[hpsdr] Problems Calibrating Pennylane and with LPU, Could Use Some Help

[Mark Leone]

On 11/28/2011 10:04 PM, Bob Mahrenholz wrote:
>
> However, if I hold the output at 500mW for too long, I hear a "poof" 
> from Pandora and everything goes dead!  All the red lights
> go out and the program stops. If I turn my power supply off and back 
> on again, things seem to recover. I suspect maybe a fuse
> blowing because of excessive current drain but the total Pandora 
> current drain including the fan only measures 1.670 amps. LPU
> has 2 amp fuses in both its 12 and 5-volt outputs.

Bob,

I just built Atlas and LPU and installed Mercury, PennyLane, and Metis. 
Even with just Metis and Mercury, the system powered off 10 min or so 
after starting, just as you describe. I took this to be a manifestation 
of what is described in the LPU Errata document. The text says that 
fuses F2 and F3 are rated for 1A but draw slightly more. Like you, I 
noticed that they are labeled as 2A, so I thought the original problem 
was fixed in a later production run.

But given that the problem is exactly as described in the errata 
document, and that the regulators have built in over-current protection, 
I went ahead and strapped out F2 and F3 as recommended. I also wondered 
if I installed the fuses in the right places. Searching online I 
couldn't find any description of SMT fuse markings that jived with what 
I saw on the parts supplied; but since F2 and F3 have the same value, 
and F4 is a different value, I assumed that the two fuses with the same 
markings were F2 and F3.

My system has been running with F2 and F3 strapped out for about 16 
hours now, with Just Metis and Mercury; but there's no smoke, fire, 
excessive heat, crackling noises, or any other adverse indications; and 
the signals are being processed just as expected.

-Mark K4XML


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