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Old 8th June 2009, 02:10 PM   #1
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Angry Fried Reel To Reel tape recorder

I was calibrating the record and play levels on my Akai 4000DS mk II Reel to Reel tape recorder, and I accidentally shorted something out and fried at least one of the transistors! I need to find some replacements, but don't know where to go, can anyone help? I don't yet know witch ones are fried, but if I replace them all I know I'll get it working again.

these are the transistors I need:

C1312
C458
C1647

It's quite an old machine, from 1972, so I don't know if those particular transistors are still in production. Can anyone tell me where I can get them? Or where I could get suitable substitute replacements?

I've added a picture to help identify them.
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Old 8th June 2009, 02:51 PM   #2
oshifis is offline oshifis  Hungary
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You can find the datasheets by referring them as 2SC1312, 2SC1647 and 2SC458, respectively. The leading 2S is just not printed on the body. I think they are all small-signal, small-voltage NPN transistors, and you can replace them with 2N2369 or BCY58 or the like if you identified the pinout.
Before replacing them, I'd measure them for short-circuit or even better for h21e using a DMM that is capable of such measurement. As a simple test, the B-E and B-C should behave as a diode, the C-E should be open circuit, measure with a DMM in 2kohm range. Test them off-circuit.
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Old 17th May 2014, 08:30 PM   #3
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Use BC550 for all of them. The higher current gain will lower distortion. If any are rated for more than 100mA then use BC337/327.

Get a CD player - design your own audio.
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With perfect linearity, it is impossible to go off on a tangent. Also; My Sziklai pairs are better than your MOSFETs/Darlingtons/Pentodes/Triodes
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Old 17th May 2014, 09:32 PM   #4
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Quote ~"The higher current gain will lower distortion."

This interesting.

It seems that I have read this some where before.

I have had and probably still to do have a few of those numbers in my parts bin from chassis I have stripped.
I remember all of those numbers from the days of repairing stuff in the 80's.

Unless it has to be a really low noise type then most any type may work well.

You can find the service Manual here,

http://www.hifiengine.com/manual_lib...i/4000ds.shtml

Good Luck !!

jer

Last edited by geraldfryjr; 17th May 2014 at 09:35 PM.
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Old 17th May 2014, 09:56 PM   #5
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I always used to use BC548 transistors when repairing old equipment (I used to nick 'em from the electronics department at school). That and new caps which I'd bought myself. Panasonic FC series are very reliable. Some of the ones I used to pull out were less than a fifth of the rated capacitance!

A higher current gain is always better as it translates to more open loop gain allows more accurate correction of non linearity. Especially the single transistor gain stages you'd find in archaic equipment from the early 70's. BC550s have 500+ beta and are the cheapest on RS. They also have much lower noise than any of the transistors you'd find in equipment from that era.

Any modern general purpose NPN will do the job nicely.
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With perfect linearity, it is impossible to go off on a tangent. Also; My Sziklai pairs are better than your MOSFETs/Darlingtons/Pentodes/Triodes
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