Zenith 10S690 Volume Control Issues

[old_coot88]

This is a long shot, but.... in post# 10, fourth photo, near the center of the shot, there is a 330K (orange-orange-yellow) resistor. To its left is a yellow capacitor labeled 333K 630V. A bare lead from the resistor looks to be lying directly across a bare lead from the capacitor when you blow up the image 300%. It may just be the camera angle, but would be worth checking.

[vortalexfan]

Originally Posted by old_coot88

This is a long shot, but.... in post# 10, fourth photo, near the center of the shot, there is a 330K (orange-orange-yellow) resistor. To its left is a yellow capacitor labeled 333K 630V. A bare lead from the resistor looks to be lying directly across a bare lead from the capacitor when you blow up the image 300%. It may just be the camera angle, but would be worth checking.

I think that's an illusion, because the resistor you're referring to isn't actually touching that capacitor because it's about a 1/4" higher than the capacitor.

Well. I'll try and take the chassis out of the cabinet again and attempt to get the speaker out of the cabinet to put it on my bench and see if I can get some voltage measurements, the only reason why I didn't want to monkey around with taking it out of the cabinet is because with my cut on my knuckle it's hard to unscrew the screws without hitting my knuckle against the cabinet.

[vortalexfan]

OK. so question, what is this coil for?
See picture attached below.

I'm asking because when I was cleaning out my volume control pot earlier with the contact cleaner I accidentally got a bunch of contact cleaner on this coil assembly and I'm wondering if me getting contact cleaner on this coil assembly might of messed something up with the radio's reception.

This is the only other thing I could think of that might of been messing things up.

Thoughts?

[vortalexfan]

OK, so I don't know what I did to it, but now the tuner is working again.

[vortalexfan]

OK well, I tried it out again now that I got the tuner working again, and the volume control quit working again and it started working like a tone control knob again.

I double checked EVERYTHING and there isn't anything wired up wrong and the volume control pot isn't open, so it seems like I'm chasing down some sort of weird electrical phantom in this radio...

Any other ideas as to what could be causing my volume control issues?

[vortalexfan]

OK so the only thing I can think of is that one of the capacitors that is attached to the negative end of the volume control pot might of went bad or were faulty, in the physical radio itself there are 2 capacitors that are going off of the volume control pot negative leg, which is weird because looking at the schematic there's only one capacitor coming off the Negative leg, which is C14 unless I'm missing something...

In the actual radio chassis, there's a mica capacitor that's going between the negative leg of the volume control pot and one of the taps on the volume control pot, which that mica capacitor isn't marked on the schematic (at least not that I can see of anyways) there's 2 capacitors marked on the schematic in that area that seem like they might fit the description of a mica capacitor value wise but the way they are drawn on the schematic they don't seem to connect from the tap of the volume control to the negative leg of the volume control pot, C12, which is a 350 pF capacitor is one possibility, the other is C9 which is a 25 pF capacitor, but like I said none of those capacitors appear to have a physical connection with the volume control pot negative lead and the tap on the schematic.

[old_coot88]

When you had the bottom lug of the control disconnected, did you actually verify with an ohmmeter that the element isn't open?

[vortalexfan]

Originally Posted by old_coot88

When you had the bottom lug of the control disconnected, did you actually verify with an ohmmeter that the element isn't open?

yes I did, it didn't measure O. L. which usually means its open, it actually gave a value of 2.5 Meg like the schematic said it should of, as for whether or not I could get a smooth up or down movement of the numbers when rotating the knob, I couldn't get it to do that because I couldn't hold the meter probes onto the terminals and turn the knob at the same time, I tried to use an alligator clip to hold one of the meter probes onto one of the terminals while I held the other one in place with my left hand and turned the knob with my right hand but the alligator clip kept coming loose and the negative lead of the probe kept falling off the negative terminal of the volume control pot so then I couldn't get any sort of readings, one way or the other.