I purchases this to calibrate a precision 200 I want to rebuild. nice device to have around if needed. Anyone know anything about this? I have no info, schematic, manual, zip. There is a adjustable capacitor I suspect is for calibration? Anyone have any ideas? thanks

this is some post info from sellers/buyers

This is from the ebay seller page.

HUABAN
Manufacturer model: HXJ10005
• Product Type: Crystal Oscillator Frequency Counter
• Frequency Range: 1Hz-50MHz ; Crystal Test Range: about 4MHz-48MHz(not include 32.768KHZ)
• Power supply : USB 5V or DC 5-12V ; Digits Resolution : Five
• PCB Size: 80*53*2mm. Net weight : about 39g
• Package Include: 1 set Frequency Counter Tester Parts( Attention: the products are in parts , the buyers need to assemble them)

Amazon info the same. Below interesting feedback from a buyer.

The kit took couple of weeks for delivery. Neatly packaged with all parts plus a few extra. Nice PCB with component values indicated on board via silk screened labels. No directions otherwise of how to use. I assembled board and originally used a combination of a uA7805 connected to a power module for the supply but it did not work properly; apparently voltage too low, so I then used a variable bench supply at 5V at the jack input, so both oscillator and processor were at 5V. I removed the capacitor between the test crystal oscillator and put in a jumper, so that the processor input would not drop below the maximum negative voltage at the input pin. The unit appears to be now working properly when tested with several different crystal frequency values. If I was using a higher voltage at the jack, I would not remove the capacitor, but I would put a Schottky diode (cathode) on pin 3 of processor with anode grounded, to keep the pin from going too far negative.
ZL2PD indicated on his website that the oscillator waveform can exceed the maximum input to the pin on the PIC chip, if the oscillator supply (voltage at the power jack) is higher than the 5V on-board regulator provides to the processor. Since the oscillator normally uses a capacitor to couple to the processor input, there is also the potential problem that the negative voltage seen by the input pin can exceed the maximum -0.3 volts allowed. It is difficult to say how the processor would tolerate any input voltage level violation, so this may be why the same kit (that shows up by different vendors on Amazon) gets such mixed ratings; some worked, some did not.

 

Buy cheap, then get cheap.

 

Buy cheap, then get cheap.

well I am cheap and continual to be cheap... keep looking I am sure many others have some experiences with this.

here's some responses for more info.

"
Sorry unfortunately we do not have any references. Please note that we do have a 30 day full money back guarantee and if you feel that the item does not suit your needs for any reason, we would be happy to accept the items back for a full refund. Hope that helps."

"
Dear friend ,
Thanks very much for your contacting , the specification of this item are listed on ad, you could have a look , hope it can help you. Any questions pls feel free to contact us.
Best regards"

 

well I am cheap and continual to be cheap...

Can't beat the price. For less than $5 delivered, I put one in my AliExpress cart for my next order.

The capacitor is probably to trim the crystal frequency to get it's nominal frequency. Kind of hard to do without already having a frequency counter.

Don't be surprised that people on Amazon, AliExpress, or eBay have no clue about the products they're selling. That seems to be the norm these days. They're just trying to make money and have no expertise to offer. I guess that applies to everything. When I went with my Daughter to buy her first car, the salesman knew almost nothing about cars (at least less than me).

 

Well another bonus is how small it is, I plan to built a Freq Counter and program it, overall it might cost a bit more, but for once it's a nice compact piece of test gear I can build from a schematics