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Old 10th June 2012, 11:14 AM   #11
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Littlediode aren't cheap but for one offs they are sometimes the last resort - other than E-Bay.
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Old 13th June 2012, 11:54 PM   #12
tomst is offline tomst  United Kingdom
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After some more testing and inspection it seams the out put transistors are blown and not he drive transistors. The originals are RCA16006 (2n3055). Am i best to replace it with the same 2n3055 or it there a drop in replacement that would be better. there are a few different versions of the 2n3055 and it looks like the main difference is the Maximum operating frequency (Ft) 2n3055(2.5MHz), 2n3055E (3MHz) or 2n3055H(0.8Mhz). I also Believe there is the option of using a TIP3055 which looks to have the same specs as the 2n3055E but this may require a circuit modification.

Thanks
Tom
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Old 14th June 2012, 08:43 AM   #13
tomst is offline tomst  United Kingdom
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The circuit diagram is at the start of this thread.
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Old 14th June 2012, 11:08 AM   #14
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Quote:
Originally Posted by tomst View Post
Hi
I have a leak Stereo 30 plus and have just burned up a BC142 (T8 on the diagram) drive transistor due to a worn out trim pot. The mentioned transistors are getting quite difficult to find. Does anyone have any ides as to a good replacement for both. The output transistor on this amp is is the RCA16006 (same as 2n3055 i believe)
thanks
Tom
I think, it is the same model than the showed by post #80 about
2N3055 inside - commercial famous amplifier models, quasi complementary power output

I would try the available versions from Magnatec, available by RS components:
Buy General Purpose Transistor PNP transistor,BC143 1A Magnatec BC143 online from RS for next day delivery.
Buy General Purpose Transistor NPN transistor,BC142 1A Ic 2Vce Magnatec BC142 online from RS for next day delivery.
For datasheet ask here:
sales@semelab-tt.com

If you observe unwanted oscillation effects, check C3 and C37 for compensation.
I miss the miller capacitor between C and B of the BC117 (T7). Maybe present and only a missprint in the schematic.

Quote:
Originally Posted by tomst View Post
After some more testing and inspection it seams the out put transistors are blown and not he drive transistors. The originals are RCA16006 (2n3055). Am i best to replace it with the same 2n3055 or it there a drop in replacement that would be better. there are a few different versions of the 2n3055 and it looks like the main difference is the Maximum operating frequency (Ft) 2n3055(2.5MHz), 2n3055E (3MHz) or 2n3055H(0.8Mhz). I also Believe there is the option of using a TIP3055 which looks to have the same specs as the 2n3055E but this may require a circuit modification.

Thanks
Tom
Today's 2N3055 are not suited to replace vintage versions. Use therefore the MJ21194 - go to
http://www.onsemi.com/pub_link/Collateral/MJ21193-D.PDF

check also this thread:
2n3055 amp claims 200 to 220 watt

Last edited by tiefbassuebertr; 14th June 2012 at 11:25 AM.
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Old 14th June 2012, 03:22 PM   #15
tomst is offline tomst  United Kingdom
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after a while I did find some new old stock RCA-2n3055H. From my research the H is the correct for this application. It has the same frequency transition (ft) as the 2n5056 also noted in the circuit diagram. It does seam little slow 0.8MHz compared to most modern transistors like the MJ21193. I am little confused as to what the H stands for some say high power some don't say anything and just note it as 0.8MHz.
If i was to go with say the MJ21193 would i need to do any modifications? I read that when these faster transistors are used in vintage equipment some people have put a 20pf capacitor between base and emitter to reduce oscillations.
Thanks
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Old 14th June 2012, 03:39 PM   #16
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Quote:
Originally Posted by tomst View Post
I am little confused as to what the H stands for some say high power some don't say anything and just note it as 0.8MHz.
Thanks
Anywhere in the first or the last URL from my previous post you will find that information.
Check out also this thread:
Vintage Transistors
so as post #20/21 about
Citation 12 Substitute Transistors

Last edited by tiefbassuebertr; 14th June 2012 at 03:44 PM.
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Old 14th June 2012, 05:37 PM   #17
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check also this:
Motorola 2N3055 info and counterfeit watch
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Old 14th June 2012, 05:42 PM   #18
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The 2N3055E and 2N3055H are very different. The H is the more difficult one to obtain, the common one is the E variant. I believe that the TIP3055 is modelled on the E variant.
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Old 14th June 2012, 08:57 PM   #19
wahab is offline wahab  Algeria
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Whatever the transistors used this amp would surely gain the most
by increasing the output capacitors from the meager 1000uF to a more
adequate 4700uF....
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