[time-nuts] NTGS50AA Power supply

[EB4APL]

Maybe I didn't explained this quite well, I'm not good writing in English.
So I try again: In the negative input first there is a forward biased 
diode, then a pair of fuses in parallel, and then the two diodes in 
series connected to the positive in the back direction, so if the input 
is reversed and the first diode became shorted, the two series connected 
diodes makes the fuses blow,(one after another or at the same time, 
giving the current involved). The diodes are schottkys and maybe they 
need two in series due to reverse voltage limits, since the 48 volts 
unit must withstand 100 V transients without failure.

Regards,
Ignacio, EB4APL


On 10/02/2013 2:17, lists at lazygranch.com wrote:
> Are the two diodes really back to back? I have use two in parallel to enhance the time the diodes will conducting. Due to current hogging, the diodes will  effectively turn on one at a time.
>
> -----Original Message-----
> From: EB4APL <eb4apl at cembreros.jazztel.es>
> Sender: time-nuts-bounces at febo.com
> Date: Sun, 10 Feb 2013 02:08:17
> To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
> Reply-To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] NTGS50AA Power supply
>
> Nate,
>
> I have it already connected to a 48 V supply according to the vendor
> instructions (fluke.l is a vendor with technical knowledge)and now I
> removed the PCB from the case that I furnished and found that my unit
> doesn´t have such bridge.  Instead it have a quite elaborate reversal
> power protection (a series diode, two fuses and a pair of back connected
> diodes which will blow the fuses if the power is reversed and the first
> diode fails shorted) so I think that there are dual supply models
> (according to my documentation) and single supply ones, as my unit
> appears to be.
> Thank you for the suggestion to change the 1/2PPS to 1PPS by software,
> I'll try it.
>
> Regards,
> Ignacio EB4APL
>
>
> El 09/02/2013 17:54, Nathaniel Bezanson wrote:
>
>> Open it up, you'll find a bridge rectifier as the first component on the incoming power.
>> It's actually much easier to solder straight to the pins of that component, rather than trying to bodge something together that would poke into the backplane connector. :)
>> I know there's a TSIP command for *other* units to change their PPS into PP2S (even second), so try throwing 8E-4E at this unit and see if you can change it the other way. Haven't had a chance to try it on the local one.
>> -Nate-
>> EB4APL  wrote:
>>>                   Hello,
>>>
>>> According to a Nortel specification document (Dual Voltage Global
>>> Positioning System Timing Module (GPSTM) OEM General Specification
>>> Dataset Name: GSBW50AA), this GPSDO is dual voltage and can be powered
>>> either from -48 V or + 24 V systems.  Mine is working from a 48 V power
>>> supply but I´m afraid to test it at 24 V because the polarity should be
>>> reversed and if my assumption is not true I can damage the unit.
>>> Do you know if these units are dual voltage or my documentation refers
>>> to other model?.  Has anybody operated it at 24 V?.
>>> Another question, is there any internal 1PPS signal available?
>>> Of course, my unit is of ebay - China origin.
>>>
>>> Regards,
>>> Ignacio EB4APL
>>> _______________________________________________
>
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