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Pioneer SX-780 no sound from one channel

Heres what I found

I'm not sure that the R258 is right. What I mean is I'm testing the one that's in schematic and that was suggested, but I don't think it is the one we are really wanting to test? here's what I have. Maybe you can show me in the photos that I've attached? appears I've been testing the ones with the white cloth wrap covering them.

R261=100

R259=151.25

R262=100.00

R258=2.223 and appears to be red, red, red, gold in color
 

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Actually, I believe you should be checking R259 and R260. Those are the emitter resistors for the drivers, both 200Ω. Those would be indicated with red-blk-brn bands. Reading 151.25Ω on R259 is not unexpected since the internal resistances of Q9, 11, and 13 would affect the reading in-circuit.

The device you are reporting with red-red-red bands would be a 2.2KΩ resistor, and would read 2.223K as you indicate. That is likely R256, which is forward of the the suspect R260 on the board.

R258 (and its compliment R57 in the left channel) are for the first stage drive bias.
 
Here's what I found this morning

These resistors in location R260 and R259 are actually Brown, Green, Brown, Gold and are both showing 150.86 and 151.30 , so are we on the same page?
I've added a picture of what I've checked. When checking these I've verified both channels resistors, even though my photo only shows one channel.
 

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The brown, black, black, gold resistor

interesting that the brown, black, black, gold, in my photo tests .090, however I have another SX-780 and when I tested it also I came up with same readings. Thought these should read 10.00 ohms , but maybe I'm confused? I was testing resistors other than what probably need testing.
 
Right channel is good

Watthour said:
That should the the RIGHT channel. The ±40VDC power supplies appear to be intact. The general suspicion is that the cement 0.22Ω resistors (the white ceramic rectangular ones) have a problem.

Please check the resistances of those resistors and report in with results. I expect the readings to be infinite instead of less than 1 Ω.
Click to expand...
Right channel is good when left channel Darlington is removed. just for reference.
 
strader61 said:
interesting that the brown, black, black, gold, in my photo tests .090, however I have another SX-780 and when I tested it also I came up with same readings. Thought these should read 10.00 ohms , but maybe I'm confused? I was testing resistors other than what probably need testing.
Click to expand...

it is because its still in circuit ..you are measuring other components at the same time .
 
strader61 said:
interesting that the brown, black, black, gold, in my photo tests .090, however I have another SX-780 and when I tested it also I came up with same readings. Thought these should read 10.00 ohms , but maybe I'm confused? I was testing resistors other than what probably need testing.
Click to expand...

That is why we introduce the concept of "lifting a resistor leg" out of circuit to measure it.

In this case the two 10 ohm resistors between the inductor coil and the orange capacitor centrally located in the picture are output filters for the power amps, and one of the two ten ohm resistors is across that big inductor, which at DC will read very close to zero ohms. At a higher frequency the resistor will predominate/
 
Ok

Ok so since I came up with color bands that are a "different color than was thought" am I lifting the R260 and R259 out to test?
or am I testing the ones not really ask to test which were "Brown Brown, black gold? and lift all legs to test.
appreciate the help. I'm very new to this and need it in layman's terms.

I have a resistor calculator I've been using.

http://www.dannyg.com/examples/res2/resistor.htm
 
in circuit components

I do understand that some components while in circuit do change readings because its still in circuit....and that I am measuring other components at the same time . Just didn't know which ones.
 
strader61 said:
These resistors in location R260 and R259 are actually Brown, Green, Brown, Gold and are both showing 150.86 and 151.30 , so are we on the same page?
I've added a picture of what I've checked. When checking these I've verified both channels resistors, even though my photo only shows one channel.
Click to expand...

150Ω is O.K. since your model has those installed. The KU factory schematic shows 200Ω resistors in those positions, but there were revisions.
 
We generally don't find the latest manuals with factory change bulletins, so what you find is important, and is usually correct.
 
strader61 said:
So what should I test or check Next?
Click to expand...

The transistors. They must be removed. Follow, read and STUDY that link and the tests. Example results and desired rigorous reporting format is in post #11, just copy and paste and edit in your results to the end of each line.

markthefixer said:
......snip.....

Next step is testing specific small transistors by removing them and performing the 6 way diode test (specific example and sample results in post #11) looking for gross faults.

I checked, you have NOT named the channel that gets sound, and thus I must complicate things by naming components in BOTH channels.

Q11, Q13, Q15 for the left channel, and q12, q14, q16 for the right channel - depending upon which channel is not working.

...snip....
Click to expand...
 
I will check the transistors in the left channel, which from what your saying are the Q11, Q13, Q15 . Is the Q11, Q13, Q15 the location from schematic? or are these letter number identifiers Q11, Q13, Q15 on the board?

Thanks
 
testing transistors

appears I get result = OL = No conduction at all on the transistor c1885, which appears to be a 2SC1885-R testing all directions and reads OL

I don't get correct readings also when doing the 6 way tests on the
2SA912-R
2SC1775A

Do these transistors convert to something that I can buy somewhere? I tried mouser and that was a no go and they referred me to Allied. would like they legs in correct position.
 
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