919

NO ! - copy the values in your unit now - don't use the parts list or the schematic. ;)

It was tested at the factory with the values you have in there now, so unless you have a conflicting Sansui Service Advisory - follow the above advice - pretty please. :thumbsup:

(Unless you have reason to believe someone has 'been in there' changing components for some nefarious purpose of course).
Don't worry I'm not messing with it right now I'm working 12 hour days the next 6 in a row so I have plenty of time to think over my next move my first day off is next friday..
 
I couldn't sleep today and decided to pull F-2833 out and check everything over well I found that I was mistaken on the right side testing good and the left bad it appears to have a problem with both the left side and the right side vr05 right channel and vr06 left channel are controlling both the positive and negative voltages the positive side of the right channel reads neg 37mv and neg side of the right channel reads pos 10v and they read about the same on the the left channel..Vr03 right channel and vro4 left channel control nothing when trying to adjust them..20171101_194255.jpg
 
I think I might have found the problem.I was studying lee stereos upgrade and restoration of a 919 thread and noticed that on his F-2833 board he had regular resistors in place of the voltage regulating trimmers vr03,vr04,vr05 & vr06 and I put the same bipolar caps in place of c03,c04,c05 & c06 as he did so I'm thinking I prabably need to switch those back to the polarized type to get the correct voltage adjustment..
 
I think I might have found the problem.I was studying lee stereos upgrade and restoration of a 919 thread and noticed that on his F-2833 board he had regular resistors in place of the voltage regulating trimmers vr03,vr04,vr05 & vr06 and I put the same bipolar caps in place of c03,c04,c05 & c06 as he did so I'm thinking I prabably need to switch those back to the polarized type to get the correct voltage adjustment..
Or try to figure out what size resistors go in place of the trimmers?
 
My best guess...

Being careful not to change / turn the VRs upon removal, I would measure between the center leg and either the left or right leg to see what ohm the VR got set to when you set it, and then use a resistor of the value you find.

Or just install a resistor that is half the ohms of the VR that was installed.

Super-techs...what do you say??
 
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I don't think swapping the electrolytics will do anything useful, I would be looking at the transistors in the regulator section (on the MM head amp) first, also grounding on the MC head amp board, also ribbon cables - broken connections? - Plus the obvious - wrong value trimmers? and incorrectly installed components? - including the trimmers. :)

Something very wrong if adjusting one trimmer moves two plus voltages or a plus and a minus :)

Also you should be able to work on one channel at a time and get +/- 10V sorted on one channel before moving to the other.
 
My best guess...

Being careful not to change / turn the VRs upon removal, I would measure between the center leg and either the left or right leg to see what ohm the VR got set to when you set it, and then use a resistor of the value you find.

Or just install a resistor that is half the ohms of the VR that was installed.

Super-techs...what do you say??
The tricky part is I'm only able to set the Neg 10v side of each channel with vr04 & vr05 the pos side vr03 & vr04 do absolutely nothing the way it is right now.Can't wait to get off work this morning and go find out the results..
 
I don't think swapping the electrolytics will do anything useful, I would be looking at the transistors in the regulator section (on the MM head amp) first, also grounding on the MC head amp board, also ribbon cables - broken connections? - Plus the obvious - wrong value trimmers? and incorrectly installed components? - including the trimmers. :)

Something very wrong if adjusting one trimmer moves two plus voltages or a plus and a minus :)

Also you should be able to work on one channel at a time and get +/- 10V sorted on one channel before moving to the other.
The transistors are all in right and are good the ribbon cables that go from F-2835 to the input terminal board F-2834 are diconnected from F-2835 at the moment,can't find any broken connections,trimmer values are right and installed the same way as the other ones that are working.I get off work in five hours and gonna try changing the electrolytics back to polarized first thing and if doesn't work it might be a jfet problem?
 
The transistors are all in right and are good the ribbon cables that go from F-2835 to the input terminal board F-2834 are diconnected from F-2835 at the moment,can't find any broken connections,trimmer values are right and installed the same way as the other ones that are working.I get off work in five hours and gonna try changing the electrolytics back to polarized first thing and if doesn't work it might be a jfet problem?
Also on most of the 25 turn trimmers that I've had experience with I'm able to get both positive and negative voltage out of them..
 
I don't think swapping the electrolytics will do anything useful, I would be looking at the transistors in the regulator section (on the MM head amp) first, also grounding on the MC head amp board, also ribbon cables - broken connections? - Plus the obvious - wrong value trimmers? and incorrectly installed components? - including the trimmers. :)

Something very wrong if adjusting one trimmer moves two plus voltages or a plus and a minus :)

Also you should be able to work on one channel at a time and get +/- 10V sorted on one channel before moving to the other.
Ok John you can say I told ya so now:) Changing the electrolytics made no difference.I double checked the trimmer values at 50k ohms.How do you find a bad jfet?DBT shows no short circuit anywhere 150w light bulb gos completely out relays click amp powers up?Been a long night I'm going to sleepy land now.
 
This is the bit of circuitry you need to look at - on the F-2835 MM Head Amp, note that the connections to VR03 & VR05 are through the ribbon cable. Leave the JFETs alone, they can look after themselves. ;)

Note well that TR105 and TR101 (the top 2) are NPN, and that TR107 and TR103 (the bottom 2) are PNP - if you changed these transistors, check what you used. These transistors comprise a kind of regulator called a capacitance multiplier - you should have around +11V on pin107 and -11V on pin113, each adjustable with the respective trimmer.

upload_2017-11-3_15-44-59.png
 
This is the bit of circuitry you need to look at - on the F-2835 MM Head Amp, note that the connections to VR03 & VR05 are through the ribbon cable. Leave the JFETs alone, they can look after themselves. ;)

Note well that TR105 and TR101 (the top 2) are NPN, and that TR107 and TR103 (the bottom 2) are PNP - if you changed these transistors, check what you used. These transistors comprise a kind of regul20171103_163528.jpg 20171103_163528.jpg 20171103_163317.jpg ator called a capacitance multiplier - you should have around +11V on pin107 and -11V on pin113, each adjustable with the respective trimmer.

View attachment 1037773
Nope not that stuff already checked all of that over 3 or 4 times however I did find the problem on F-2844 power supply board TR05 is shorted on both sides.Anyone know what replaces this?
 
Perhaps two ksc1845's with their emitters soldered together would work?And two ksa992's vice versa.
 
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