Zenith 10S690 Volume Control Issues

[init4fun]

Originally Posted by vortalexfan

Ground end of the volume control? There's no ground connection indicated on the schematic for the volume control pot, and the volume control pot isn't connected to ground anywhere according to the schematic, there's a reference to ground on the tone control keyboard itself but not not on the volume control pot.

I think ol Levi here could use some schematic reading lessons , the side of the volume control pot at resistor R12 is at B- potential , which is a HELL of a lot closer to "ground" than it is to B+ , that's for sure .

Old coot 88 knows his stuff , so don't be SO quick to jump on people trying to help you especially when you don't appear to have a clue as to how that circuit actually works ......

[vortalexfan]

Originally Posted by init4fun

I think ol Levi here could use some schematic reading lessons , the side of the volume control pot at resistor R12 is at B- potential , which is a HELL of a lot closer to "ground" than it is to B+ , that's for sure .

Old coot 88 knows his stuff , so don't be SO quick to jump on people trying to help you especially when you don't appear to have a clue as to how that circuit actually works ......

When I said that I was thinking of an actual chassis ground connection and yes I do know how to read a schematic but like I said, when he said "ground connection" I was thinking he meant a physical chassis ground connection, not B- connection.

Also how would of that ground connection of just suddenly broke when it was working just fine previously?

All I touched in this radio was the capacitors I never touched any of the wiring.

[init4fun]

Originally Posted by vortalexfan

When I said that I was thinking of an actual chassis ground connection and yes I do know how to read a schematic but like I said, when he said "ground connection" I was thinking he meant a physical chassis ground connection, not B- connection.

Also how would of that ground connection of just suddenly broke when it was working just fine previously?

All I touched in this radio was the capacitors I never touched any of the wiring.

Ok , so we've got the "ground" and "B-" thing worked out , great .

Now , just know that while you didn't purposefully touch any wiring that doesn't mean a wire couldn't have got bumped or nudged as you were changing your capacitors . Your best troubleshooting clue that you've given us here is that the volume control worked before you changed the capacitors , that in itself is telling you to check the installation of those new caps very carefully , it's all too easy to make a mistake and sometimes it's not easy to spot a mistake we have ourselves made (a great reason for having at least one electronics savvy friend who might spot something you've missed) ...

[vortalexfan]

Originally Posted by init4fun

Ok , so we've got the "ground" and "B-" thing worked out , great .

Now , just know that while you didn't purposefully touch any wiring that doesn't mean a wire couldn't have got bumped or nudged as you were changing your capacitors . Your best troubleshooting clue that you've given us here is that the volume control worked before you changed the capacitors , that in itself is telling you to check the installation of those new caps very carefully , it's all too easy to make a mistake and sometimes it's not easy to spot a mistake we have ourselves made (a great reason for having at least one electronics savvy friend who might spot something you've missed) ...

Thanks, I'll probably monkey around with it more tomorrow as I spent most of the evening at the doctor's office because I accidentally cut my right pointer finger knuckle on a 1907 GE Pancake Fan Blade when I was trying to turn it off after demonstrating it to a friend of mine, and wound up with 2 stitches in my finger and a tetnus shot.

[init4fun]

Originally Posted by vortalexfan

Thanks, I'll probably monkey around with it more tomorrow as I spent most of the evening at the doctor's office because I accidentally cut my right pointer finger knuckle on a 1907 GE Pancake Fan Blade when I was trying to turn it off after demonstrating it to a friend of mine, and wound up with 2 stitches in my finger and a tetnus shot.

Man that sucks , and I can totally sympathize with you . One of my other hobbies is RC planes and 10 or so years ago I almost lost a finger to a hungry propeller , by my luck it was a carbon fiber prop that disintegrated when it hit my finger after slicing what looked like a shark's gills into it , and it took about 5 hours for them to fish out all the carbon fiber chunks and sew up the mess (had like 4 different sets of X rays till they were satisfied they got all the propeller chunks out) .

Just for the heck of it , post up a few closeup pics of some of the caps you replaced , who knows something may look familiar (or unfamiliar) enough to spot the problem

[old_coot88]

Sorry, I shoulda been more specific. 'Ground end' simply means the lowest potential or no-signal end. In this case, there's a 40 ohm resistor (R22) from there to chassis ground. See if there's 40 ohms from the low end lug of the control to chassis.

(R22 may be physically distant from the control since it's part of the negative bias supply circuit.)

[vortalexfan]

Originally Posted by old_coot88

Sorry, I shoulda been more specific. 'Ground end' simply means the lowest potential or no-signal end. In this case, there's a 40 ohm resistor (R22) from there to chassis ground. See if there's 40 ohms from the low end lug of the control to chassis.

(R22 may be physically distant from the control since it's part of the negative bias supply circuit.)

The Candohm is still good, it measures a little high but still within tolerance, I'm getting about 53 Ohms there at the 40 Ohm section and about 215 Ohms at the 200 ohm section.

I have some pictures of the radio underside showing the capacitors I changed, there was one little spot that looked like it could of been from a component that was cut out at some point in time but there wasn't anything near by that matched it so I chalked it up to maybe a sloppy part placement job from the factory.

See pictures below.

And yes there's 53 Ohms on the low side of the volume control pot to the chassis, so that means that the negative side of the volume control pot is fine it seems.