Humming psu

Comments

• itsallgood

  November 2004 edited November 2004

  No ideas, anyone?
  
• Steve(spt)

  November 2004 edited November 2004

  
  This might help I relaced some diodes in PSU and it stopped buzzing .. some stuff below here, i thinks theres a copy in the Docs info pages.
  
  You can get the diodes from maplins.
  
  Steve(spt)
  
  
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  POWER SUPPLY FAULTS & REPAIR
  
  The Spectrum PSU suffers mainly from the wire/s in the premoulded plug, or lead exit from the box, snapping or going intermittent.
  The power plug fault is easily cured, by fitting a replacement 2.1mm female plug. Ensure that Negative goes to centre, which should be the traced wire. When the plug has been fitted, fill the plastic cover with silicon rubber before screwing up. This has the effect of not only stopping future internal shorts in the plug, but also helps take the strain off the solder connections when the wire is pulled.
  
  At the other end of the lead, if the moulded exit is found to be at fault, then split the PSU box, making sure that it is disconnected from the mains and computer first. Cut off the faulty section, tie a double knot some three inch down the cable. Now slide one inch of protective sleeving onto the lead, resolder the wires from where the old ones came, taking note where the traced wire came from. Now replace the top, with the knot on the inside of the box and trap the sl eevi ng at the exit point. The knot obviously stops the internal solder connections from being strained when the lead is pulled and the sleeving protects the wire at the exit point.
  
  In some cases, the wire will be bare at the plug or box. This obviously shorts out the PSU, with the effect of blowing the Thermal fuse and/or taking out all the rectifiers, IN4001/-7?s. These faults can be repaired. In some cases the transformer can also be faulty and if this is the case it is beyond an economic repair. To repair the PSU see
  fig 5.8
  The thermal +usable link can be replaced, by spot soldering a fuse holder fitted with a 160ma slow blow 20mm fuse across the old device.
  
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• chaosmongers

  November 2004 edited November 2004

  Anyone got any similar info on repairing SNES / NES power supplies?
  
  I've got shed loads of dead PSU's for these about, that have working machines to go with them.
  
  Getting generic replacements is expensive, as they're 9v 1.3A AC rather than the nice ?2.00 low current DC ones that will power a Megadrive, Master System or Atari 2600.
  
  
  
  
• guesser

  November 2004 edited November 2004

  If the laminations of the core of the transformer have seperated they can work like a solenoid conected to AC, the transformer has a constantly reversing magnetic field and the bits of metal will shoot from one side to the other.

  My rubbish website including the redrawn Amstrad schematics and the Sinclair Wiki.