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

Philco Model 20 Deluxe
#1

Hi All, I just finished up on the restoration of a Model 20 Philco radio.
I successfully restored one of these about 5 years ago.
I have a few dumb questions, first of all I replaced all block capacitors
and also the ones in the big can, using the 630 V yellow jackets, like I did 
before. Also replaced any resistors that were out of spect's..
I just fired her up this morning...No smoke Icon_thumbup But nothing else Icon_cry 
Here is what I done before. This set was physically in bad shape, very rusted.
The cabinet I had to rebuild the grill work.
Also the output transformer, the primary was open, and the speaker was toast.
So I got a new output transformer, the P T 291 from AES. I am using the old
field coil winding which reads 3115 ohms. I hooked the 71-A plate's from each
71A tube to the new Primary to an 8 ohm pm speaker, and the center tap to one
side of the field coil. Now the schematic says I should be getting around 190vdc.
Now is that 190 vdc to ground or to each plate of the 71A's? If it's to ground
then I'm getting about 50mv ?? Also where it the best place to get the B+ voltage
I get on the 80 rectifier and am getting 5.45VAC on the filiments and 525vdc accross
each small pins and nothing to ground. Where is the best place to read B+ voltages?

Thanks for any help,
Gary
#2

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

>If it's to ground then I'm getting about 50mv ??
Not so good. All of the wires connecting to the fc and the pri of the opt should have HV.
I would measure the HV from the 80 filament (+) and terminal 6 (-)on the power transformer. Should see several hundred volts there.

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#3

Ok, Just checked, 505 VDC From 80 filament to pin #6 on power
xfmr. Should I use pin #6 to check for all B+ voltages. #6 as the most Neg.
point?
#4

Yup. You'll probably find that the choke is bad or bias resistor has an open section.
Happy hunting!

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#5

Ok, here is some readings..
Tubular resistor, Pin's 5-6 900 ohms, should be 2470
                        Pin's 6-7 757 ohms, should be 975
All others spot on.

#24 plate 250 vdc,other #24 250 vdc
 #27 plate 317 vdc...should be 120 vdc
#71A plate 3.5 vdc should be 215 vdc
#71A plate 4.0 vdc should be 215 vdc
Choke # 23 418 ohms dc resistance Icon_cry 

Oh yes, all cap's replaced, including the can cap's
used all 630V yellow jackets...As before in last working model 20.

Gary
#6

See what voltage you have where the center tap of your new opt. trans., choke, and field coil connect. point d on schematic.
https://philcoradio.com/library/download...l.%201.pdf
#7

It sounds to me like the choke is open.

Steve

M R Radios   C M Tubes
#8

I was thinking same thing but he did show a reading across the choke. Maybe could bypass the choke.
#9

Ok, Can't do anything more to day...
Will hook everything back up tomorrow including the new o p
xfmr and a 4 ohm speaker. I'll re check the voltages and if nothing I will
bypass the choke.
will report back tomorrow...
Gary
#10

Check the ground connection on #25

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#11

Gary,  I restored a Philco 20 a few years ago and I had an open choke. I replaced is with a Triad C-7X. As I recall if fit perfectly and is still working to this day. So in case you need a new choke here is a link to the one I used:

https://www.mouser.com/ProductDetail/Tri...aP3g%3D%3D
#12

Thanks Joe, I have already checked the choke for DC resistance
ohms out at 418 ohms. I know this isn't the way to check chokes,
It's impendence. But thanks anyway, I'll write down that info in case
it is the choke. This is the 2nd model 20 I have restored, didn't have
any trouble with the first one.

Gary
#13

Replace the resistor from terminal 6 to ground (abt 200 ohms).

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Jackson 715 not working
Mrfixr55, its working now. I cleaned the switches and sockets with spray cleaner. Thanks for helping on this one.daveone23 — 06:26 PM
Jackson 715 not working
Now that you posted the schematic, I don't know why that Sprague electrolytic cap is across the meter, as it is not indi...MrFixr55 — 05:51 PM
HiFi (Chifi) tube amp build - but my own design.
What may be lacking in the PP Tube amps may be the 2nd harmonics, which some, especially RCA back in the day called &quo...MrFixr55 — 05:32 PM
Jackson 715 not working
Usually in an emission tester, the tube under test is measured as if it were a diode. So, some testers connect all the g...RodB — 04:17 PM
Restoring Philco 37-604C
Yep. F5 is green, D5 is Red. Red is Bad. Green is Clean.morzh — 01:30 PM
Jackson 715 not working
I did start to do that but I stalled out because I could not figure out how the grid and plate get voltage. In this diag...daveone23 — 11:52 AM
Restoring Philco 37-604C
(Insert Homer Simpson "DOPF" Here.) When all fails, look at the can. Took the Ron Ramirez advice, red Caig D...MrFixr55 — 09:23 AM
Philco 91 Speaker Replacement
From your text I am not sure if you intend to use the existing speaker with a resistor instead of the field coil. It wo...morzh — 08:44 AM
Philco 91 Speaker Replacement
My field coil is bad. I am still hoping to find an original, but if I can't I will go with a fitting Philco speaker, 125...dconant — 08:34 AM
Philco 91 Speaker Replacement
As Rod said, it is OK to use a fitting speaker, and then look for an original one. If you buy a Hammond 125 output tr...morzh — 08:15 AM

[-]
Who's Online
There are currently 3974 online users. [Complete List]
» 1 Member(s) | 3973 Guest(s)
Avatar

>