I am currently working on a Philco 41-220. This has been my most challenging one to date. This thing was not well cared for, had a few botched previous fixes and almost every wire had insulation issues. Some were just bare...

Anyhow.... about 10 hours later I have this thing working. All recapped, new wiring where needed etc. Here is my issue though...

I seem to only have 2 degrees of volume with this one, none and full. I have treated the control with contact cleaner and still no help. No matter where I set the control I only get maximum volume.

I was working blind on this one since I could not find a schematic. The schemation on this site for a 41-220 must be wrong because it is only one page and is for a phonograph.

Can anyone direct me on where to start looking to figure this out. I assume it may be as easy as a bad volume pot but that just seems to obvious to me....

Sounds almost like the pot is broken at the low end. Since you are able to turn the sound off, this indicates a broken element, causing the volume to be gone at the low end, but then it jumps up to full. Changing position may slightly increase treble. Normally a volume control has one side of the element connected to the signal source and the other connected to the chassis or some other similar point (which happens to be out of phase with the signal source). As you turn down the volume, the signal is sent through more and more resistance, the connection to the chassis reduces in resistance at the same time, shunting out the signal. The combination of the two achieve optimum tonal quality and volume control.

Take your control out and measure across the end terminals, and also make sure that the low terminal (shaft facing you, terminals facing down, this would be the left terminal) is connected to wherever it's supposed to be connected to.

Thomas

That was it. Thanks for the help. Just seemed to obvious at the time. I have to start thinking simpler.

For now I have one I grabbed from a junker I had but the shaft is way to long and not correct for the knob.

Where can I get a replacement? It is 500K 1-3/8 half rounded shaft. I checked AES and Radio Daze but they only have the ones that are completely round

Thanks,

Chris

:Sounds almost like the pot is broken at the low end. Since you are able to turn the sound off, this indicates a broken element, causing the volume to be gone at the low end, but then it jumps up to full. Changing position may slightly increase treble. Normally a volume control has one side of the element connected to the signal source and the other connected to the chassis or some other similar point (which happens to be out of phase with the signal source). As you turn down the volume, the signal is sent through more and more resistance, the connection to the chassis reduces in resistance at the same time, shunting out the signal. The combination of the two achieve optimum tonal quality and volume control.
:
:Take your control out and measure across the end terminals, and also make sure that the low terminal (shaft facing you, terminals facing down, this would be the left terminal) is connected to wherever it's supposed to be connected to.
:
:Thomas

I've had that very same problem, just yesterday again. When I opened the pot up the carbon coating on the low end was worn away.
You can go to mouser.com
They have everything you'd need including shaft extenders and coupling thingies.

But I do it differently for generally quick fixes.

It's kinda hard to find pots with the exact shaft length or type anymore. So I keep some in my 'stash' that I can "make" into what I need without too much hassel.
The pots from AES are great. I buy the 500k with a switch... Cheap.
And the shaft length I order from them is 1-1/2".
That shaft is round... but because it's aluminum it is easy to cut to length if I need it shorter and easy to file a flat side on it as well.

I also buy from Kelvin.com
They have 500k pots w/switch too... but the shaft is only about 3/4" long and knurled with a split in the middle. But these are very easy to solder to.
So just yesterday I needed a longer knurled shaft. So I hack-sawed off the needed length from the old pot's brass shaft and soldered it right onto the end of the short shaft of the new pot.
I just lay the ends next to each other holding the short end on the very end with a vise-grip. Heat up the joint where they meet... flow solder in there and position the two shafts so they align straight.... A little fiddling.. but great success.
Kelvin's part number is:
Code: 110029
Price: $1.50

Regarding the original control, you can easily fix the cracked spot by super gluing the carbon element to the phenolic "back board"--what it sits on. DO NOT GET ANY GLUE ON THE CARBON SURFACE!!!!!!!!!!! Then mend the crack with rear windshield window defogger mending material--find this at your automotive parts store. This will make for a very small dead spot in the control where the volume doesn't change. Otherwise the control will work perfectly, and will be kept original. If the control also seems to be worn where the wipers slide, bend them so that they contact a new surface area. Coat the carbon with a VERY THIN film of di-electric grease--found at your automotive parts store. Make sure that the wipers have no sharp edges or else they'll scrape away the carbon.

Regarding soldering two shafts together, for a little extra strength, saw a slot in one shaft and file the mating shaft so that it has a "key" to fit into the slot. Solder. This may make the joint a little stronger if you experience breakage with butt-end soldering. If you aren't brutal with your controls, though, simply butt-end soldering them should work wonders.

Thomas

I don't ever seem to have enough luck with the pots i find bad... not lucky enough to be able to be fixed.
The one I just replaced had worn carbon off the first 20% of wiper area. But you can't do anything to get around it as the carbon area is a band or ribbon that follows the walls and the wiper is the full width of the ribbon.

As far as soldering the shaft ends.. it's so solid you wouldn't believe it! The solder even flow-ed (flew?)lol... right down the groove a ways too.

Pretty good. Last time I soldered on a shaft (years ago, like 1990), I sawed a groove and everything. I guess that wasn't necessary. Then again, I also remember having trouble since the add-on shaft was made of aluminum. I didn't quite understand the problem with aluminum, yet. I haven't had the need for soldering on shafts, yet, but when I do, I will try simply butt-ending them.

Thomas

:I am currently working on a Philco 41-220. This has been my most challenging one to date. This thing was not well cared for, had a few botched previous fixes and almost every wire had insulation issues. Some were just bare...
:
:Anyhow.... about 10 hours later I have this thing working. All recapped, new wiring where needed etc. Here is my issue though...
:
:I seem to only have 2 degrees of volume with this one, none and full. I have treated the control with contact cleaner and still no help. No matter where I set the control I only get maximum volume.
:
:I was working blind on this one since I could not find a schematic. The schemation on this site for a 41-220 must be wrong because it is only one page and is for a phonograph.
:
:Can anyone direct me on where to start looking to figure this out. I assume it may be as easy as a bad volume pot but that just seems to obvious to me....

CMcKenna,

May want to check out Philco 41-225 on this site.

Radiodoc