Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Model 90 Cathedral stopped receiving
#31

Wow, this is all a lot to take in.
You Gentlemen have been so very helpful.
Please give me a couple days to catch up on things.
(Replace vol pot, inspect mica, measure resistors, etc)
After a couple days, expect to hear back from me with all my new woes....
Thanks again!!!

Scott Jensen
(ZboltMan)
[b]For maximum attention, nothing beats a good mistake[/b]
#32

Hello to all,
I replaced the volume control and good semi good results.
I can now hear oscillator pitch sounds which vary when I tune, the cool part is they happen at a station where I hear faint fuzzy voices. (I promise, the voices are not in my head...)
Over the whole range of tuning, I get this about 4 places.

Now I am very interested in the comment made about the MICA. So I took some pics for further evaluation.
Here is where I need help.
1: What is the purpose of the MICA
2: IS the MICA damaged to the point of needing to be replaced.
3: Can the damaged MICA cause any of the issues that I am currently having, (see above)


Attached Files Image(s)
   

Scott Jensen
(ZboltMan)
[b]For maximum attention, nothing beats a good mistake[/b]
#33

These are trimmer capacitors. The mica is the insulator between the two plates. The capacitance is changed through tightening/loosening of the nut that gets the plates closer/further from each other thus changing the capacitance.
The capacitance is small and is used to trim the band limits to be exactly where they are wanted after they are roughly adjusted.

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
#34

Good, progress!  I wouldn't worry about the mica just yet, but would start measuring resistors and replacing capacitors.  Replace any resistor that measures higher than 10 or 20% of their original value.  I'd do one resistor and one capacitor at a time and then recheck how the radio plays.... that way if you make a wiring error you'll know right where to look.

I think I posted a link on how to restuff the little Bakelite blocks, but you don't really 'need' to do it that way, it is just neater.  BUT, what you need to do is look at the #'s on each block and make sure you use what is supposed to go in there, and not every block has been replaced or jumpered yet.  If you decide not to restuff the blocks you need to cut ties to the old capacitors still in there.  In the picture below you can see tiny wires coming out of the eyelets:

   

Use a small drill bit to break that wire before you jumper in a new capacitor.  If you decide to restuff then you can ignore this step.  Below are two methods, but Mike's is easier, but use whichever method works best for you:

https://philcoradio.com/library/index.ph...soldering/

https://www.philcorepairbench.com/how-to...te-blocks/

Link to a chart showing block #'s:

https://philcoradio.com/library/download...%20289.pdf

I think the best way to find a resistor value is to find it on the schematic, but there were some changes Philco made.  If the following gets confusing we can answer any questions:

https://philcoradio.com/library/index.ph...t-numbers/

One good source for capacitors:

http://www.tuberadios.com/capacitors/

John KK4ZLF
Lexington, KY
"illegitimis non carborundum"




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Shadow Meter Bulb
Phorum members, I am trying to find the bulb # for PHILCO Shadow Meter part number 45-2180 that is from a 37-640 chassis...georgetownjohn — 06:53 PM
Philco 41-608 changer coupler
3D-printing...short of machining, of course. Or molding.morzh — 05:20 PM
Philco 41-608 changer coupler
Thanks, Morzh. That solves the issue of the rubber pieces. Now, I need to find a way to replicate the pot metal piec...alangard — 05:07 PM
12' Philco
If it is 12', either Kareem or Andre would have to jump pretty high to look at the front panel. Kareem would have an e...morzh — 01:48 PM
12' Philco
And here's a story about the tires on the truck. Same "no-stoop" guy must have installed these! Take care a...GarySP — 01:17 PM
Hickok AC51 tube tester
I think they have only shown the secondaries of the transformer. Two of them feed the rectifiers' filaments.morzh — 12:58 PM
IF can wire size and Rubber mounts?
Arran If the wire inside cans is the gauges you mentioned, the sole reason for that would be mechanical, to stiffen t...morzh — 12:56 PM
12' Philco
Rod, Yes, I know, but the Giant Philco is not around anymore either, so I go by whoever was alive fairly recently. H...morzh — 12:54 PM
Hickok AC51 tube tester
Absolutely no one is going to reverse engineer that circuit. Even the iron core is missing.RodB — 10:37 AM
IF can wire size and Rubber mounts?
Thanks to both members for your help regarding wire and tuner mtg supports. regards--Johngeorgetownjohn — 09:33 AM

[-]
Who's Online
There are currently 6306 online users. [Complete List]
» 1 Member(s) | 6305 Guest(s)
Avatar

>