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TX-9500 II stereo indicator lamp out

aj_chicago

aj_chicago

Spin 'em if ya got 'em
Just rescued this tuner from the junk heap and have it cleaned up and performing pretty good now. Had 6 of 8 lamps go out on it and with the help of the lamp supplier, DGWOJO here at AK, I was able to replace 4 of them and have a couple to go. However, after replacing the stereo indicator with the same lamp as the WIDE and NARROW band indicator it was still out. I tuned it to a known stereo broadcast along with the receiver I have it hooked up to (both tuned to same station). Although I do hear stereo out of it I don't get any voltage across the lamp wires to light the lamp. Kinda lost looking at a schematic. Can anyone lead me to test points or has anyone ever shot this problem before? I am pretty green when it comes to reading a schematic, but was able to verify the right voltage and current for the replacement lamps and get them in and recently replaced a cassette belt. Getting cocky and dangerous. Anyone with the patience to help would be greatly appreciated. Got the TX-9500 II almost up to snuff. If anyone knows how I could get my hands on a scan of a service manual it would be greatly appreciated, too. Not available through the AK Pioneer database.
 
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I have a TX-9500II Schematic but not sure how to get a scan. I can take it into the office next week and make copies of the sections and you could paste them together?
 
Hi,

Your Stereo Lamp is 6V/30mA; the same as the WIDE/NARROW lamps.
Have a little patience, the scan is on it's way to the AK database. Not the whole manual unfortunately, just schematics.
Should be available in a week or so.


Kind regards,

/tri-comp
 
Thanks Spok, they worked out FINE!!

The stereo indicator lamp is lit up by the pa1001 chip's pin 6 ALMOST directly, there is a 180 ohm (brown grey brown) resistor in series. The chip pulls it's pin 6 to near ground (zero volts) to light the lamp.

So, here goes:

The lamp gets it's (about +12 volts) power from (i think i is wire wrapped) pin 49 on one pc board.
The other lead of the lamp is connected to pin 43 of the same board.
Then the pattern on the pc board is connected to pin 42.
There is a jumper wire from pin 42 to pin 2 of another pc board.
pin 2 on that board is connected to one side of the 180 ohm (brown grey brown) resistor
the other side of the resistor is connected to the pa1001 chip's pin 6.

When the lamp is UNLIT, the 12 volts should show up EVERYWHERE I just described, up to AND INCLUDING the pin 6 of the integrated circuit.

if a wire is broken or the resistor is bad the 12v will disappear.

You can also do ohmmeter tests with the power off to trace continuity from the bulb to the resistor, test the resistor itself, and test continuity from the resistor to the integrated circuit.

With the lamp LIT, the lamp side of the 180 ohm resistor will be at about 6 volts, and the integrated circuit side of the resistor will be 2 volts or less.

There is one slightly RISKY test that can be done, by grounding the integrated circuit side of the resistor, which should light the lamp.
The risk is shorting to any other part of the circuit with the ground.
and if the wrong side of the resistor is choosen, the 6 volt bulb will get 12 volts, not good. Don't try to short at the integrated circuit's pin 6, it's too easy to slip.

if the bulb can be coaxed to light, AND continuity verified all the way to the integrated circuit, then the integrated circuit is falling down on the job.
 
Thanks Mark. That's what I was hoping for (I think). I do have the schematic in hand from the Pioneer database. What a great resource that is. I've just never read one before. Let me see if I can digest what you gave me here and meter a few things. Was wondering what the little numbered circles on the schematic were. Was thinking those were posts, right?
 
I believe the TX-9500 II schematic can be downloaded from fmtunerinfo.com I downloaded it a few months ago. Good Luck. CC
 
I do have a copy, Charlie, but I went ahead and tried to download the PDF file from fmtunerinfo.com to see if it was a better copy and I cannot. I get some Adobe/Explorer error that says I don't have some add-on enabled and to go to "manage add/ons section" in explorer and enable Adobe add-ons. When I do, I see I have only two and they are, of course, enabled, and disabling and re-enabling them has no effect. I tried via Firefox browser and got a similar error, but I am able to view PDFs from other places. Wondering if this is my problem or the PDF's problem. Are you able to download it?
 
aj_chicago said:
Thanks Mark. That's what I was hoping for (I think). I do have the schematic in hand from the Pioneer database. What a great resource that is. I've just never read one before. Let me see if I can digest what you gave me here and meter a few things. Was wondering what the little numbered circles on the schematic were. Was thinking those were posts, right?
Click to expand...

Correct, those are the (square posts with the wires wrapped around them) connections that go off of the pc board to other points.

If you have trouble with identifying things, and can take digital pictures and email them, I can mark up the pictures and send them back. PM for my email address.

IF you feel that your hand is steady enough to probe integrated circuit pins with 1/10 inch spacing , just put the black probe on a metal chassis ground and the red probe on the pa1001 chip's pin 6.

To find pin 6, there is a notch on one end of the chip, and with the chip's notch facing away from you (there may be a little molded in dot on the LEFT side of the notch) on the left side starting with the furthest pin, which is pin 1 , then increasing in number as the pins get closer to you.
Then when you run out of pins switch to the right side, and continue with the closest pin as the next number, ending with the furthest pin on the right side having the largest number.

1 16
2 15
3 14
4 13
5 12
6 11
7 10
8 9
 
Well, I learned another lesson today. Always try two bulbs and test voltage at least two different times when you're not preoccupied or distracted. I hooked up the whole setup on the kitchen table today (where the best light is), opened it up and measured across the two lamp wires and guess what..... got 12 volts. Hooked up another lamp and it lit just fine. I don't know why I got no voltage last time, but it probably was something stupid. Either that or something is flakey (probably me). Mark, I so wanted to get into testing and probing to learn something. Actually, did learn a few things and thanks for the tips. Got a new Protek multimeter on the way so I will get in there and poke around and try not to short anything out. Plan on keeping it around so have a good schematic now. Thanks again, Mark, and all.
 
All's well that ends well!!

Your best friend when probing is a sharp tip on the end of the probe, and all but the very end of the tip should be insulated, heat shrink tubing works well. Also a pair of Mini-Grapper clips will enable you to get a secure connection with the power off, then turn on the power for the reading.
 
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