Philco 610 Volume Pot - Need Advice

[compucat]

The volume pot has gone bad in my beloved daily service 37-610. It is a 2 meg pot with a loudness tap and I am having trouble finding a replacement. I am wondering if there is any way the more common 1 meg pot could be made to work. Could I put a 1 meg resistor in series with a 1 meg pot and still have the proper level of volume control? Where can I find a 2 meg pot with or without a loudness tap? Evwry place I look online does not seem to have a 2 meg in an audio taper.

[Ampico-kid]

Originally Posted by compucat

The volume pot has gone bad in my beloved daily service 37-610. It is a 2 meg pot with a loudness tap and I am having trouble finding a replacement. I am wondering if there is any way the more common 1 meg pot could be made to work. Could I put a 1 meg resistor in series with a 1 meg pot and still have the proper level of volume control? Where can I find a 2 meg pot with or without a loudness tap? Evwry place I look online does not seem to have a 2 meg in an audio taper.

"Play Things of the Past" has quite a few 2 meg. pots of all configurations. Check it out here: http://www.oldradioparts.com/potindex.txt

[compucat]

Originally Posted by Ampico-kid

"Play Things of the Past" has quite a few 2 meg. pots of all configurations. Check it out here: http://www.oldradioparts.com/potindex.txt

Thanks, that is one place I didn't think to look. They have a few that I might be able to make work. This Philco is the oldest tube set in my collection and a superb performer. I can't wait to get it going again.

[Ampico-kid]

Originally Posted by compucat

Thanks, that is one place I didn't think to look. They have a few that I might be able to make work. This Philco is the oldest tube set in my collection and a superb performer. I can't wait to get it going again.

If you can't find anything there let me know.....I might have something you can use. I've got quite a stash of NOS universal controls. Bob

[Reece]

You could also get your control fixed or a new one made up by Mark Opatt, the "control king."

http://www.oldradioparts.net/controls.html

[compucat]

Originally Posted by Reece

You could also get your control fixed or a new one made up by Mark Opatt, the "control king."

http://www.oldradioparts.net/controls.html

I contacted him and he sent me a custom built replacement control. The Philco is working again.

[Reece]

Ain't the internet wonderful? If we were doing all this back before the web, we'd be isolated without knowing there are all of those sources out there.

[compucat]

The only thing strange about this replacement pot is that I have to turn the control further than i used to with the old one to obtain the same volume level. For example, I used to give it a quarter turn with the old pot to get a satisfactory volume level. With the new pot installed, I have to set the control at about one third to get the same level. Could it be that I have a linear taper pot instead of an audio or is it a normal difference between two controls? The values of the control are correct. With the loudness tap removed I get louder volume but the tone switch won't work if I do that.

[Reece]

If it were a linear taper the volume change would not be spread out over the whole range but would happen quickly towards one end of the control. You've got an audio taper control but there were different tapers. If you ohmed your old vs. new controls at the same dial settings throughout their range this difference would show up. The ear responds more to subtle changes in lower volume levels thus the audio taper pot spreads out these changes more in the first half or so of rotation so it's easier to control.

[compucat]

Originally Posted by Reece

If it were a linear taper the volume change would not be spread out over the whole range but would happen quickly towards one end of the control. You've got an audio taper control but there were different tapers. If you ohmed your old vs. new controls at the same dial settings throughout their range this difference would show up. The ear responds more to subtle changes in lower volume levels thus the audio taper pot spreads out these changes more in the first half or so of rotation so it's easier to control.

It sounds like you are saying that what I observe is just a difference in the characteristics of the new pot. I suppose the average person would not notice this difference but I am very particular about these things. The radio works great again. The Philco 610 is a fine performing chassis. I suppose it time I will get used to turning the knob a bit higher and won't even question it.