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<  Firmwares, enhancements and upgrades  ~  PSU capacitor replacement.

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PaulR
Posted: Fri Jan 20, 2012 11:50 am Reply with quote
Joined: 16 Sep 2005 Posts: 13
I just wanted to mention that measuring the voltage can be a useful check to see if the capacitors need replacing but the PSU might still be on its way out and need some capacitors replacing even if the voltages read fine.

I have a 6 year old Toppy and did the 6 capacitor fix about 3 years ago. Over the last month or so my machine had been doing some strange things again (occasional crashes on startup, loss of signal from a tuner etc) and with increasing regularity so I suspected the PSU and measured the voltages. The voltages were fine but AndyFras convinced me to try the full 13 capacitor repair anyway as some can wear out and affect things other than the measured voltages. (PSU Startup etc).

I did the full repair last night and so far haven't seen any further unreliability.
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mstombs
Posted: Sat Jan 21, 2012 11:26 am Reply with quote
Frequent contributor Joined: 31 Dec 2006 Posts: 654
Multimeters in DC range only measure average voltage, capacitors with reduced capacitance/higher impedance may not be so good at reducing noise on the voltage rails when supplying the peaks of current the MHz processor demands.
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andyfras
Posted: Sat Jan 21, 2012 1:08 pm Reply with quote
Frequent contributor Joined: 25 Jul 2005 Posts: 3004 Location: Fleet, Hampshire (Hannington)
PaulR wrote:
I have a 6 year old Toppy and did the 6 capacitor fix about 3 years ago. .... The voltages were fine

If C22 is still OK, the voltages will still measure OK for the most part. However as mstombs mentions, there may be noise that doesn't show up on a multimeter reading, but can seriously upset the circuitry.

I am seeing many of these Toppies which had 6 or less capacitors changed some time ago, but are now playing up as the remaining capacitors fail. In some cases the PSU appears totally dead, but a new set of capacitors can revive it.

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