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)?
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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....
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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.
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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.
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Tom
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Re: HP attenuator O-rings
I jist purchased a fistful of these, they are silicon so hpefully shouldn't have a problem with deteriorating for a long time.
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Jared.
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Re: Thermal Couple attached to heat sink
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Re: Thermal Couple attached to heat sink
Hello John, The usual insulator for thermocouples is mica. 73 de Brian, VK2GCE
----- Original Message -----
To: <[email protected]>
Cc:
Sent: Sat, 14 Sep 2024 17:49:28 -0700
Subject: Re: [HP-Agilent-Keysight-equipment] Thermal Couple attached to heat sink
Thanks Jim,
Does anyone know what would make a good spacer?
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John
Email sent using Optus Webmail
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Re: Thermal Couple attached to heat sink
Thanks Jim,
Does anyone know what would make a good spacer?
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John
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Re: 8566B Attenuator Service
Vladan,
You're the boss! Okay, I'll not do that.
More tomorrow... I'm off to bed now.
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Re: 8566B Attenuator Service
Jinxie, don't touch those gold pads, just fix the o-rings. Gold is soft and it's supposed to smear a little by design.
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Vladan
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Re: HP attenuator O-rings
On Sat, Sep 14, 2024 at 12:30 PM, Dan Rae wrote:
For those looking for O rings, ...
which are buna.
So good, if you want those.
The OP was asking about Viton.
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Re: 8566B Attenuator Service
Yes, I did notice those marks on the gold plating. I'll take a better look tomorrow under the stereoscope to see if they're invasive. I have some 24kt gold wire which I could use to sputter those pads if they're beyond repair - assuming that would adhere, of course. 25 mil wire coil @ 1000 amps should do it surely?
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Re: HP attenuator O-rings
For those looking for O rings, there was extensive discussion about them way back in 2016 of course on the Yahoo group which has now vanished I presume.? I did buy 800 of them from PAI, their Part number:
23-41 5747
70 Duro Black Buna N
In stock
C/s .023 ¡À .002 x ID .041 ¡À .003
Tasha Johnson
Customer Service Representative
Precision Associates Inc.
Direct: (612) 334-9120
Toll Free: (888) 724-4712
which I was able to pass on at $10 for 50 post paid, the hardest part of which was counting them...
No idea even if they are still in business.
Dan
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Re: 8566B Attenuator Service
Well done, gentlemen, loads of good suggestions here; plenty for me to get on with tomorrow when I next get a session in.
So here's where I am now. From the advice here it seems the best course is to replace the front panel of the attenuator so the contacts can bear against the pads. Then re-attach the ribbon cable to the motherboard. Both of these steps I have now taken. Tomorrow I'll squirt some RF and some DC (at different times!) through the input and monitor the output in the time and frequency domains. Seems that RF and DC show up different issues, so fine, I'll try both.
Now, the sharp-eyed (extremely sharp-eyed!) fellow who pointed out that O ring was perfectly correct. It is indeed heavily perished. One or two of the others are also showing signs of age, too, but that one is the worst by far.
Now I've had to remove A6A9 to get the attenuator out and detached some of its cables in the process. Will I be okay to turn the SA on with this section in this state? I would have thought so, but don't wish to fry something at this stage!
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Re: HP attenuator O-rings
On Sat, Sep 14, 2024 at 03:43 AM, Alan Bain wrote:
there are various comments that they need to be
Viton/FKM in order to last
Viton is type of fluoroelastomer.
It's a type of high-performance synthetic rubber, valued for its excellent resistance to heat/temperature... compared to buna
There are different grades of Viton; but AFAIK, all those grades of Viton outperform buna... unless there is some specific chemical that buna can resist, and Viton cannot.
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I'm not sure (I haven't checked the posts) to know if it's the temperature that matters in this application... but, I assume it is.
That is... yes... buna degrades over time, much faster than Viton... but, so do we.
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Anyway the 'longest lasting' synthetic rubbers are
viton, silicone, polyurethane,buna
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I was able to find 'general purpose' 1.78 ID, 1.78 CS? Viton o-rings... here (not Europe) for 20 cents, at 100... net (not including shipping)
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Re: HP 141T Power Supply Help Needed
The worst bugs make the instrument diverge from the schematic, often in ways that would look like nonsense if you drew it there.
toggle quoted message
Show quoted text
"From
over 40 years of fault finding and repair experience in a wide range of electronic products, not just instrumentation, the weirdest symptoms often have a really simple root cause!"
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This
has been my experience as well! Makes it very easy to go down a rabbit hole. Which is why I always do a thorough visual inspection first. Also checking mechanical components of switches, pots, etc. Giving them a good clean right off the bat and testing those
first can save you a lot of headache.
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-Frank
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Re: 8566B Attenuator Service
There seem to my eye to be ridges on some of the gold plating on those pads.? This can cause issues.? Gentle use of a paper eraser can help here (but the gold is thin, don't over do it). I've also found deoxit gold can be helpful in cleaning the contacts.
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Re: HP 141T Power Supply Help Needed
Nice one Bill.
??? Dave B.
From: Bill
Berzinskas
Date: Sat, 14 Sep 2024 15:55:06 GMT
F4 had blown when I was getting 24v.??? I replaced it
and q4, soldering both pins of q4 temporarily.?? It's possible the
"one good" inseption clip was not.???
I'm just glad to be over that for now...
--
Created on and sent from a Unix like PC running and using open source software:
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Re: HP 141T Power Supply Help Needed
"From over 40 years of fault finding and repair experience in a wide range of electronic products, not just instrumentation, the weirdest symptoms often have a really simple root cause!"
?
This has been my experience as well! Makes it very easy to go down a rabbit hole. Which is why I always do a thorough visual inspection first. Also checking mechanical components of switches, pots, etc. Giving them a good clean right off the bat and testing those first can save you a lot of headache.
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-Frank
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Jinxie
Jared Cabot
Brian
Frank Mashockie