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SX-D7000 Problem

tczech2003

tczech2003

New Member
Hi I'm new to the forum and am hoping someone can help me. I recently aquired a SX-D7000 receiver that was working fine the day before a Texas thunderstorm (complete with lightening.) All the indicators work and the tuner works however the protection circuit is keeping the speaker relay from energizing. I had this problem on a Sansui 7070 that turned out to be resistors that had changed value but I'm less familiar with the Pioneer circuit. Are there any "common culprits" to look for or some preliminary voltage checks I can do to steer me in the right direction? I have a soft copy of the service manual. Thanks in advance.
 
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OK, I did some quick voltage checks and they appear to be correct; +70 -70, +60 -60, +54 -54, +32 -32, +13, +8.6. It was late so I didn't really get into it but I did notice something that I don't think is correct. At the junction of R187 & L1 and R188 & L2 (on the power amp board) there is -47v present. These are the points that connect to the relay contacts that when energized connect to the speakers.
 
Introduction

I realize I may have put the cart before the horse and I skipped right over introducing myself to the forum. I'm retired from the Air Force and getting closer to 60 than I'd like but that's something I can't control so I try not to dwell on it. My background is in electronics repair and I'm currently working as a IT person. Audio has been my prevelant hobby for decades and I'm still a 2-channel stereo guy preferring the vintage gear over the stuff that's currently available. I have a friend here who is also retired military and between the two of us and the local garage sales and pawn shops we have more vintage gear than our wives would like but we both have difficulty turning down "good deals" on vintage stereo gear. In fact I just got a "free" CT-F1000 cassette deck that needs repair. I've always tried to do my own repairs but its been a while since I worked on some of these circuits so I'm having to clear the cobwebs from the old gray matter. I really appreciate the valuable resources such as this forum and hopefully I can return the favor and contribute rather than just take.
 
tczech2003 said:
OK, I did some quick voltage checks and they appear to be correct; +70 -70, +60 -60, +54 -54, +32 -32, +13, +8.6. It was late so I didn't really get into it but I did notice something that I don't think is correct. At the junction of R187 & L1 and R188 & L2 (on the power amp board) there is -47v present. These are the points that connect to the relay contacts that when energized connect to the speakers.
Click to expand...

Hi, welcome from one transistor head to another, well, you picked a nasty one to fix...:D the sx-d7000 has the NSA circuit in it, the "Non-Switching Amplifier".

That negative voltage on the protection relay contacts means the amp has been driven to the rail, signifying internal problems. It is a bit unusual that both channels are showing it. The amp runs off of the +54 regulated and -54 regulated supplies. The protection signalling voltage signal is the other input, of about 25v(?).

The only time I have seen that is when one channel popped so violently it took out the protection circuit and used the protection circuit to cross over to the other channel.

I strongly suggest you carefully read the technical description of the amp in the manual, to get your mind ito the concepts..

In a nutshell, in this push pull circuit, the negative going portion of a sine wave is being chopped off to the + drivers and the positive going portion to the - drivers. Think of a half wave rectifier.

My best results in fixing these circuits has been to remove and test out of circuit ALL transistors. Start with the to-220 driver transistors. You might get lucky and the to-220's solder joints cracked - BUT they usually don't get THAT hot. BUT when any of them blow, they usually take out signal diodes, zener diodes, and a mess of 220 ohm resistors, so you may want to lay in a supply of each of them. I have gotten a parts list together (but not typed anywhere yet) of the parts, their replacements, and inexpensive industrial sources without minimum orders. :D (diodes & transistors $0.05 ea etc )

WATCH OUT for those 8 socketed power transistors. Let's HOPE they're good.... And the sockets making contact.

I'm actually working on the SAME amp right now, out of a SX-3900... ANd have TWO SX-d7000's on the shelf, one with a (now) fixed amp, and one waiting for some digital tuner display signals troubleshooting....

OH, and what part of Texas..... it's a BIIIIG State!!
 
Welcome and thanks for the introduction. I too am a proud owner of the SX-D7000 and an Air Force veteran (stationed in San Antonio 1986-1990). Mark has been helping me with an intermittent power supply problem in my 7000 and he and Echo are outstanding. Again, welcome and am anxious to see you get your 7000 back up to speed. I'd love to see a pic of yours.
 
Thanks for the detailed feedback. I agree, I was surprised to find the same thing in both channels. All day long I've been pondering the notion that it acts like a problem with something that's common to both channels. Now that you mention it perhaps it is indeed the protection circuit itself. If I can muster the energy I'll do some more snooping and studying tonight. As I mentioned lightning struck the house where this receiver was plugged in but powered off so there's no telling. To answer your question I'm in S. Central Texas just NE of Austin.
 
The protection circuit in that case was just a common path for trouble, there shouldn't be any way to get either amp channel to a supply rail with a protection circuit fault.

Since both channels were showing that fault, I suspect induced charges backfed up the speaker wires, since the regulated power supplies survived.

Some of the first transistors to pop would be the small signal NSA circuits, because some of them either have 30 or 50 volt Vceo ratings.Plus the diodes can only handle about 50v in reverse...
 
OK, I think I'm making some progress. I double-checked for the 25V input on pin 8 of the amp board and it read 3.7V. After some checking I found that Q139 is shorted. D132 and D134 are also shorted. I have a replacement 2sa1100 but I'm going have to dig in the parts bin to see if I have suitable diodes. I plan to check the rest of the transistors while I have the board loose. More to come.
 
Update

As you predicted Mark, the casualties are mounting but so far its not as bad as I've had in some other amps. The latest is Q109 (2SC1915) which is shorted. I'm having a hard time locating a replacement. None of the normal sources I use seem to have it. The pioneer parts site lists a 2SC3245 as a sub. but it doesn't seem to be available. I found a cross reference sheet from a Japanese transistor manual that also shows a 2SC2229 as a sub. and I just happen to have a couple of those available on the circuit board from an old PC monitor so I may give that a try. Hows that list of parts and suppliers coming along? :)
 
Well, I think I'm making progress. After replacing Q109 that channel no longer has -47V on the speaker output but the other channel still does. I thought I had checked every component on both channels but apparently I missed one. BTW the big transistors and sockets all appear to be fine. I plan to do some intense troubleshooting this weekend.
 
tczech2003 said:
As you predicted Mark, the casualties are mounting but so far its not as bad as I've had in some other amps. The latest is Q109 (2SC1915) which is shorted. I'm having a hard time locating a replacement. None of the normal sources I use seem to have it. The pioneer parts site lists a 2SC3245 as a sub. but it doesn't seem to be available. I found a cross reference sheet from a Japanese transistor manual that also shows a 2SC2229 as a sub. and I just happen to have a couple of those available on the circuit board from an old PC monitor so I may give that a try. Hows that list of parts and suppliers coming along? :)
Click to expand...

amplifier transistors:

Q101 Q102 2sc1775 ecb 90v 50ma .3w 200mhz 400-1200 hfe

Q103 Q104 2sa979 dual transistor 100v 50ma .2w unkmhz 250-800hfe
Q105 Q106 2sc2291 dual transistor 100v .1a .2w 100mhz 250-1200 hfe

Q107 Q108 2sa750 ecb 50v 50ma .25w 100mhz 450 hfe
Q111 Q112 2sa750
Q117 Q118 2sa750
Q109 Q110 2sc1915 bce 120v 50ma .80w 200mhz 150-800 hfe
Q113 Q114 2sc1400 ecb 100v 50ma .25w 100mhz 500 hfe
Q119 Q120 2sc1400
Q115 Q116 2sa905 bce 120v 50ma .80w 200mhz 150-800 hfe
Q121 Q122 2sa904 bce 90v 50ma .25w 150mhz 250-1200 hfe
Q123 Q124 2sc1914 bce 90v 50ma .25w 150mhz 250-1200 hfe


Q135 Q136 2sa985 bce 120v 1.5a 25w 180mhz 150 hfe
Q133 Q134 2sc2275 bce 120v 1.5a 25w 200mhz 150 hfe

protection:
Q125 Q126 2sc2575 bce 50v .2a .3w 200mhz 90-800 hfe
Q137 Q138 2sc2575
Q139 2sa1100 bce 50v .2a .3w 200mhz 90-500 hfe
Q140 2sc1384 ecb 60v 1a .75w 200mhz 160 hfe
---------------------------------

replacements

Q101 Q102 - KSC1845
. . . .
Q107 Q108 Q111 Q112 Q117 Q118 - KSA992
Q109 Q110 - KSC2310
Q113 Q114 Q119 Q120 - KSC1845
Q115 Q116 - KSA910
Q121 Q122 - KSA910
Q123 Q124 - KSC2310

Q133 Q134 - KSC2073
Q135 Q136 - KSA940


protection:
Q125 Q126 Q137 Q138 - KSC2383YBU
Q139 2sa1100 - KSA1013
Q140 - ZTX1056A edit, use KSC2073


Fairchild transistors from mouser.com, parts numbers:

512-KSA992FBU (low noise)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea
512-KSC1845UBU (low noise)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

************************************
start edit 9/12/2010 replacements
512-KSA910YSHTA to-92 ecb 150v .05a .8w 100mhz 40-240hfe $0.07 ea Q115, Q116, Q121, Q122 9/12/2010 obsoleted
512-KSC2310YBU to-92 ecb 150v .05a .8w 100mhz 40-240hfe $0.11 ea Q109, Q110, Q123, Q124 9/12/2010 large to-92 discontinued
these (ksa910/ksc2310) ran hot...

edit 9/12/2010 possible ksa910/ksc2310 replacements
512-KSA1013YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17 (R=60-120, O=100/200, Y=160/320)
512-KSC2383YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17
---or---
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
---or---
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


***********************
original transistors:
2sa985/a pnp to-220 bce 120v/150v 1.5a 25w 180mhz 35-320hfe orig 180mhz nsa driver
2sc2275/a npn to-220 bce 120v/150v 1.5a 25w 200mhz 35-320hfe orig 200mhz nsa driver

these:
***************!!!!!!!!!!!!!!!!!!!!
757-2SA1930(Q,M) pnp to-220 bce 180v 2a 20w 200mhz 50-320hfe 200mhz nsa driver
757-2SC5171(Q,M) npn to-220 bce 180v 2a 20w 200mhz 50-320hfe 200mhz nsa driver
***************!!!!!!!!!!!!!!!!!!!!
old and slow:
512-KSA940TU_Q pnp to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54 Q135, Q136
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54 Q133, Q134

***************************
9/12/2010 end possible replacements

and this one from zetex
522-ZTX1056A NPN TO-92E ebc 150v 3a 1w (Vce(sat)=0.3v @ 3a) 120mhz 30-1200 hfe editt no longer available, use:
512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.40


whew...
This applies to the sx-3800, sx-d5000 (both with allowances for q numbers), sx-3900 and the sx-d7000.

There is a minor difference in the protection circuit, the Q139 2sa1100 WAS 2sc2575 in the older circuits, but in later models of the 3800 and 3900 and in all D5000 & D7000 units, the polarity of the protection voltage from the power supply (-25v) was reversed (to +25v), and the circuit rewired.
 
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Wow, thanks for the comprehensive parts list. Regarding the reciever, I have good news and bad news. After checking all the transistors & diodes out of circuit and replacing the bad ones I fired it up and it worked briefly then the protection circuit kicked back in. During the brief period it was working, there was popping and crackling coming from the speakers. It reminded me of the sound of and AM radio during a thunderstorm. Now one channel has +50v at the speaker output. Any ideas about the crackling? Noisy transistor maybe? I may just do some "shotgun maintenance" and replace every semiconductor on the board. Mercy me, this is very frustrating. Any advice/help is greatly appreciated.
 
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Marginal, damaged part that didn't pop right away went.... :dunno: start over....

Hopefully the dual transistors are ok.
 
I had a feeling you were going to say that. :tears: What's at the root of your concern about the dual transistors? No longer available?
 
tczech2003 said:
I had a feeling you were going to say that. :tears: What's at the root of your concern about the dual transistors? No longer available?
Click to expand...

Harder to find, and the most prolific source (nte) is the LEAST reliable....

nte (41 for the 2sa, 44 for the 2sc)

So far I haven't run up against any that were blown out.

But it's just a pita, not a disaster

KSA992's that are gain matched should substitute for the 2sa979's differential amp

and KSC1845 that are Vbe matched should substitute for the 2sc2281 current mirror

temperature coupling them should help
 
Thanks for the info. Yep I agree - more of a pita than anything. It is a bit disheartening esp. after having just gone through the whole board. Time to set it aside for a while and come back with a fresh start armed with spare parts. I've been down this road before and have ultimately persevered. Its part of the challenge but I've finally learned to take a time out when it ceases to be fun. Not quite ready to put it on Ebay as an "as is" Parts receiver just yet.
 
tczech2003 said:
Thanks for the info. Yep I agree - more of a pita than anything. It is a bit disheartening esp. after having just gone through the whole board. Time to set it aside for a while and come back with a fresh start armed with spare parts. I've been down this road before and have ultimately persevered. Its part of the challenge but I've finally learned to take a time out when it ceases to be fun. Not quite ready to put it on Ebay as an "as is" Parts receiver just yet.
Click to expand...

I've got a few of mine on the shelf too...
sx-3800 fixed amp, as well as other things, waiting on sweetening....
sx-d7000 fixed amp, waiting for sweetening
sx-d7000 fixed amp, waiting on digital problem fix in tuner and sweetening
sx-1050, sx-3600, sx-626,sx-525, sx-990 waiting....

and a few that aren't:
sx-3900 working on amp, WAS a basket case.... everything else works

Try going through an entire amp like that, with a 50% replacement rate, setting up a partial power test circuit with new to-220 output transistors because it hasn't settled down and you are unsure of the original output transistors, and are just going to do a 3 watt max test (5 vac, 10 ohms) to check bias operation, and have the entire thing go up in a series of flashes, smoke and SHRAPNEL.....

edit: I have to add that it powered up normally (my usual cautious powerup) and ran for over 1/2 hour before the blooie.
 
Ouch! Now THAT is discouraging. That happened to me once a long time ago. Replaced a host of parts including outputs but I missed an open bias potentionmeter and when I went to test - kapow! Everything I had just replaced was gone again in a puff of smoke. Fortunately so far on this receiver I haven't experienced that.

Parts for the receiver should be here today. In the mean time I was able to get the freebie CT-F1000 cassette deck going. The guy that gave it to me had just put in a belt kit but it also needed a FF RW pulley which I found from a post on this forum. You know this Internet thing might just catch on. It sure is handy. :)
 
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