Beomaster 901 TR1 in FM : MPF120

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aragorn83 Posted: Sat, Dec 18 2021 2:48 PM

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Hi all,

initialy I have problem similar of this topic : https://archivedforum2.beoworld.org/forums/t/35755.aspx

I change caps and some resistance and it's works BUT FM is not normal... 

As i have 2 Beomaster i can identify the guilty :)

In FM section, the Dual Gate MOFSET TR1 ( MPF120) doesn't work, i switch with the other beomaster 901 (who works fine)

So i need to change it but it seem not very common... in fact in my second beomaster it a RCA 605 40822 but same thing... i can't really find it.

Someone know with which parts i can change it ?

Thanks a lot :)

(soorry for my english, i'm french ! )

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Dillen replied on Sat, Dec 18 2021 3:08 PM

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RCA 40822 can be found on Ebay
https://www.ebay.de/itm/203085023724
(I don't know and have never dealt with this seller).

MPF120 can also be found:
https://www.ebay.de/itm/174312361573

Martin 

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aragorn83 replied on Sat, Dec 18 2021 3:12 PM

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Thanks ,

For 40822  15€ for 2 

For MPF120 22€ for 1

i think it's too expensive.

there is no equivalent transistor more common i can use ?

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Dillen replied on Sat, Dec 18 2021 4:15 PM

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You can buy the correct parts.
That's a good price, I think.

But of course, it's for you to decide.

Actually, I was surprised to find them on Ebay, so if you don't buy them, I could feel tempted, just to have them in the drawer.

Modern mosfets usually have a much higher gain, requiring a bit of circuit redesign, and it's rare to see dual-gates used today anyways.
But go ahead if you prefer, - take your time and look around for something with similar specs to the originals.
Do let us know if you find something.

Martin

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aragorn83 replied on Sat, Dec 18 2021 5:06 PM

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Thanks a lot for your response and good advice, as always ! :)

I found this : https://picclick.fr/3-x-RCA-3N204-273077271460.html

description : "RCA 3N204 Dual Gate MOSFET 40673 40822 3N201 remplacement Transistor" i don't know if it will help me or not.

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Dillen replied on Sat, Dec 18 2021 5:58 PM

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Here on Ebay:
https://www.ebay.de/itm/402290096014

Not exactly cheaper...
I never tried that type, so I cannot say if it'll work. But you could try.

Martin

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aragorn83 replied on Tue, Jan 4 2022 10:31 PM

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hi,

so i decide to buy 2 3N204 on aliexpress for 8,30€ include 4€ of 15 days delivery.

Now the FM works normaly; i listen radio for 2hours in stereo and a perfect sound for any station.

i'm happy :)

For the moment, I confirm that it works to spare with a 3N204

Thanks and see you soon certainly for help with my other repair project :)