Joe,
Interesting tests.
So, in your previous problem, loss of -12V caused loss of communication
while in your recent tests, you didn't lose communication, regardless of
whether the -12V failure was open or grounded. Okay, now I'm totally
confused!
Regarding the frequency / locking behaviour, did you happen to notice
what your DAC voltage was before and during the failures? If the
voltage was positive, the unit may have been able to compensate for the
grounded -12V line, but when the -12V line was open, it wasn't possible
to pull the EFC line low enough to maintain lock. The drop in frequency
is consistent with a rise in EFC voltage, at least in direction. If
that theory is correct, a Tbolt with a negative EFC voltage wouldn't be
able to maintain lock with either an open or grounded -12V failure. In
both cases, the frequency would drop with the open -12V failure causing
a larger drop.
Ed
On 5/11/2012 9:16 PM, J. L. Trantham wrote:
Well, this prompted a short experiment to test my observations in the past.
I have a TBolt that requires +5, +12, and -12 VDC as separate inputs along
with the antenna. A year or more ago, another list member posted a question
about a failure of his TBolt, the specifics I do not remember, other than it
included a 'failure to communicate'.
I paid little attention to his issue at that time other than the fact that I
had had another TBolt die in years past while connected to a switching power
supply (computer type) in my shop which had a habit of having frequent power
failures as a result of how a GCFI outlet had been wired. I still suspect
one of these power failures triggered a 'spike' on the power supply that did
my TBolt in.
However, a couple of days after his post, I noted my current TBolt had
exactly the same failure the list member had posted, interrupting
communication via the serial connection to TBoltMon. I then noted that my
-12 V supply had died. I changed power supplies and my TBolt came back to
life.
I posted the observation and the other list member found a poor connection
at the connector to his TBolt on the -12 V pin. He repaired the connection
and his problem was resolved.
Tonight, I turned on a CS unit and compared the 10 MHz from the TBolt to the
5 MHz from the CS (5061A) after the TBolt had been up and operational for a
couple of weeks and the CS up and 'Continuous' for about 30 minutes.
I noted that the two were 'locked', as shown by triggering my scope with the
TBolt 10 MHz and with the CS 5 MHz connected to the vertical.
I then disconnected the -12 V supply and immediately connected it to ground.
This left TBoltMon showing 'red' for 'Power Supply' and everything else 'as
it was'. Even the SV indications were 'green' and AMU indications were
normal. In addition, the outputs of the TBolt and the CS were still
'locked'.
I then disconnected the -12 V supply from ground and let it 'float' in air,
simulating the failure I had before. This immediately resulted in 'yellow'
for 'Satellite Tracking', all the SV indications went 'white', and the TBolt
frequency dropped about 24.6 Hz thus proving loss of 'lock'.
'COM 1' on TBoltMon remained 'green' for both situations.
I then reconnected the -12 V lead to 'ground' and all observations reverted
to the prior observations with the -12 V input grounded with the
frequencies, again, 'locked'.
So, I conclude that the observations are based on exactly what the failure
of the -12 V is, open or short. Both my prior power supply failure and the
other list member who had posted the question were 'open' failures.
Hope this helps.
Joe
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Ed Palmer
Sent: Friday, May 11, 2012 12:39 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Tbolt failure modes
Are there multiple hardware versions of the Tbolt (other than the
Tbolt-E)? My Tbolt has an Intersil 232IBE dual TTL to RS232 converter -
similar to MAX232. It generates it's own -12V. This is the version
shown on Brooke Clarke's Thunderbolt page:
http://www.prc68.com/I/ThunderBolt.shtml
Ed
On 5/11/2012 10:56 AM, [email protected] wrote:
The -12V is only used to support the RS-232 driver. The CPU should be running
and you should have discipline even without the -12V
Didier KO4BB
Sent from my BlackBerry Wireless thingy while I do other things...
-----Original Message-----
From: "J. L. Trantham"<[email protected]>
Sender: [email protected]
Date: Tue, 8 May 2012 21:29:06
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] Tbolt failure modes
I had a failure of my -12 V supply that interrupted communications that was
resolved by fixing the -12 V supply. You might want to make sure you are
getting the -12 V supply in the unit. I suspect your 24 V supply provides
power to an internal supply that generates +12, +5 and -12 V.
Might want to check if that is the case for your unit and if the -12 V is
present.
Hope this helps.
Joe
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of [email protected]
Sent: Tuesday, May 08, 2012 4:52 PM
To: [email protected]
Subject: [time-nuts] Tbolt failure modes
Hi group!
Just got a few Thunderbolts. It is a few PN 39448-61 and one PN 38223-61.
Date codes from 9932 to 0025. This is the "normal" version with a 24VDC
power board and Tbolt board integrated in a small AL box with red
markings. One of the receivers is having a problem. Measuring from the
outside there is:
1) Takes the same amount of power as the working units.(to the
resolution measured)
2) Has 10MHz output.
3) Has 4.9VDC on antenna center pin.
4) -8.9VDC stable on rs232 Tx pin (pin2 in DB9)
5) 10MHz is 0.7Hz off after many power on hours with known good antenna
6) TP9& TP10 (close to the GPS board power connector) has 4.9VDC
7) Tboltmon will not talk to the board.
8) There is no serial output at all from the Tbolt.
Differences compared to a good Tbolt
1) Tboltmon will ofcause communicate.
2) After locking 10MHz will be very close to nominal
3) TP9 and TP10 shows a square wave (ca 7V pp, 9.795625000kHz)
I have looked at Tom's page at
http://www.leapsecond.com/tbolt-faq.htm
Brooke's at
http://www.prc68.com/I/ThunderBolt.shtml#IC
and John's at
http://www.ke5fx.com/tbolt.htm
Are there other good Thunderbolt sites?
Has anyone done debugging of faulty Tbolts? Comments on what might be
wrong with my faulty unit? (I am not that experienced in hardware
debugging...)
--
Björn
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