[sdradioman]

Recapping a 37-630 code 125 and have found that all 4 110 pF caps are missing. Chassis is untouched with all original tubular caps and electrolytics along with resistors. Can’t find any service info stating these caps where removed for this run nor is there any signs they where ever there. Anyone seen this in the endeavors?” Part numbers on the schematic are 33, 35, 42, and 46.

[sdradioman]

https://philcoradio.com/library/download...20251A.pdf

[RodB]

Hi sdradiomwan,

I have a 37-630 code 125 on my bench waiting for a re-cap and restore. I just checked and all four are installed. Three are mica and one is a tubular. They are pretty much where the pictorial shows.

[sdradioman]

Is it possible for you to post a pic of them so I know where they all go correctly? Also maybe one of the entire bottom of the chassis for comparison? Also, one of the 110 pF is a tubular?? Thank you!!

[morzh]

Tubular or not (yes there were paper 100pF caps) they should be replaced by mica caps today.

[DaleHCook]

Bear in mind that some molded capacitors are not mica capacitors. If they are labeled "Micamold" they are may be not mica, but might actually be paper dielectric caps which should be replaced. Micamold started making paper caps during WWII when mica was scarce.

I have found most of the Micamold caps which I have had on my bench to be defective. A well-equipped radio restoration shop such as mine has both a high-quality LCR meter (I use a DER EE DE-5000) and a way to test capacitor leakage at working voltages (I use a General Radio Type 544-B Megohm Bridge with a Bio-Rad 500/200 regulated adjustable power supply as an external voltage source).

Any caps which I know to be paper dielectric are always replaced.

[morzh]

>>>Bear in mind that some molded capacitors are not mica capacitors. If they are labeled "Micamold" they are may be not mica, but might actually be paper dielectric caps...

or resistors

[DaleHCook]

If they are resistors they are poor-quality resistors. 

[morzh]

No, I mean Micamold resistors. Look like capacitors, but are resistors.

[RodB]

And,

If they are paper resistors you definitely need to replace them or have an extinguisher handy.

[Arran]

The Micamold resistors I have encountered were usaully wire wound, or at least higher wattage. The Micamold brand paper caps are also thicker then actual mica caps, like almost 1/4'' thick, 110 mmf/pf ones are not going to look like that. Since this set is apparently a 1937 model I don't think that Micamold paper caps would be in there unless they were replacements, Philco was still using some Bakelite block caps in 1937 however, and those are not trustworthy, if only because of the age.
On the parts list it states that those 110 mmf/pf caps are mica, given where they are used I'm guessing that they were omitted for some reason, either they were not needed, or maybe the earlier production models did not include them, but the later ones did. It looks like most of them are bypass caps, either for tone correction, or to bleed off some RF or IF. The replacement parts list has them posted at $.20 each, even assuming Philco paid $.05 for them wholesale leaving those out would have netted some cost savings, over 1000 or more units, if they didn't need to include them.
Regards
Arran

[DaleHCook]

That's a new one to me. The only Micamold resistors I have seen are ceramic-coated wirewound power resistors. From the few photos I have seen online I would be unlikely to confuse one of the low-power Micamold resistors with a Micamold cap. Bear in mind that I own a number of Micamold capacitors for work, but those are mica transmitting capacitors, in relatively large packages which are totally unlike anything in a radio.

[RodB]

I've seen those wirewound MicaMold resistors in AA5 radios as inrush low resistance, higher power, voltage droppers. From what I've read, the higher wattage, low resistance carbon resistors were difficult to make, making them more expensive than wirewound.

[morzh]

Dale

Feast yer eyes. I actually says "Micamold".
This is a wirewound 2W 22 Ohms resistor, the dropping one for the selenium rectifier in Zenith 7H920 I have recently finished.

   
   

[DaleHCook]

I've seen photos of low wattage Micamold resistors similar to that, but the Micamold resistors I've seen are ceramic coated wirewound power resistors of 25 watts or more.