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Yamaha newbie A-700 resto thread

Nashou66 said:
Anyone else have something better from he these?
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I just ordered a buttload of these from china but haven't tried yet. The threads say so far so good from the folks that have used them...
IMG_20240306_173151.jpg

If ya wanna take your chances with NTE transistors. Check out NTE2576 & NTE2577. 60Mhz. Some folks have opinions about NTE & I understand. I've used them without issue. I was desperate.
EDIT: Just wanted to chime in on the 1306 & 3298 pairs cuz they're sooo hard to find. You're in good hands with @Nashou66
:lurk:
 
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All these devices I'll need to replace are testing fine on the other channel. Should I leave them alone? If there will be a big sound difference or other problem I don't mind replacing them if I need to.
 
analogwisdom said:
Thanks. I want to continue, I feel like I need to with the time I've already put into it.


I found these parts on eBay, I made sure to avoid China sellers. Should I buy these as replacements, or try to look for modern substitutes?

2SA1333
2SC3370 (R)

2SA1306A
2SC3298A

2SA1145

Here's what I found for the two burnt resistors. I believe these are the flame proof ones, please correct me if these won't be good substitutions:

R302 - CPF1220R00FKE36 (220Ω, 1W)
R394 - CPF21K8000FKE14 (1.8KΩ, 2W)
Click to expand...

For 2SA1333/2SC3370 I used 2SA1494/2SC3858 from bdent, and in the process also ordered many off eBay from "reputable" sellers but 100% of the eBay ones ended up being fake (you can tell if you weigh them).

I'm not sure where to find them now that bdent went under. I think some AK members stocked up before that happened, so if you make a WTB post in Barter Town someone may dig some out of their stash.

For 2SA1306/2SC3298 I used 2SA1837/2SC4793 also from bdent also not sure who might still carry them.

Wish I could help more. In my A-1000 repair I went through the process of chasing down blown channels more than once. I finally figured out I had a bad diode causing the problem!
 
Just looked over everything closely. R114 burnt up as well, missed that one earlier.

1709771369272.png

So my theory is that one of the mounted devices overheated and shorted out, sending too big voltage to these parts. I guess the flame-proof resistors did their job and committed sudoku, so no other parts past them died, but TR130 was caught in the crossfire and exploded, then R394 that's connected to that also died. Am I way off here? The thing that confuses me is that if this is the case, why aren't more parts blown up? I'm in over my head but I'm trying to figure it out.

analogwisdom said:
why aren't more parts blown up?
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Hmm, now that I think about it more, maybe by the time it reached parts that I feel like should be blown up, maybe there was added resistance somewhere so the voltage wasn't as big by the time it got to them? Or maybe I killed the power quick enough once the magic smoke started happening. I dunno...
 
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Also, I just wanted to say thank you to everyone who's taken the time to help me out and reply to my thread. I've read so many threads where people don't say thank you, so I just wanted to make it a point to do so. I really do appreciate it.
 
analogwisdom said:
Also, I just wanted to say thank you to everyone who's taken the time to help me out and reply to my thread. I've read so many threads where people don't say thank you, so I just wanted to make it a point to do so. I really do appreciate it.
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Well thank you for a good thread. It's good to see a young man put the smart phone aside and tear into some good ol fashioned analog Yamagoodness.
 
Thanks @avionic. I placed a Mouser order, my 4th one for this amp (lol). I'll probably be bugging you eventually. Hopefully replacing these devices and burnt resistors will be enough to bring the channel back to life. Then I still get to figure out why it was only working in Mono mode... :whip:

On the bright side, the Darlington Labs MM6B I've been waiting for since December is coming tomorrow. Very excited about that.
 
analogwisdom said:
Thanks. I want to continue, I feel like I need to with the time I've already put into it.


I found these parts on eBay, I made sure to avoid China sellers. Should I buy these as replacements, or try to look for modern substitutes?

2SA1333
2SC3370 (R)

2SA1306A
2SC3298A

2SA1145

Here's what I found for the two burnt resistors. I believe these are the flame proof ones, please correct me if these won't be good substitutions:

R302 - CPF1220R00FKE36 (220Ω, 1W)
R394 - CPF21K8000FKE14 (1.8KΩ, 2W)
Click to expand...
Good that you scanned the schematic, the HFE one that I was looking at is crap and I can't find R302 & R394.
If they are for sure 1W and 2W respectively then your CPF choices are good, I have used that series before, they are good.

2SA1333, 2SC3370. The above mentioned 1494/3858 are 200W parts, overkill but nice if you can find them. A better choice might be 2SA1493/2SC3857 150W parts. Note that both choices are 20mhz rather than the original 30mhz but that should not be a problem at all.
If you do not find any 1493/3857 anywhere in the USA contact me by Conversation.

2SA1145/2SC2705, as you asked, yes, I think that KSA1381ESTU/KSC3503DS will work. Mouser has them both.
https://www.mouser.de/ProductDetail/onsemi-Fairchild/KSA1381ESTU?qs=ljbEvF4DwOPBpIGy5LsaNQ==

Gotta go, friends just arrived, I'll be back.
James
 
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Bratwurst7s said:
Good that you scanned the schematic, the HFE one that I was looking at is crap and I can't find R302 & R394.
If they are for sure 1W and 2W respectively then your CPF choices are good, I have used that series before, they are good.

2SA1333, 2SC3370. The above mentioned 1494/3858 are 200W parts, overkill but nice if you can find them. A better choice might be 2SA1493/2SC3857 150W parts. Note that both choices are 20mhz iather than the original 30mhz but that should not be a problem at all.
If you do not find any 1493/3857 anywhere in the USA contact me by Conversation.

2SA1145/2SC2705, as you asked, yes, I think that KSA1381ESTU/KSC3503DS will work. Mouser has them both.

Gotta go, friends just arrived, I'll be back.
James
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The SM says they are 1/4 watt flame-proof resistors. Is it important that I match that rating? I didn't consider that. It makes sense that I probably should. I guess if they are bigger wattage than spec, they will not fail at the voltage they're supposed to?

and I already placed my Mouser order. Damn it.
 
analogwisdom said:
The SM says they are 1/4 watt flame-proof resistors. Is it important that I match that rating? I didn't consider that. It makes sense that I probably should. I guess if they are bigger wattage than spec, they will not fail at the voltage they're supposed to?

and I already placed my Mouser order. Damn it.
Click to expand...
It is absolutely important to match the 1/4W rating. Otherwise it's like putting a penny under a screw in fuse.
 
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