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Akai Professional GX-4000D
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Akai Professional GX-4000D

Multipiste analogique de la marque Akai Professional appartenant à la série GX

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Sujet Réparation transistors + condo

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1 Réparation transistors + condo
Bonjour,

j'ai une des deux pistes qui a des bruits parasites..Bref je vais refaire un petit recapping dessus + transistors etc...Alors j'aimerai savoir quelle transistors mettre et dans quel sens (BCE etc..) bien évidemment. Idéalement serait de pouvoir les mettre dans le meme sens.

Merci d'avance

Ludo

Cutting Edge

2
Transistors pour Akai DS4000

Something I noticed though was that transistors designated 2SC458 could be either a square package with a sloped top or cylindrical with a flat front. It confounded me at first because oddly, their pin outs were mirror images of each other.




how would one know what the designations with same # transistors that exist with different pinouts?

Your meter is your friend. Takes about 15 seconds to determine which lead is the base. I always check as a sanity check when replacing transistors.
Meter in diode test ohms.
NPN + lead on one lead conducts to the negative lead on either of the other leads - that lead is the base. Reverse it for PNP.

https://audiokarma.org/forums/index.php?threads/top-ten-worst-transistors-noisy-failure-prone-whatever-and-replacements.731653/page-3

They've got black legs so reason enough to change them as far as I'm concerned.

FWIW and if I remember correctly, one occasion when I went to replace some of those, I discovered that the pin out of the original sloped top Hitachi's is opposite that of a later TO92 version !
I noticed this thing with reversed pins of same transistors from different period.

Actually the 2SC1815/ KSC1815 is a much closer sub than a KSC1845.. As in exact replacement.

https://audiokarma.org/forums/index.php?threads/are-there-any-good-versions-of-the-2sc458.725020/

« I think the older outhouse sc458 do have opposite pinouts from what some might be finding in the current datasheets. Do check your pinouts... « 

From what I have been able to investigate, the slant front c458s are marked on the back of the transistor. The TO-92s are marked on the front of the transistor. For this reason they appear to have different pin outs but they are the same when the transistors are positioned properly. The fact that the slant front tranny has the label on the back is confusing. Can I get any confirmation of this? Hard to find a datasheet for the old style transistor.
Confirmed !
https://audiokarma.org/forums/index.php?threads/so-2sc458-has-the-upper-hand.758586/

ziq : sinkmusic.com | drum samples : waveshaper.org

3
Like some other Akai's from the same era (215, 255, 620, 625 and 635) the GX-4000D also suffers from faulty
2SC458 transistors in de audio amplifier board. These transistors usually turn bad after 20 25 years or so.
This leads to audible hiss only in playback and/or recording amplifiers. The best way to solve the problem is
to replace these transistors.

ziq : sinkmusic.com | drum samples : waveshaper.org

4
Merci à toi en tout cas. I've invested into a capacitor reader, it will be easier for me. I do not have much skills in reading electrical diagram etc..Thank again for helping me =).

Cutting Edge

5
Avec plaisir, you're welcome :)

ziq : sinkmusic.com | drum samples : waveshaper.org