Hi Everyone,
Bit of a novice her, but enjoying trying to fix junk old amplifiers, especially with the helps from you guys.
I have a Scott A417, where the output & driver transitors are complete toast on one channel, together with a whole bunch or resistors in the near vicinity. Also all 4 diodes on the rectifier are burntout, so this amp is a complete basket case.
Taking this opportunity I intend to change all the transistors on the power board, caps & of course all burnt resistors. There are a couple of antiquated low power transistors 2SC374 & 2SA495, where I can't find any equivalent transistors referring to on-line sites for equivalence, I guess this is because of their body type (TO98-1), but really the form or shape of the transistor isn't important as they are all free standing off the board.
These transistors both have very low Vce & Vcb voltage ratings compared to modern available types & hFE of 40.
Question. I presume the key important parameter for their replacement is the amplification factor (hFE), so maintaining the same value of 40. Is this correct ?
Also practically would fitting transistors with (much) higher max voltage ratings & collector current be an issue, or is it better to try to find ones with similar ratings ?
Many thanks,
Bit of a novice her, but enjoying trying to fix junk old amplifiers, especially with the helps from you guys.
I have a Scott A417, where the output & driver transitors are complete toast on one channel, together with a whole bunch or resistors in the near vicinity. Also all 4 diodes on the rectifier are burntout, so this amp is a complete basket case.
Taking this opportunity I intend to change all the transistors on the power board, caps & of course all burnt resistors. There are a couple of antiquated low power transistors 2SC374 & 2SA495, where I can't find any equivalent transistors referring to on-line sites for equivalence, I guess this is because of their body type (TO98-1), but really the form or shape of the transistor isn't important as they are all free standing off the board.
These transistors both have very low Vce & Vcb voltage ratings compared to modern available types & hFE of 40.
Question. I presume the key important parameter for their replacement is the amplification factor (hFE), so maintaining the same value of 40. Is this correct ?
Also practically would fitting transistors with (much) higher max voltage ratings & collector current be an issue, or is it better to try to find ones with similar ratings ?
Many thanks,
You could likely use jellybean 2N3904/2N3906, or whatever you might happen to have laying around. Just be careful of pin out, some old jap types were ECB, others were BCE (and 2N types are EBC).
Sorry a bit of mis-information here, 2SC374 has a hFe min 350, not 40.
Still struggling to find anything except much high power rating ones.
Still struggling to find anything except much high power rating ones.
1. Based on Max power dissipation, decide proper package and pinout that you desire.
2. Check Max continuous Ic
3. Check Max Vce
Usually, hFe is not the criteria among those. Without the circuitry, generally, I would say the higher the better.
2. Check Max continuous Ic
3. Check Max Vce
Usually, hFe is not the criteria among those. Without the circuitry, generally, I would say the higher the better.
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