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Date
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
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
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.
?
?
?
?
Jared.
Re: Thermal Couple attached to heat sink

 

According to the manual it is a 100K thermistor.

-Chuck Harris


On Sun, 15 Sep 2024 11:03:16 +1000 "Brian"
<brianclarke01@...> wrote:
Hello John,
The usual insulator for thermocouples is mica.

73 de Brian, VK2GCE

----- Original Message -----
From: [email protected]
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?
?
John
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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?
?
John
Email sent using Optus Webmail
Re: Thermal Couple attached to heat sink

 

Thanks Jim,
Does anyone know what would make a good spacer?
?
John
Re: 8566B Attenuator Service

 

Vladan,
You're the boss! Okay, I'll not do that.
More tomorrow... I'm off to bed now.
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.
?
Vladan
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.
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?
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 ± .002 x ID .041 ± .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
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!
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.
?
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.
?
Anyway the 'longest lasting' synthetic rubbers are
viton, silicone, polyurethane,buna
?
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)
?
?
Re: HP 141T Power Supply Help Needed

 

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The worst bugs make the instrument diverge from the schematic, often in ways that would look like nonsense if you drew it there.

From: [email protected] <[email protected]> on behalf of Frank Mashockie <fmashockie@...>
Sent: Saturday, September 14, 2024 9:57 AM
To: [email protected] <[email protected]>
Subject: Re: [HP-Agilent-Keysight-equipment] 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.
?
-Frank
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.
Re: HP 141T Power Supply Help Needed

 

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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:
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.
?
-Frank
Re: 8566B Attenuator Service

 

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Hard to be sure from the picture but how do the O-rings look, the lower one on the far left actuator rod (the 'ribbon cable' end) looks a bit odd?
Sometimes the O-rings go gooey and sometimes they harden, either way it can affect the 'throw' of the actuator solenoid - especially the lower one - which might lead to the symptoms you describe.

On 14/09/2024 17:03, Jinxie via groups.io wrote:

Hi all,
?
So I've removed the attenuator and stripped it down to a point where I can see the important bits and I cannot, from careful inspection alone, see anything amiss with it (photo attached). The pads all look nice and there are 4 of them! I'm guessing one 10dB and the rest 20dB ones. The longer ones measure about 82 ohms each across their terminals with minor variations between them and the shorter measures 52 ohms approx. The springs underneath look like brand new and the plungers do flip from on to off with just a bit of pressure from a screwdriver but I haven't tried to actuate them under power (24V) yet. I thought I'd best pause and get some suggestions before I do something which could cause damage.
Some of you may recall from a previous thread that when the attenuator was in circuit and I attempted the calibration procedure, I saw no signal visible with the 0dB and 10dB settings. The 20, 30, 40, 50 and 60dB settings seemed okayish (some a bit noisy) but 70dB was *very* noisy.? Any suggestions as to how to proceed?
?
Thanks,
?
J.

Attachments:
Re: 8566B Attenuator Service

 

开云体育

That's an old one! The newer versions have a PCB with one-shots on board. These attenuators are pulsed on/off so I'd be warry of using a bench supply to activate the solenoids; you might burn them up and then you're toast!

The better option is to plug it in to the unit and activate that way. You should be able to verify that the spring fingers are moving up and down.

With the pad assemble in place (just a few screws to hold it) you can do a few things. Place an ohmeter between the two ports and verify you have resistance (pretty low) for all combinations. Even better is to used an RF generator and a spectrum analyzer to measure it. (a scope would also work)

You can try cleaning the springs and pads with IPA but be very careful!

Good luck.

Mark

From: [email protected] <[email protected]> on behalf of Jinxie via groups.io <paul666@...>
Sent: Saturday, September 14, 2024 9:03 AM
To: [email protected] <[email protected]>
Subject: [HP-Agilent-Keysight-equipment] 8566B Attenuator Service
?
Hi all,
?
So I've removed the attenuator and stripped it down to a point where I can see the important bits and I cannot, from careful inspection alone, see anything amiss with it (photo attached). The pads all look nice and there are 4 of them! I'm guessing one 10dB and the rest 20dB ones. The longer ones measure about 82 ohms each across their terminals with minor variations between them and the shorter measures 52 ohms approx. The springs underneath look like brand new and the plungers do flip from on to off with just a bit of pressure from a screwdriver but I haven't tried to actuate them under power (24V) yet. I thought I'd best pause and get some suggestions before I do something which could cause damage.
Some of you may recall from a previous thread that when the attenuator was in circuit and I attempted the calibration procedure, I saw no signal visible with the 0dB and 10dB settings. The 20, 30, 40, 50 and 60dB settings seemed okayish (some a bit noisy) but 70dB was *very* noisy.? Any suggestions as to how to proceed?
?
Thanks,
?
J.
Re: 8566B Attenuator Service

 

Hello Jinxie,
It seems you have indeed one 10dB, one 20 dB and two 20dB combined to make 40.
From what you say I'd think the 10dB is the culprit. 60 ok, 70 not?
Remember for the test what someone above suggested: Why not try it with low voltage CC? Very easy to measure the attenuation and to see on a scope if it's noisy!
Not much, just my 2�cents!
Best,
Renaud
4661 - 4680 of 151162