This Packard-Bell
model 1R5 is an Electronic Kits training radio.
This AA5 was part of a student lab
used to teach theory and practical assembly skills with this hands on trainer
radio. This radio suffered from what sounded like Silver Mica
disease. It turns out to have been a cracked silver mica capacitor with in
the first IF transformer. It was the last capacitor disk changed. It fell
apart when de-soldered. All the ceramic disk caps in the IF cans have been
replaced with Silver Mica capacitors rated at 500 volts. I suspect these
caps will last a life time.
All out of tolerance resistors were
replaced. The carbon composition resistors usually go high with time
and if they are overheated during soldering. There was also a questionable
0.047 uf cap that also has been replaced. The original filter caps are
still good. All tubes tested and a full electronic alignment has been
performed. I found an identical chassis model number 531 to verify the alignment
specs. The 531 is a production model sold in stores. I have been
listening to "When Radio Was." on 1410 KQV am radio. Chandu the
Magician was the story tonight.
The rest of this document can be found at
www.Radiomuseum.org.
All
the disks tested near 59pf.
This
cap is chipped. I suspect this was the source of the
crackling. I simply measured both chips in the cap meter. The
total cap added to ~95pf.
100pf
silver mica caps fit the bill nicely.
The IF transforms peaked nicely at
455 kHz. The top end frequency was set at 1620khz (spec). The low
end receives down to about 490khz. That is out of the standard broadcast
band. You may hear the occasional air port beacon or boot-leg station
below the standard bands. The dial is a bit off at the lower
frequencies. This seems to be an anomaly of this particular chassis.
I verified the IF frequency to be sure. A wrong IF can throw off dial
scale. Unfortunately when peaking the 600khz slug in the oscillator coil
the lower scale sometimes slides off of the marked dial scale to obtain peak sensitivity.
This is a compromise between low end sensitivity and dial scale accuracy.
Some radios have a compensated dial scale (i.e. not linearly printed). I
see this often.
This is a rather sensitive little
radio. It picks up the local Disney station on 540khz strongly. The
location of that station is a considerable distance and through a hill from this
shop. Most radios need an external antenna to receive this station.