Transtube 212 EFX

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Guitarwannabe918
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Transtube 212 EFX

Post by Guitarwannabe918 » Fri Jan 21, 2022 4:04 am

Can anyone tell me if Q3 and Q6 is a NPN? or PNP transistor?

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Enzo
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Re: Transtube 212 EFX

Post by Enzo » Fri Jan 21, 2022 1:48 pm

In the preaamp or in the power amp? The preamp has many darlington pairs of small transistors, they are all NPN.

I am guessing from context you mean the power amp output devices, so:

Q3 is a 70483100 Industry type MJ15016

Q6 is a 70473100 Industry type MJ15015


Don't have those? I'd probably just use MJ15024 and MJ15025 and never look back.

What is wrong with your amp?

Guitarwannabe918
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Re: Transtube 212 EFX

Post by Guitarwannabe918 » Fri Jan 21, 2022 2:04 pm

The volume starts cutting out on the dirty side of the amp. Cut out bad then it will come back really strong and loud.

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Enzo
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Re: Transtube 212 EFX

Post by Enzo » Fri Jan 21, 2022 8:48 pm

Well, anything is possible, or course, but that really is not likely a bad transistor.

Oh and I neglected to tell you the Q3 is NPN and Q6 is PNP.

Your description is usually due to dirty jacks. On the rear panel are two pairs of jacks. One is the FX loop, the other is the Preamp Out and the Power Amp In jacks. Electrically dirty internal contacts can cause your symptom. Plug a spare cord from Preamp Out to Power amp in. Any help? Also try the same trick in the FX loop send and return jacks. If either of those helps, then the return jack needs service.

Randy Ortigo
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Re: Transtube 212 EFX

Post by Randy Ortigo » Mon Oct 24, 2022 1:26 pm

Thanks for allowing me to be on this form I have and transistor question.
Is a 70483100 a NPN or aPNP and the same on a 70473100.
I also have an Express 112 that I need a schematic for.
The circuit board has
Express 112/Studio Pro 110. The Ser# on the tag is
00-05633201
Any information would be helpful just trying to repair an amp for a friend of mine.

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Pappy B
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Re: Transtube 212 EFX

Post by Pappy B » Tue Oct 25, 2022 10:22 am

70483100 is a NPN and 70473100 is a PNP.

For other cross reference's try searching for Peavey Semi-conductor/Transistor Cross Reference. It's pretty handy.
The more I learn the more I realize how much I don't know.

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