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WARNING — Anyone with an FS-5000 in his or her collection, who wishes to use or demonstrate the device, MUST read the following notice. Inside the mains power supply unit (PSU) are a number of capacitors that are likely to explode after a number of years. It is important to replace all RIFA capacitors in the PSU before connecting the it to the mains.  Learn more...
FS-5000 PSU
Power Supply Unit

The FS-5000 radio station can be powered from two rechargeable batteries (recommended), from an external 12V source (via the power inverter that is part of the battery charger), or directly from the Power Supply Unit (PSU) that is normally mounted on top of the battery charger.

The image on the right shows the PSU which has no controls. At the right is a socket for input from the mains. The wide-range PSU accepts any AC voltage between 110 and 240V. To the left of the mains socket is the main fuse (4A slow-blow). A spare fuse is stored below the plastic cap on top of the unit.

At the bottom of the PSU are two large contact pins that carry the 14V DC output voltage. When the PSU is mounted on top of the battery charger, these pins line-up with similar pins in the top lid of the charger.
  
Mains power supply (PSU)

Mains power supply (PSU)
Connections at the bottom of the PSU
Mains socket and fuse on the front panel of the PSU
Stacked combination of PSU and Charger
Stacked combination of PSU and Charger
Complete FS-5000 radio station
Charging batteries
Two FS-5000 batteries
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Mains power supply (PSU)
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Connections at the bottom of the PSU
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Mains socket and fuse on the front panel of the PSU
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Stacked combination of PSU and Charger
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Stacked combination of PSU and Charger
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Complete FS-5000 radio station
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Charging batteries
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Two FS-5000 batteries

Interior
The PSU is a Switched Mode Power Supply (SMPS) with a wide-range input (110-240V AC). The advantage of the SMPS principle is that PSUs can be made much smaller, as they don't need a bulky transformer, and are highly efficient (approx. 80% at the time this PSU was designed).

Because of the high voltages, a protective plastic cover is present between the PCB and the top lid. The image on the right shows the interior of the PSU after the plastic cover has been removed. The PSU consists of a single PCB with an SE5560 controller at its heart [1].

One of the disadvantages of an SMPS is that it generates rather strong (unwanted) spurious signals that can cause interference with the reception of weak radio signals. Such side-effects are generally classed as EMC-problems, which are extremely difficult to solve.
  
PSU interior

Although the designers of the FS-5000 made an enormous effort to avoid any EMC problems with this kit, the spurious signals from the PSU are not sufficiently suppressed. As the FS-5000 was specified for a range of no less than 6000 km, it was advised to power the radio station always from the batteries. In some countries a modification was carried out that made it impossible to connect the PSU/Charger to the transmitter. The modification consisted of a plastic panel that was mounted over the input connector of the transmitter.

PSU without top lid
Removing the plastic top cover
PSU interior
Active switching components
Switched Mode Power Supply controller (SE5560)
Mains socket and filtering
Transmitter with shielded power input connector
Power input connector on the transmitter
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PSU without top lid
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Removing the plastic top cover
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PSU interior
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Active switching components
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Switched Mode Power Supply controller (SE5560)
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Mains socket and filtering
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Transmitter with shielded power input connector
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Power input connector on the transmitter

Restoration
It should be noted that inside the PSU – on the primary side – are a number of capacitors that are connected directly to the AC mains. These capacitors – made by RIFA – are likely to explode. Over time, they will have developed cracks, as a result of which moisure can enter the body and react with the aluminium foil inside. RIFA capacitors are notorious for this [2], and one FS-5000 user in Germany has already reported an explosion, which caused the main 16A house fuse to blow [3].

Several RIFA capacitors from and FS-5000 PSU. Photograph by Karsten Hansky [3].

If you want to use or demonstrate your FS-5000, it is mandatory to replace all RIFA capacitors inside the PSU, before connecting it to the AC mains again. To do this, take the following steps. In case of doubt, make a photograph of the interior first, so that you know what goes where. Do this only if you know exactly what you are doing. If you are uncertain, ask someone else for help.

  1. Remove the top lid from the PSU (4 screws in the corners)
  2. Pull the fabric threads to remove the protective plastic high-voltgage shield
  3. Desolder the two white wires from the AC mains receptacle
  4. Desolder the two wires (red and black) that go to the output terminals
  5. Desolder the two wires (red and black) that go to the LED
  6. Remove the two screws that hold the PCB
  7. Remove the three plastic screws that hold the heat sinks
  8. Remove the cover of the + and - contacts
  9. Remove the PCB from the enclosure
  10. Remove all RIFA capacitors from the PCB
  11. Install alternatives of the same capacity and the same or higher voltage
  12. Re-assemble the PSU in the reverse order
Important
  • Note that some components carry the live 220V AC mains voltage, which may potentially be lethal. If the device has recently been used, some capacitors may still be charged.

  • Use a proper desoldering tool, preferably a desoldering iron. If you have no experience with desoldering components from a double-sided PCB, you might want to ask someone with the appropriate skills to do the job for you.

  • Be careful not to damage the PCB tracks when desoldering the 4700 pF Y-capacitors. Note that it is a double sided PCB and that the through-plated holes are easily damaged.

  • The two 6800 pF at the bottom edge of the PCB must also be swapped. They are series connected and are responsible for the supply voltage to the control logic. Substituting them with a different value may damage the electronics.
RIFA capacitor from FS-5000 PSU. Photograph by Karsten Hansky [3].
RIFA capacitor from FS-5000 PSU. Photograph by Karsten Hansky [3].
RIFA capacitor from FS-5000 PSU. Photograph by Karsten Hansky [3].
RIFA capacitor from FS-5000 PSU. Photograph by Karsten Hansky [3].
RIFA capacitor from FS-5000 PSU. Photograph by Karsten Hansky [3].
Several RIFA capacitor from an FS-5000 PSU. Photograph by Karsten Hansky [3].
RIFA capacitor from FS-5000 PSU. Photograph by Karsten Hansky [3].
PCB with the RIFA capacitors removed. Photograph by Karsten Hansky [3].
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RIFA capacitor from FS-5000 PSU. Photograph by Karsten Hansky [3].
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RIFA capacitor from FS-5000 PSU. Photograph by Karsten Hansky [3].
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RIFA capacitor from FS-5000 PSU. Photograph by Karsten Hansky [3].
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RIFA capacitor from FS-5000 PSU. Photograph by Karsten Hansky [3].
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RIFA capacitor from FS-5000 PSU. Photograph by Karsten Hansky [3].
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Several RIFA capacitor from an FS-5000 PSU. Photograph by Karsten Hansky [3].
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RIFA capacitor from FS-5000 PSU. Photograph by Karsten Hansky [3].
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PCB with the RIFA capacitors removed. Photograph by Karsten Hansky [3].

References
  1. Philips (NXP Semiconductors), SE5560 Switched-mode power supply control circuit
    31 August 1994. Retrieved April 2012.

  2. Leon Crampin, Beware Rifa Class X Capacitors!
    UK Vintage Radio forum. Retrieved October 2020.

  3. Karsten Hansky, Personal correspondence
    October 2020.
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Crypto Museum. Created: Friday 20 August 2010. Last changed: Wednesday, 14 October 2020 - 15:47 CET.
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