[sdradioman]

Im currently going through what I believe is a code 122 16B... The gold label on the chassis was missing, as well as what rectifer tube to use on the label in the cabinet... It currently has a 5Z3 with the tall upright power transformer, not the flat pancake style... Anyway, my tone control is what I believe to be a run 15 pot due the fact there was a tubular .006 mfd after the tone contol going to the plate of the 77... There is only a single black wire coming out the tone control tar and then 4 tiny leads coming out of the tar, one lead going to the first tab, 2 leads going to the center tab, and the 4th lead going to the top tab... According to the schematic I have which is for the codes 121,22,23, it shows the 3 3000pfd caps inside the pot, with a single wire going the the plate of the 77 tube, but no where in the schematic does it show the tubular .006mfd... Is there a proper schematic that shows this change? I just need to know do I need to replace the 3 caps with .003mfds, even though there are 4 leads coming of the tar and then install a fresh .006mfd?

[Radioroslyn]

If you have 3x .003 or 3x.003 and a .006. the difference is going to be negligible.

[Ron Ramirez]

There were at least three different tone control circuits used in the early (5-band) model 16.

First version:

   

This version was apparently not used very long, and was replaced with this second version:

   

This one is commonly found in 5-band 16 sets, and adds a dual .025 uF bakelite block while removing the 0.5 and 0.15 uF metal can caps.

Late in production of the 5-band 16, the circuit was changed to this third version, using three .033 uF caps inside the control and eliminating the .006 uF cap between tone control and plate of the 1st AF tube:

   

This last version was carried over into production of the 4-band 16 (codes 125, 126, 127).

There may have been another variation in between the "second version" and "third version" posted above; I don't remember right now.

Now a word regarding code numbers. All 16 cathedrals and the earliest tombstones used the Code 121 chassis. Code 122 chassis were strictly intended for consoles, running a higher B+ voltage and necessitating a 5Z3 rectifier in place of the 80 used in Code 121. Code 123 was a chairside unit with an upside-down dial scale.

Likewise, the 4-band 16 models may be broken down as follows:

Code 125 - Tombstones
Code 126 - Consoles
Code 127 - Chairsides

[EdHolland]

Great info Ron.

I note also that the earliest schematic has a volume pot of 0.35 Meg as opposed to the 2 Meg control of the later schematics. Also differences in the resistor (Part no. 56) connected to the wiper.

Somewhere, in the paperwork I bought from Chuck Shwark, are detailed some service notes, including recommended changes. One of these detailed mods to the tone control. I will try and find these, as it is always possible that sets were changed after leaving the factory.

Cheers,

Ed

[Stall-U-Rated]

My tone control (30-4069) is represented in the second picture using the .09 and.003 caps and the dual .025 external bakelite block. I replaced the caps with exact uf#s and 2 of the 3 positions sound the same..  I didnt see a modification page in my package 

Steve

[sdradioman]

So I for sure have the third version, but on top of that there was a .006mfd tubular cap inline with the single wire running up to the plate of the 77 that appears to be original, or possible added back in if the 3rd design went to the three .003mfd caps with elimination of the .006mfd... I read in one of the service changes about it being part of a "15th run" modification... So I should be able to just replace the three .003 caps which is no big deal but do I replace this inline tubular cap as well? It shows up nowhere on the schematics... It is a Philco cap that dates to 1936 by the part number on it...

[sdradioman]

So Ron, is it possible that mine was a late run 3rd design with the three .003mfd caps in the tone control can and was put in prior to elimination of the .006 tubular cap? So should I just install the 3 caps in the tone control can and leave the .006 out altogther? Would putting it back in since I already have it going to hurt anything? Here is a link to what I have been reading:

http://www.nostalgiaair.org/Resources/139/M0013139.htm

On page 5-15 at the top it talks about the different tone controls... It says that the run #15 switches to the tio of .003's and adding of the .006 for smoother change of tone... Then in run 16 it talks about changing tone controls and eliminating the .006... Is this when they went to just the trio of .003's straight to the #77 plate? I guess my question is should I just go with three .003's with no .006 or will it affect anything to install the .006 like what appeared to be original and was in there already?

[Ron Ramirez]

I would just install the three .003 uF caps and eliminate the .006 uF tubular cap. The tone control will work fine in this manner.

If the cap does indeed date to 1936, it would have been added later since the radio was likely built in early-mid 1934. Maybe the radio's tone control was repaired early in its life and that .006 uF cap was added? It could have happened...

[sdradioman]

Awesome! Thanks Ron!!

[Ron Ramirez]

Unlike the results Stall-U-Rated experienced with his tone control (with the two .025 uF caps), you will hear a very noticeable difference as you change the tone control with the three .003 uF caps. In fact it may be too drastic to your liking. If so, you can always reduce the value of the first one or two to .002 or .001 uF. They add as you turn the tone control to the right, so you have nothing in the first position, .003 uF in the second position, .006 uF (.003 + .003) in the third position, .009 uF (.003 + .003 + .003) in the fourth and final position.