Hello everybody.
I'm looking for the following transistors (to try to repair 2 Yamaha amplifiers):
2SD845 + 2SB755 (Yamaha A-760);
2SA663 + 2SC793 or 2SA745 + 2SC1403 (Yamaha Ca-610).
Can you recommend one or more "reliable" sellers where to buy them?
On ebay, aliexpress etc etc there are many fake branded Toshiba and Sanken, for this reason I ask the experts for advice.
Thanks in advance for any suggestions ...
Rob
I'm looking for the following transistors (to try to repair 2 Yamaha amplifiers):
2SD845 + 2SB755 (Yamaha A-760);
2SA663 + 2SC793 or 2SA745 + 2SC1403 (Yamaha Ca-610).
Can you recommend one or more "reliable" sellers where to buy them?
On ebay, aliexpress etc etc there are many fake branded Toshiba and Sanken, for this reason I ask the experts for advice.
Thanks in advance for any suggestions ...
Rob
Equivalents also must be there.
You can first find the European parts numbers, and the American ones. Also, if needed, go for the next higher rating, and if cheap, buy extra, in case they blew up because of other fault, so the new ones might go too.
Then check with the parts suppliers like Digi-Key, element14, others.
Whoever you have experience with, and gives the best price delivered to your location.
Then get those, and enjoy the music.
You can first find the European parts numbers, and the American ones. Also, if needed, go for the next higher rating, and if cheap, buy extra, in case they blew up because of other fault, so the new ones might go too.
Then check with the parts suppliers like Digi-Key, element14, others.
Whoever you have experience with, and gives the best price delivered to your location.
Then get those, and enjoy the music.
@NareshBrd: thanks for the quick reply.
2SD845 + 2SB755 (Yamaha A-760) = 2SC2565 + 2SA1095?
2SD845 + 2SB755 (Yamaha A-760) = 2SC2565 + 2SA1095?
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For the sa663 / sc 793 pair I could also use the BD245C / BD246C pair?
although I doubt the sonic result is similar.
although I doubt the sonic result is similar.
The sa663 / sc 793 pair are conventional transistors in TO-3. Can be replaced with 3055/2955. You can TIP41C / 42C. You can use BD245C / BD246C.
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OldDIY thanks.
the 2N3055/MJ2955 they are also easily found in Hungary 😀.
after the power transistors have been replaced, does the amp need no modifications or adjustments?
Rob
the 2N3055/MJ2955 they are also easily found in Hungary 😀.
after the power transistors have been replaced, does the amp need no modifications or adjustments?
Rob
and the idling current value must be equal?
same as if the original / obsolete transistors were fitted?
in this specific case 11 mV (+ -2mV).
Rob
same as if the original / obsolete transistors were fitted?
in this specific case 11 mV (+ -2mV).
Rob
Both drivers
Emitter resistors
All components in the bias stack
Any resistors between base and emitter of drivers or outputs
Base stoppers (if they exist)
All components in the VI limiters (if they exist)
Should all be considered suspect and individually checked. Any could cause repeat failure. If there was a fire on the PCB I would usually change them *all*, in addition to cleaning all the carbon off the board. If the failure were more gentle, I would only replace what went bad - but check them all.
Emitter resistors
All components in the bias stack
Any resistors between base and emitter of drivers or outputs
Base stoppers (if they exist)
All components in the VI limiters (if they exist)
Should all be considered suspect and individually checked. Any could cause repeat failure. If there was a fire on the PCB I would usually change them *all*, in addition to cleaning all the carbon off the board. If the failure were more gentle, I would only replace what went bad - but check them all.
In the Yamaha CA-610 the original transistors are 2SA663/2SC793.
The previous owner replaced a pair of these transistors (a channel) with 2SA757/2SC1030.
There are no signs of bursts or burns, or other components in critical conditions.
The 2SA663/2SC793 that are on the market to 99% are fake so I would like to mount 2 pairs of equal complementary transistors (2N3055 / MJ2955?).
Furthermore, the 6800UF / 50V filter capacitors are to be replaced.
The previous owner replaced a pair of these transistors (a channel) with 2SA757/2SC1030.
There are no signs of bursts or burns, or other components in critical conditions.
The 2SA663/2SC793 that are on the market to 99% are fake so I would like to mount 2 pairs of equal complementary transistors (2N3055 / MJ2955?).
Furthermore, the 6800UF / 50V filter capacitors are to be replaced.
What is the actual power supply rail voltage? That will determine what output transistors you really need. 2N3055 are really only good to +/-30 volts (or 60V single supply). You *can* go higher, but only if you select them for voltage, and then you have to watch it that the current gain isn’t too low (the two are inversely related). Many manufacturers cherry picked them back when there wasn’t much of a choice.
@wg_sky: if I read well on the service schemetic the power transistors are "powered" at +/- 33v.
in the shop where I usually supply I found the 2n3055G by On Semiconductor and the MJ2955 by ST.
Rob
in the shop where I usually supply I found the 2n3055G by On Semiconductor and the MJ2955 by ST.
Rob
2N3055G
Structure - n-p-n
Collector-emitter voltage, no more: 60 V
Collector-base voltage, no more: 100 V
Emitter-base voltage, no more: 7 V
Collector current, no more: 15 A
Collector power dissipation, no more: 115 W
DC Current Gain (hfe) - 20 to 70
Transition Frequency - 3 MHz
Package: TO-3
2SC793
Pc max Ucb max Uce max Ueb max Ic max Tj max, ° C Ft max Cc tip Hfe
60W 100V 80V 5V 7A 150 ° C 5MHz 400 85/200
2SA663
Pc max Ucb max Uce max Ueb max Ic max Tj max, ° C Ft max Cc tip Hfe
60W 100V 60V 5V 7A 150 ° C 3MHz - 40MIN
MJ2955
Structure - p-n-p
Collector-emitter voltage, no more: -60 V
Collector-base voltage, no more: -100 V
Emitter-base voltage, no more: -7 V
Collector current, no more: -15 A
Collector power dissipation, no more: 115 W
DC Current Gain (hfe) - 20 to 70
Transition Frequency - 3 MHz
Structure - n-p-n
Collector-emitter voltage, no more: 60 V
Collector-base voltage, no more: 100 V
Emitter-base voltage, no more: 7 V
Collector current, no more: 15 A
Collector power dissipation, no more: 115 W
DC Current Gain (hfe) - 20 to 70
Transition Frequency - 3 MHz
Package: TO-3
2SC793
Pc max Ucb max Uce max Ueb max Ic max Tj max, ° C Ft max Cc tip Hfe
60W 100V 80V 5V 7A 150 ° C 5MHz 400 85/200
2SA663
Pc max Ucb max Uce max Ueb max Ic max Tj max, ° C Ft max Cc tip Hfe
60W 100V 60V 5V 7A 150 ° C 3MHz - 40MIN
MJ2955
Structure - p-n-p
Collector-emitter voltage, no more: -60 V
Collector-base voltage, no more: -100 V
Emitter-base voltage, no more: -7 V
Collector current, no more: -15 A
Collector power dissipation, no more: 115 W
DC Current Gain (hfe) - 20 to 70
Transition Frequency - 3 MHz
At +/-33V, real 2N3055’s from major makers (On Semi, ST) or NOS from GE/RCA and Motorola from 1985 or newer will be ok. Its around the upper limits of voltage that you would want to run. 1970’s devices or some second sources can’t guarantee suitability over 60V and they *would* have to be checked. Anything made today will block at least 120V and are rated to 70 Vcer. You still can’t use them at +/-50V because of the SOA fall-off above 40V and the low current gain above 10A which will overload the drivers.
The fT of these devices is considerably lower than any Japanese 2SA/2SC devices. You *are* stuck with this problem if you are replacing T0-3’s. No one except questionable sources makes a TO-3 with an fT above about 4MHz anymore. But in most older circuits they will be fine. If the amp uses high fT drivers (which you can still get, at least for now) there usually isn’t any problem - the NAD 30xx series used 3055/2955 and no one complains that they sound bad because of slow output transistors. Whether it changes the sound is debatable - in most older circuit designs it is not the limiting factor. In the few cases where it s - like a .0005% THD spec that 3055s could never achieve - you might have to retrofit for TO-3P Sanken LAPTs.
The fT of these devices is considerably lower than any Japanese 2SA/2SC devices. You *are* stuck with this problem if you are replacing T0-3’s. No one except questionable sources makes a TO-3 with an fT above about 4MHz anymore. But in most older circuits they will be fine. If the amp uses high fT drivers (which you can still get, at least for now) there usually isn’t any problem - the NAD 30xx series used 3055/2955 and no one complains that they sound bad because of slow output transistors. Whether it changes the sound is debatable - in most older circuit designs it is not the limiting factor. In the few cases where it s - like a .0005% THD spec that 3055s could never achieve - you might have to retrofit for TO-3P Sanken LAPTs.
