RE-Stuffing Model 90 Tone Caps? - Printable Version
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RE-Stuffing Model 90 Tone Caps? - Pepperoni - 03-25-2012
I looked through the Philco Radio site and I couldn't find the procedure for re-stuffing the cap block attached to the tone control on my model 90. It's gotta be there somewhere. Does this procedure exist and does anyone know where to find it? I found lots of topics on the 90 tone control but nothing specific to what I need to do.
Thanks,
Pepper
RE: RE-Stuffing Model 90 Tone Caps? - TA Forbes - 03-25-2012
Have never done one, but believe it's similar to re-stuffing bakelite block caps.
RE: RE-Stuffing Model 90 Tone Caps? - Pepperoni - 03-26-2012
You know I just jumped into it last night and I believe it's gonna be a piece of cake. It's a small metal can that has ends that can be folded open and the old rectangle of tar and caps just pops out. Of course you have to cut the three (3) cap wires that go the the switch contacts themselves. I'll try to post some pics.
Pepper
RE: RE-Stuffing Model 90 Tone Caps? - Chuck Schwark - 03-26-2012
(03-26-2012, 12:35 PM)Pepperoni Wrote: You know I just jumped into it last night and I believe it's gonna be a piece of cake. It's a small metal can that has ends that can be folded open and the old rectangle of tar and caps just pops out. Of course you have to cut the three (3) cap wires that go the the switch contacts themselves. I'll try to post some pics.
Pepper
I open the can just enough to let the slug fall out with a heat gun on low. Re-stuff with your fav. caps.
Chuck
RE: RE-Stuffing Model 90 Tone Caps? - Pepperoni - 03-27-2012
I think opening the front of the can may have been easier then opening the ends. I had problems with the slug interfering with the bottom of the wiper. But it still came out easy enough. Here's the pics.
Clean assembly ready for new caps.
[Image: http://speakeasyradios.com/yahoo_site_admin/assets/images/Philco_90_Tone_Control_002.8690540_std.jpg]
Caps wired into can. The rubber grommet fit perfectly in the hole so I used it and I also put a piece of insulating material in the bottom of the cans so the caps could rest in peace.
[Image: http://speakeasyradios.com/yahoo_site_admin/assets/images/Philco_90_Tone_Control_005.8690628_std.jpg]
Tone control complete.
[Image: http://speakeasyradios.com/yahoo_site_admin/assets/images/Philco_90_Tone_Control_007.8690736_std.jpg]
EDIT: Also on this Philco 90... What is the polarity of the 1.0ufd #30 cap? I ask because it's in parallel with a 70K resistor to ground but the other end goes through a 25K resistor, through the 3 section resistor to the CT of the high voltage output which I thought was the most negative part of the radio. So which end goes to chassis ground? + or -? Assuming this is a lytic cap.
Pepper
RE: RE-Stuffing Model 90 Tone Caps? - Pepperoni - 03-28-2012
(03-27-2012, 12:22 PM)Pepperoni Wrote: Also on this Philco 90... What is the polarity of the 1.0ufd #30 cap? I ask because it's in parallel with a 70K resistor to ground but the other end goes through a 25K resistor, through the 3 section resistor to the CT of the high voltage output which I thought was the most negative part of the radio. So which end goes to chassis ground? + or -? Assuming this is a lytic cap.
Got the cap figured out.
Pepper
RE: RE-Stuffing Model 90 Tone Caps? - Chuck Schwark - 03-28-2012
None of these caps are electrolytic, so polarity is not an issue.
One can see all three are metal-film types from the picture.
Chuck
RE: RE-Stuffing Model 90 Tone Caps? - Ron Ramirez - 03-28-2012
The other (ungrounded) end of the 70K resistor and 1.0 uF capacitor are connected to the screen grid B+ line - the screen grids of the RF, 1st det. & IF tubes. This is positive voltage, so if you use an electrolytic, your + lead should go to this point and the - lead to the can (ground).
It would be better if you use a mylar cap instead of an electrolytic here, but you can use an electrolytic if you wish. If space is a consideration within the can of (30), use two 0.47 uF caps in parallel which adds up to 0.94 uF - close enough to 1 uF.
RE: RE-Stuffing Model 90 Tone Caps? - Pepperoni - 03-29-2012
Thanks guys! Got it.
I pulled the schematic from philcoradio.com on this Philco 90 with all of the component values added. My Philco 90 (single 47 output) has a 250K volume pot in it and the part number 5366 is on the volume control which matches the parts list. But the schematic calls out a .5 meg pot. Is this a discrepancy on the edited schematic or is my volume pot not functioning properly? It seems to be functioning properly with my Fluke 179 hooked up to the CT and each leg but reads 250K across it.
Pepper
RE: RE-Stuffing Model 90 Tone Caps? - Chuck Schwark - 03-29-2012
(03-29-2012, 07:08 PM)Pepperoni Wrote: Thanks guys! Got it.
I pulled the schematic from philcoradio.com on this Philco 90 with all of the component values added. My Philco 90 (single 47 output) has a 250K volume pot in it and the part number 5366 is on the volume control which matches the parts list. But the schematic calls out a .5 meg pot. Is this a discrepancy on the edited schematic or is my volume pot not functioning properly? It seems to be functioning properly with my Fluke 179 hooked up to the CT and each leg but reads 250K across it.
Pepper
All my Philco Parts Catalogues show the volume pot to be Part No. 5724 for the 1-47 tube version, which is 500,000 or 0.5 meg pot. Part No. 5366 only shows up in my 1945 Parts Catalogue as subbed with p/n 45-5019 (a 1945 version part) with also a value of 0.5 Megohms.
From all this info, it appears that 0.5 meg for the pot is the correct value. The schematic (90 w/1-47) on this site also shows Part No. 20 as 0.5 Meg.
Be sure you are measuring the resistance of the pot from the outer two terminals, not from the each end to the center terminal, which is the wiper.
Regards,
Chuck
RE: RE-Stuffing Model 90 Tone Caps? - Pepperoni - 03-31-2012
As usual Chuck you are thinking more clearly then I. This pot is of the audio taper and not linear taper. Measuring across the two outer terminals Im reading 250K. But read from CT to either outer leg and it's not linear but does go thru 500K. But I still don't understand 250K across the outer terminals.
Pepper