
Diagnostic Sheet for DuraDry B-770, B-778 Dryers
Problem Possible Cause Possible Solution
AUTOMATIC
1. Dryer does not run a) No electricity supply Check main supply / wiring
b) Installation fault Check service manual for possible wiring mistakes
c) Worn motor brushes Check length of brushes; replace if less than ½''
d) Element open circuit Return dryer to Bobrick for repair
e) Control nonstart Replace control
f) Triac open circuit Replace triac
2. Sparks from dryer Worn motor brushes Replace motor brushes
3. Dryer runs at low speed a) Worn motor brushes Replace motor brushes
b) Triac halfwave
Remove white wire from triac; no dierence, replace
triac
c) Control halfwave
Remove white wire from triac; dryer stops, replace control
4. Dryer runs continuously a) Triac short circuit
Remove white wire from triac; no dierence, replace triac
b) Control faulty
Remove white wire from triac; dryer stops, replace control
5. Dryer cycles on and o Control Replace control
6. Dryer sometimes runs Dirty control lens Clean control lens
Control Replace control
7. Dryer is oversensitive Control Replace control
8. Dryer blows cold air or motor runs fast Heating element Return dryer to Bobrick for repairs
9. Grinding noise from dryer a) Worn motor brushes Replace motor brushes
b) Fan cage is bent or
damaged Return dryer to Bobrick for repairs
10. Dryer does not run and heating element glows Worn motor brushes Replace motor brushes; if still not functioning after
replacing the motor brushes, return dryer to Bobrick for repairs.
TOUCHBUTTON
1. Dryer does not run a) No electricity supply Check main supply / wiring
b) Installation fault Check service manual for possible wiring mistakes
c) Tabs are not connecting Turn o power, remove cover and bend tabs closer to
sensor board
d) Worn motor brushes Check length of brushes; replace if less than ½ʺ
e) Element open circuit Return dryer to Bobrick for repair
f) Timer assembly nonstart Perform Screwdriver Test (see test instructions)
2. Sparks from dryer Worn motor brushes Replace motor brushes
3. Dryer does not run and heating element glows Worn motor brushes Replace motor brushes; if still not functioning after
replacing the motor brushes, return dryer to Bobrick for repairs.
4. Dryer runs at low speed a) Worn motor brushes Replace motor brushes
b) Timer assembly Replace timer assembly
5. Dryer runs continuously b) Timer assembly Replace timer assembly
6. Dryer blows cold air Heating element Return dryer to Bobrick for repair
7. Grinding noise from dryer a) Worn motor brushes Replace motor brushes
b) Fan cage is bent or damaged Return dryer to Bobrick for repair
8. Dryer is oversensitive and a) Button loose Pack button O ring with tape
switches on or o randomly
b) Timer assembly or crystal board Perform Screwdriver Test (see test instructions)
9. Dryer cycles on and o Timer assembly or crystal board Perform Screwdriver Test (see test instructions)