[mythtv-users] HD-PVR power supply (wall wart) gone bad

Bob mythtv at cox.net
Sun Dec 16 01:06:13 UTC 2018

On 12/3/18 8:37 AM, Allen Edwards wrote:
> I will repeat, you will almost certainly burn out your device if you 
> power it from +12 volts.  I just looked at your cable and it looks 
> fine.  Therefore I would ask why do you think the old supply is bad?  
> Did you use a voltmeter or an oscilloscope to test it.  If so, you 
> should be able to test the output of your cable.  If you didn't test it, 
> and given you want to put +12 into a +5 device, I would guess you did 
> not test it, perhaps it is the PVR that is bad and not the power supply.
> The other possibility, mentioned already, is that there are ground 
> problems.  The wall wart is almost certainly not grounding your PVR as 
> the supply from the computer is.  If your PVR is grounded on a ground of 
> different potential than where the computer is grounded that could cause 
> problems. Plug them both into the same outlet and see if that helps.
> Allen

No worries, I never planned to use the +12V because it seemed like a 
mistake that someone on the list said to use it.

I had a bad power supply and a "good" one, I just wanted to fabricate a 
cable so when my next supply went bad I would be ready. I'm already on 
my 4th so it's probably a matter of time. Currently I'm using my "new" 
wall wart power supply since my newly fabricated cable isn't working so 

I did test the new cable after I soldiered it. Some interesting readings:

Old wall wart reading at 1/2 inch from the brick: 5.14 V
New wall wart reading at the barrel connector: 5.09 V
Newly fabricated cable that uses PC power supply (at the barrel 
connector): 5.04 V

I suspect it may be a current/amperage issue and am hoping to make time 
to move to a different connector on the PC power supply.


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