Pioneer SX-950 lamps dim when I select speakers

mckern

mckern

New Member
Hi all,
with all of the help and information on this forum, I've rebuilt the AWR-101 and AWF-011 boards in my SX-950 and it sounds great. I feel like I'm in my last-mile problems though: the selector lamps (input and speakers) dim when I select a pair of speakers.

The voltages on AWR-101 pins 2 and 3 are 7.8v with nothing selected, and 5.7v with speakers selected. All other output pin voltages on that board are within tolerance for listed spec. Any idea what I might have missed or what's not quite right? Or is this expected behavior?
 
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Is it? I should clarify that I mean "without any speakers selected"; as in "I want to use headphones, not speakers". Any input at all can be selected; that doesn't affect the voltage on those pins.
 
You are refer to the no-load/full-load voltage regulation on the +5.4V regulator, which operates 8V spec'd lamps(FMstereo,Speakers,input channel/function selection).
The channel/function selector is a interlocking type switch, which means normally it is in one of the five positions. In other words, one lamp is on all the time, so normally there should not be a no-load condition, unless a lamp is out or you defeat the switch interlock.
So it is not a problem.
 
@kramden, I did use a 512-KSC2383YTA for Q10. I'll order a 2N5551 today and swap that in when it arrives. It should be safe to use in the meantime?
 
Before you order you could just put the 2SC869 back in to see if the lights work correctly. Just make sure it is the one that came from that location and not one of the other ones. If you didn't keep track of which one went where then you probably shouldn't try any of them as most of the time they will not check bad on a meter but fail under load.
 
Red herring. You want to diagnose this, post the ecb voltages for q10 and q9 without load, and with load. There's something else wrong.

The differences between the 2sc869, the ksc2383 and the 2n5551 are inconsequential in that circuit position.

Now if q10, q9 OR R20 are damaged....

and rcs is right about the lack of a "no-load" condition. Is this a LED conversion or incandescent lamps?

I WILL be slow to answer, on top of my dad's death and dealing with his estate including getting the house ready for sale, now his house has a burst water supply line in the front yard. Things have gone from hectic to almost untenable.
 
@markthefixer take your time. Sorry to hear about your father AND the water main. Thanks for taking some time at all to think about this.

Q9, Unloaded: VB8.18, VE8.12, VC24.8
Q9, Loaded: VB6.1, VE5.8, VC21.2 (should be VB6, VE5.4, VC16.5)

Q10, Unloaded: VB6.5, VE8.2, VC24.8
Q10, Loaded: VB6.6, VE6.1, VC21.2 (should be VB6.6, VE6, VC16.5)

So, looks like it's running high on the shared joint between the collectors but the other legs seem sane? I have no idea what that implies. Should I lift a leg on R20 and test it?

It's still using incandescent lamps.
For completeness, here's some photos that better illustrate what I'm describing.

IMG_2260

IMG_2260

  • Media owner mckern
  • Date added
No speakers selected
IMG_2259

IMG_2259

  • Media owner mckern
  • Date added
Speakers selected
 
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I have seen this twice before. Once on a hack job restore and one other. Both were fixed by using either the original 869 or a 2N5551.
 
I can't remember the details exactly, but I remember that replacing the TO-220 transistor with an MJE15032 for the 5.4v regulator caused a nasty oscillation that could only be seen on the scope. It oscillates because the lamp supply has no load capacitance, the original transistor is ~4MHz but the OnSemi is ~30MHz. Mine was going at 50MHz and burned out the stereo lamp (~15v) before I could figure it out. Either putting back the original transistor (2SD313) or putting a 0.1uF ceramic on the output fixed it (pin 1 and 2 on the PS board, IIRC).
 
@DRecovery that's on the AWH-050 board (power supply assy.) but I haven't touched that board. I rebuilt the AWR-101 (power supply assy.) and the AWF-011 (equalizer amp).
 
So I think that's the power amp (AWH-050) not the power supply. The transistor I am talking about is on the power supply. Erk, looking it up..... Yep, Q9 on the power supply is the pass transistor for the 5.4V regulator. If that's faster transistor, could be causing what you are seeing.
 
K, you are probably good, so you don't have that problem. The 2073 is the correct transistor and the one I was trying to think of. I got as far an 2SA949 as it's complement; it's actually 2SA940. Never can remember that one.

Anyway, I wonder if Kramden and I aren't talking about two sides of the same coin, each a different transistor in the Darlington pair. Have you tried the original 869 and do you have a scope? Gives you something to do until MTF can get back to you. :)
 
As I remember, I could use either the MJE15032 or the 2SD313 as Q9 and have it work correctly as long as Q10 was a 2SC869 or 2N5551. A couple other notes; just so you know, your indicator lamps are lit correctly when they are "dim". A lamp as bright as the one in picture #1 could melt the lense in front of it over time. Also, if you decide to do the protect pcb, be careful what you use to replace the transistors. The ones suggested by the same BOM made the units relay engagement and disengagement points incorrect allowing for turn on/off thumps (dc).
 
Kramden,
Could you please elaborate on the components used in the protect board? I have the thump on/off deal with my sx-950. Which transistor(s) cause this? What should I be using?

Thanks
Bubba57
 
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