Assistance with troubleshooting an SX-780 requested!

[KEV31779]

Kev31779,
You sound like a swell guy, helping out your fellow friends and AK'ers. I watched your video, good lessons for the crowd to follow and learn from. I could suggest that you measure THD/IMD to verify that they meet the Pioneer published specs. Looking at a sine wave on a scope, it is hard to tell sub 0.1% THD. Maybe you do not own a analyzer, so that is why you could not perform this test.
I get your point about others not having the ability to make the stk-0050 replacement. Those are the ones that I am not calling cheap, but in fact HBrown was willing to start to make/sell them and many people who inquired would not pay what he was asking for, which I thought he was asking a reasonable price for the effort involved. Those are the people I am calling cheap, in my mind at least.
To bad you do not want to disclose the source of your stk-0050 for others to obtain them. It has nothing to do with bashing anyone other than of the retailer that sells sub par replacement parts.. So much for helping the AK community in that regard. The whole point is to help others find a reliable source for these parts. We need to weed out the ones that do not perform correctly or fail prematurely, as others have experienced.
Thanks for the suggestion, but at this point in time, I am not going to start to sell pcb's on eBay. They are useless, unless I have the AL plate to go with them. Fabricating the Al plate is the labour intensive part of the build, so to make this an economical exercise it is best that I do not do it for them. Based on what we have experienced, a few of the members will not pay a reasonable price to obtain these parts. The ones that will, usually can do it for themselves, so I will leave it at that. I do not need to profit from something that I have offered for free to begin with.

Your right, I do not have an analyzer otherwise I would love to test for that. I guess the point of the oscilloscope test is to show that it was comparable in amplitude and linear at reproducing the same signals that the "original" ones were producing over the amplifiers specified range. Those analyzers can be in the thousands of dollars to have. Most hobbyist would only use it once in a while so it's not justified to purchase one. I wish I had one though. If anyone has one and not using it, I would give it a nice home HAHA. I don't mind giving my source If people understood that I have no idea the reliability of these reproductions. There is no datasheets on these reproductions and if you would even get the same ones as I did when you order them would be a gamble. They are all a crapshoot and almost seems pointless to recommend them where they only been in service for 2 days. All I did was search for a selling lot pair of repros on Ebay. As we all know and it's not a secret that this is where you can almost only get them these days . Many know the originals are not available unless you get real lucky. If I got them and they were complete crap I would have put the old parts back in handed him back the amp and said, sorry cant help you the reproduction parts are not producing good sound or just junk. I couldn't tell the difference from channel to channel even bye ear. An analyzer could show THD/IMD no problem but can be subjective to the individual ears unless it is really bad.

 

[ZOOM]

Don't call the fakes reproductions! They aren't equivalent to the original parts. They run no bias current as a means of not blowing up directly, and they can only deliver power in the milliwatt range (with huge THD!). Not a reproduced part at all, simply garbage marked as something else.

 

[KEV31779]

Don't call the fakes reproductions! They aren't equivalent to the original parts. They run no bias current as a means of not blowing up directly, and they can only deliver power in the milliwatt range (with huge THD!). Not a reproduced part at all, simply garbage marked as something else.

Delivering power in miliwatts? To the speakers? C'mon, that's ridiculous. If that was true at that level the "original" power meter circuit couldn't even excite and wouldn't even move the needles. Your not adding anything substantial to these claims of the integrity for these aftermarket parts. Show us your comparisons from the originals against the "fakes".

 

[beatcomber]

Will it last 40 years? I dunno, but whatever KEV31779 installed in my Pioneer does not sound like "garbage."

 

[rcs16]

They run no bias current as a means of not blowing up directly, and they can only deliver power in the milliwatt range (with huge THD!). Not a reproduced part at all, simply garbage marked as something else.

Interesting, no bias, class B operation, can anyone other than "ZOOM" confirm this statement?
Simple enough to check, measure the voltage drop across the emitter R (0.22ohm) with no i/p signal.
milliwatt range = more BS, if one of your claims is BS, then how can we take anything you say as the truth?
Time will tell how long they last, hopefully it will be for a long while.

I wish I had one though. If anyone has one and not using it, I would give it a nice home HAHA.

The economically way these days for a analyzer, is a good sound card and FFT software. But you still need a low THD oscillator, spot freq osc are easy to come by, unless you want a variable freq. Take a look at the diyaudio site where the experts have been working on this vary subject.
http://www.diyaudio.com/forums/equipment-tools/205304-low-distortion-audio-range-oscillator.html
Lots to learn.

 

[KEV31779]

Interesting, no bias, class B operation, can anyone other than "ZOOM" confirm this statement?
Simple enough to check, measure the voltage drop across the emitter R (0.22ohm) with no i/p signal.
milliwatt range = more BS, if one of your claims is BS, then how can we take anything you say as the truth?
Time will tell how long they last, hopefully it will be for a long while.


The economically way these days for a analyzer, is a good sound card and FFT software. But you still need a low THD oscillator, spot freq osc are easy to come by, unless you want a variable freq. Take a look at the diyaudio site where the experts have been working on this vary subject.
http://www.diyaudio.com/forums/equipment-tools/205304-low-distortion-audio-range-oscillator.html
Lots to learn.

I have FFT on my scope but it sucks.. Well the scope is not high end.

 

[Arthur Smith]

It lives!

Some of you were unknowingly discussing this with the actual tech who did the work, @KEV31779 .

Tonight I picked it from him, and after getting home I hooked up a pair of nice Wharfedale Denton 80th Anniversary speakers. I first tuned in some classical music on FM, and then listened to some Charles Mingus on vinyl (via a resto-modded by @marcmorin Acoustic Research AR-TX turntable with a nice Grado 8MR cart). I am literally stunned by how wonderful it sounds! I am mainly a vintage tubes guy, and did not expect to be this impressed by a modest '70s solid state Pioneer receiver.

I'd also like to say that KEV31779 was super to work with, and he turned it around in just about a week, including the time for the Darlingtons to arrive. Bravo!

A special thanks to @Arthur Smith for the referral, and thanks also to everyone who contributed to this thread!

I saw the video. Kevin is a wizard, and a gentleman. I don't think he has encountered a component once that he was not capable of repairing. I would recommend him to anyone. But not only is he skilled, he is a true gentleman.

 

[Arthur Smith]

Kev31779,
You sound like a swell guy, helping out your fellow friends and AK'ers. I watched your video, good lessons for the crowd to follow and learn from. I could suggest that you measure THD/IMD to verify that they meet the Pioneer published specs. Looking at a sine wave on a scope, it is hard to tell sub 0.1% THD. Maybe you do not own a analyzer, so that is why you could not perform this test.
I get your point about others not having the ability to make the stk-0050 replacement. Those are the ones that I am not calling cheap, but in fact HBrown was willing to start to make/sell them and many people who inquired would not pay what he was asking for, which I thought he was asking a reasonable price for the effort involved. Those are the people I am calling cheap, in my mind at least.
To bad you do not want to disclose the source of your stk-0050 for others to obtain them. It has nothing to do with bashing anyone other than of the retailer that sells sub par replacement parts.. So much for helping the AK community in that regard. The whole point is to help others find a reliable source for these parts. We need to weed out the ones that do not perform correctly or fail prematurely, as others have experienced.
Thanks for the suggestion, but at this point in time, I am not going to start to sell pcb's on eBay. They are useless, unless I have the AL plate to go with them. Fabricating the Al plate is the labour intensive part of the build, so to make this an economical exercise it is best that I do not do it for them. Based on what we have experienced, a few of the members will not pay a reasonable price to obtain these parts. The ones that will, usually can do it for themselves, so I will leave it at that. I do not need to profit from something that I have offered for free to begin with.

New Darlington Power Packs that are "authentic" are one thing- unobtanium. The ones that are made today do indeed have varying quality control. If you are wanting new ones made by Sanyo? Good luck. If you use used replacements, there is no guarantee they will work. what Kevin explains in his video is a statement of fact.

 

[Awesomeaudio]

This has been a very interesting discussion .
I've actually watched a few of kevs you tube videos previous to finding out about him here.
What a cool guy.
I have a dumb question .
This is not a thread hi jack either.
I have an SX-690 with a possible faulty Darlington pack. Too early to tell as I haven't even cleaned the controls to know for sure, but how can one tell the Original Darlington from the replacements ??
There are so many on ebay, even ones that are marked Sanyo...lol.

 

[rcs16]

Having a picture of the original ones, or one in hand, to compare against, unless the newer subs have copied the original in every detail.
Tearing them apart, de-cap and using a microscope to take a pic of the way that they are built but once again you need an original to compare against.
There are probably are electrical ways of testing them but it gets involved with device characterization. Sometimes that means destruction to figure out safe operating areas. Even then if the newer subs are designed with the same characteristics, it is difficult.