Blown mje350 and led [REPAIR VID AT END] [resolved]

Rob C · 150150

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Offline Rob C

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Reply #15 on: November 09, 2023, 06:25:36 PM
MJE5731A looks discontinued.  Recommend a sub? Think ebay has genuine?


Offline sl-15

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Reply #16 on: November 10, 2023, 03:50:42 AM
Nicely done with the mod, thanks for sharing.
I bought some transistors on eBay once for my Foreplay and they crapped out after a month or so. If you do all that work I would spend a few more bucks and order from a reputable seller even if shipping is higher in the end than the parts.
This seems to be the same the only difference that I saw is the Watt rating which is 50 instead of 40: MJE5731AG

https://www.mouser.com/c/?q=MJE5731A

But Paul will know better, in case I am wrong.
« Last Edit: November 10, 2023, 03:55:00 AM by sl-15 »

Stefan Hampel
Soundsmith Carmen, modded Technics SL-1200mkII, Thorens TD 125 mk2 with SME V, Eros, Extended Foreplay III, BeePre2, Crack, Pioneer Spec 4, Sonus Faber Electa

Offline Rob C

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Reply #17 on: November 10, 2023, 09:26:51 AM
I really appreciate all the help and knowledge.  I could however benefit from a parts list. I could make one but I don't know the zener diode part. I'd assume there are different ones? Thank you.


Offline Paul Birkeland

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Reply #18 on: November 10, 2023, 02:32:08 PM
Quote from: Rob Capizzi on November 09, 2023, 06:12:44 PM
Good to know. Thank you. can I buy what I need from BH?
We no longer use or stock the 2N2907, so this is probably a better order for Mouser.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Paul Birkeland

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Reply #19 on: November 10, 2023, 02:33:30 PM

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Rob C

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Reply #20 on: November 10, 2023, 03:20:48 PM
Thank you everyone!


Offline Rob C

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Reply #21 on: November 13, 2023, 06:59:59 AM
Ohm question. I have sonus faber concertino and concerto. Thoes are 6ohm. I assume there shouldn't be a problem there hasn't been for over a year. I have to look if the opt is wired 4 or 8. Which is recommended?


Offline Paul Joppa

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Reply #22 on: November 13, 2023, 07:11:15 AM
Quote from: Rob Capizzi on November 13, 2023, 06:59:59 AM
Ohm question. I have sonus faber concertino and concerto. Thoes are 6ohm. I assume there shouldn't be a problem there hasn't been for over a year. I have to look if the opt is wired 4 or 8. Which is recommended?
"Which is recommended?"

I recommend the one that sounds better to you.

:^) Both are reasonable choices from a technical perspective. But they will interact differently with the speakers, and the differences will likely be audible.

Paul Joppa

Offline Rob C

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Reply #23 on: November 13, 2023, 07:28:58 AM
Quote from: Paul Joppa on November 13, 2023, 07:11:15 AM


:^) Both are reasonable choices from a technical perspective. But they will interact differently with the speakers, and the differences will likely be audible.

Ok thought so, thank you.  I've obviously googled it a bunch. I went to 4 ohms on the dynaco vta st120. I like it.


Offline Rob C

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Reply #24 on: November 13, 2023, 07:30:39 AM
Since I'm replacing both 12at7, I'm looking at matched JJ. Any reason not to?


Offline Paul Birkeland

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Reply #25 on: November 13, 2023, 07:41:20 AM

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Rob C

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Reply #26 on: November 13, 2023, 07:46:05 AM
Nice find. Thank you. Bid is in.


Offline Rob C

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Reply #27 on: November 13, 2023, 07:51:20 AM
Once all the new components and tubes are in should I start the amp with a variac and take measurements or just turn it on with fingers crossed?


Offline Rob C

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Reply #28 on: November 14, 2023, 04:05:16 AM
On the mje350
1.emitter
2 collector
3 base
MJE5731g
1 base
2 collector
3 emmiter
So I will install backwards.


Offline Rob C

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Reply #29 on: November 14, 2023, 04:20:47 AM
The MJE5731G I ordered is 350v
There is an mje5731AG that's 375v and available.
Should I have ordered the MJE5731ag ?
https://www.mouser.com/ProductDetail/onsemi/MJE5731AG?qs=R2UZ7gjkEjIIBIrVFKMX3w%3D%3D


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