Pioneer HT receiver... blown channel?

I bought a Pioneer Elite VSX-56TXi home theater receiver new in August '07 and was enjoying it until last week. I'd been using its passive bi-amplification feature to bi-amp my speakers--it doubles the front channel outputs through the rear-surround outputs.

A few days ago, I turned on the receiver and noticed that the left speaker's tweeter wasn't playing. After some troubleshooting, I determined that the left rear-surround output was only outputting a faint signal relative to the other channels.

Have I fried/blown a channel? What steps should I take to determine the cause?

I plan to try a factory reset tomorrow (couldn't hurt), and if that doesn't help, I'll open it up, give the inside a visual inspection, and post some pictures.
 
I opened up the VSX-56TXi today and took some pictures. It's a beast! It's fairly clear to me that I won't be able to troubleshoot it myself, but perhaps I can narrow down the problem to make the fix easier for a technician later.

Overall View
[IMGDEAD]http://jhrhodes.iweb.bsu.edu/diyaudio/56txi_1.jpg[/IMGDEAD]

Power section, main capacitors, speaker outputs at top
[IMGDEAD]http://jhrhodes.iweb.bsu.edu/diyaudio/56txi_2.jpg[/IMGDEAD]

Closer view of speaker outputs, faulty channel is left-most output
[IMGDEAD]http://jhrhodes.iweb.bsu.edu/diyaudio/56txi_3.jpg[/IMGDEAD]

I saw a lot of capacitors from Chemi-Con, but a lot of blue Elnas used elsewhere. Feel free to comment on what you see... I also have other pictures if it would help to see the rest of the receiver.
 
No toroids :(

Why is it that manufacturers always insist on using EI lamination transformers and not toroids which are better all-around? Cost?

Anyways, I don't want to divert from the original topic too much.

Couldn't find any datasheets on those chips, def looks like something proprietary. Possibly some kind of chip-amp or multiple FETs in a single package. Gonna be kinda hard tracking down the signals not knowing how this thing works. The techs will have access to service manuals, which in a case like this are going to come in very handy.
 
Thanks for the response! I don't mind any diversions if I'm learning more about amplifier technology. What's the difference between a toroid versus a square laminated transformer?

Do you have any idea how difficult or expensive this will be to diagnose and repair? I'm not sure what's reasonable to expect to pay for this sort of fix.
 
The main advantage is due to very low stray magnetic fields, which reduces electromagnetic interference, lowers idle current, improves efficiency thus the transformer also runs cooler. Toroids also have better regulation than EI lamination transformers, meaning the output voltage does not drop as much as the load is increased, which makes these transformers ideal for audio applications. Too much supply voltage fluctuations in an audio amplifier application is undesirable. Smaller size and weight for a given power rating.

Disadvantages are that they are typically more expensive, as the manufacturing process is somewhat more complicated. Whereas EI transformer windings can be wound before being inserted onto the core, toroids have to be wound around a one-piece donut shaped core. I'm guessing this is what's keeping many manufacturers of consumer audio equipment from using them, cost.

Here's a neat video showing how these things are wound: http://youtube.com/watch?v=_EJ0nzvgN-E

Last but not least, because of all the advantages of toroids, comes a side effect. That is, power-on inrush current is much higher which necessitates a "soft start" circuit when using large toroid transformers.


You could say I'm a big fan of toroids, and probably many of the other people on this forum are too.:)
 
Pretty cool. That will be something to look for if/when I get a separate power amplifier. Even the little Radio Shack Accurian amp I hacked apart had a toroid, after all... :D

Do you have any opinion or advice about my other question: how much should I expect to pay to have this fixed?
 
infinitesymph said:
A few days ago, I turned on the receiver and noticed that the left speaker's tweeter wasn't playing. After some troubleshooting, I determined that the left rear-surround output was only outputting a faint signal relative to the other channels.[/B]
Did you ever get to reset it?
Áre you sure it is not the settings, the speakers or the wires?
You should doublecheck in the setting menu, the test tone, and by switching the cables for left and right surround.

There is no need to fix something unless it is broken.
 
Re: Re: Pioneer HT receiver... blown channel?

Nrik said:

Did you ever get to reset it?
�re you sure it is not the settings, the speakers or the wires?
You should doublecheck in the setting menu, the test tone, and by switching the cables for left and right surround.

There is no need to fix something unless it is broken.

I tried a factory reset, but it didn't fix the issue. The first day I discovered it, I performed a bunch of tests to determine the actual problem; it's definitely the amplifier's left rear-surround channel. In all tests, whatever was connected to the left rear-surround only emitted a constant faint hiss, and made a popping noise when the source was changed or the amplifier was turned on or off.

This isn't a speaker problem, though I wish it were, since that would be simple to fix. Different speakers exhibited the same problems when connected to that channel.
 
hissing and popping when changing input suggests to me a fault in some preamp/decoder section. Does the amp have any multi-channel analogue input connections ? (not digital of any kind!)

To confirm you would have to find the power amplifier responsible for that channel, trace its input and inject a signal straight there. You'd really need a service manual for that though.

As for repair costs - beats me - is it ever economical to have anyone repair anything these days?
 
Yes, it has a bunch of analog inputs, including 7.1 analog surround. I've mostly been using it for two-channel stuff via the analog RCA outputs of my CD player. The problem seems to happen regardless of analog or digital input.

Your question gave me an interesting idea... I wonder what would happen if I plugged one of the CDP channels into the dedicated left rear-surround input. I'll try it and report back.

About repair costs... I hope it's economical! I bought the receiver new less than six months ago. Unfortunately, the warranty is not valid because I purchased it for much less than retail from a liquidator. This was the last piece of gear I expected to have problems with, given my history with the Pioneer brand. :(
 
No difference with the 7.1 inputs vs. regular CD player inputs...

I guess my next step is calling up the nearest Pioneer service center, which thankfully is not far from me--no shipping costs to pay. At least I'll get an estimate of how much it will cost to diagnose the problem. Otherwise, I may be jumpering the left speaker's binding posts from now on.