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    Transistor issue sony TC-280

    I`m currently working on a Sony TC-280 Reel to Reel and I`m looking to swap out the noisy transistors.

    They are , 2sc631a , 2sc632a and 2sc634a .

    I know I would have to rotate them clockwise one hole but could I use BC107b`s in there ? I have a load of them here so would be easier .

    Hope this isnt a daft question , I`m still learning .

    Thanks for any help .

    #2
    Re: Transistor issue sony TC-280

    Answer is "Who knows."

    Sometimes it will work, sometimes it won't. Without knowing the transistor's biasing circuit, it's hard to tell. From a cursory search, other than the pinout issue as you said, it looks like it should work... but no guarantees...

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      #3
      Re: Transistor issue sony TC-280

      I personally prefer to replace transistors with exact replacement. It may be less costly for you to use what you have but if you want to do a proper job spend a little. They are not that expensive. 2SC transistors are silicone are the BCs you have silicone or germanium??

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        #4
        Re: Transistor issue sony TC-280

        They're both silicon.

        I think the main reason for swapping them versus using NOS is that historically these old 2sc631s are noisy transistors, and in hifi equipment, this is not acceptable.

        I saw another site suggesting using KSC1845s but they need to be hand picked for gain. The BC107B seems like they were already binned for the use, so they may just work. But there's no way to tell for sure without either trying or studying the circuit.

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          #5
          Re: Transistor issue sony TC-280

          I woundn't replace a 2SCxxxx with a BCxxx in any of my amps.

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            #6
            Re: Transistor issue sony TC-280

            Why's that? pinout? case? something else?

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              #7
              Re: Transistor issue sony TC-280

              Replacements for 2SC631 I would use 2SC2240, KSC1845 as low noise transistors.
              Don't cheap out on tape head preamp parts, the hiss will drive you crazy. Why would you put crapola BC's in there.

              The 2SC634 is a Sony only part, it did not seem as critical so I would use the same 2SC1845 or 2SC1815.

              Sony TC-280 schematic

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                #8
                Re: Transistor issue sony TC-280

                Originally posted by redwire View Post
                Replacements for 2SC631 I would use 2SC2240, KSC1845 as low noise transistors.
                Don't cheap out on tape head preamp parts, the hiss will drive you crazy. Why would you put crapola BC's in there.

                The 2SC634 is a Sony only part, it did not seem as critical so I would use the same 2SC1845 or 2SC1815.

                Sony TC-280 schematic
                you must never have come across bc550c and bc549c ..both low noise .

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                  #9
                  Re: Transistor issue sony TC-280

                  Originally posted by eccerr0r View Post
                  Why's that? pinout? case? something else?
                  as redwire already said and I fully agree with his last post: El cheapo, crapola dinky transistor. It is correct that the BCxxx may work on some, but at the end of the day that crap would not be in my amp. Just saying...
                  A KSC1845 would be the proper replacement. Some may need to be put in backwards, so always compare the pinouts.
                  Last edited by CapLeaker; 07-15-2018, 03:29 PM.

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                    #10
                    Re: Transistor issue sony TC-280

                    Which make were you thinking? I've never seen the BC550C's used in audio gear.
                    NXP calls BC550 NPN general purpose transistors, On-Semi BC550C Low Noise Transistors, but no noise figure graphs.

                    Japanese discretes are the best in the business- too bad they obsolete them every year and make something new.

                    It depends on how good OP wants his repair.

                    I got literally thrown out of a recording studion for using TI NE5532 in place of Philips NE5532 op-amps, on a Studer reel-reel machine. The TI parts are shit and much noisier than Signetics/Philips parts.

                    People blow up the tape head pre-amp when demagnetising the tape heads.
                    The high voltage AC can do it if you put the demagentizer close to the head, transformer action.

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                      #11
                      Re: Transistor issue sony TC-280

                      Hmm maby it's just my opinion but the Sony 2SC634A in a tape recorder such as the 280, can be replaced by the Panasonic 2Sc1815 or the NTE 85 (never tryed the NTE one).

                      Sincerely
                      The DaneDude

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                        #12
                        Re: Transistor issue sony TC-280

                        Originally posted by iksDK View Post
                        Hmm maby it's just my opinion but the Sony 2SC634A in a tape recorder such as the 280, can be replaced by the Panasonic 2Sc1815 or the NTE 85 (never tryed the NTE one).

                        Sincerely
                        The DaneDude
                        Just checked my memorycircuit or the one i didn't have lol.. The correct NTE-cross for 2SC634A is NTE-293, the 85 one is for the 2SC631A

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