• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

SA 9500II Issue: New Thread Old Problem: I Need Help Please!!!!

goat67 said:
I think you are reading to much into this.
I would just measure the Test points I specified.

From what I got from Mark's request was he was just telling you the electronic point in
the schematic not to have you verify the connections or the trace.
Click to expand...

Unfortunately correct, I was just trying to unambiguously pin down the measuring point, and to give you a selection of easy points to probe for the one reading. When I (just) first read KB's first post after that I winced.
Then I looked at the numbers a bit closer. And there may be something in them.

No disassembly please, but REPEAT exactly how you took the readings for the good side. The extra data you captured

Looking at the numbers on the "bad" channel:

98.9mv / 3.7mv = a measured gain of 26.729
1 / (R8 / (R9+R8)) = 26.833 is the theoretical gain
62.5K. R8, a 2.4K, comes in at 2.42K.
Click to expand...
using those numbers, gives a result of 26.826


thus we STOP looking at R8 & R9. They are doing their job.

I am now HIGHLY interested in the good channel readings

PLUS this now takes on greater significance:

Pin 22 106.9mv
pin 23 .3mv

R2 bottom 106.9
R2 top 3.7mv

R1 bottom 106.3mv
R1 top .3mv
R3 bottom 3.7mv
R3 top .3mv
Q1 bottom base 3.7mv
Caps will be added later after the flip
Click to expand...

Something's rotten IN the input section...

is R2 too high? Is R3 too low? WHAT is destroying the input level?

Can you post PICTURES of both of those boards? I have a sneaking suspicion.

hint: there is something in the numbers..... :D anybody else game?:deal::naughty:
 
I am hoping for time to do the left side today. That remains to be seen at this point. I do not have my camera here today so that will have to be a tomorrow or later thing.

As far as me understanding what it is that you want, I remain a bit confused in that you made a list of resistors, but I was uncertain which end of the resistors you wanted read. I just read all of it to be safe. At your request I will duplicate my readings on the left side, when I can.

You see the problem, for me, is that I understand the math when you lay it out as you did. What I don't understand is the paths of the circuits that lead you to the math that you are coming up with. When I look at a schematic, I see the connections, but I don't understand what current is flowing and in what direction. I'm sure, if I did understand that, I would be a much better student of your art. I am trying to not make you wince, but I probably will again and I apologize for that ahead of time. Thanks for all the help.

Gary
 
The wince was for all the "extra" work, but it was serendipitous in that it may have revealed the underlying fault.

clue: there shouldn't be much of a difference in the voltages at both ends of R2.

the rest is just what I'm good at, everybody's an expert at something...
 
I believe the guessing game may be over. R2 and R3 are transposed on the the right card. I just looked at the solder points and the R3 solder joints are still factory. R2 and R1 have been replaced and the joints are shiny and new. I never remove more than one component at a time so I am puzzled about how this could be. On the left side, I only replaced R1. I am now going to test the left side and see what it shows for trace #1.

It is apparent from looking at the pictures from the parent thread to this thread, that I did remove more than one resistor at one time because R2 and R3 are in the correct place in the picture. That will teach me to break my own rules.
 
Last edited:
AWH-052 Left

Trace #1

Pin 22 106mv
R1 bottom 106mv
R1 top .3mv
R2 bottom 106mv
R2 top 102.4mv
R3 bottom 102.3mv
Q1 base bottom 102.4

This is more like what we should see on the right side. Yes? :yes: :D

I am not swapping anything until I hear back about this, but my guess is I should be swapping R2 and R3 on the right board. :thmbsp:

If this swap does it for the right board, I am now ready for your observations about the left board, Mr. Goat67, sir. :bigok: Thanks for being patient with me.:thmbsp:
 
Last edited:
Gary
If you are sure that R2 and R3 are installed in the wrong place (reversed) I would suggest correcting this.

I think we are getting close.

Love it when a plan comes together...............
 
All I can say is Kenny Loggins and Led Kaepanna "The Island" never sounded so good through a pair of cheap ass Insignias before. :yes: :thmbsp: :banana::banana:

Once again, Many thanks to all for their help, perseverance and patience. It is an amplifier again!!!!!

Goat67, if there was some points about what you saw on left, I would welcome your observations please. :yes::yes: :D
 
Last edited:
goat67 said:
Code: 
AWH-052 L               AWH-052 R  
Q6                      Q6
C  -52.75               C -51.56  (-51.4)
B  -1.15                B -1.16  (-1.2)
E  -.6                  E -.60  (-0.6)

Q5                      Q5
C  +52.6                C +51.4  (51.4)
B  +1.09                B +1.09  (1.2)
E  +.55                 E +.53  (0.6)

Q4                      Q4
C  +1.0                 C +1.1  (1.2)
B  +46.81               B +46.4  (46.6)
E  +47.5                E +47.05  (47.2)

Q2                      Q2
C  +13.5                C +7.08  (5.0)
B  -47.37               B -46.9  (-46.4)
E  -47.99               E -47.5  (-47.0)

Q3                      Q3
C  -1.13                C -1.16  (-1.2)
B  -47.7                B -46.9  (-46.4)
E  -47.99               E -47.5  (-47.0)

Q1                      Q1
C  -47.1                C  -47.2 and -47.1  (-46.4)
B  +.03                 B  +.033 and +.031  (0.0)
E  +.65                 E  +.65  (0.6)
Click to expand...

What seems off from this post is the following

Q4
is it possible you have E and B readings reversed? Because the Emitter should be more positive than the Base

Q2 Q3
is it possible you have E and B readings reversed? Because the Base should be more positive than the Emitter


Q1 B and E reversed? and wrong polarity on readings?

But I will defer to Mark and see what he thinks.

Hey it is playing. :banana::banana:

I will bet Mark will want you to set the Bias and Dc offset

Getting close.
 
Last edited:
That was one of the puzzling points, the bias and offset HAD set more or less normally.
 
Yup, the foil side reversal got me again. I have to keep reminding myself that this damn diagram is the bottom not the top. There was also one or two plain old typos and using a dash for a visual connector, a definite bad idea in this case. Goat67, you have a good eye. Once again, my apologies for the errors. This error was also corrected on page one where the original errors occurred.

Q4
C +1
B +46.81
E +47.5

Q2
C +13.5
B -47.37
E -47.99

Q3
C -1.13
B -47.7
E -47.99

Q1
C -47.2 top and -47.1 bottom
B +.033 top and +.033 bottom
E +.65

Since it appears that my horrid paperwork skills seem to be the issues that you brought up, can either Mark or Goat think of any other items to be dealt with. If not I will reassemble this beast and go for the bias setting again. This amp has no DC offset adjustment (cap coupled?). Thanks for the extra eyes.

Edit: I was thinking of replacing the power light with an LED. Original lamp is rated 8V at 50ma. I added an LED with a 470ohm resistor which should be good for 12v and spliced it in temporarily. It blew almost instantly. A voltage test shows 50V ac at the wiring. Something about this seems wrong to me. The glass bulb had previously been burning normally, albeit a bit dim. Any guesses?
 
Last edited:
Regarding the power for the lamp, part PL1, I see from the schematic, on board AWS-109, that that circuit passes through R52 910ohm and then what appears to be a rectifier from D9 > D12. Once again I can't figure the path of current, but it does appear that the lamp is placed in series on a 50v line. Is the bulb acting like a dim bulb tester, in a sense? I am merely speculating all this as I try to figure out what is going on here. If this is correct, then can I assume that the 50ma rating, of the original bulb, has something to do with current or voltage limiting of the circuit. Please excuse my ignorance here.
 
Patience and persistence definitely pays off in the end. Congrats, Gary, to you for hanging in their and not giving up on your amp and congrats to Mark and Goat67 for all of the insight and experience and suggestions given out in helping you fix your Pioneer.

It is commendable that these guys can be so patient with us when we (at least me anyway) struggle with the gist of the things that seem to baffle us and for the patience in hanging in there from start to finish.


The SX-3800 that Mark helped me with is singing beautifully in my living room driving a pair of DQ10's without effort.

Kudos to all of you!
 
pilot lite

KingBubba said:
Regarding the power for the lamp, part PL1, I see from the schematic, on board AWS-109, that that circuit passes through R52 910ohm and then what appears to be a rectifier from D9 > D12. Once again I can't figure the path of current, but it does appear that the lamp is placed in series on a 50v line. Is the bulb acting like a dim bulb tester, in a sense? I am merely speculating all this as I try to figure out what is going on here. If this is correct, then can I assume that the 50ma rating, of the original bulb, has something to do with current or voltage limiting of the circuit. Please excuse my ignorance here.
Click to expand...

Just check the volt across R52. MTF & I had a discussion re this when I replaced my pilot lite with a 12V 60ma automotive bulb that fit perfectly. the diodes should have no real bearing on the volt getting to the bulb. ( according to what my minimal knowledge allows me to assume). what blew, the bulb,resistor you put in,or both? I would show you our thread if I knew how to implant here. (labelled sa9500II Oct/09) good luck once again:scratch2: :thmbsp:
 
OUCH, that poor LED.... rest in peace there sparky....

Yes, a very clear idea as to what happened....

50 volts AC, with a 910 ohm 3 watt dropping resistor.

To use a LED, ADD a resistor , 50v / 0.02A (20 mA) = 2500 ohms.

2500 + 910 = 3410 ohms... 50v / 3410 ohms = ~ 15mA

AND ADD a 1n4004 diode in series with the LED !!! The LED CANNOT withstand 50 volts in reverse...

You may want to go even higher in resistance to dim the LED more....

to re-hash: add a series resistor of 2500 ohms minimum and a series diode 1n4004, THEN the LED...
 
Last edited:
That makes perfect sense. What I still can't comprehend is why is the original lamp an 8v lamp, not a 50v lamp. I could have used a LED calculator to come up with 2600 ohm resistor, but, with me running on the assumption that the voltage was only 8v, I did not think a diode was required. I'll try the new instructions and see what happens. Thanks.
 
A 3 watt resistor and an 8 volt lamp is easier to find than a 50v lamp.

There wasn't an 8v winding on the amp, like they have in the receivers...

that 910 ohm resistor dropped about 42 volts.
 
Gary
I am just glad that you had the perseverance to finish the job.
When I was so adamant on the left board being the problem was because of
the readings you posted.

But all is well that ends well. now you get the three :banana::banana::banana:
and the big grin :D
 
As the old saying goes, "It's not over until it's over". :thumbsdn:

Left channel bias set easily like it did last time. The right side does not have a bias voltage at all. I tested the VR on both sides. The left side VR is at around 10 ohms. The right side started at 0 ohms and I finally stopped at 34 ohm with no response on the bias test points. The meter showed 0.000 volts DC at test points 3 and 9 and also at 6 and 12. This is a puzzlement. If anyone is still alive out there, would it be possible to once again give me a few hints or places to start looking. I did touch the jumper under R8 with the meter set on AC volts at one point and I wonder if that may be the cause of this problem.

The amps is performing and sounds more than decent. The left output heat sink is warm and the right heat sink is cool. I assume this is from no bias voltage keeping the transistors in play.
 
You must log in or register to reply here.
Back
Top Bottom