Posts: 10
Threads: 4
Joined: Oct 2013
City: New York
State, Province, Country: New York
Hello Philco people!
I have a 48-200 that definitely needs alignment, but before I get the alignment tools out I just want to make sure I'm understanding what the service data is saying. From what I'm reading it's saying for the 455 adjustment to connect the output lead of the signal generator through a .1mfd cap to pin 6 of the 7AB tube and the ground lead to pin 7 of the 14A7, am I reading that correctly? Also can anybody suggest using something other than a .0001 mfd cap for adjusting the high side of the dial? Thanks.
Posts: 7,270
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Use an isolation transformer and you could just connect the output of the generator to the ant connection. Set the dial for 550kc. There's enough signal leakage thru the 7A8 that you'll hear it fine.
As for the adjustments on the tuning cap one is going to set the placement of the stations @ the top end of the dial and the other sets the sensitivity. Both of these you could use local stations the adjust. Or you could use a gimmick cap.
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
Posts: 10
Threads: 4
Joined: Oct 2013
City: New York
State, Province, Country: New York
Thanks for the reply Terry.
Yes I am definitely using an isolation transformer. If I work with your method and connect the positive lead to the of the antenna instead of the 7A8 I would also connect the ground lead to the chassis, correct?
As far as the adjustments on the tuning cap, what is the gimmick cap you're reffering to? Thanks!
(This post was last modified: 09-24-2024, 07:30 PM by
transitony.)
Posts: 7,270
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Yup.
The gimmick is to take the place of the 100mmfd cap you don't have.
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
Posts: 919
Threads: 38
Joined: Feb 2015
City: Roseville, MN
Hi, in this case I would be certain that pin 7, which is B-, of the 14A7 is not "hot". If it is then reverse the power plug. This is a hot chassis radio and when you attach the negative side of the generator to B- you don't want sparks. Instead of using the 100pf cap run the generator output hot lead to a loop of wire of several turns about 6 inches dia. Put the loop close to the loop antenna of the radio. Increase or decrease the distance to change the signal strength to the radio.
Posts: 919
Threads: 38
Joined: Feb 2015
City: Roseville, MN
Terry's gimmick cap is two insulated wires twisted together about 2 inches long, one wire attaches to the generator output and the other to the radio circuit. The wires act as a capacitor.
Posts: 10
Threads: 4
Joined: Oct 2013
City: New York
State, Province, Country: New York
Thanks to everybody for all the info so far.
RodB, thanks for the additional info. I worked on this radio years ago and put in a new AC cord and a polarized plug. I'm pretty sure I wired it so the hot side goes to the switch, I'll have to check. If that is in fact the case I'm imagining that the 14A7 is not hot and I'm good to connect to pin 7?
Posts: 10
Threads: 4
Joined: Oct 2013
City: New York
State, Province, Country: New York
Just checked the power cord and I did in fact wire it so the hot side (small prong) goes to the switch.
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
