• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Small Pioneer SX-636 problem...

mattsd

mattsd

Super Member
Hey everyone!

I have a new problem receiver, this time all the outputs are intact. But it would appear that either the drivers or something else is messed up on the left channel. There is a varying DC voltage at the left speaker terminals between 1.72 and 1.96v. Here are the voltages for the transistors:

Q1 Base: 55mv
Collector: 36.20v
Emitter: .617v

Q3 Base: 63mv
Collector: 37.26v
Emitter: .617

Q5 Base: 36.4v
Collector: Varying between .914 and 1.3v
Emitter: 37.1v

Q7 Base: Varying between 3.08 and 3.26v
Collector: 28.70v
Emitter: Varying between 2.48 and 2.80v

Q9 Base: Varying between .711 and 1.05v
Collector: 28.70:
Emitter: Varying between 1.21 and 1.42v

In contrast, here are the right channel voltages:

Q2 Base: 12.5mv
Collector: 36.20v
Emitter: .562v

Q4 Base: 19.3mv
Collector: 37.26v
Emitter: .562

Q6 Base: 36.4v
Collector: 1.24v
Emitter: 37.1v

Q8 Base: 1.16v
Collector: 28.70v
Emitter: .564v

Q10 Base: 1.24v
Collector: 28.70v:
Emitter: .641v

The question is which component is failing. I've diode checked all the left channel transistors and they checked just fine. Q1 and 3 are 2sa726's, which I know have bad reputation on here for failing or becoming noisy. Q2 and 4 have been replaced with Motorola 2n4126 transistors, but not by me. I have not connected any speakers to it yet.

Update: Since the right channel seems to be working properly I connected a speaker to it and gave it a listen with a CD player through the AUX input, and another problem has presented itself. It's like listening to a FM station with a lot of static. I have cleaned the volume control and I varied it while listening to see if the static changed or went away and it stayed the same, no matter where the volume control was. I also did a little more reading and the 2sc1451 has a bad rep as well. Could this be why it sounds the way it does?
 
Last edited:
Register to hide this ad
Put ksa992's in for q1,2,3,4
512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea


and ksc3503's in for Q5, Q6.
512-KSC3503estu to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe $0.28 ea


for completeness:
q9,10 2sa777
512-KSA1013YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17

q7,8 2sc1509
512-KSC2383YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17

(although
512-KSA1220AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.39 (R=60-120, O=100/200, Y=160/320)
512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.40
could be used)

q11,12 2sd371
863-MJ21194G npn to-3 250v 16/30A 250W 8-75hfe 4mhz $4.23


q13,14 2sb531
863-MJ21193G pnp to-3 250v 16/30A 250W 8-75hfe 4mhz $4.56

here's the capacitors:

awh-034 c1 0.33 25 cssa 0.33 50 598-DSF050J334
awh-034 c2 0.33 25 cssa 0.33 50 598-DSF050J334
awh-034 c7 220 6 cea 220 10 647-UPW1A221MED
awh-034 c8 220 6 cea 220 10 647-UPW1A221MED
awh-034 c9 47 35 cea 47 35 647-UPW1V470MED1TD
awh-034 c10 47 35 cea 47 35 647-UPW1V470MED1TD
 
Thanks, Mark! I will be doing a total recap of the EQ and the AF amp, so I am ordering UPW caps for those as well. I will let you know when I have them in my hands, which will probably be Monday, since the mail does not come on Sunday.
 
Not all are best UPW's... I wish people would ask before leaping...

eq amp
awf-014 c1 3.3 10 csza 3.3 50 647-UEP1H3R3MDD
awf-014 c2 3.3 10 csza 3.3 50 647-UEP1H3R3MDD
awf-014 c3 0.47 50 cea 0.47 100 667-ECQ-E1474KF
awf-014 c4 0.47 50 cea 0.47 100 667-ECQ-E1474KF
awf-014 c5 100 35 cea 100 35 647-UPW1V101MPD1TD
awf-014 c6 100 35 cea 100 35 647-UPW1V101MPD1TD
awf-014 c11 22 10 cea 22 50 647-UPW1H220MDD
awf-014 c12 22 10 cea 22 50 647-UPW1H220MDD
awf-014 c13 0.47 35 csza 0.47 100 667-ECQ-E1474KF
awf-014 c14 0.47 35 csza 0.47 100 667-ECQ-E1474KF

af amp
awk-035 c5 1 25 csza 1 50 647-UKL1H010KDDANA
awk-035 c6 1 25 csza 1 50 647-UKL1H010KDDANA
awk-035 c9 100 16 cea 100 35 647-UPW1V101MPD1TD
awk-035 c10 100 16 cea 100 35 647-UPW1V101MPD1TD
awk-035 c13 4.7 25 cea 4.7 50 647-UPW1H4R7MDD
awk-035 c14 4.7 25 cea 4.7 50 647-UPW1H4R7MDD
awk-035 c21 4.7 25 cea 4.7 50 647-UPW1H4R7MDD
awk-035 c22 4.7 25 cea 4.7 50 647-UPW1H4R7MDD
awk-035 c23 4.7 25 cea 4.7 50 647-UPW1H4R7MDD
awk-035 c24 4.7 25 cea 4.7 50 647-UPW1H4R7MDD
awk-035 c25 2.2 25 cssa 2.2 50 647-UKL1H2R2MDDANA
awk-035 c26 2.2 25 cssa 2.2 50 647-UKL1H2R2MDDANA
awk-035 c27 47 10 cea 47 35 647-UPW1V470MED1TD
awk-035 c28 47 10 cea 47 35 647-UPW1V470MED1TD
awk-035 c31 100 35 cea 100 35 647-UPW1V101MPD1TD

plus there's some 2sa726's in the AF amp that could benefit being changed over to ksa992's.

text block to make it easier:

647-UEP1H3R3MDD
647-UEP1H3R3MDD
667-ECQ-E1474KF
667-ECQ-E1474KF
647-UPW1V101MPD1TD
647-UPW1V101MPD1TD
647-UPW1H220MDD
647-UPW1H220MDD
667-ECQ-E1474KF
667-ECQ-E1474KF
647-UKL1H010KDDANA
647-UKL1H010KDDANA
647-UPW1V101MPD1TD
647-UPW1V101MPD1TD
647-UPW1H4R7MDD
647-UPW1H4R7MDD
647-UPW1H4R7MDD
647-UPW1H4R7MDD
647-UPW1H4R7MDD
647-UPW1H4R7MDD
647-UKL1H2R2MDDANA
647-UKL1H2R2MDDANA
647-UPW1V470MED1TD
647-UPW1V470MED1TD
647-UPW1V101MPD1TD

all in block are currently in stock
 
Last edited:
Okay, from now on, I am asking questions, even if I think I know the answer. Also I ordered a lot of ksa992's, plus several ksa1013's and ksc2383's, so I will have all I need to redo the 726's on the AF amp and anything else that comes my way.

By the way, I have a question that's slightly off topic, I got a bunch of KSC945's made by Fairchild at a excellent deal, could those sub for anything? And I'm not just meaning on the 636, can they used in others?
 
They are a lower voltage, but can be used in other places

BUT

care is needed, they came in two lead layouts from Fairchild:
ksc945 = ebc
ksc945C = ecb

always test the lead layout before installing - even if they come from the same bag.
 
I found the full part number: KSC945CGTA

So I would assume that it would be ECB for the layout, and the data sheet says so, but as I have been learning, never assume!

Would you have a list offhand of transistors that these could sub?
 
512-KSC945LBU to-92 eBc 50v .15a .25w 300mhz 40-700hfe $0.05 ea
512-KSC945CLTA to-92 eCb 50v .15a .25w 300mhz 40-700hfe $0.05 ea

NO

It's not really possible to generate a list - it depends upon the circuit the unknown transistor is operating in.

50v is kind of low.
 
Got my parts today, and have replaced all of the caps on the AF amp, EQ amp and the main amp. Also replaced the the two 726's on the AF and almost all of the transistors on the main amp. However, I have a small problem in the fact I somehow forgot to buy ksc3503's, and I really don't want to pay $7 for $1.00 in parts. Would you have any you could send me?

Thanks
 
mattsd said:
Got my parts today, and have replaced all of the caps on the AF amp, EQ amp and the main amp. Also replaced the the two 726's on the AF and almost all of the transistors on the main amp. However, I have a small problem in the fact I somehow forgot to buy ksc3503's, and I really don't want to pay $7 for $1.00 in parts. Would you have any you could send me?

Thanks
Click to expand...

posted just a few weeks ago:

Re: 2sc1451 replacement.
KSC3503 , decided recently, so recently in fact I only have a few on hand,
Click to expand...

I think the current count is 3. might only be 2.
 
Last edited:
That's just fine, as I only need one. I had one here from another project, so the right channel is completely redone. Should I PM you?
 
mattsd said:
Got my parts today, and have replaced all of the caps on the AF amp, EQ amp and the main amp. Also replaced the the two 726's on the AF and almost all of the transistors on the main amp. However, I have a small problem in the fact I somehow forgot to buy ksc3503's, and I really don't want to pay $7 for $1.00 in parts. Would you have any you could send me?

Thanks
Click to expand...

markthefixer said:
posted just a few weeks ago:

Re: 2sc1451 replacement.
KSC3503 , decided recently, so recently in fact I only have a few on hand,
Click to expand...

I think the current count is 3. might only be 2.
Click to expand...

mattsd said:
That's just fine, as I only need one. I had one here from another project, so the right channel is completely redone. Should I PM you?
Click to expand...

No, It is not fine.....

Sir, you presume too much. And are either unwilling or unable to read between the lines, so I will say it explicitly:

I have none to send.

Two (I looked) is dangerously low for me, AND I have not been in a financial position to get a bunch of them since that post made several weeks ago, nor will I be for several weeks until the current bench project is finished. I'm even very low on First Class Stamps, just enough to get by, so the 2 to 4 stamps to mail it would also have to be gotten as well...

I am sorry for your purchasing oversight/error, and any possible contribution to it that I may have had in the timings of forum postings and your ordering of parts. I think Mouser still ships first class mail at 3 to 5 bucks shipping.

Many's the time I had to bite the bullet and "fill the need" hitting me with additional unwanted shipping costs that I had to "eat" due to oversights in ordering.
 
Last edited:
Please excuse me, sir, I misread your post. I did not mean to be rude or presumptuous, I did read it as saying you had some you could send.

Please accept my apologies.
 
mattsd said:
Please excuse me, sir, I misread your post. I did not mean to be rude or presumptuous, I did read it as saying you had some you could send.

Please accept my apologies.
Click to expand...

accepted, no sweat - I should have been a bit more direct, not everybody is running critically low of a part with two of them on hand...

I usually get a bunch of anything inexpensive at a crack so I don't even have to think about that part for a while.

I think I started with 20 a while back....
 
Last edited:
I finally got my parts, and no, they do not ship first class mail. Translation: ouch! Oh well.

However there is still a problem with the bias. It's hovering around 51mv for the left channel and 26mv for the right at zero ohms. That's after waiting 10 minutes with nothing connected to the AUX, the volume at zero and speakers connected to the A speaker terminals.

What next?
 
Read the voltage between the base of Q7 (red dmm lead) and the base of Q9 (black dmm lead). see if it goes up slightly as you slightly increase the resistance setting, then turn it back down.

Leave the black lead on the Q9 base, and touch the red lead to both sides of D3 (one at a time) and post those readings

And then read the voltage between the base of Q10 (red dmm lead) and the base of Q8 (black dmm lead).see if it goes up slightly as you slightly increase the resistance setting, then turn it back down.

Leave the black lead on the Q10 base, and touch the red lead to both sides of D4 (one at a time) and post those readings.

---

Read the voltage between the emitter of Q7 (red dmm lead) and the emitter of Q9 (black dmm lead). see if it goes up slightly as you slightly increase the resistance setting, then turn it back down.

And then read the voltage between the emitter of Q10 (red dmm lead) and the emitter of Q8 (black dmm lead).see if it goes up slightly as you slightly increase the resistance setting, then turn it back down.

----

It may be the choice of the output transistors that is giving the higher idle current. It may be able to be compensated for by shorting D3 and D4 and removing their voltage contribution to the diode stacks between Q7/9 and Q8/10.
 
Read the voltage between the base of Q7 (red dmm lead) and the base of Q9 (black dmm lead). see if it goes up slightly as you slightly increase the resistance setting, then turn it back down.

And then read the voltage between the base of Q10 (red dmm lead) and the base of Q8 (black dmm lead).see if it goes up slightly as you slightly increase the resistance setting, then turn it back down.

Read the voltage between the emitter of Q7 (red dmm lead) and the emitter of Q9 (black dmm lead). see if it goes up slightly as you slightly increase the resistance setting, then turn it back down.

And then read the voltage between the emitter of Q10 (red dmm lead) and the emitter of Q8 (black dmm lead).see if it goes up slightly as you slightly increase the resistance setting, then turn it back down.
Click to expand...

Yes to all, they all increase with a slight increase of the pot

Black lead to Q9 base, red lead to D3:
Voltage 1: 0.649v
Voltage 2: 0.6mv

Black lead to Q10 base, red lead to D4:
Voltage 1: 0.656v
Voltage 2: 1.3mv

These readings are at zero ohms, just to confirm.
 
You must log in or register to reply here.
Back
Top Bottom