel right now so I'm going to isolate B+ and B- for that channel, pull out the incorrect trannies and try again, if the rest still works I can order the right parts and use it 4.1 until they arrive lol

[srt1]

Re: Pioneer VSX-520-K Protection problem

Hey folks, im back after a long time due to work load. OK as for updates, i manage to fix the amp as on the power amp side, a couple of regulators seems faulty triggering the protection circuit. Now the amp powers up perfectly, all relays clicking fine.

BUT, I measured using DMM @ 200mV setting,

Left speaker output there's -31.3mV present while the right side -7mV dc offset present. What do i do now? Checked the big caps, they read just fine and measure as it should using a cap meter.

All the driver amp transistors seems to be fine as well as none blown or short.

Update : All surround speakers and center speakers, L&R speaker outputs are working perfectly fine with all under 10.0mV. Weird.

Could it be the big caps failing intermittently?

Can you explain what cause the DC offset on Speaker output?

[srt1]

Re: Pioneer VSX-520-K Protection problem

If you find nothing wrong then measure the voltage at both ends of the input capacitors, C206FL, C206FR.

Hi i Hav pioneer VSX 522 it have DC offeset on all channel can i checked Can you explain what cause this DC offset

[rievax_60]

Re: Pioneer VSX-520-K Protection problem

What voltage and polarity are the offsets?

[srt1]

Re: Pioneer VSX-520-K Protection problem

What voltage and polarity are the offsets?

its around 54 volt (positive polarity) with ground

[rievax_60]

Re: Pioneer VSX-520-K Protection problem

If the input differential transistor pairs lose Emitter current, the amplifier outputs will go to a high positive voltage. There is a 12v rail that is common to all channels.