Re: LBA DAS problem at Hart
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From: Brett Reid <Brett.Reid_at_email.protected>
Date: Wed, 17 Jun 2015 14:40:39 +0000
Jon,
Have you tried different DAS profiles or examined the one you are using
in case it is corrupt for the first channel?
We have found it is easy to hit a wrong key and accidentally edit and
save a profile when you wanted to load one.
At Hobart we run a DOS program on an outdated Windows machine. Win ME,
only 15 years old.
At Ceduna we run a DOS emulator of some sought on Linux.
Contact me if you want either of these.
The DAS profiles are probably similar files in either case.
Regards,
Brett
On 17/06/15 13:58, Jonathan Quick wrote:
> Hi Dick
>
> It's been a while! I hope life is treating you well.
>
> So the modules fans are all running and there are no over-temperature alarms.
> If I swap either or both modules between channels the fault is always in the
> first channel (ie. the modules are good), so it looks like is a connection
> issue on the back plane. With no signal attached, both level and offset servos
> are out of range, but the offset comes right when I put in a reasonable
> signal.
> The 5MHz and 1PPS signals show as being OK, so I don't think it's an input issue.
>
> Unfortunately my control software doesn't allow setting manual control. So I
> will need to spend some time getting a DOS emulator going on our control PC so
> I can run LBA_DAS.EXE. It's been so long that this incarnation doesn't even
> have an emulator installed!
>
> Regards
> Jon
>
> On Sat, June 13, 2015 5:12 am, Dick.Ferris_at_email.protected
>> Hi Jon,
>>
>> That's a new one on me. The only faults I'm aware of are fans stopping,
>> usually due to a hairline crack in the Sampler PCB, and in one case an ADC
>> chip which cooked due to said fan stoppage. Present symptoms seem to indicate
>> the AGC circuit is running open-loop, which could arise from faults in either
>> the Sampler or Filter modules, or the connections between them via the back
>> plane.
>>
>> First up I suggest listening to the fans, then checking the module
>> temperatures. If dead or slow, or hot then stop and remove the affected
>> module to limit the damage.
>>
>> Next put the gain under manual control and see if you can set the gain such
>> that the signal level is on scale. If so then you can continue to operate
>> normally as the self adjusting thresholds on all of the outputs will keep the
>> statistics spot on.
>>
>> To get a quick idea of the general health of the signal path connect in turn a
>> CRO and a spectrum analyser to the BandSplitter monitor port and see if the
>> signal looks normal, can display a test tone, looks the same on both IFPs etc.
>>
>> It must be going on 15 years since I last fired up a DAS so it's all a bit
>> hazy! Come Monday I'll have a copy of the User Manual (Temporary) at hand and
>> should be able to be more specific.
>>
>> Good luck,
>> Dick
>> ________________________________________
>> From: Brett Reid [Brett.Reid_at_email.protected
>> Sent: Friday, 12 June 2015 9:11 PM
>> To: Jonathan Quick; vlbiobs_at_email.protected
>> Cc: Ferris, Dick (CASS, Marsfield); Mirtschin, Peter (CASS, Narrabri); McFee,
>> Jock (CASS, Narrabri)
>> Subject: Re: LBA DAS problem at Hart
>>
>> Hi Jon,
>> Although I am not aware of this problem, I am adding several people who
>> may or may not be members of the LBA observers group, but I know have
>> experience with the DAS hardware, since they have helped us at UTAS.
>> They are Dick Ferris, Peter Mirtschin and Jock McFee.
>>
>> Also, I am at Ceduna currently, involved in H-maser and telescope
>> maintenance, and I can easily refer to the DAS manual on the shelf here
>> or make some measurements here if it would help. Our DAS manual does not
>> have detailed schematics either though.
>>
>> If it were me I would be swapping Sampler 1 with 2 module positions to
>> see if the behaviour swapped channels. Then if not changed I would be
>> swapping filter 1 with filter 2 module positions. Also, I have learnt to
>> not switch the red illuminated power switch off as the grease in the
>> switch goes hard and prevents the contacts coming back to the on
>> position nicely and burns the contacts sometimes. Best to leave the
>> power switch on and switch it at the power outlet.
>>
>> Regards,
>> Brett
>>
>> On 12/06/2015 8:11 PM, Jonathan Quick wrote:
>>> Hi All
>>>
>>> My apologies if this is a little off topic for some. but I'm trying to tap
>>> into collective wisdom here.
>>>
>>> One channel of our LBA DAS hardware appears to have developed some sort of
>>> fault. The symptom is that the input level detector seems always to read
>>> either too high or two low. To switch from one state to the other only
>>> takes
>>> a 0.1dB change in level and the level readout then takes a few seconds to
>>> slide across from one end to the other. This problem seems to have
>>> developed
>>> spontaneously overnight last weekend,
>>>
>>> Has any one else ever encountered such behaviour in their DAS and if so how
>>> did you fix it?
>>>
>>> We only have high level block diagrams and no extension cables so it is
>>> going
>>> to be extremely difficult for us to trace the fault ourselves.
>>>
>>> All advice welcome!
>>>
>>> Regards
>>> Jon
>>>
>>> .
>>>
>> --
>> Brett Reid
>> Observatory Manager, Radio Astronomy Group
>> University of Tasmania, School of Mathematics and Physics
>> 03 6248 5285 Observatory 0407 955 283 mobile
>> email brett.reid_at_email.protected
>> web http://users.on.net/~cdadsl
>>
>>
>> University of Tasmania Electronic Communications Policy (December, 2014).
>> This email is confidential, and is for the intended recipient only. Access,
>> disclosure, copying, distribution, or reliance on any of it by anyone outside
>> the intended recipient organisation is prohibited and may be a criminal
>> offence. Please delete if obtained in error and email confirmation to the
>> sender. The views expressed in this email are not necessarily the views of the
>> University of Tasmania, unless clearly intended otherwise.
>>
>>
>
> .
>
Date: Wed, 17 Jun 2015 14:40:39 +0000
Jon,
Have you tried different DAS profiles or examined the one you are using
in case it is corrupt for the first channel?
We have found it is easy to hit a wrong key and accidentally edit and
save a profile when you wanted to load one.
At Hobart we run a DOS program on an outdated Windows machine. Win ME,
only 15 years old.
At Ceduna we run a DOS emulator of some sought on Linux.
Contact me if you want either of these.
The DAS profiles are probably similar files in either case.
Regards,
Brett
On 17/06/15 13:58, Jonathan Quick wrote:
> Hi Dick
>
> It's been a while! I hope life is treating you well.
>
> So the modules fans are all running and there are no over-temperature alarms.
> If I swap either or both modules between channels the fault is always in the
> first channel (ie. the modules are good), so it looks like is a connection
> issue on the back plane. With no signal attached, both level and offset servos
> are out of range, but the offset comes right when I put in a reasonable
> signal.
> The 5MHz and 1PPS signals show as being OK, so I don't think it's an input issue.
>
> Unfortunately my control software doesn't allow setting manual control. So I
> will need to spend some time getting a DOS emulator going on our control PC so
> I can run LBA_DAS.EXE. It's been so long that this incarnation doesn't even
> have an emulator installed!
>
> Regards
> Jon
>
> On Sat, June 13, 2015 5:12 am, Dick.Ferris_at_email.protected
>> Hi Jon,
>>
>> That's a new one on me. The only faults I'm aware of are fans stopping,
>> usually due to a hairline crack in the Sampler PCB, and in one case an ADC
>> chip which cooked due to said fan stoppage. Present symptoms seem to indicate
>> the AGC circuit is running open-loop, which could arise from faults in either
>> the Sampler or Filter modules, or the connections between them via the back
>> plane.
>>
>> First up I suggest listening to the fans, then checking the module
>> temperatures. If dead or slow, or hot then stop and remove the affected
>> module to limit the damage.
>>
>> Next put the gain under manual control and see if you can set the gain such
>> that the signal level is on scale. If so then you can continue to operate
>> normally as the self adjusting thresholds on all of the outputs will keep the
>> statistics spot on.
>>
>> To get a quick idea of the general health of the signal path connect in turn a
>> CRO and a spectrum analyser to the BandSplitter monitor port and see if the
>> signal looks normal, can display a test tone, looks the same on both IFPs etc.
>>
>> It must be going on 15 years since I last fired up a DAS so it's all a bit
>> hazy! Come Monday I'll have a copy of the User Manual (Temporary) at hand and
>> should be able to be more specific.
>>
>> Good luck,
>> Dick
>> ________________________________________
>> From: Brett Reid [Brett.Reid_at_email.protected
>> Sent: Friday, 12 June 2015 9:11 PM
>> To: Jonathan Quick; vlbiobs_at_email.protected
>> Cc: Ferris, Dick (CASS, Marsfield); Mirtschin, Peter (CASS, Narrabri); McFee,
>> Jock (CASS, Narrabri)
>> Subject: Re: LBA DAS problem at Hart
>>
>> Hi Jon,
>> Although I am not aware of this problem, I am adding several people who
>> may or may not be members of the LBA observers group, but I know have
>> experience with the DAS hardware, since they have helped us at UTAS.
>> They are Dick Ferris, Peter Mirtschin and Jock McFee.
>>
>> Also, I am at Ceduna currently, involved in H-maser and telescope
>> maintenance, and I can easily refer to the DAS manual on the shelf here
>> or make some measurements here if it would help. Our DAS manual does not
>> have detailed schematics either though.
>>
>> If it were me I would be swapping Sampler 1 with 2 module positions to
>> see if the behaviour swapped channels. Then if not changed I would be
>> swapping filter 1 with filter 2 module positions. Also, I have learnt to
>> not switch the red illuminated power switch off as the grease in the
>> switch goes hard and prevents the contacts coming back to the on
>> position nicely and burns the contacts sometimes. Best to leave the
>> power switch on and switch it at the power outlet.
>>
>> Regards,
>> Brett
>>
>> On 12/06/2015 8:11 PM, Jonathan Quick wrote:
>>> Hi All
>>>
>>> My apologies if this is a little off topic for some. but I'm trying to tap
>>> into collective wisdom here.
>>>
>>> One channel of our LBA DAS hardware appears to have developed some sort of
>>> fault. The symptom is that the input level detector seems always to read
>>> either too high or two low. To switch from one state to the other only
>>> takes
>>> a 0.1dB change in level and the level readout then takes a few seconds to
>>> slide across from one end to the other. This problem seems to have
>>> developed
>>> spontaneously overnight last weekend,
>>>
>>> Has any one else ever encountered such behaviour in their DAS and if so how
>>> did you fix it?
>>>
>>> We only have high level block diagrams and no extension cables so it is
>>> going
>>> to be extremely difficult for us to trace the fault ourselves.
>>>
>>> All advice welcome!
>>>
>>> Regards
>>> Jon
>>>
>>> .
>>>
>> --
>> Brett Reid
>> Observatory Manager, Radio Astronomy Group
>> University of Tasmania, School of Mathematics and Physics
>> 03 6248 5285 Observatory 0407 955 283 mobile
>> email brett.reid_at_email.protected
>> web http://users.on.net/~cdadsl
>>
>>
>> University of Tasmania Electronic Communications Policy (December, 2014).
>> This email is confidential, and is for the intended recipient only. Access,
>> disclosure, copying, distribution, or reliance on any of it by anyone outside
>> the intended recipient organisation is prohibited and may be a criminal
>> offence. Please delete if obtained in error and email confirmation to the
>> sender. The views expressed in this email are not necessarily the views of the
>> University of Tasmania, unless clearly intended otherwise.
>>
>>
>
> .
>
-- Brett Reid Observatory Manager, Radio Astronomy Group University of Tasmania, School of Mathematics and Physics Phone +61 3 6248 5285 Mobile 0407 955 283 email brett.reid_at_email.protectedweb http://users.on.net/~cdadslReceived on 2015-06-18 00:39:24