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Pioneer SX-890 problems again...

T

tk3768

New Member
Hi there!

My Pioneer SX-890 is having problems again, this time the problems are a lot bigger. I was listening to it at low volume when there was loud pop and and the relay kicked in. I switched it off quickly just in case and then opened it up and checked the power transistors. Darn it, the 2sb705a for the left channel is shorted between the collector and the emitter! I also checked the 2sa1913 and the 2sa913 for that channel and found the a913 was also shorted between the collector and the emitter.

The question I have is, are there other components that might be shorted or bad, and what would be good replacements for the ones that I've found bad? I know that the b705a is very hard to find genuine.

I checked all the other power transistors and this is what I found:

2sd745a for the left channel: red to base, black to emitter: 524
red to base, black to collector: 521

2sd745a for the right channel: red to base, black to emitter: 522
red to base, black to collector: 518

2sb705a for the right channel: black to base, red to emitter: 478
black to base, red to collector: 449

Everything else was OL.

I did check the bias about a week ago and it was fine, but when I first got it, the bias was too high in the left channel and I had to remove the jumper in order to get the bias where it was supposed to be.

Thanks in advance for any advice

Todd
 
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Update on parts!

I did manage to find, through this thread: http://audiokarma.net/forums/showthread.php?p=3684461 the 2sa913. However the closest match I could find regarding the 2sb705a was the 2sb755.

Specs for the 2sb705a are as follows: 150v 10a 120w 17mhz
Specs for the 2sb755 are as follows: 150v 12a 120w 20mhz

Is this a good replacement, or should I try to find the original? Bdent has the sb755, Toshiba brand, for $9.33.

Thanks for any advice you can give me, it has been stressful trying to dig up these parts.

Todd
 
First off, relax - I'm sorry that somehow I missed this the first time through.

first the power outputs:
2sb705 is a power to-3 transistor (150v 10a 120w 17mhz), thus:
either>>>>>>>>>>>
........534-4662 to-3 mica insulators $0.16 each.................
863-MJ21193G pnp to-3 250v 16/30A 250W 8-75hfe 4mhz $4.56
863-MJ21194G npn to-3 250v 16/30A 250W 8-75hfe 4mhz $4.23
or>>>>>>>>>>>>>>
mouser
511-2ST2121 PNP to-3 250V, 17/34A 250W 35-160hfe 25MHz $3.93
511-2ST5949 NPN to-3 250V, 17/34A 250W 35-160hfe 25MHz $2.33
digikey
497-8739-ND 2ST2121 PNP to-3 250V, 17/34A 250W 35-160hfe 25MHz $3.00
497-6953-ND 2ST5949 NPN to-3 250V, 17/34A 250W 35-160hfe 25MHz $3.00

for your drivers...

your 2sa913 and 2sc1913
to-220 150v 1.5a 15w 50-330hfe 120mhz

when using the MJ transistors:
512-KSA940TU_Q pnp to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54
from mouser.com

but when using the 2st transistors
b&d - www.bdent.com
2sa913/a to-220 bce 150/180v 1a 15w 65-330hfe 120mhz sa-7800 nsa driver
2sa1011 pnp to-220 bce 180v 1.5a 25w 100mhz 50-200hfe 100mhz nsa driver
2sc2344 npn to-220 bce 180v 1.5a 25w 100mhz 50-200hfe 100mhz nsa driver

then, your bias circuits, 2sa899, 2sc1904, 2sc1775a
2sa899/2sc1904 150v 50mA 1w 150hfe 100mhz
512-KSA1381es x to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe $0.27 ea
512-KSC3503estu to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe $0.28 ea

2sc1775 120v 50mA 0.3w 400-1200hfe 200mhz
512-KSC1845UBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

let's hope those dual transistors in the input stage are ok...
 
Hey Mark!

Thanks a lot for the reply, I don't think I could have come up with a list like that, not that quickly anyway :-)

On the power transistors, you might want to know they are not a to-3 case, but are a mt-200 case. I was also poking around and testing some more stuff and found that the infamous hot transistor, the one in front of the two 100uF caps, has been replaced with 2sd613, instead of a 2sd712. Is this okay, or not okay?

Since it seems I'm going to be doing a complete overhaul, I also noticed that when it was still working, the THD was a lot higher than it should be. My SX-434 sounded better then it did in terms of the THD. Would it have been caused by the bad bias in the left channel, or something else?

Thanks

Todd
 
tk3768 said:
Hey Mark!

Thanks a lot for the reply, I don't think I could have come up with a list like that, not that quickly anyway :-)

On the power transistors, you might want to know they are not a to-3 case, but are a mt-200 case. I was also poking around and testing some more stuff and found that the infamous hot transistor, the one in front of the two 100uF caps, has been replaced with 2sd613, instead of a 2sd712. Is this okay, or not okay?

Since it seems I'm going to be doing a complete overhaul, I also noticed that when it was still working, the THD was a lot higher than it should be. My SX-434 sounded better then it did in terms of the THD. Would it have been caused by the bad bias in the left channel, or something else?

Thanks

Todd
Click to expand...

He was probably looking at the original data sheet. There
they have it listed as a TO-3 device

Outputs,
Replace the 2SD745 with Sanken 2SC2921 NPN
Replace the 2SB705 with Sanken 2SA1215 PNP
Bdent has both.
Question, Did you recap the board?
 
Last edited:
original
2sd613 to-220 100v 6a 40w 40-320hfe 5mhz

replacement
2sd712 to-220 100v 4a 30w 55-300hfe 8mhz

In my manual, Q26 (the 52 to 13v series pass regulator, near a pair of 100uf 50v caps: C422, C423) IS a 2sd712... and I can find no reference to a 2sd613.
if it IS running hot, the
863-MJE15032G npn to-220 bce 250v 8a 50w 30mhz 70hfe $0.87
can handle the heat "better"... although a larger heat sink that "fits" might be a good idea.

And the datasheet tripped me up, TO-3 my a@@... I should have looked at the outline drawing page or the exploded view page...
3 lashes with a wet noodle for me....
The Sankens are fine.

I've been in 780's and in 980's but NEVER an 880 (yet), and I wasn't aware of, or it didn't immediately come to mind (NOT any more....) that the 880 had more in common with the 780 (vertical plate heat sinks) instead of extruded form heat sinks like the 980 (with those unobtainium transistor packages), in which to-3's would have been remotely plausible...
 
Don't be so hard on yourself Mark, we all make mistakes :D

In reply to glen65, no, I have not recapped anything. I've only had this thing a couple of months, bought it off a guy for $35 who said it would go into protection if it was played hard. As I mentioned in the previous post, the left channel bias was too high and I had to remove the jumper to get it where it was suppose to be. Bad transistor?

I think I'll go with mouser for the replacements of the sa1913 and the sa913, unless the bdent products would be better. I also did more research on the 2sd613 and I found this, it says that its a okay replacement for the 2sd712. However, it still generates enough heat to burn your finger on contact. From the Transistor Substitution Data Book 1993 http://www.datasheetarchive.com/pdf-datasheets/Databooks-5/Document266155.html

Thanks again for all the advice so far, I really want to get this thing running again.

Todd
 
tk3768 said:
In reply to glen65, no, I have not recapped anything. I've only had this thing a couple of months, bought it off a guy for $35 who said it would go into protection if it was played hard. As I mentioned in the previous post, the left channel bias was too high and I had to remove the jumper to get it where it was suppose to be. Bad transistor?
Click to expand...

That's always a possibility but if the bias is going out of spec
with jumpers in and no signal source is present, then you could be
picking something up from the preamp section that doesn't belong.
Given the age of the unit you don't want to rule out bad caps and
solder joints.
I think I'll go with mouser for the replacements of the sa1913 and the sa913, unless the bdent products would be better. I also did more research on the 2sd613 and I found this, it says that its a okay replacement for the 2sd712. However, it still generates enough heat to burn your finger on contact. From the Transistor Substitution Data Book 1993 http://www.datasheetarchive.com/pdf-datasheets/Databooks-5/Document266155.html

Thanks again for all the advice so far, I really want to get this thing running again.

Todd
Click to expand...

Bdent wouldn't be better but Mouser doesn't carry the output transistors
that you need.
 
Update, another problem with pics!

Man, I should have looked at this thing really close before I put any music through it. The foil that is between Q3 and Q4, it goes from collector to collector, is broken!

IMG_0496.JPG


Sooo, is there a way to fix this?

Todd
 
You can neatly solder a piece of insulated solid jumper wire between the two
points, like below
Don't try to just go across it since the trace is pretty much wasted.

pioneer890board2.jpg
 
I blew a 2SB705A and a 2SA913 on an SX-880 (I learned my lesson about how easily a DMM probe can slip, and why you should cover everything but the very tip). I used a 2SB705 and a 2SA1111 from Consolidated to replace them. I think it was about $6 between them.
 
You had better backtrack that circuit path past the jumper and D5...

Did Q15 blow?

Check R257, 150 ohms 1/2 watt.

also R275 4/7 ohms 1 watt.
 
Thanks guys!

You can neatly solder a piece of insulated solid jumper wire between the two
points, like below
Click to expand...

Glen, I will do that.

Mark, I went and tested q15, r267 I believe you meant? and r275 and here are the results:

Q15: red to base, black to emitter: 555
red to base, black to collector: 544
black to base, red to emitter: OL
black to base, red to collector: OL
black to emitter, red to collector: OL
red to emitter, black to collector: OL

R267: 151.3 ohms

R275: 5.4 ohms

Everything looks okay to me. However q17 is shorted between the collector and the emitter. Since that is shorted I tested r265 and d7

R265: 150.6 ohms

D7: black to cathode, red to anode: 554
red to cathode, black to anode: OL

I was going to order the parts listed above in the previous posts, but I'll wait until you give me the okay, Mark.

Thanks

Todd
 
Compare the reading of R281 (4.7 ohms) to R275 (s/b 4.7 ohms - you read 5.4 ohms), if they don't match - lift a lead each and recheck. R275 is high, and resistors increase in value during failure.

We're seeing if your meter or the resistor (R275) is "off", by using another 4.7 ohm resistor....

Everything else looks ok.
 
Mark,

I went and tested r281 and got the same reading, however I forgot to mention that I was testing these in the circuit. Out of the circuit r267 reads 4.8 ohms. Sorry for the lack of communication and brains at the moment :tongue:

Glen, I soldered a wire across and here is the result

IMG_0496.JPG


Tell me what's next, I'm ready for more :yes:

Todd
 
Quick question...

Since I'm ordering this stuff from Mouser, I might as well replace the main caps now and save on shipping. Any suggestions?

Thanks

Todd
 
The 15,000uf 50v caps are somewhat harder to replace because of the physical difference in size (old versus new), especially with mounting them.
 
Found some possibility's regarding caps...

The original caps specs are as follows: 50v 15000uF 40x85mm 85°C

Digi-key has several different caps that fit at least the diameter, all Panasonic. Mouser has the same ones but they are on backorder.

ECE-T1JA153FA THA series 63v 15000uF 3000hrs 40x50mm -40°C-105°C http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P10027-ND

ECE-T1JP153FA TUP series 63v 15000uF 3000hrs 40x50mm -40°C-85°C http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P10638-ND

Or,

ECE-T1KA153FA THA series 80v 15000uF 3000hrs 40x80mm -40°C-105°C http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P10647-ND

ECE-T1KP153FA TUP series 80v 15000uF 3000hrs 40x80mm -40°C-85°C http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P10035-ND

They are all snap-in, I know, but I think that you can work around that if I'm not mistaken.

Thanks for any advice you can give me,

Todd
 
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