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JBL SA600 preamp transistor help.

daveyh

daveyh

Super Member
I am working on a JBL SA600 amplifier and it has a built in pre-amplifer. I have recapped the amplifier section and I would like to replace the current transistors in the preamp board with new in case some of them are bad. The ones which read:

12593 and 12594

The NTE equivalent is:

12593 = NTE 123AP
12594 = NTE 159

That is all the information I can find. Does anyone have any idea as to where to find a substitute besides NTE?
 
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Why do you want to replace those transistors? Do you have a curve tracer, do you have any reason to believe they are out-of-spec in any way?
 
I have not got there yet. Still recapping the pre-amp board. Trying to find replacements is case some are bad. I have corrected my first post. Thanks.
 
I am confronted with the same problem here....trying to find a substitute for the 12593. My first stop usually is the KSC1845 considering this is an NPN small signal transistor. However, since all we have to go by is the specs for the NTE123AP, the KSC1845 does not match up well. The NTE123AP specs as Ic=.6A, dissipation of .625 watts. The KSC1845 specs as Ic=.15A, dissipation of .4 watts. Looks like the KSC1008 is a better choice - .7A, .8 watts. What do you all think?
 
I went ahead and installed the KSC1008. The amp works normally again. Voltages around this transistors are correct, and fidelity is restored. Not saying this substitute will work in all cases, but in the SA-600 it is a good substitute for the 12593.
 
From some research of others who have replaced these transistors the following is suggested- NPN- 2N5827/PNP 2N6003/BC550

I have not tried these- but hope this helps,I think many low noise types could be suitable
 
Thanks, pwauk12......I think I'll leave the KSC1008s in there. I have had the unit running for many hours, and no problems.
 
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