I have a problem with H field pre, need replacement.
#1
Water damaged the H-field pre, I need to purchase a new one, please tell me who can I contact to purchase one.

Thanks.

Jonathan
STATION ID 2631
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#2
Interesting in that my H-field PreAmp also got fried, but not by water. 
The outputs of the diff amps went shorted internally.

I sent this email to Egon, but was using the email normally used for password reset so it likely went to the spam folder and likely why I never got a response.

Posting it here in case other have similar issues, and how I arrived at the conclusion.

"Hello Egon ...

I would like a price for a replacement H-Field PreAmp kit.
For some unknown reason, after a number of years of operating without
issues, at least two of the three THS4531id diff amps appear to have
shorted outputs.

It took weeks of troubleshooting to arrive to this.  I wasn't getting
any signal waveforms when lightning was near.  Cranking up the gain
really high seemed to help on one input, but the waveform was nothing
like an expected strike.  It had a sharp poitive spike, followed by a
negative one, then quiet.  The other channel didn't show any.

Also, the controller's mode led would go off after long periods of
being powered on.  This usually signifies an issue with the internal
power.  Checking the voltage on the controller'd web page showed 4.4
volts which I thought was low, so I suspected maybe the USB power
adapter may have become unstable with age.  I tried serveral other
adapters, and using the signal page to monitor the noise floor I was
able to find one that generated lower switching noise (amazing to see
the difference in swithing noise between different manufacturers) ,
and finally a voltage of 4.8 volts. Still low I thought, but better. I
replaced the USB cable (shorter length) which brought it up to 4.85v.
Although not ideal, i thought it should be ok.

I decided to open the controller unit and checked inside.  The first
thing I noticed was that inductors L500 and L502 were quite warm,
which was odd.  The unit should not be drawing that much power I
thought.  I checked the voltage across C513. Should have been 4.5 to
5v, I was reading 3.8v.  Obviously something was dragging the voltage
down and causing L502 to be extremely warm.

Networking and GPS appeared to work ok, as I got an alert alarm for a
strike that occured within the range I had set it for, so I was
getting messaging from the server.

The LED on the H-field pre-amp was turned on, which mis-lead me
thinking this was not the source of the problem as there was power
there.  I attemped the reset procedure of holding down the board's
REST button, and pressing the BOOT1 button for 10 seconds until long
beep (I never got the long beep).

After several hours of troubleshooting, i disconnected the H-field
cable from the controller just to have less cables as I flipped the
controller board back and forth.  All of a sudden the voltage across
C513 became 4.53volts (I believe the IC503 regular is designed for
4.5v).

So I now suspected the Ethernet Cat 6 cable which I replaced twice
with same results, so it was not the cable.

I then focused on the IC5 TLV70033  3.3v regulator on the H-field
preamp itself.  The input acoss C14 was reading 3.58v, and the output
across C15 was reading 2.15v.  In addition, the 3 amplifier chips IC2
to IC4 were on the very warm side; 2 warmer than the 3rd.

So I suspect these have internally shorted outputs.
I don't know what the output resistance of the output VOUT- and VOUT+
is suppose to be (no power) but I get between 5 to 12 ohms when
measured either against GND or the 3.3+v rail.

I was thinking of simply ordering the chips locally, but I don't have
the smt equipment to replace these.

I'm a little baffled as to what may have happened, especially for all
3 to go.  We have had higher than usual humidity and tempearture in
recent weeks, and the ethernet cable between the pre-amp and
controller is quite long (maybe 100 feet, and coiled up to).  Possibly
the coiled ethernet picked up a strong emf from a close strike at some
point ?"


In my case i suspect either EMF in the long coiled cat6 network cable to the H-filed preamp, or possibly a static discharge (that room where the loops are have carpet and it is very dry in the winter.) .  It could very well have happened months ago during the winter as we don't normally have lightning in the winter here, so I would never have followed up.

Anyways, I don't think Egon will want to break a board up just to sell the H-Field preamp.  The chips themselves are about 5$ each, so no big deal.  I guess I just need to bite the bullet and buy myself that hot air SMT soldering station I've been dreaming about  Smile
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#3
I did my own repair, bought the components and carefully solder them. It was the voltaje regulator on the board. Egon reply and said that he could send only blank board without components, so is was better to repair it myself.
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#4
@Rejean, You don't really need a hot air soldering station for that size chips. A good soldering iron with 1mm chisel point tip will work just as well. But, if you are like me, I like new 'toys' .

There are two ways to remove those small chips. Place a solder blob across all four legs on both sizes, then heat each side until the chip just slides off. The other option which is more suitable for through hole chips, is to use a cutter with a small tip and cut all the legs, remove the chip and then the remove the legs one by one.

PS. this post really needs to be on the internal forum but you have not yet registered as a operator.
https://forum.blitzortung.org/showthread...articipant

Thanks
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Station: 2100
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