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, [email protected] 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 <[email protected]>
Sender: [email protected]
Date: Sun, 10 Feb 2013 02:08:17
To: Discussion of precise time and frequency measurement<[email protected]>
Reply-To: Discussion of precise time and frequency measurement
<[email protected]>
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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