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MX-1 had a great fall.

"Chernobyl'd"

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Good news is I have solid and clean 70V and 32V coming out of the power supply after my repair to those traces. And the ground is getting to all the correct points now. All of the traces that blew were ground traces. So far all of the damage I have found has been on the left side of all the circuit boards. Maybe I'll get a subwoofer amp out of this. That would be sad.

We could update "Chernobyl'd" to "Fukushima'd". It's even got some of the right syllables in it. . .
 
You might want to consider my experience with my MX-2 that had much less damage in the V-AMP and left channel I-AMP sections. After all my repairs were made I came to find out that IC201 (BA3122N) had failed and I couldn't set the idle current. This chip is almost impossible to get new and the supply of donor amplifiers are limited. You might pull IC201 and check for resistance between pins 1-2 (~1.4k ohms); 2-3 (~1.0k ohms); 3-4 (~1.0k ohms); 4-7 (~1.0k ohms); 7-8 (~1.0k ohms); 8-9 (~1.4k ohms); my measurements from a known good BA3122N.
 
Good thing to check bmanone. I was worried about those "hyperbolic conversion amps". I looked closely and there appears to be carbon on the top of the chip. I pulled the chip out and none of the measurement come close to what you indicated. :mad:.

I'm thinking of calling this "time of death". :(

I'll do a little research first. I've only been searching "MX-1" so I would not have found any MX-2 posts.
 
A brief search of the internet found some 2012 searches from bmanone on some other websites. As for vendors there were many hits from Alibaba. I trust those about as far as I can throw the MX-1.
I did send an availability question to LittleDiode. I don't expect any miracles based on the other desperate people I found searching for this part. But when I did my AU-X1 if got original Sanken transistors shipped from overseas. But the source was a referral that I was told I could trust.

I searched AK for that part and found lots of sad stories also. "brutal" says he had some back in 2011. . .
 
FireGuruMN said:
A brief search of the internet found some 2012 searches from bmanone on some other websites. As for vendors there were many hits from Alibaba. I trust those about as far as I can throw the MX-1.
I did send an availability question to LittleDiode. I don't expect any miracles based on the other desperate people I found searching for this part. But when I did my AU-X1 if got original Sanken transistors shipped from overseas. But the source was a referral that I was told I could trust.

I searched AK for that part and found lots of sad stories also. "brutal" says he had some back in 2011. . .
Click to expand...

Bmanone got one of the last two remaining BA3122N NOS chips anyone knows about. He also most overly generously traded it for some unobtanium transistors that may someday be needed in my B-2x should it ever have a meltdown.

Sorry, but the one I have left as a spare for my MX-1 isn't up for grabs. If you review his post, you'll see we discussed donor amps (mostly AX series receivers) that have that HCA.

Sad to say, but I've been watching this thread and it's starting to become evident that this particular MX-1 is probably best used as a parts donor.
 
Just for curiosity I looks at the circuit for my MX-830. It appears to have a HCA built out of discrete components. But I don't want to go there.
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Has anyone gone down the Alibaba road?
 
I laid out a similar circuit on my bread board that was a hybrid between the one above and the circuit diagram (MX-830 HCA) for the BA3122N. It rang out similar but a bit off on the diode test between pins 1 though 9 (72 combinations). My breadboard connections are not stable enough to try in the MX-2 left channel. The next step is to make a prototype circuit board and try it out, but my efforts have stalled since brutal very generously traded me a replacement BA3122N. This is a fairly pricey possible solution, the four dual transistors alone are at least twenty dollars and are becoming hard to find.
I didn't have any success with Alibaba, they list them but when I inquired they were all out of stock.
Possible donor units that use the BA3122N ICs are: AX-730; AX-930; AX-1050; AX-1070; AX-1090; MX-2 & MX-1.
According to Yamaha USA the MX-1 was on sale for twelve years until 2005 and brutal had hard time getting this chip in 2011. What a shame!
 
FireGuruMN said:
Just for curiosity I looks at the circuit for my MX-830. It appears to have a HCA built out of discrete components. But I don't want to go there.

Has anyone gone down the Alibaba road?
Click to expand...

Since Alibaba is basically the (bigger) Chinese version of Amazon. I'd expect sourced parts are 99.9% fakes.

Better luck finding pulls from ebay or looking for one of those donors for sale as parts.
 
Thanks to all for the priceless information:D. I will keep my eyes open for places to salvage the unobtainium chip.
Until then I have a Pioneer Spec 4 with the lights on but no body home. Oh no, am I allowed to mention Pioneer in the Yamaha forum!:rockon:
 
And to answer my own previous question about what the letters mean after the transistor numbers I found this on another website:

https://www.electro-tech-online.com/threads/transistors-what-is-a-gr-bl-y-suffix.6082/

They are selected gain figures,

2SA970 - 200 min.
2SA970GR - 200/400
2SA970BL - 350/700

I wouldn't expect them to make a great deal of difference, there's still going to be a very high open-loop gain - it might make a very slight difference to the distortion figures, but nothing audible.

Just trying to fill my brain.
 
avionic said:
Most cases its Hfe ranking codes.
Click to expand...

FireGuruMN said:
And to answer my own previous question about what the letters mean after the transistor numbers I found this on another website:

https://www.electro-tech-online.com/threads/transistors-what-is-a-gr-bl-y-suffix.6082/

They are selected gain figures,

2SA970 - 200 min.
2SA970GR - 200/400
2SA970BL - 350/700

I wouldn't expect them to make a great deal of difference, there's still going to be a very high open-loop gain - it might make a very slight difference to the distortion figures, but nothing audible.

Just trying to fill my brain.
Click to expand...
 
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A very interesting post I saw on Epray recently.

Yamaha BA3122N IC Custom SMD PCB - MX1 MX2 AX730 AX930 AX1050 AX1070 AX1090 WOW!

I ordered one. But they seem a bit "wet behind the ears" based on the sellers description. Since there are SOOOO many other things wrong with my MX1 mine is probably not a good place to experiment with such products.

But if someone out there has one with just a chip failure or is willing to swap out a good chip then it might help the community of BA3122N starved technicians.
 
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