38-9 Restoration

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The Beginning
Don't Plug it In
3.  Pre-Flight Checks
The Plan

 1.  Get the Data

 2.  Block Diagram

 3.  Pre-Flight Checks

 4.  What Needs Replacement?

 5.  Ordering Parts

 6.  Install Electrolytics

 7.  First Power-On Checks

 8.  Triage Problems - more trouble!

 9.  Complete Electrical Restoration

10.  2nd Pre-Flight and Power-On, and The Last Problem

Additional Resources

 o  Antenna in the attic

 o  Shortwave Listening Guide

 o  Philco and Radio History

 o  Other Links

 

A) Visual Checks


(click for high res image)

There were five visible issues

  1. The power cord insulation was badly cracked, taped up and needed replacement.
  2. The speaker wires were exposed at the point where they came through the chassis.
  3. There was a "mystery wire to no where."
  4. This cap wasn't original; how old is it?
  5. Something black is oozing from this bakelite "universal" capacitor.  That can't be good!

I replaced the power cord and speaker wires, and removed the "mystery wire."  I just assumed that the cap (4) was suspect, and needed replacement.

The slightly oozing tar filled "universal condenser" would be a mini project on it's own.  I tackled this (with help from the Philco Repair Bench) as part of the complete electrical restoration.

B) Spot Checks
I checked the power transformer with an ohm meter.  The schematic identifies the nominal resistances, and as long as my ohm meter didn't indicate a short or open winding, I was happy.  There are 5 distinct windings, and the largest deviation was a reading of 197 ohm instead of the prescribed 130 ohm.

I spot checked resistors with an ohm meter.  (You'll need to be able to read the schematic pretty well for this, otherwise you'll be fooled by loops and nearby capacitors).  I found several resistors that were off by more than 20%, but nothing open or shorted.

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Lilian Vernon
Copyright 2004 look4000@verizon.net 
Last modified: November 01, 2008