Zenith 10S690 Volume Control Issues

[old_coot88]

Originally Posted by vortalexfan

... so that means that the negative side of the volume control pot is fine it seems.

Not necessarily. There could still be an open in the resistive element itself. If you float the negative lug (disconnect everything from it), see whether the element measures called-for resistance, or if it's open.

[vortalexfan]

Originally Posted by old_coot88

Not necessarily. There could still be an open in the resistive element itself. If you float the negative lug (disconnect everything from it), see whether the element measures called-for resistance, or if it's open.

yikes that's going to be a pain in the butt to do, as there's like several things hooked up to that volume control pot that will need to be disconnected as there are 5 lugs on that volume control pot and all 5 lugs have something hooked to them...

[old_coot88]

Disconnect only what's going to the negative (low end) lug. Measure from that lug to the wiper lug, and rotate the control stop-to-stop. The meter should show a smoothly-changing ohms value, from very low to very high. (The wiper is the middle lug between the bottom and top-end lugs.)

Or does the meter show open circuit (infinite resistance) thru the full range of rotation?

[vortalexfan]

Originally Posted by old_coot88

Disconnect only what's going to the negative (low end) lug. Measure from that lug to the wiper lug, and rotate the control stop-to-stop. The meter should show a smoothly-changing ohms value, from very low to very high. (The wiper is the middle lug between the bottom and top-end lugs.)

Or does the meter show open circuit (infinite resistance) thru the full range of rotation?

Well I figured out what it was, a piece of capacitor lead wire got down into the volume control pot and was shorting it out, so I flushed it out with some contact cleaner and now the volume control pot seems to be working fine now.

The biggest give away was that the volume control pot wasn't measuring open but it was being rather difficult to turn so I took some contact cleaner and sprayed it into the volume control pot and sure enough that piece of capacitor lead wire flew right out of the pot and it now rotates perfectly.

[vortalexfan]

OK I got the volume control issue fixed but now I've got a new problem, I'm not getting any stations in on any of the bands on this radio, and it was working just fine before I worked on the volume control issue.

It seems like this radio is developing one problem after another...

I guess I should of just left it alone seeing as it was working fine before I replaced the capacitors in it.

I don't think I've ever repaired a radio that was this touchy before.

[old_coot88]

Do you get any noise when turning the bandswitch, or is it silent?

[vortalexfan]

Originally Posted by old_coot88

Do you get any noise when turning the bandswitch, or is it silent?

All I get is the electrical sound of the band switch making contact at each position and when I tune through the tuning dial all I get is a hissing noise across the dial.

I disconnected the B- Wire Lead from the volume control like you told me to when I was testing the continuity of the volume control and I also disconnected a capacitor that went to that terminal as well, but I reconnected them just like they were originally and I wouldn't think that disturbing the B- connection to the volume control pot would mess with the radio's reception capabilities.

The aforementioned disconnecting of the wires from the negative terminal of the volume control pot was the only thing I disturbed in the radio this time around, so I'm kind of confused as to what could of happened to make the radio lose reception.

[dieseljeep]

Originally Posted by vortalexfan

OK I got the volume control issue fixed but now I've got a new problem, I'm not getting any stations in on any of the bands on this radio, and it was working just fine before I worked on the volume control issue.

It seems like this radio is developing one problem after another...

I guess I should of just left it alone seeing as it was working fine before I replaced the capacitors in it.

I don't think I've ever repaired a radio that was this touchy before.

After working on these old relics for well over 60 years, I learned from my mistakes. For one thing, I never "shotgun" the project. I replace components in stages. Taking out the chassis and speaker and putting it on the bench to check or find out what the real cause is. If the set works, so much the better!
Then do the electrolytics and audio coupling caps.

[vortalexfan]

Originally Posted by dieseljeep

After working on these old relics for well over 60 years, I learned from my mistakes. For one thing, I never "shotgun" the project. I replace components in stages. Taking out the chassis and speaker and putting it on the bench to check or find out what the real cause is. If the set works, so much the better!
Then do the electrolytics and audio coupling caps.

That's probably what I should of done with this set, because it was working for the most part, except for the AVC circuit which was acting wonky, it would make distant stations that would come it pretty clear at night fade in and out audio wise which were otherwise coming in really well, and the schematic for this radio didn't have the AVC circuit marked very well.

So that's why I just decided to replace all of the paper caps in this radio because I wasn't sure which caps were part of the AVC circuit in this radio (the AVC Bypass Cap).

Also I know for a fact that this radio's orginal Filter caps are still good in this radio because a.) the radio has no 60 Hz Hum whatsoever, and b.) I just got a nasty jolt from it when I was trying to take the chassis out of the cabinet even after the radio had been unplugged for more than a half hour.

Also the interesting thing is that this radio was bone stock original, there were no capacitors replaced underneath the chassis, it still had all of the original Zenith Capacitors underneath the chassis when I got this thing and it was working like new with the original caps still in place and the capacitors didn't show any signs of having any wax dripping from them in fact about 99% of the original capacitors underneath still had their factory molding marks in the wax on the sides of the capacitors yet.

This radio has all of its original Zenith tubes in it yet except for the 6A8 and the 5Y4 rectifier tube which are the only non-Zenith re-placements in the radio.

Besides the water marks on the top of the cabinet that is presumably from a plant being set on top for years, this Radio was like brand new, almost like it was mostly a display unit for most of its life.
I'm thinking maybe once the family got a TV in the 1950s the Radio just became a display piece, which might explain why it was such a low hours set.