Mods to Phillys

[Joe Miller]

Were Philly's modified in later production runs without updating the schematic?

I found the IF AGC tube's cathode grounded rather than connected to ground through a 600 ohm resistor with a bypass cap as shown on the Rider's schematic.

Was this a factory change or the result of some one before me making changes?

Thanks,

Joe

[Bill Liers]

Good news Norman,

I also noticed that on this set, the treble cut is a simple cap and variable to ground after the first audio. Would you know the approximate date of this change? The SN is BB-443 and apparent DOM is early 1940.

[Norman S Braithwaite]

Bill:

An original beam of light chassis bearing the inspection date Nov 23, 1938 does not have the tapped volume control.  Another original bearing the inspection date of Oct 1, 1939 does.  I have a couple remote control chassis sets having earlier inspection date stamps that were both subsequently modified to incorporate the tapped volume control and later voltage divider (later style resistors used in chassis full of earlier style resistors).

Norman

[Joe Miller]

Bill, Norman,

Just finished the recapping of my Philly (both the amp and tuner are now done).  I have to jury rig my speaker connector (my 15 inch speaker is from an organ) to fit the chassis. (I have the speaker modified to work once I get the connector pinning fixed).  Hope to power it up early this week.

I am looking ahead to alignment once I get the basic checks done and it playing.  I am puzzled about the unusual connections for the signal generator and the output meter.  I usually connect the signal generator to the grid cap and chassis ground and use my DMM to monitor the output.  Why are both of these connections (sig generator and the output meter) different for the Philly?  I don't have a 50 micro amp meter.  I think my DMM has a 400 micro amp scale--maybe that would work?

[Bill Liers]

Joe,

The hookup for the converter grid cap is not so unusual. There are many differences in test equipment and also over the years that they have been made. The converter grid needs a ground reference and a 1 Meg ohm is typical. Also, the small value cap in series, de-couples any DC reference presented by the generator and limits low end hum and noise from getting into the equation. On the detector side, when these tests were designed, voltmeters were relatively low in impedance and could load down a circuit. A microammeter eliminated this possibility. I personally use a DVM connected to the detector diode or even the AGC line to the eye tube for peaking.

The connections from the RF & IF AGC lines to the bias divider effectively disable these circuits at close to their typical output values so that they can't affect the levels as you adjust.

Good luck, Bill

[Norman S Braithwaite]

A VTVM may also be used in lieu of the 50ua meter.  I find the analog meter easier to work with when aligning a receiver.  It is easier to see the peak in meter needle movement than it is to ascertain the peak reading a digital display.

Norman

[Bill Liers]

Norman,

Agree on the ease of use of an analog meter. I got away from it with a set that had a crummy screen divider one time and levels were shifting on their own. The DVM gives me a solid "digit" reference. Maybe on the next set I'll use both. ;)

[Joe Miller]

Thanks guys,
I'll use a VTVM and connect the sig gen as noted.
Norm, I really appreciate your diagrams for alignment

[Joe Miller]

BTW I did not open the enclosure around the main tuning assembly.  I assume there are not caps under it. Can you confirm?

[Norman S Braithwaite]

Bad assumption!  There are two wax paper capacitors under the shield.

Norman

[Scott Seickel]

There are also a couple of 1 meg resistors there that you will want to check.

[Joe Miller]

Got em!

Glad I checked.  Resistors tested okay.

Thanks

Joe

[Ken Carr]

Scott .. I posted photos of the Bass Choke here: http://goo.gl/2K72dJ
If that link does not work, just look me up on this site and you will see it in my photos section.
Regarding the main discussion here, I also have noticed instances where my Philharmonic does not match the circuit drawing. I usually replace components with exactly what I find on the radio.


Scott Seickel said:

There is a recent thread called "Bass Choke Renewal" that has a couple of pics and may be helpful.  I would post the link, but it looks like a copy and paste does not work on this forum software.