Well, the 16 is humming along rather nicely. Sound is sometimes a little mushy, like just a bit of sandpaper on the edges of words. Minimized with careful tuning. I've tried substituting a new speaker and that helps somewhat, don't know if the old one should be re-coned. Or is this just normal? It's not terrible, but we're so accustomed to digital sound -- hmm.

Question is: when I switch the tone control clockwise toward more bass there is a strong click at each position. Something wrong? Can this be eliminated?

Thanks!!

David Sligar

could try some de-clicking contact cleaner ?

Thanks, contact cleaner has already been used -- unless there is some special "de-clicking" cleaner? This doesn't sound like dirty contacts. Sounds like it could be minimized by using, for example, .05 mF caps between these contacts, but I'm not sure what that might do for the tone. Might be worth a few experiments.

Maybe I should do that and report results? Apparently this is not a well-known problem. I'm surprised.

David

Did some of them use a multi posistion switch for tone?

Do you mean that the click is heard from the speaker, a sort of "pop?"
If so, it could be because your replacement caps at the tone control are too good!

The tone switch selects a cap or combination of caps to shunt off certain frequencies to ground. The caps can keep a charge on them that suddenly discharges when they are switched in, causing the "pop" from the speaker. This would be especially true of new modern caps with low leakage.

One solution sometimes used is to connect a resistor in parallel with each of them to equalize the charge across them when they are not switched in. For those caps that are in the volume control circuit, 100k, 1/4 watt resistors might help. For those caps that are in the plate circuit of the 77 tube, you'll want to use something higher or it will draw too much current and may even make things worse. Probably not much smaller than 500k, 1/4 watt.

If you wanted to give it a try, you could just temporarily "tack solder" them in to see if it does the trick before making it permanent.

There are a couple different versions of the model 16. (there's the model 16, code 125, for example) and they have different switching arrangements for the tone control.

Thanks, Terry -- That's kind of what I was thinking -- about the resistors. In fact, those caps were the only ones I didn't replace, so, if this is a symptom of no leakage (sounds right) then I probably shouldn't replace them. I was thinking maybe I would string 1 meg resistors across the switch contacts / cap high sides. This tone control does bleed the higher audio frequencies off the plate of the 77 (this is a code 125), so I feel like even 500k might have some undesired effect. Experimenting should tell what would work here. Your description of the sound is exactly right.

Thank you again,

David

Another question here, for you Philco gurus. The bass compensation switch doesn't seem to have any effect, on any tone setting. It's wired in exactly as the schematic dictates. Is this a well known problem? Is there a well known solution?

Thanks in advance,

David Sligar

There might be nothing wrong.
For one thing, that switch will have an effect only at low volume settings.
When the switch is open, all frequencies above the so-called "roll-off point" will be attenuated giving the effect of increased bass.
But the roll-off point for a .05 cap is pretty low, maybe around 100 Hz or so.
If the material you are listening to has no deep bass content (simple voice, for example), nothing is likely to be noticed. You'll probably need music with a lot of deep bass to tell the difference.
You could raise the roll-off point by decreasing the value of the cap, .04, .02, etc, to suit your taste, but too much might make the sound "muddy."
But check the resistor that is connected in series with the cap. If it has gone high in value, that would decrease the effectiveness of the control.

Thanks, Terry -- I see there's a lot to learn here. I appreciate your input, and I'll check the resistor.

David

Yep I second that. Any resistors near or directly connected to the volume control / tone control should be checked. I made the mistake of putting in a 1K resistor in place of a 1 Meg resistor. The volume was noticeably weaker, and there wasn't much difference between tones when using the tone control. Put the correct resistor in and it works great now.

Installed new caps in the tone circuit -- problem is almost gone. There's a small pop -- once. As long as the caps are charged everything's OK.

Thanks!