Re: 8566B Attenuator Service
Adrian, there are no markings on this attenuator body which indicate that it's a 33320 series one. It says on the front label "85660-60121 ATTENUATOR / 70dB" so I'm not sure how much - if any - similarity there is between them and whether we can rely on that manual excerpt?
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Re: 8566B Attenuator Service
Not sure if you saw my other reply a few minutes back?? I'm assuming
this attenuator is the style that has the internal coil switch
contacts - if it's the 'select' coil that's stuck on, have you
checked that the N/C contacts have opened and the N/C contacts have
closed for the solenoid in question?
On 15/09/2024 13:33, Jinxie via
groups.io wrote:
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Yeah, I get that, Steve, but this is not the issue with
this pad's solenoid. It flicks back and forth freely when
there's no power applied. But once it's energized to 'on'
it's stuck there and can't be pried away again. That coil
is remaining energized. Once that happens, there's no
changing it. If I enter 0dB or 10dB, that 20dB one is
always in circuit.? So for example, entering 10dB will
result in me getting 30dB of attenuation and 0dB will get
me 20dB. No wonder I couldn't calibrate it!
Adrian - it's the? second one from the left in the
photo.
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Re: 8566B Attenuator Service
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On Sep 15, 2024, at 7:29?AM, Jinxie via groups.io <paul666@...> wrote:
? Yeah, I get that, Steve, but this is not the issue with this pad's solenoid. It flicks back and forth freely when there's no power applied. But once it's energized to 'on' it's stuck there and can't be pried away again. That coil is remaining energized.
Adrian - it's the? second one from the left in the photo.
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Re: 8566B Attenuator Service
Yeah, I get that, Steve, but this is not the issue with this pad's solenoid. It flicks back and forth freely when there's no power applied. But once it's energized to 'on' it's stuck there and can't be pried away again. That coil is remaining energized. Once that happens, there's no changing it. If I enter 0dB or 10dB, that 20dB one is always in circuit.? So for example, entering 10dB will result in me getting 30dB of attenuation and 0dB will get me 20dB. No wonder I couldn't calibrate it!
Adrian - it's the? second one from the left in the photo.
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Re: 8566B Attenuator Service
One of the most common causes I’ve seen of stuck attenuator sections is decomposing o-rings caused by attempts to clean the attenuator contacts with chemicals that attacked the o-rings. They become sticky like glue and will latch an attenuator section inline no matter what the solenoid does.? A broken or damaged push rod will have the same effect.?
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On Sep 15, 2024, at 3:40?AM, Jinxie via groups.io <paul666@...> wrote:
? Incidentally, if anyone can explain why partially perished o-rings which are still in-situ can cause problems to the functioning of these attenuators I'd like to be disabused of my ignorance on the matter!
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Agilent E4406 fails to turn on
Hi all,
My E4406 won't turn on so I've pulled it out the PSU, and apart from some suspicious RIFA caps it appears OK.
I've also gone over the Fan control board on the suggestion that some 10k or 100k resistors might be open circuit but a simple in circuit test shows them to be OK.
While this might be not sufficient to reveal an open circuit device since the surrounding circuit might provide the return path for a resistance measurement of near value, if someone knows which resistors I should de-solder to check, please tell :)
Any other pointers to common faults to look for or a path to take would be great.
thanks
Tim
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Re: 8566B Attenuator Service
Hi, just realised that the attached page 5 of the 33320 service
manual will probably explain it way better than me!
On 15/09/2024 12:20, Jinxie via
groups.io wrote:
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Okay. Well I have an 'intermediate update.' Cycling through 0
to 70dB I can see all solenoids switching seemingly normally -
apart from the second from left in the photo. Commencing with
all attenuators in the 'up'/off position, It flicks 'on' okay
but then remains stuck there and won't release again. And
clearly its coil is remaining energized as it can't be manually
flicked off, either. Not sure if this could account for the
problem I've had or whether there are other things amiss (such
as the perished o-ring) also.
So, anyway, once that first 20dB attenuator is switched in,
it cannot be switched out again and there's a minimum of 20dB
attenuation permanently in-circuit. Could there be an issue with
the control logic?
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Re: 8566B Attenuator Service
Okay, are you sure the internal switching contacts are working as
intended?
It's been a few years since I was inside one but my memory is that
there are two per solenoid?
Effectively a N/C one when the solenoid is in the 'de-selected'
state and a N/O one that closes when it is selected.
They function in a break before make way where the power to the
'select' coil is routed through N/C contact and the power to the
de-select coil through the N/O contact.
So, if the actuator rod is gunked up with gooey o-ring and not?
moving freely over it's full travel I guess that might explain what
you are seeing - which coil is remaining energised?
On 15/09/2024 12:20, Jinxie via
groups.io wrote:
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Show quoted text
Okay. Well I have an 'intermediate update.' Cycling through 0
to 70dB I can see all solenoids switching seemingly normally -
apart from the second from left in the photo. Commencing with
all attenuators in the 'up'/off position, It flicks 'on' okay
but then remains stuck there and won't release again. And
clearly its coil is remaining energized as it can't be manually
flicked off, either. Not sure if this could account for the
problem I've had or whether there are other things amiss (such
as the perished o-ring) also.
So, anyway, once that first 20dB attenuator is switched in,
it cannot be switched out again and there's a minimum of 20dB
attenuation permanently in-circuit. Could there be an issue with
the control logic?
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Re: GPIB scripting software?
I access GPIB devices directly (GPIB) or via USB using Visual Basic.
It is free as part of Visual Studio, easy to use and understand, and works with NI VISA and KEYSIGHT.
?
ed
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Re: 8566B Attenuator Service
Okay. Well I have an 'intermediate update.' Cycling through 0 to 70dB I can see all solenoids switching seemingly normally - apart from the second from left in the photo. Commencing with all attenuators in the 'up'/off position, It flicks 'on' okay but then remains stuck there and won't release again. And clearly its coil is remaining energized as it can't be manually flicked off, either. Not sure if this could account for the problem I've had or whether there are other things amiss (such as the perished o-ring) also.
So, anyway, once that first 20dB attenuator is switched in, it cannot be switched out again and there's a minimum of 20dB attenuation permanently in-circuit. Could there be an issue with the control logic?
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Re: GPIB scripting software?
Hello Ulf,
Python is another possibility. If you have not used python before, you should find a lot of info online.? Even ChatGPT has gotten fairly good at writing python code, so if you give it a good description you will have a good starting point. It will probably not be able to make it perfect, but a good starting point for beginners.
Regards, Askild
On Sun, Sep 15, 2024 at 11:12?AM Ulf Kylenfall via <ulf_r_k= [email protected]> wrote: Looking for suggestions regarding useable GPIB script routines
that can be used for setting up a system with 897B/8971C and a Local
oscillator system. It does take some time doing this step by step.
?
No need for retrieving data but using a routine that initializes
all parts would be nice.
?
I saw a thread about Matlab routines but not having an account
with Mathworks since I left the university and not wanting to try
either 30 days trials or 20 hours "online" a month, I am looking for
a lasting alternative.
?
Cheers
?
Ulf Kylenfall
SM6GXV
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Re: GPIB scripting software?
Hi Ulf,
I have developed some Python routines that do just that: control
the HP8970B/HP8971C/HP8673B. I can send them to you. They are
basically testroutines, but set up the system correctly and wil
allow to make measurements. It assumes the Keysight IO system
works correct. Run from Windows command prompt.
Let me know if interested.
Best regards,
Harke, PA0HRK
On 15/09/2024 11:12, Ulf Kylenfall via
groups.io wrote:
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Show quoted text
Looking for suggestions regarding useable GPIB script
routines
that can be used for setting up a system with 897B/8971C and a
Local
oscillator system. It does take some time doing this step by
step.
?
No need for retrieving data but using a routine that
initializes
all parts would be nice.
?
I saw a thread about Matlab routines but not having an
account
with Mathworks since I left the university and not wanting to
try
either 30 days trials or 20 hours "online" a month, I am
looking for
a lasting alternative.
?
Cheers
?
Ulf Kylenfall
SM6GXV
|
Re: GPIB scripting software?
Simple GPIB routines can be sent to devices using MS Excel if you enable the developer tab in Excel. This gives access to a Visual Basic GUI.
|
Looking for suggestions regarding useable GPIB script routines
that can be used for setting up a system with 897B/8971C and a Local
oscillator system. It does take some time doing this step by step.
?
No need for retrieving data but using a routine that initializes
all parts would be nice.
?
I saw a thread about Matlab routines but not having an account
with Mathworks since I left the university and not wanting to try
either 30 days trials or 20 hours "online" a month, I am looking for
a lasting alternative.
?
Cheers
?
Ulf Kylenfall
SM6GXV
|
Re: 8566B Attenuator Service
I believe it's because the 'push' and 'pull' forces from the
solenoid to the actuator rod are applied axially through the
O-rings, so if the ring is too squishy or thin (or hardly there at
all!) then you will not get the full range of movement on the rod
and thus not the correct movement and contact pressure on the switch
blades.
On 15/09/2024 09:40, Jinxie via
groups.io wrote:
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Show quoted text
Incidentally, if anyone can explain why partially perished
o-rings which are still in-situ can cause problems to
the functioning of these attenuators I'd like to be disabused of
my ignorance on the matter!
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Re: HP attenuator O-rings
Hm, the description there says: "Silicone elastomers as a group have relatively low tensile strength, poor tear and wear resistance." Which might be a problem in this application (moving shaft)?
?
It is resistant to beer, though :-)
?
?
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Re: 8566B Attenuator Service
Incidentally, if anyone can explain why partially perished o-rings which are still in-situ can cause problems to the functioning of these attenuators I'd like to be disabused of my ignorance on the matter!
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Re: 8566B Attenuator Service
Dan, you are quite right of course and it's good to point that out for anyone who may be reading this thread for advice in the future.
For the DC test I was only going to use 200mV and of course - IRO DC - there'd be no point examining that on a spectrum analyzer. I'll be using an oscilloscope for the DC testing.
Many thanks indeed for the offer of the o-rings. I have some nitrile rings which could work if they can be sliced through the 'equator' as it were. They're a bit too thick to use unmodified. That'll be fun with my eyesight and shaky hands!
I'm still reeling from Adrian being able to spot that faulty o-ring from the rotten photo I took! So much for my claimed "careful inspection"!
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Re: 8566B Attenuator Service
Hi again....
?
1. I have the o-rings if you want some...
2. do NOT put DC if the attenuator is attached to the Spec An input. It would fry the mixer diode for the low band if the 0-2.5 GHz button is selected. Certainly it would take out the limiter also.
?
Dan in Chandler, AZ
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Re: 8566B Attenuator Service
You can operate the attenuator with a bench supply. Just make sure to operate the solenoids through the breaker contacts in place so the current will be interrupted. But also if you don't, if you break the current manually within a second or so, no harm will be done. Have done this many times.
?
Tom
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Jinxie