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

[Bob Camp]

Hi

(yes this post is *after* the data from opening the unit).
> On Dec 12, 2014, at 5:36 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <drkirkby at kirkbymicrowave.co.uk> wrote:
> 
> On 12 December 2014 at 03:54, Peter <timenut at exemail.com.au> wrote:
>> Hi David
>> 
>>> "The fact it does actually work, probably indicates there's nothing too serious wrong with it."
>> 
>> In my opinion, you potentially (pun intended) have a very serious problem.  Your LOG shows the 15V supply rail out of tolerance at 19.46V.  That is, nearly 30% high - it could be even higher at other times.  This should never happen.  Such excesses may permanently damage board components.  Do not tempt fate - power off the equipment immediately before it self-destructs.

I would bet that the power supply its self is fine. It’s likely pretty well sealed against being soaked in water. Tin whiskers on the attenuator resistors in front of the ADC are likely the issue here. 

> 
> I did consider that possibility. It does however appear to be working
> ok. The log looks ok now, it is locked to gps, the output is "about"
> 10 MHz. I can't check it too carefully. It is agreeing with my
> frequency counter that has an 10811A not been calibrated in 20+ years.
> I don't yet have the SR620 TI counter I purchased to see how much they
> differ.

I would watch the logs for lock / unlock issues. Also keep track of the “estimated holdover” time number. That’s something that the Z3801 has and I *assume* this box has it as well. It’s a good internal estimate of the unit’s health. 

> 
>> Replacement of the PS brick may be required and while they are available at reduced prices they are not inexpensive.
> 
> Yes, I noticed that.
> 
>> You have purchased a non-functional fake and I would instigate action to recoup my payment.  I regularly purchase electronics out of China via eBay/PayPal and fakes are everywhere.  My policy is to never return fakes ("it is against the law to post fake items" and in any case they are worthless - particularly if they are faulty) and demand a full refund.  While this may require some effort in communication, PayPal has always come to the party.  In my opinion, if you return fakes they are simply on-sold to other victims.
> 
> It would be next to impossible to prove this is a fake. If it was a
> current, or fairly current Keysight product, they might take a look
> for nothing. But Keysight are not going to want to get involved about
> a product line that HP sold to Symmetricom a long time ago.

I suspect that rust and fake stickers might help prove things ….

> 
> I am sure I can convince eBay/Paypal it is non-functional, but
> convincing them it is a fake is a completely different matter - not
> helped by the fact that people who do get problems tend to keep quite
> about them. I got an email from someone yesterday which described the
> problems he had, but ended in
> 
> "And like the others I chose not to talk too publicly..."
> 
>> Yixunhk is well known as an eBay seller who will take you for a ride, both financially and technically.
> 
> I'm amazed yixunhk keeps the 100% positive feedback, but I guess if
> people don't leave appropriate feedback, it is hardly surprising.
> Someone recently emailed me to say they had a problem with a GPS
> receiver from yixunhk, but returned it to a US address they were
> given, and got a full refund, including the shipping costs. What
> feedback they leave is up to them of course. Some might consider that
> a positive outcome.
> 
> That said, I emailed a friend about this, who has bought from yixunhk
> and had no problems - that was on a tracking generator for a spectrum
> analyzer - not a time-nuts related item.

Based on a lot of eBay deals, yes simply getting your money back does put a deal in at least the upper 50% range …

Bob

> 
>> If you are considering a purchase from him, first do your research - Google the blog of fellow time-nut Mark Stephens VK2HMC, and his time-nuts posts.  As another victim, he has a few words to say.
>> 
>> Peter
> 
> Yes, I found VK2HMC's  blog, which just seems a rant about yixunhk,
> but does not contain any real substance.
> 
> Dave
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