(1) First of all, find out what type of power supply your set has. The power
supply you'll use may be any of the following: Rectifier type, battery,
dynamotor, or vibrator.
(2) These are a few checks that you can make, regardless of the type of set
you're working on.
Check the power supply input circuit.
continuity check for open or shorts in the input cables, ac line cords, or
Don't overlook fuses, as a burned-out fuse may be the
A continuity check should also be made of the output
circuit of your power supply. Remember, a continuity check is always made
with the power off.
(3) Then turn on your set and see if the B plus voltage is normal.
e. Points to Look For.
Here are a few specific points to look for in the
various types of power supplies:
(1) Rectifier type.
Check all cables leading to or from the power supply.
Then check for the following:
(a) Bad rectifier tube.
(b) Open filter choke in the power supply.
(c) Filter choke shorted or choke leads shorting to chassis.
(d) Open or shorted power transformer windings.
If shorted, there is a
good possibility the fuse will blow.
(e) Shorted filter capacitor.
If this is the trouble, the rectifier tube
will glow with a bright red color and probably burn out.
(f) A short or open in the B plus line leading to any stage using power
from the power supply.
If shorted, there is a good possibility the
fuse will blow. If open, the voltage will be removed from the stage.
(g) Open bleeder resistor (if used as voltage divider also).
(2) Battery type.
If your set is battery-operated, then noisy, weak, or
unstable operation is usually caused by weak batteries. Be on guard for
signs of corrosion around battery terminals. If the supply voltage is not
normal, replace the batteries without checking further.
If your set is
not going to be used for a long period of time, remove the batteries.
(3) Vibrator type.
The function of a vibrator is to change a steady dc
voltage to a pulsating dc voltage.
This pulsating dc voltage is then
converted to a higher ac voltage by a step-up transformer. Most vibrator
supplies contain a vibrator, a power transformer, a rectifier, and a
Complete inoperation is usually caused by a defective vibrator.
If the vibrator is operating normally,