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Power  Supply  (Overall)  Repair  and  Troubleshooting  

Description  #   Text  Box   Comments  
1   Begin:  Power  Supply   Begin  diagnostic  process  for  a  work  order  on  Power  Supply.  Testing  and  maintenance  is  advised  when  a  device  fails  to  turn  on.  
2   Does  device  utilize  batteries?   A  device  may  run  on  primary  or  chargeable  batteries.  This  can  be  in  addition  to  a  wall  input.  
3   Troubleshoot  batteries.  See  battery  flowchart.   Refer  to  the  battery  troubleshooting  guide  to  ensure  the  proper  functionality  of  the  device  batteries.  
4   Does  device  turn  on?   If  after  successfully  troubleshooting  the  batteries,  the  device  power  supply  problem  may  resolve.  
5   Does  device  utilize  an  outlet  and  plug?   A  device  may  run  on  the  AC  voltage  input  from  wall  sockets.  
6   Troubleshoot  outlet  and  plug.  See  outlet/plug  flowchart.   Refer  to  the  output/plug  troubleshooting  guide  to  ensure  the  proper  functionality  of  the  device’s  input  power.  
7   Does  device  turn  on?   If  after  successfully  troubleshooting  the  outlet  and  plug,  the  device  power  supply  problem  may  resolve.  
8   Does  device  utilize  an  external  transformer?   A  device  may  require  that  the  AC  wall  input  is  transformed  into  the  appropriate  voltage  for  device  functioning.  
9   Troubleshoot  transformer.  See  transformer  flowchart.   Refer  to  the  transformer  troubleshooting  guide  to  ensure  the  proper  functionality  of  the  device’s  transformer.  
10   Does  device  turn  on?   If  after  successfully  troubleshooting  the  transformer,  the  device  power  supply  problem  may  resolve.  
11   Power  supply  is  working.  Be  sure  to  calibrate  and  troubleshoot  device  before  putting  it  back  into  service.  

Be  sure  to  troubleshoot,  calibrate,  and  appropriately  test  medical  device  before  releasing  to  clinician.    
12   Inspect  the  cable  from  AC  input  feeding  power  into  the  device.   Notice  any  deformities  or  exposed  wires  in  power  cord.  
13   Is  the  cable  in  good  condition?   If  any  deformities  or  exposed  wires  are  found,  the  cable  is  not  in  good  condition.  
14   Using  BTA  skills,  repair  or  replace  cable.   Cable  can  be  resoldered,  taped,  and  assembled  such  that  the  cable  is  functional  and  safe.  Replace  it  if  these  methods  are  not  adequate.  
15   Carefully  open  up  the  device.  Use  a  voltmeter  to  check  that  voltage   Follow  the  power  cord  into  the  device.  Immediately  check  the  voltage  at  the  point  where  the  cord  does  not  pass  through  any  

has  made  it  into  the  device.   circuit  components.  
16   Does  voltage  make  it  into  the  device?   Voltage  may  not  properly  conduct  through  a  poorly  conducting  cable.  
17   Check  the  switching  capabilities  by  testing  the  input  voltage  to  the  rest  of  the  device  when  in  on/off  stages.  

Using  voltmeter  to  measure  voltages  in  on  and  off  states  of  the  device’s  power  switch.  
18   Device  should  yield  the  appropriate  voltage  when  switched  on  and  no  voltage  when  switched  off.  

When  turned  on  and  connected,  the  voltage  should  conduct.  When  device  is  switched  off,  there  should  be  an  open  current  in  which  no  electrical  conduction  occurs.  
19   Does  the  device  switch  properly?   If  voltage  conducts  when  switch  is  on,  and  fails  to  conduct  when  switch  is  off,  the  device  switches  properly.  
20   Using  BTA  skills,  repair  switch  or  replace  components  to  ensure  the  device  switches  properly.  

Mechanical  switches  require  simple  observation  and  repair.  An  electrical  transducer  and/or  relay  will  require  the  engineer  uses  the  voltmeter  to  determine  if  an  open  circuits  are  occurring  in  any  of  the  circuit  components.  These  parts  will  have  to  be  replaced  as  necessary.  See  BTA  skills  on  Mechanical  Switches  and  Electrical  Simple.  
21   Does  device  utilize  a  fuse?   Use  a  mulitmeter  to  assess  whether  or  not  the  fuse  shorts.  A  shortage  indicates  a  functioning  fuse.  
22   Troubleshoot  fuse.  See  fuse  flowchart.   If  the  fuse  shorts,  it  is  still  functioning.  
23   Inspect  condition  of  components  within  power  supply.   Are  any  capacitors  puffy?  Are  any  components  melted  or  burnt?  Are  there  any  signs  of  rust  or  corrosion?  These  obvious  faults  should  clearly  indicate  any  problem  within  the  power  supply.  
24   Do  any  components  need  replacing?  

If  any  components  are  not  found  to  be  in  good  condition,  they  will  need  to  be  replaced  exactly.  This  may  not  always  be  possible,  and  harvesting  components  from  old,  dysfunctional  equipment  is  always  a  safe  bet.  

Replace  leaking  or  corroded  components  with  exact  replacements  if  possible.  Otherwise  power  supply  will  need  replacing.  
The  determined  components  should  be  removed  and  replaced  using  solder  and  a  soldering  iron.  If  exact  or  equivalent  replacements  cannot  be  made,  the  power  supply  will  need  replacing.    

26   Does  the  device  utilize  a  bulky  internal  transformer?   After  opening  the  device,  and  large  transformer  with  input  and  output  specification  should  be  obvious  in  a  linear  power  supply.  

27   Device  uses  a  “linear  power  supply.”  
Linear  power  supplies  are  characteristic  of  bulky  and  large  devices.  These  power  supplies  use  a  transformer,  rectifier,  regulator,  and  filter  in  series  to  achieve  the  desired  and  necessary  voltage  signal  for  the  device.  

28   Troubleshoot  transformer.  See  transformer  flowchart.   Refer  to  the  transformer  troubleshooting  guide  to  ensure  the  proper  functionality  of  the  device’s  transformer.  
29   Use  voltmeter  to  check  for  shorts  within  any  components.   Using  the  connection  mode  on  the  voltmeter,  methodically  move  through  each  component  of  the  power  supply  to  determine  if  there  are  any  shorts  to  ground.  
30   Do  any  connections  short  to  ground?   It  should  be  clear  if  a  component  is  not  conducting  properly  by  assessing  with  a  multimeter.  
31   Power  supply  is  working.  Be  sure  to  calibrate  and  troubleshoot  device  before  putting  it  back  into  service.  

Be  sure  to  troubleshoot,  calibrate,  and  appropriately  test  medical  device  before  releasing  to  clinician.  
32   Troubleshoot  voltage  regulator.  Pull  out  3-­‐pin  regulator.   Voltage  regulator  handles  large  spikes  in  voltages.  Pull  out  the  3-­‐pin  to  determine  if  the  regulator  has  failed.  
33   Does  short  go  away  in  overall  circuit?   Using  the  connection  mode  on  the  voltmeter,  methodically  move  through  each  component  of  the  power  supply  to  determine  if  there  are  any  shorts  to  ground.  
34   Replace  voltage  regulator.   If  the  circuit  does  not  short  when  voltage  regulator  is  removed,  the  voltage  regulator  needs  replacing.  
35   Replace  shorted  components  with  exact  replacements  if  possible.  Otherwise  power  supply  will  need  replacing.  

The  determined  components  should  be  removed  and  replaced  using  solder  and  a  soldering  iron.  If  exact  or  equivalent  replacements  cannot  be  made,  the  power  supply  will  need  replacing.  
36   Device  uses  a  “switching  power  supply.”   Switching  power  supplies  are  characteristically  lighter  than  linear  power  supplies.  They  also  use  a  transformer,  but  less  bulky  ones.  They  fit  amount  the  other  smaller  circuit  components.  
37   Use  voltmeter  to  check  for  shorts  within  any  components.   Using  the  connection  mode  on  the  voltmeter,  methodically  move  through  each  component  of  the  power  supply  to  determine  if  there  are  any  shorts  to  ground.  
38   Were  any  shorts  detected?   It  should  be  clear  if  a  component  is  not  conducting  properly  by  assessing  with  a  multimeter.  
39   Replace  shorted  components  with  exact  replacements  if  possible.  Otherwise  power  supply  will  need  

The  determined  components  should  be  removed  and  replaced  using  solder  and  a  soldering  iron.  If  exact  or  equivalent  replacements  cannot  be  made,  the  power  supply  will  need  

replacing.   replacing.  
40   Using  a  voltmeter,  check  for  the  presence  of  DC  voltage  after  rectification  and  before  the  small  internal  transformer.  

Using  the  voltage  mode  on  the  voltmeter,  methodically  move  through  each  component  of  the  power  supply  to  determine  if  there  the  appropriate  DC  voltage  is  being  conducted.  
41   Troubleshoot  internal  transformer.  It’s  important  that  the  input  and  output  is  of  the  appropriate  voltage.  

Refer  to  the  transformer  troubleshooting  guide  to  ensure  the  proper  functionality  of  the  device’s  transformer.  If  the  internal  transformer  in  a  switching  power  supply  is  not  functioning,  it  will  need  to  be  replaced.  
42   Using  a  voltmeter,  check  for  the  presence  of  DC  voltage  after  rectification  after  the  transformer.  

Using  the  voltage  mode  on  the  voltmeter,  methodically  move  through  each  component  of  the  power  supply  to  determine  if  there  the  appropriate  DC  voltage  is  being  conducted.  
43   Is  voltage  present  in  all  components?   It  should  be  clear  if  a  component  is  not  conducting  properly  by  assessing  with  a  voltmeter.  

Replace  any  non-­‐function  components  with  exact  replacements  if  possible.  Otherwise  power  supply  will  need  replacing.  
The  determined  components  should  be  removed  and  replaced  using  solder  and  a  soldering  iron.  If  exact  or  equivalent  replacements  cannot  be  made,  the  power  supply  will  need  replacing.  

45   Power  supply  is  working.  Be  sure  to  calibrate  and  troubleshoot  device  before  putting  it  back  into  service.  
Be  sure  to  troubleshoot,  calibrate,  and  appropriately  test  medical  device  before  releasing  to  clinician.  


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