[mythtv-users] FE replacement recommendations

Brian Wood beww at beww.org
Fri May 29 16:11:54 UTC 2009

On Friday 29 May 2009 09:40:21 Alan Marchiori wrote:
> Well, I swapped out the RAM, no change.  Then I swapped the PSU and
> low and behold it has been stable ever since.  I have been working
> with PCs for a long time and have never seen a "bad" PSU where you
> could still boot the machine (usually it's just dead).  It is a
> Seasonic PSU with a 5 year warranty but they say if the fan turns on
> the PSU is not bad (and the fan does turn on).  I guess it could have
> been a loose connection somewhere.  I could swap it back and try to
> fiddle with it, but I'm just happy to have my myth box working again.

"If the fan turns on the PSU is not bad" is perfectly horrible advice. The fan 
will turn with poorly-filtered DC power, incorrect voltage and a host of 
other problems. DC motors are far less demanding in their power requirements 
than solid-state electronics.

I'd guess you have a filter capacitor that is breaking down shortly after 
power is first applied, resulting in poorly-filtered power (an oscilloscope 
would confirm this).

PSU problems that still permit the machine to boot up are really quite common, 
though often mis-diagnosed. Often the entire machine is replaced and the 
actual problem never discovered.

The "testers" that sell for under $20 are pretty much worthless, they merely 
indicate the presence of the various voltages, not the accuracy or quality of 
the power produced. They also do not load the supply. They can reliably 
diagnose only a total failure of one or more of the rails.

I'm glad you're back in business. Upgrading is always nice, but only when it's 
your idea.

beww at beww.org

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