@ fromnowon: good spot, you are right 2SB357 was a typo, 2SD357 is correct?
Will replace them all with the newer TO 220 types. The 2SC1451 with KSC3503 together with a little TO 126 type heatsink attached.
I love this forum and all the help we get. For every other newbie, here are the datasheet values from the original transistors and the recommended replacement.
Only one major question from a newbie to the experts. Which numbers are most important in that area, if you look for a new and better substitute?
Original: 2SD357, NPN, pinout BCE, TO-220
Maximum Collector Power Dissipation (Pc): 10 W
Maximum Collector-Base Voltage |Vcb|: 110 V
Maximum Collector-Emitter Voltage |Vce|: 100 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 0.8 A
Max. Operating Junction Temperature (Tj): 150 °C
Transition Frequency (ft): 35 MHz
Forward Current Transfer Ratio (hFE), MIN: 55
Replacement 1: KSC2690A, NPN pinout ECB, TO-126
Maximum Collector Power Dissipation (Pc): 20 W
Maximum Collector-Base Voltage |Vcb|: 160 V
Maximum Collector-Emitter Voltage |Vce|: 160 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 1.2 A
Max. Operating Junction Temperature (Tj): 150 °C
Transition Frequency (ft): 175 MHz
Collector Capacitance (Cc): 19 pF
Forward Current Transfer Ratio (hFE), MIN: 60
Replacement 2: KSC2073, NPN, pinout BCE, TO-220
Maximum Collector Power Dissipation (Pc): 25 W
Maximum Collector-Base Voltage |Vcb|: 150 V
Maximum Collector-Emitter Voltage |Vce|: 150 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 1.5 A
Max. Operating Junction Temperature (Tj): 150 °C
Transition Frequency (ft): 4 MHz
Forward Current Transfer Ratio (hFE), MIN: 40
2SB527, PNP, pinout BCE, TO-220
Maximum Collector Power Dissipation (Pc): 10 W
Maximum Collector-Base Voltage |Vcb|: 110 V
Maximum Collector-Emitter Voltage |Vce|: 80 V
Maximum Emitter-Base Voltage |Veb|: 6 V
Maximum Collector Current |Ic max|: 2 A
Max. Operating Junction Temperature (Tj): 130 °C
Transition Frequency (ft): 35 MHz
Forward Current Transfer Ratio (hFE), MIN: 50
Replacement 1: KSA1220AY, PNP, pinout ECB, TO-126
Maximum Collector Power Dissipation (Pc): 20 W
Maximum Collector-Base Voltage |Vcb|: 160 V
Maximum Collector-Emitter Voltage |Vce|: 160 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 1.2 A
Max. Operating Junction Temperature (Tj): 150 °C
Transition Frequency (ft): 175 MHz
Collector Capacitance (Cc): 26 pF
Forward Current Transfer Ratio (hFE), MIN: 160
Replacement 2: KSA940TU, PNP, pinout BCE, TO-220
Maximum Collector Power Dissipation (Pc): 25 W
Maximum Collector-Base Voltage |Vcb|: 150 V
Maximum Collector-Emitter Voltage |Vce|: 150 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 1.5 A
Max. Operating Junction Temperature (Tj): 125 °C
Transition Frequency (ft): 4 MHz
Collector Capacitance (Cc): 110 pF
Forward Current Transfer Ratio (hFE), MIN: 40
Will replace them all with the newer TO 220 types. The 2SC1451 with KSC3503 together with a little TO 126 type heatsink attached.
I love this forum and all the help we get. For every other newbie, here are the datasheet values from the original transistors and the recommended replacement.
Only one major question from a newbie to the experts. Which numbers are most important in that area, if you look for a new and better substitute?
Original: 2SD357, NPN, pinout BCE, TO-220
Maximum Collector Power Dissipation (Pc): 10 W
Maximum Collector-Base Voltage |Vcb|: 110 V
Maximum Collector-Emitter Voltage |Vce|: 100 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 0.8 A
Max. Operating Junction Temperature (Tj): 150 °C
Transition Frequency (ft): 35 MHz
Forward Current Transfer Ratio (hFE), MIN: 55
Replacement 1: KSC2690A, NPN pinout ECB, TO-126
Maximum Collector Power Dissipation (Pc): 20 W
Maximum Collector-Base Voltage |Vcb|: 160 V
Maximum Collector-Emitter Voltage |Vce|: 160 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 1.2 A
Max. Operating Junction Temperature (Tj): 150 °C
Transition Frequency (ft): 175 MHz
Collector Capacitance (Cc): 19 pF
Forward Current Transfer Ratio (hFE), MIN: 60
Replacement 2: KSC2073, NPN, pinout BCE, TO-220
Maximum Collector Power Dissipation (Pc): 25 W
Maximum Collector-Base Voltage |Vcb|: 150 V
Maximum Collector-Emitter Voltage |Vce|: 150 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 1.5 A
Max. Operating Junction Temperature (Tj): 150 °C
Transition Frequency (ft): 4 MHz
Forward Current Transfer Ratio (hFE), MIN: 40
2SB527, PNP, pinout BCE, TO-220
Maximum Collector Power Dissipation (Pc): 10 W
Maximum Collector-Base Voltage |Vcb|: 110 V
Maximum Collector-Emitter Voltage |Vce|: 80 V
Maximum Emitter-Base Voltage |Veb|: 6 V
Maximum Collector Current |Ic max|: 2 A
Max. Operating Junction Temperature (Tj): 130 °C
Transition Frequency (ft): 35 MHz
Forward Current Transfer Ratio (hFE), MIN: 50
Replacement 1: KSA1220AY, PNP, pinout ECB, TO-126
Maximum Collector Power Dissipation (Pc): 20 W
Maximum Collector-Base Voltage |Vcb|: 160 V
Maximum Collector-Emitter Voltage |Vce|: 160 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 1.2 A
Max. Operating Junction Temperature (Tj): 150 °C
Transition Frequency (ft): 175 MHz
Collector Capacitance (Cc): 26 pF
Forward Current Transfer Ratio (hFE), MIN: 160
Replacement 2: KSA940TU, PNP, pinout BCE, TO-220
Maximum Collector Power Dissipation (Pc): 25 W
Maximum Collector-Base Voltage |Vcb|: 150 V
Maximum Collector-Emitter Voltage |Vce|: 150 V
Maximum Emitter-Base Voltage |Veb|: 5 V
Maximum Collector Current |Ic max|: 1.5 A
Max. Operating Junction Temperature (Tj): 125 °C
Transition Frequency (ft): 4 MHz
Collector Capacitance (Cc): 110 pF
Forward Current Transfer Ratio (hFE), MIN: 40
Last edited:
merlynski
Curmudgeon Electronicist
The application the transistor is used in is more important than just raw datasheet numbers. Maximum collector current can be very important, but may not be the most important in specific locations. I usually search AK for suggested replacements in BOMs from folks who do a lot of troubleshooting and rebuilding. Then I look to see if the circuit the suggested replacement is used in is similar to the one I am looking to replace.
I would be very hesitant to replace a TO-220 packaged transistor with a TO-126 packaged transistor.
I would be very hesitant to replace a TO-220 packaged transistor with a TO-126 packaged transistor.
Last edited:
The last parts arrived today and I can start rebuilding the Power Supply.
The aim is, to measure several parts to find always matching pairs for both sides.
During the last weeks, I tried to find more information about the 2SC1451 and some other parts used with the SX-737.
And I found a very interesting thread some years back with this recommendation for the 2SC1451 by EchoWars.
https://audiokarma.org/forums/index.php?threads/2sc1451-transistors.550878/#post-7536976
I know, every BOM-List recommends the SC3503 as replacement for the SC2451 but comparing the values of all three, I ordered as well the 2SC2911 and will give it a try.
But compare the transistors by yourself:
2SC1451 SI NPN transistor
Uce/Ucb: 120/150V
Ic: 50mA
β (Ic/Ib): -
N: 700mW
F: 130MHz
SC 3503 Bipolartransistor, NPN, 300V, 0,1A, 7W, TO-126
Typ: Bipolartransistoren (BJT)
Technologie: NPN
Package: TO-126
Uceo: 300 V
Ic: 0,1 A
Ptot: 7 W
fT: 150 MHz
hFE: 40 ... 320
SC 2911 HF-Bipolartransistor, NPN, 160 V, 0,14 A, 10 W, TO-126
Typ: Bipolartransistoren (BJT)
Technologie: NPN
Package: TO-126
Uceo: 160 V
Ic: 0,14 A
Ptot: 10 W
fT: 150 MHz
hFe: 100 – 400
The aim is, to measure several parts to find always matching pairs for both sides.
During the last weeks, I tried to find more information about the 2SC1451 and some other parts used with the SX-737.
And I found a very interesting thread some years back with this recommendation for the 2SC1451 by EchoWars.
"The absolute best part for the job was some Panasonic transistors that were discontinued a few years ago (2SA0914 and 2SC1953). I should have bought hundreds of them before they disappeared. Damn... Anyway,
the best replacement now for the C1451/52 and A809/810 are the Sanyo 2SA1209 and 2SC2911."
the best replacement now for the C1451/52 and A809/810 are the Sanyo 2SA1209 and 2SC2911."
https://audiokarma.org/forums/index.php?threads/2sc1451-transistors.550878/#post-7536976
I know, every BOM-List recommends the SC3503 as replacement for the SC2451 but comparing the values of all three, I ordered as well the 2SC2911 and will give it a try.
But compare the transistors by yourself:
2SC1451 SI NPN transistor
Uce/Ucb: 120/150V
Ic: 50mA
β (Ic/Ib): -
N: 700mW
F: 130MHz
SC 3503 Bipolartransistor, NPN, 300V, 0,1A, 7W, TO-126
Typ: Bipolartransistoren (BJT)
Technologie: NPN
Package: TO-126
Uceo: 300 V
Ic: 0,1 A
Ptot: 7 W
fT: 150 MHz
hFE: 40 ... 320
SC 2911 HF-Bipolartransistor, NPN, 160 V, 0,14 A, 10 W, TO-126
Typ: Bipolartransistoren (BJT)
Technologie: NPN
Package: TO-126
Uceo: 160 V
Ic: 0,14 A
Ptot: 10 W
fT: 150 MHz
hFe: 100 – 400
It would be interesting to know the hFE of the 1451s when you pull them. I found "Forward Current Transfer Ratio (hFE), MIN: 150" for the 1451 just searching.
Apparently there are different gain groups for 3503s - but we may not be able to get them. The 3503s I have around are 512-KSC3503DSTU - I was planning to use them in my SX-737.
This is for 3503:
Hmmm that's not min 150 (but the upper end is relatively close?)
I guess your 2911s could be as low as 100 as well.
I'll bet many SX-737s have been rebuilt with 3503s in Q5/Q6 and are happily playing away for years but I admire your thoroughness pa_200!
Apparently there are different gain groups for 3503s - but we may not be able to get them. The 3503s I have around are 512-KSC3503DSTU - I was planning to use them in my SX-737.
This is for 3503:
Hmmm that's not min 150 (but the upper end is relatively close?)
I guess your 2911s could be as low as 100 as well.
I'll bet many SX-737s have been rebuilt with 3503s in Q5/Q6 and are happily playing away for years but I admire your thoroughness pa_200!
@fromnowon: You can have every information of the old parts you want, because I still have everything still around and I always take down the values from each part after desoldering.
The original SC1451 hat a hFE of 221 and 223.
The new SC3503 I got are between hFE 145 and 153. The SC2911 are all spot on hFE 176 so I will use them instead of the SC3503 and keep you informed about the result.
My plan on this project is a sound test between three SX-737.
One still original, one only with the troublemaking caps and transistors replaced,
and this one with some different parts and film electrolytic for all caps below 1µF.
My favorite side to collect information from all transistors is this one:
https://www.web-bcs.com/index.php?lan=en
That’s a European Website and mainly based on the famous “Jaeger electronic catalog”, turned out to be very helpful even for the old Asia parts. Gives Infos for the European similar types as well.
The original SC1451 hat a hFE of 221 and 223.
The new SC3503 I got are between hFE 145 and 153. The SC2911 are all spot on hFE 176 so I will use them instead of the SC3503 and keep you informed about the result.
My plan on this project is a sound test between three SX-737.
One still original, one only with the troublemaking caps and transistors replaced,
and this one with some different parts and film electrolytic for all caps below 1µF.
My favorite side to collect information from all transistors is this one:
https://www.web-bcs.com/index.php?lan=en
That’s a European Website and mainly based on the famous “Jaeger electronic catalog”, turned out to be very helpful even for the old Asia parts. Gives Infos for the European similar types as well.
Last edited:
The Power Amp has now all new parts and both STV4 reinstalled, but I need a rest for today. Tomorrow will recheck everything before I start with a test on 60 watt DBT.
Q11 - Q14 will remain out until everything run fine on DBT.
@merlynski. VR1 and VR2 will go full left to minimum, or what’s the safest way to make sure it’s at minimum? Something like resistance between pointer VR1 and R19?
I don’t want to fry another STV4 while testing the BIAS.
And what about VR3 and VR4 (DC-Offset)?
EDIT:
We shall not forget that the SX-737 Service Manual is wrong. They have the VR's listed backwards
VR 1 and VR 2 adjust the BIAS (IDLE CURRENT)
VR 3 and VR 4 adjust the Center Voltage/ offset
So we should stay with the VR Numbers and describe what to do next.
Q11 - Q14 will remain out until everything run fine on DBT.
@merlynski. VR1 and VR2 will go full left to minimum, or what’s the safest way to make sure it’s at minimum? Something like resistance between pointer VR1 and R19?
I don’t want to fry another STV4 while testing the BIAS.
And what about VR3 and VR4 (DC-Offset)?
EDIT:
We shall not forget that the SX-737 Service Manual is wrong. They have the VR's listed backwards
VR 1 and VR 2 adjust the BIAS (IDLE CURRENT)
VR 3 and VR 4 adjust the Center Voltage/ offset
So we should stay with the VR Numbers and describe what to do next.
Last edited:
audiocrzy
Super Member
Stay with that. Identify and replace any bad parts to get it working before you replace any other parts
merlynski
Curmudgeon Electronicist
The bias adjustment VRs should have 0Ω across them at the minimum setting. With 0Ω the current through them will drop 0vdc, minimizing the bias spreader voltage between the bases of the driver transistors. Then the only voltage drop between their bases will be the STV4 voltage.
The dc offset VRs can be centered.
The dc offset VRs can be centered.
One is never to old to learn something new! Thank you for that hint!
Finished the Power Amp today, good start on DBT, VR1 and VR 2 responded. Then on to full power, later all outputs reinstalled with new glimmer and thermal paste and again test on DBT passed.
Was no deal at all to adjust bias and offset with the new trim pots. VR 3 /4 close to -0,5mVDC, VR1 /2 both -19,8mVDC after 15 minutes.
Unfortunately, the first audio test with tuner failed, must find that issue later.
Second audio test with AUX was successful, sounds really good, will let it run for some hour’s tomorrow.
Must find the tuner issue, Ass’y AWM-043 has 13,5vdc on pin 20 coming from pin 19 Power supply as a start. Tuner worked before I started with the power supply board.
Will give you more details around the job on the Power Amp over the weekend, at least after I have fixed the tuner issue.
If you like, there is one picture from the Power Amp with the new parts. Have a look in the center where I replaced the 2SC1451 with the 2SC2911 together with that nice heatsink. All transistors stay cool around 30° C / 86°F
Was no deal at all to adjust bias and offset with the new trim pots. VR 3 /4 close to -0,5mVDC, VR1 /2 both -19,8mVDC after 15 minutes.
Unfortunately, the first audio test with tuner failed, must find that issue later.
Second audio test with AUX was successful, sounds really good, will let it run for some hour’s tomorrow.
Must find the tuner issue, Ass’y AWM-043 has 13,5vdc on pin 20 coming from pin 19 Power supply as a start. Tuner worked before I started with the power supply board.
Will give you more details around the job on the Power Amp over the weekend, at least after I have fixed the tuner issue.
If you like, there is one picture from the Power Amp with the new parts. Have a look in the center where I replaced the 2SC1451 with the 2SC2911 together with that nice heatsink. All transistors stay cool around 30° C / 86°F
Last edited:
Would be great if someone can give help, bringing the tuner back to life.
Nothing has been done yet in that area, but it worked before. All wires on the board are good, no lose/broken ones on the first check.
Only C5 on AWX-071 has been changed.
Switching to FM triggers the indicator light, BUT no movement is seen from Signal or Tuner indicator when moving the dialing wheel.
Nothing, not even a faint signal can be heard. The only move is the function light indicating the switch from AUX or Phono to FM.
Nothing has been done yet in that area, but it worked before. All wires on the board are good, no lose/broken ones on the first check.
Only C5 on AWX-071 has been changed.
Switching to FM triggers the indicator light, BUT no movement is seen from Signal or Tuner indicator when moving the dialing wheel.
Nothing, not even a faint signal can be heard. The only move is the function light indicating the switch from AUX or Phono to FM.
No progress with the tuner in the meantime. Pin 20 and 3 have 13,3vdc but nothing happens.
Tried to understand the schematic of the Power Supply board and the voltage going to pin 19, 20 and 21.
I would like to understand the voltage for Q3 and Q4, something must be wrong in the area.
The voltage is
Q3 E= 13,2vdc, C= 37,4 B= 13,8
Q4 E= 13,8vdc, C= 37,4 B= 14,3
If I compare the voltage with the working tuner, the voltage is
Q3 E= 13,4vdc, C= 29,6 B= 14,0
Q4 E= 14,0vdc, C= 29,6 B= 14,5
Every idea is highly welcome
Edit: mixed Q3 and Q4 voltage, sb correct now. All voltage on full power. DBT tested good.
Tried to understand the schematic of the Power Supply board and the voltage going to pin 19, 20 and 21.
I would like to understand the voltage for Q3 and Q4, something must be wrong in the area.
The voltage is
Q3 E= 13,2vdc, C= 37,4 B= 13,8
Q4 E= 13,8vdc, C= 37,4 B= 14,3
If I compare the voltage with the working tuner, the voltage is
Q3 E= 13,4vdc, C= 29,6 B= 14,0
Q4 E= 14,0vdc, C= 29,6 B= 14,5
Every idea is highly welcome
Edit: mixed Q3 and Q4 voltage, sb correct now. All voltage on full power. DBT tested good.
Last edited:
The transistors used as pass regulators are silicon. The typical forward voltage drop across a silicon semiconductor junction is around 0.5 to 0.6V. As a result, what you are measuring shows the forward drop from base-emitter. Your reported measurements show it to be consistent at around 0.6V, just as it should be.
The fact that the "working tuner" has base voltages which are about 0.2V higher than the "other" tuner is within the acceptable tolerance range, but still maintains the approximate 0.6V drop from base to emitter in every instance.
They are working properly, and as the diagram for the AWE-043 tuner board indicates, the allowable supply voltage is 13V ± 1V.
@Whatthour, I still consider myself a newbie to HI-FI electronics and want to understand and learn as much as I can, to keep this beautiful Old-Hifi running for long.
What really puzzles me, is not the base or emitter voltage, it’s the big difference with the collector voltage between both receivers. 37,4vdv with the rebuild power supply but dead tuner, and on the other side, the low 29,9vdc with the old power supply but a working tuner.
It’s probably the effect with the new parts and has nothing to do with the dead tuner.
Sorry for that stupid question, but at the time while fishing in the dark, I can only compare the difference and hope for more input where to look at.
Will move this issue to the other tuner thread and continue here with more info to all the other work on my SX-737.
What really puzzles me, is not the base or emitter voltage, it’s the big difference with the collector voltage between both receivers. 37,4vdv with the rebuild power supply but dead tuner, and on the other side, the low 29,9vdc with the old power supply but a working tuner.
It’s probably the effect with the new parts and has nothing to do with the dead tuner.
Sorry for that stupid question, but at the time while fishing in the dark, I can only compare the difference and hope for more input where to look at.
Will move this issue to the other tuner thread and continue here with more info to all the other work on my SX-737.
