Hi guys,
Recently I've been trying to fix the yamaha cr-220:
Please see schematic
Blown transistors are:
TR712 (2SA844)
TR716 (2SC1175)
TR717 (2SA659)
I've replaced them with European BC557 and BC547.
I think of replacing also the complimentary drivers (TR715, TR718 - marked 818 by mistake in the schematic diag.)
Been testing it for several hours and the amp seems work really nice at the moment.
I'm wondering if maybe there are better replacements for this kind of amp?
Im thinking:
KSA992/KSC1845 OR
KSA1013/KSC2383
1) Should I replace the complimentary driver transistors even though everythig seems to sound fine?
2) Should I use any of the transistors above or should I look at other options? If so, What are they?
3) Any opinions regarding the amp in general or this specific repair?
Thanks,
Liquias.
Recently I've been trying to fix the yamaha cr-220:
Please see schematic
Blown transistors are:
TR712 (2SA844)
TR716 (2SC1175)
TR717 (2SA659)
I've replaced them with European BC557 and BC547.
I think of replacing also the complimentary drivers (TR715, TR718 - marked 818 by mistake in the schematic diag.)
Been testing it for several hours and the amp seems work really nice at the moment.
I'm wondering if maybe there are better replacements for this kind of amp?
Im thinking:
KSA992/KSC1845 OR
KSA1013/KSC2383
1) Should I replace the complimentary driver transistors even though everythig seems to sound fine?
2) Should I use any of the transistors above or should I look at other options? If so, What are they?
3) Any opinions regarding the amp in general or this specific repair?
Thanks,
Liquias.
The BC range you chose is rated up to 50volts, there is more than that across the rails, to which they will see when you crank it up!
Always fit the designers specified parts, for reliability unless of course, you know more than the designer does about parrameters and the required specifications that is.
Never buy from suppliers that are not verrified; fleabay, anazun etc.
BC557/547 are obsolete types.
Always fit the designers specified parts, for reliability unless of course, you know more than the designer does about parrameters and the required specifications that is.
Never buy from suppliers that are not verrified; fleabay, anazun etc.
BC557/547 are obsolete types.
OK,
1) I don't see more than 50V, I think there are only about 30v in these rails, but,
2) BCs are obsolete, and other considerations included, what are some recommended replacements?
Original components are also obsolete of course.
1) I don't see more than 50V, I think there are only about 30v in these rails, but,
2) BCs are obsolete, and other considerations included, what are some recommended replacements?
Original components are also obsolete of course.
KSA992/C1845
Considered low noise with higher voltage rating
if I remember in the 100 volt range so Ft is should be reasonable around 100 MHz
The grading system for gain is different, as with most the highest grade is highest gain.
Hfe should be over 160 for higher grades.
Not much point in using them unless amplifier voltages require it.
Same with 1013/2383
Voltage is higher and Ft is likely a tradeoff.
No need to use them.
Doesn't seem like the originals are much more than 50 to 55 volts
So the BC varieties mentioned should have faster Ft and good gain.
Usually 150 MHz
Should follow typical A,B,C gain ratings C grade or B grade ideal for higher gain.
C grade highest gain
BC556 / 546 Vceo should be 65 volts , 10 volts more than originals
B or C grade gain being ideal.
For high voltage most just use 2N5551/5401
Since they dont trade off as much speed for higher voltage than other variants.
Should remain well up to 160 to 300 MHz
with typical B grade gain, unless noted.
OnSemi still makes all the BC and 2N transistors mentioned
long as you dont damage traces de soldering. No harm changing transistor.
Of course if they havent failed or have not gone noisy.
No loss no benefit
Unless of course better matched pairs are used, and you hunt down all C grade
and match them. Could exceed what the factory put in there, who knows.
Considered low noise with higher voltage rating
if I remember in the 100 volt range so Ft is should be reasonable around 100 MHz
The grading system for gain is different, as with most the highest grade is highest gain.
Hfe should be over 160 for higher grades.
Not much point in using them unless amplifier voltages require it.
Same with 1013/2383
Voltage is higher and Ft is likely a tradeoff.
No need to use them.
Doesn't seem like the originals are much more than 50 to 55 volts
So the BC varieties mentioned should have faster Ft and good gain.
Usually 150 MHz
Should follow typical A,B,C gain ratings C grade or B grade ideal for higher gain.
C grade highest gain
BC556 / 546 Vceo should be 65 volts , 10 volts more than originals
B or C grade gain being ideal.
For high voltage most just use 2N5551/5401
Since they dont trade off as much speed for higher voltage than other variants.
Should remain well up to 160 to 300 MHz
with typical B grade gain, unless noted.
OnSemi still makes all the BC and 2N transistors mentioned
long as you dont damage traces de soldering. No harm changing transistor.
Of course if they havent failed or have not gone noisy.
No loss no benefit
Unless of course better matched pairs are used, and you hunt down all C grade
and match them. Could exceed what the factory put in there, who knows.
Last edited: