Project Logs

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• PSU #099, an EX354RD

  Keith • 03/05/2024 at 16:23 • 0 comments

  This is a switch-mode PSU, so the mains is rectified to around 400 volts DC inside.

  Extra care is required to avoid touching this dangerous part of the PCB.

  Instruction manual:

  EX354RD+EX354RT_Instruction_Manual-Iss6.pdf
  

  Fault:

  Not marked on unit.

  Suspected cause:

  ....

  Examination:

  ...

  Action:

  ...

  Result:

  ....

  Status:

  Unknown.

  Photos:

  Plenty of room allows passive cooling:

  Front panel:

  Power inlet area:

  IC8 is an L4981A, a power factor corrector that does most of the control work:

  https://www.st.com/resource/en/datasheet/l4981.pdf

• PSU #095, a CPX400SP

  Keith • 03/05/2024 at 16:21 • 0 comments

  This is a switch-mode PSU, so the mains is rectified to around 400 volts DC inside.

  Extra care is required to avoid touching this dangerous part of the PCB.

  This can be remote controlled by GPIB, RS232, USB or Ethernet.

  The user manual is here: CPX400S+SA+SP_Instruction_Manual-Iss9.pdf

  I have requested the service manual.

  Fault:

  Output trips at over 20 watts.

  Error on display.

  Suspected cause:

  ....

  Examination:

  ...

  Action:

  ...

  Result:

  ....

  Status:

  ...

  Examination:

  Remove three screws at the back:

  Pop the plastic rivets at the sides:

  They would not pop out so I ran a knife between the metal side and bottom.

  You can see the display and controller boards (left), the power board (nearest), network board (furthest right) and GPIB board (middle right):

  A better view from this side:

  Be very careful, don't poke around willy nilly!

  It is densely packed. The case forms a tube that the fan blows air through.

  Networking boards:
  

  Front panel display and control boards:

  I can't see what that microcontroller is.

  I suspect the 4-way cable is a serial comms link to the networking board. Maybe I2C?

• PSU #084, an EX1810R

  Keith • 03/05/2024 at 16:19 • 0 comments

  This is a switch-mode PSU, so the mains is rectified to around 400 volts DC inside.

  Extra care is required to avoid touching this dangerous part of the PCB.

  Fault:

  Sparking at back of unit.

  Suspected cause:

  Faulty power connector or EMC capacitors.

  Examination:

  The power inlet was loose in the PCB, because of repeated cable insertions and no attachment to the case. Thus the strain goes direct to the PCB joints.

  Action:

  Resoldered power connector joints.

  Result:

  No sparking.

  Status:

  Fixed. Awaiting re-assembly and PAT test.

• PSU #077, a PL154

  Keith • 03/01/2024 at 10:51 • 0 comments

  Fault label: "Faulty current limit".

  Suggested action: Check current sensing circuitry.

• PSU #075, a PL154

  Keith • 03/01/2024 at 10:49 • 0 comments

  Fault label: "Current readout and limit vastly wrong".

  Suggested action: Check voltage entering digital meter chips.

• PSU #073, a PL154

  Keith • 03/01/2024 at 10:47 • 0 comments

  Fault label: "Missing sense plate, wrong voltage".

  Suggested action: Check voltage entering digital meter chips.

• PSU #010, a PL320QMD

  Keith • 03/01/2024 at 10:46 • 0 comments

  Fault label: "Numbers keep changing".

  2024-03-01

  Switched on, set dials to maximum. Leftt around 28.8V and drifiting, right around 32.88

  Dials set to minimum.

  Left side very slowly descends to 14.3 volts, terminals are at -0.424 volts.

  Right side slowly descends to 1 volts, terminals measures 0.017 volts and quickly rise to 32 volts when dial turned.

  Voltage displays take a very long time to change when dials adjusted.

  A look inside shows no disconnected cables. It is essentially two power supplies in the same case, with some push-buttons to connect them in parallel, serial, or not at all.

  Therefore it seems odd that both sides should be failing at the same time.

• PSU #001, a PL320

  Keith • 03/01/2024 at 10:44 • 0 comments

  Fault label: "Sparky".

  2024-03-01

  Opened case. Mains cable enters through grommet and is wired to the front-panel mains switch. There is no IEC filtered inlet.

  No sparking seen, even if wires poked with an insulated plastic rod (a Biro).

  Dials set to maximum, voltage reads 29.75, current limit reads 2.1.5.8.

• Diagrams

  Keith • 02/26/2024 at 02:56 • 0 comments

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