[time-nuts] Errors on HP 58503A GPS time & frequency reference receiver bought from yixunhk.

Dr. David Kirkby (Kirkby Microwave Ltd) drkirkby at kirkbymicrowave.co.uk
Thu Dec 11 16:46:33 EST 2014

On 11 December 2014 at 01:10, Bob Camp <kb8tq at n1k.org> wrote:
> Hi
> I suspect that if you look closely at the board in the unit, it’s got water stains on it ….
> Bob

I suspect you might be right Bob, but I am not going to break the seal
to open it up to find out. I will be contacting the seller, to see
what they offer.

Does anyone have any experience with these having the voltages going
unstable? These two log entries show the 15 V is going both too high
and too low.

Log 004:20141017.00:00:11:  15V is out of tolerance, value: 16.62
Log 007:20141017.00:00:11:  15V is out of tolerance, value: 13.78

This shows the 5V rail has gone too high

Log 078:20141210.00:00:11:  5V is out of tolerance, value: 5.54

This shows the oven current is out of spec - whether it is too high or
too low is anyones guess

Log 022:20141205.04:42:26:  Primary oven current is out of tolerance,
value: 115.81

I'm guessing the 115.81 is mA, but I don't know. If it is mA, 116 mA
doesn't seem an unreasonable number. I assume this will have an
oscillator "similar" to a 10811A - lets not worry about the exact
type. According to the data sheet for the 10811A, the oven resistance
has a minimum of 42 Ohms. Supply voltage is 20-30 V. So a quick
calculation shows the turn-on current could be as high as 30/42 =  714
mA, so 116 mA doesn't sound unreasonable. The 10811A data sheet says
the power consumption is typically 2 W steady state at 20 V. So that's
a current of 0.1 A @ 20 V, so once again, 116 mA seems quite normal
for a steady state value, and a bit low for heating up.

I've not opened a case on eBay yet. I will do at some point, but would
like to know the likely fault on this. The fact it does actually work,
probably indicates there's nothing too serious wrong with it. I
suspect a cap(s) is failing, which is quite common with age, and
fairly easy to fix.

Having looked carefully, there are a few tell-tale signs this case is
actually not an original HP one, but I am not overly bothered by that.
It looks good, and if the unit worked, I would be happy.

It is rather annoying that people leave this seller positive feedback,
or no feedback if they get their complaints resolved. I've had a few
people email me about this seller, but they all seem keen not to say
anything on a list, and looking at the feedback of the seller, it is
still 100% positive. There is definitely something fishy about this
seller, but the 100% positive feedback does not reflect that.

I also wonder why they cleared the log, as the first log entry shows
Log 001:20141017.00:00:00:  Log cleared

I wonder if they had problems that they thought they had solved?


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