I think I can explain how the difference can be explained. The STK4221 and STK4201 are 22 pin devices and the STK4192 is an 18 pin device. If the STK4192 is inserted into the board with it's pin 1 in pin 3 position on the board then I think all the pins connect correctly. This leaves two unused holes in the board at each end. So 1 & 2 go in holes 3 & 4. 17 & 18 go in holes 19 & 20. 10 & 13 go in holes 12 & 15.
Spike, can you confirm that there are two unused holes in the board at each end of IC301.
If ic301 is not inserted like that then DON'T get another IC and insert it without doing some tests that we will suggest without IC301 inserted into the board.

Les.

 

I think I can explain how the difference can be explained. The STK4221 and STK4201 are 22 pin devices and the STK4192 is an 18 pin device. If the STK4192 is inserted into the board with it's pin 1 in pin 3 position on the board then I think all the pins connect correctly. This leaves two unused holes in the board at each end. So 1 & 2 go in holes 3 & 4. 17 & 18 go in holes 19 & 20. 10 & 13 go in holes 12 & 15.
Spike, can you confirm that there are two unused holes in the board at each end of IC301.
If ic301 is not inserted like that then DON'T get another IC and insert it without doing some tests that we will suggest without IC301 inserted into the board.

Les.

Yes pin 1 of the ic301 is inserted in hole 3 of the board.
pin 1 and 2 and pin 19 and 20 on the board are unused . Cheers

 

Sorry the second lot are wrong, pin 1 and 2 and pin 21 and 22 are unused

 

Here is a screen capture of the output section showing the DC blocking capacitors.

Les

 

Here is a screen capture of the output section showing the DC blocking capacitors.
View attachment 285808
Les

Here is a screen capture of the output section showing the DC blocking capacitors.
View attachment 285808
Les

Hi Les
Not sure what you are asking me, I do have the full schematic from the service manual !.
Cheers
Spike

 

I think that MisterBill commented that he could not see that part of the schematic clearly. So The screen capture was to see he could see that part of the schematic any better.
The fact that you say that hole numbers 1,3,21 and 22 are not connected to your IC301 means that the different pin numbering does NOT cause a problem.
I don't have access an amplifier like yours so left and right ON THE BOARD has no meaning to me. I thought that I has specified left and right ON THE SCHEMATIC in a previous post but I cant find it. This means that I have not known exactly on the schematics where the readings referred to. (So I could have drawn the wrong conclusion as to where problems might be.
Can you tell me if your marking of the ends of C301 are the same way on the schematic or reversed.

Les.

 

Here is a screen capture of the output section showing the DC blocking capacitors.
View attachment 285808
Les

Hi
I take it we don't want any DC coming out of pin 12

I think that MisterBill commented that he could not see that part of the schematic clearly. So The screen capture was to see he could see that part of the schematic any better.
The fact that you say that hole numbers 1,3,21 and 22 are not connected to your IC301 means that the different pin numbering does NOT cause a problem.
I don't have access an amplifier like yours so left and right ON THE BOARD has no meaning to me. I thought that I has specified left and right ON THE SCHEMATIC in a previous post but I cant find it. This means that I have not known exactly on the schematics where the readings referred to. (So I could have drawn the wrong conclusion as to where problems might be.
Can you tell me if your marking of the ends of C301 are the same way on the schematic or reversed.

Les.

Hi
Thanks again for your reply and help.
Both sides of C01 is 0.056v a/c , measured in DC Left 27.5v and Right o.1mV .

cheers
Spike

 

Spike, With no power to the amplifier and the volume control set to about half volume measure the resistance between the sliders of RV202 (Volume control ) and the left hand sides (Positive side of capacitor.) and of C301 and C351 Each slider should read very close to zero ohms to one of these capacitors. Report the results.

Les.

 

Spike, With no power to the amplifier and the volume control set to about half volume measure the resistance between the sliders of RV202 (Volume control ) and the left hand sides (Positive side of capacitor.) and of C301 and C351 Each slider should read very close to zero ohms to one of these capacitors. Report the results.

Les.

Hi Les
Thanks again for keeping with me , measured from each Cap to every point !, on the RV202 as follows.
C301 + Right side 0 Ohms, Left side around 50K Ohms. C351 , Right side 0 Ohms ., Left side around 80kOhms .

cheers
Spike

 

Not sure when taking voltage readings whether I should be measureing in a/c or dc !, I know you are not asking voltage at this time .

 

There is still confusion about your left and right labelling. You you say that you get zero ohms from the sliders on the potentiometer to the right hand side of the two capacitors but the right hand side of both capacitors is the negative side on the schematic. The right hand side connects to one end of R352 / R302. Are you still insisting on using left and right on the board ? I have NO WAY to convert the position on the board to the position on the schematic. To do this I would need to have the same amplifier that you have and know how you were positioned with respect to the amplifier.
All the voltage readings I request are DC. When we get to the stage of following audio signals through the amplifier a meter will not be much use. An oscilloscope is much better for that.

Les.

 

There is still confusion about your left and right labelling. You you say that you get zero ohms from the sliders on the potentiometer to the right hand side of the two capacitors but the right hand side of both capacitors is the negative side on the schematic. The right hand side connects to one end of R352 / R302. Are you still insisting on using left and right on the board ? I have NO WAY to convert the position on the board to the position on the schematic. To do this I would need to have the same amplifier that you have and know how you were positioned with respect to the amplifier.
All the voltage readings I request are DC. When we get to the stage of following audio signals through the amplifier a meter will not be much use. An oscilloscope is much better for that.

Les.

Thanks for your reply.
Ok let me see if I can clarify the position .
Spike

 

Hi Les
Thanks again for still keeping with me .

Ok, is this any better ? :
Measured from each Cap to every point (6) on the RV202 as follows.

C301: Positive side of the Cap: 0 Ohms. Negative side of the Cap. around 50K Ohms.
C351: Positive side of the Cap: 0 Ohms, Negative side of the Cap. around 80kOhms .

cheers

 

Yes, the Negative side of the C301 and C351 side connects to one end of R352 / R302.
Spike

 

The last I recall there was a very large DC voltage on the output of the amplifier module. I also recall that there are no series capacitors between that terminal and the speaker connection. Or has that problem been solved and I missed it?? So the big problem is the DC on the output of the amplifier module. Or is the volume control the cause of the DC offset voltage??

 

Can you measure the following voltages again.
C351 +
C351 -
Both ends of R352
Both ends of R351
Both ends of R354

C301 +
C301 -
Both ends of R302
Both ends of R301
Both ends of R304

Les.

 

Can you measure the following voltages again.
C351 +
C351 -
Both ends of R352
Both ends of R351
Both ends of R354

C301 +
C301 -
Both ends of R302
Both ends of R301
Both ends of R304

Les.

Ok will do.
Tks
Spike

 

Comments for MisterBill.
There is still a large DC offset on the outputs of both channels. (One positive. One negative.)
I was tracing back from the + sides of C351 and C301 to see if there was any voltage that could leak through them if these capacitors had become electrically leaky. They came from the slider on the volume control pot so they should be at ground potential. I have had problems with Spike reliably telling me which end of components measurements are being taken. I have asked for them with reference to the schematic but he has been giving them with reference to the position on the PCB. I have now started to ask for readings on a number of components that connect to the same point.

Les.

 

OK here goes.

C351 + = 150mV ( it actually started of at -5mV , then went into + 150mV ) !
C351 - = 26.7v
Both ends of R352 = 26.7v ( both ends)
Both ends of R351 = 0v and 27.2v
Both ends of R354 = 35.7v and 26.7v

C301 + = -0.5mV ( showing as minus )
C301 - = 26.5v
Both ends of R302 = 26.5v and 26.5v
Both ends of R301 = 50mV then down to 0v and 26.5v
Both ends of R304 = 41.9v and 26.5v
Spike

 

Comments for MisterBill.
There is still a large DC offset on the outputs of both channels. (One positive. One negative.)
I was tracing back from the + sides of C351 and C301 to see if there was any voltage that could leak through them if these capacitors had become electrically leaky. They came from the slider on the volume control pot so they should be at ground potential. I have had problems with Spike reliably telling me which end of components measurements are being taken. I have asked for them with reference to the schematic but he has been giving them with reference to the position on the PCB. I have now started to ask for readings on a number of components that connect to the same point.

Les.

OK, that makes sense. Good call to check that.