PIONEER SX-440 Output Transistor Replacement?
- Thread starter JB8
- Start date
Great, (I'm starting to get some inklings) but not far enough, I need the output transistor readings on that as well.
what part number ARE q1 q2 q3 q4? ........
stopped using the to-220's?
JB8
Well-Known Member
Never made it that far, still working from the original set. I thought one of them was failing, but then discovered at least two of the .5K ohm emitter resistors had some bad junctions on them, brittle, so I swapped them out and that brought the voltages back some, so I moved on, started testing voltages, etc., figuring the 226's were actually working close enough to spec. I would have thought if the voltages were terribly off the transistors would be considered faulty, but thus far it didn't sound like that was the case. (I have an SX-770 where I'm doing the conversion but I also stopped that project to finish this one, that one has it's own thread as well...)
I'm guessing you think it's been the output transistors the whole time?
I'm guessing you think it's been the output transistors the whole time?
no. we'll keep the outputs.
tl:dr the ksc1845 in q311/q312 can only do 50mA of collector current, the original 2sc734 can do 3x that at 150mA.
now read this to the end:
Thinking back to the beginning:
You still had the 2sd226a connected,
You started out with distortion.
The first change you did, there were 2sc870, 2sc734 , 2sc734, 2sa561 in originally.
did you do them all at once?
the way this amp lays out:
Q307/308 2sc870 is an input stage, a ksc1845 is an appropriate substitute
Q309/310 2sc734 is the voltage amplifier stage, which also does duty with the stv diode as the bias splitter for the driver stage.
a ksc1845 is an appropriate substitute,
the Q311/312 2sc734 (pos) and the Q313/314 2sa561 (neg) form the driver stages of the push pull section.
The 2sc734 has both gain and a small current drive capability. So they used it in two spots.
back in the voltage amplifier Q309/310 and
also as the positive driver of the push pull Q311/312
The substitution of a ksc1845 at q311/312 is inappropriate as the ksc1845's drive capability is 1/3 the 2sc734's.
The Q313/314 negative driver 2sa561, a ksa1015 is an appropriate substitute.
The ksa1015 has a complement, ksc1815 (mouser expects them 9/6/22, digikey )
do you have any ksa1013 and ksc2383 ?
tl:dr the ksc1845 in q311/q312 can only do 50mA of collector current, the original 2sc734 can do 3x that at 150mA.
now read this to the end:
Thinking back to the beginning:
You still had the 2sd226a connected,
You started out with distortion.
The first change you did, there were 2sc870, 2sc734 , 2sc734, 2sa561 in originally.
did you do them all at once?
the way this amp lays out:
Q307/308 2sc870 is an input stage, a ksc1845 is an appropriate substitute
Q309/310 2sc734 is the voltage amplifier stage, which also does duty with the stv diode as the bias splitter for the driver stage.
a ksc1845 is an appropriate substitute,
the Q311/312 2sc734 (pos) and the Q313/314 2sa561 (neg) form the driver stages of the push pull section.
The 2sc734 has both gain and a small current drive capability. So they used it in two spots.
back in the voltage amplifier Q309/310 and
also as the positive driver of the push pull Q311/312
The substitution of a ksc1845 at q311/312 is inappropriate as the ksc1845's drive capability is 1/3 the 2sc734's.
The Q313/314 negative driver 2sa561, a ksa1015 is an appropriate substitute.
The ksa1015 has a complement, ksc1815 (mouser expects them 9/6/22, digikey )
do you have any ksa1013 and ksc2383 ?
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That is why a number by number ennie-meenie-miney-mo substitution falls flat on it's face.....
i would be very chagrined if you were to prove i suggested the substitution there.
i would be very chagrined if you were to prove i suggested the substitution there.
JB8
Well-Known Member
As luck would have it, I have all three - KSC1815's, KSA1013's and KSC2383's.
I think my subs were all based on the other SX-440 AK rebuild threads I'd read, and I do remember some discrepancies. I also have that big doc that some AK member put together that showed replacement options for huge list of transistors, but in some cases the BEST replacement was not clearly delineated, and I'm still learning so much of this, so I likely just went with the 1845's since they were on the list and I have a grip of them.
It would be awesome if the issue is just choosing the wrong components! Feels like we're getting close!
I think my subs were all based on the other SX-440 AK rebuild threads I'd read, and I do remember some discrepancies. I also have that big doc that some AK member put together that showed replacement options for huge list of transistors, but in some cases the BEST replacement was not clearly delineated, and I'm still learning so much of this, so I likely just went with the 1845's since they were on the list and I have a grip of them.
It would be awesome if the issue is just choosing the wrong components! Feels like we're getting close!
I worked hard to make a coherent easily understood explanation for that...
and at 0.150 amp I still do not consider the 2sc734 to be an adequate driver.
2sc734 Icmax = 0.150A
ksc1815 Icmax = 0.150A
ksc1845 Icmax = 0.05A
remember this:
.
So.... yes....
meanwhile:
512-KSA1013YBU to-92L ecb 160v 1a .9w 100mhz 160-320hfe $0.34
512-KSC2383YTA to-92L ecb 160v 1a .9w 100mhz 160-320hfe $0.17
(R=60-120, O=100/200, Y=160/320)
mouser has such lovely HIGH GAIN CODE Y ksa1013 & ksc2383...
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reread the edited post. i'm done
JB8
Well-Known Member
Thank you, Mark, I appreciate the explanation and apologize for not grasping some of this initially, learning a ton!
I have some of the 1013's and 2383's in the code Y and will replace the 1845's in the Q311/312 positions with one or the other since the specs are identical.
Have a great evening, I'll check in tomorrow with a result!
I have some of the 1013's and 2383's in the code Y and will replace the 1845's in the Q311/312 positions with one or the other since the specs are identical.
Have a great evening, I'll check in tomorrow with a result!
no no no not one or the other!!
KSC2383 is NPN for Q311/Q312
KSA1013 is PNP for Q313/Q314
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
KSC2383 is NPN for Q311/Q312
KSA1013 is PNP for Q313/Q314
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
JB8
Well-Known Member
Replaced exactly as you suggested:
KSC2383 is NPN for Q311/Q312
KSA1013 is PNP for Q313/Q314
No change, distortion across all functions still.
I'm going to put this machine away for now and maybe pull it out in a few months to take another crack at it.
Thank you for all of your efforts, sorry it was frustrating, really appreciate your time.
KSC2383 is NPN for Q311/Q312
KSA1013 is PNP for Q313/Q314
No change, distortion across all functions still.
I'm going to put this machine away for now and maybe pull it out in a few months to take another crack at it.
Thank you for all of your efforts, sorry it was frustrating, really appreciate your time.
can you post an updated set of voltage readings with the current transistor population? (eventually?)
check the idle currents by measuring voltage across all 8 (4 good 4 bad) 0.5 ohm emitter resistors one at a time.
a decent reading would be 15 millivolts.
I'm still chewing on the earlier voltage reading table.
hmmm, do we still have R356 / R357 at other than 4.7k (to turn down the idle current?)
if so, the 4.7k go back in and the experimental values come out.
You see, now they are too low.
after some massaging:
a decent reading would be 15 millivolts.
I'm still chewing on the earlier voltage reading table.
hmmm, do we still have R356 / R357 at other than 4.7k (to turn down the idle current?)
if so, the 4.7k go back in and the experimental values come out.
You see, now they are too low.
after some massaging:
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