[Ron Ramirez]

> Were you happy with the cap specs you chose for the tone switch? Or where those of known values?

Known values; you can see them here:
https://philcoradio.com/library/images/schem/90b.jpg

> insofar as the speaker, is the polarity of the voice coil and field coil critical? Do they need to be in a specific phase?

I'd say likely not; however, I will defer to the other guys (morzh, RadioRoslyn, et al).

[morzh]

Ron

Yes polarity of the VC COULD BE critical IF it has the humbucking coil.

[Mike_RF]

How does one tell?  If its wrong, does it create damage? Or just sound funky? Hence swap the VC leads.


Cheers

[Ron Ramirez]

> Yes polarity of the VC COULD BE critical IF it has the humbucking coil.

Agreed: however, Model 20, 70 & 90 speakers have no humbucking coil so this is not an issue.

For what it's worth, I put together a speaker for my 90 from pieces coming from two or three donor speakers. I did not worry about field or voice coil polarity, and I had no issues.

[Mike_RF]

Ron, Morzh,

Thanks kindly gentlemen.

  "For what it's worth, I put together a speaker for my 90 from pieces coming from two or three donor speakers. I did not worry about field or voice coil polarity, and I had no issues."

Great to know. These speaker assy are starting to get hard to find and last thing I would wish to do is burn one up due to lack of knowledge.

Ron, In your restoration notes, you mentioned the antenna coil primary has 250 turns of #38. The Philco notes on this site says 100 or #34. Or are we talking about different coils?



Cheers

[morzh]

Mike


No damage. Humbucking coil counters hum induced by the fact that the magnetic field is produce by the electric coil (field) and not a Perm magnet. It simply has a few turns in the opposite direction to the VC, but is not a part of moving system. So it will compensate for the hum part of the field.



Ron

And I stand self-corrected: the polarity is not important because the two lugs are the end off VC/HBC curcuit, and whether it is one or the otehr direction, the HBC is always in opposite to the VC. So it does not matter how it is connected to the secondary of the OT.
If, and onlu if the HBC is separate and connected in series with VC explicitly (could be unsoldered and then re-soldered) - only then it is important to watch that polarity.

The HBC should always be in opposite to the VC.

[Ron Ramirez]

250 turns of #38 AWG refers to the little bobbin up inside the antenna coil, part (2) on the schematic. It's the winding which connects between the set's antenna terminal and chassis. Often these windings were badly burned due to a lightning strike back in ye olden days when these radios were being used on a daily basis by their original owners.

Now, where did you get that chart which shows 100 turns? I can't seem to find it. Please post a link.

[Ron Ramirez]

Mike

Again, let's remember that model 20, 70 & 90 speakers do not have a humbucking coil. Let's not confuse the issue needlessly.

[Ron Ramirez]

PHILCO SPEAKERS HAVING NO HUMBUCKING COIL

K - 8" - models 20, 21
K-2 - 8" - model 90 (early - 2-45)
K-3 - 8" - model 70, also model 90 (mid - 1-47)
K-4 - 8" - models 470, 490 (1-47)
K-5 - 8" - model 90 (late - 1-47)
E - 8" - model 86
F-10 - 8" - models 65, 76
G - 10-1/2" - models 65, 76, 87, 95
H - 10-1/2" - models 77, 96
H-2 - 10-1/2" - models 90, 112 (early - 2-45)
H-3 - 10-1/2" - model 90 (mid - 1-47)
H-4 - 10-1/2" - model 112 (late - 2-47)
H-5 - 10-1/2" - model 90 (mid - 1-47)
H-6 - 10-1/2" - models 90X, 112X (late - 2-47)

Philco began to use the humbucking coil in their speakers starting with their 1932 model line (71, 91, etc.).

[Mike_RF]

Ron,

Here is the link you have requested.

Rewinding Philco Coils – Philco Library (philcoradio.com)


Great discussion guys. Image i am sitting back crunching on popcorn and reading with great interest. Just like an old Potato. Im all eyes

Cheers

[morzh]

Ron


Yes, I understand. I think no K-type speaker has a humbucker in the firts place.

I simply made an incorrect statement (well, half-correct) and corrected myself.



Mike

As Ron said, no worries about humbucker.

[Ron Ramirez]

Mike

Exactly. No offense intended. I merely did not want to confuse Mike_RF.

[Mike_RF]

How fussy are the main filter caps? Will the choke tolerate 10uF on both the output and the input?

Ron did you check that link out??


Cheers

[Ron Ramirez]

Mike_RF

I read the link, thanks. On my computer when on the Philco Library home page, if I hover my mouse over the Shop Talk > Techniques link, the lower portion of the drop-down menu is not visible so I could not find the page originally. But if I click Techniques, then I can find the link.

Anyway...

That page does not specify which version of model 90 it is talking about - whether it be part (2) in all three versions; part (5) in the early and mid versions, part (7) in the early and mid versions, or part (8) in the late version. So, I cannot tell.

What I can tell you is that the primary winding of coil (2) of your set is the little bobbin mounted at the top of the coil form. The exact number of turns is not critical as long as it is in the neighborhood of 250 turns, and may be scramble wound if it needs to be rewound. As you know in my blog, I cheated and used a bobbin assembly from another Philco coil (not from a 90, but close enough) to fix mine.

[morzh]

>> How fussy are the main filter caps? Will the choke tolerate 10uF on both the output and the input?

This is not about the choke tolerating the caps, but about the rectifier tube's tolerance.

If your primary filter (right at the tube's K) cap is too large, the tube might not like it.
Also any increase in its value results in the increase of the rectified voltage value, and you might not want it as then your B+ is higher and your tubes run hotter.

The output cap after the choke is not critical, and is OK to be larger value (not smaller though). I almost always increase it two-fold. It improves filtering and does not affect anything else.

Prefer the film caps if possible, and high ripple/low impedance electrolytics by well-regarded mfrs, like Rubycon, Panasonic and such, if the electrolytics are desired.