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Attenuator "O" Rings

 


Does anyone know what size and where I could get "O" rings for my HP 8714 VNA.Attenuator??
One is not there and attenuator is not working properly.

wally KC9INK
 

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Do not know the (exact) size but I bought an o-ring kit for watches. From Amazon I think.

From: [email protected] <[email protected]> on behalf of Wallace Gasiewicz via groups.io <wallydoc@...>
Sent: Friday, May 3, 2024 4:08 PM
To: [email protected] <[email protected]>
Subject: [HP-Agilent-Keysight-equipment] Attenuator "O" Rings
?

Does anyone know what size and where I could get "O" rings for my HP 8714 VNA.Attenuator??
One is not there and attenuator is not working properly.

wally KC9INK

 

Same here. It's pretty likely you'll find your size if you get one of those kits.?


On Fri, May 3, 2024, 4:55 PM Mark Bielman via <mbielman=[email protected]> wrote:
Do not know the (exact) size but I bought an o-ring kit for watches. From Amazon I think.

From: [email protected] <[email protected]> on behalf of Wallace Gasiewicz via <wallydoc=[email protected]>
Sent: Friday, May 3, 2024 4:08 PM
To: [email protected] <[email protected]>
Subject: [HP-Agilent-Keysight-equipment] Attenuator "O" Rings
?

Does anyone know what size and where I could get "O" rings for my HP 8714 VNA.Attenuator??
One is not there and attenuator is not working properly.

wally KC9INK

 

Is the attenuator the same form factor as the 8568/8566 attenuator - HP 33321A? If so the attenuator o-rings are spelled out in the 8566 attenuator notes on this site. They are n-butyl rubber and are available from Apple Rubber Co. In New York. They may also still be available from Keysight.
Don Bitters
 

I did a bulk buy a few years ago which made a few folks happy. They came from: ? 
 Precision Associates Inc. ()
Part number:? 
23-41 5747
70 Duro Black Buna N
.023 ± .002 x ID .041 ± .003

Quite cheap if you got 500 then, no idea now...
Dan
 

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In metric-land I got a bunch of 1mm ID 2mm OD watch stem seals, eBay or Amazon I seem to recall. That was about 10 years back on an 8566A - still working fine - done several other attenuators since.
However while they seem OK at the moment, nowadays having had cheap plumbing 'rubber' seals go gooey after about 5 years, I have little faith in unbranded stuff and I'll bet it's just a matter of time until they start to return to their original liquid hydrocarbon form.
Probably worth finding some of that size from a known (and trusted) manufacturer?

On 04/05/2024 00:08, Wallace Gasiewicz via groups.io wrote:


Does anyone know what size and where I could get "O" rings for my HP 8714 VNA.Attenuator??
One is not there and attenuator is not working properly.

wally KC9INK

 

Interesting idea, Adrian. I've used Amazon as source of o-rings when I repaired my 8657B. But to your pertinent point, I think I'd go McMaster-Carr or similar today:?. Their products are very good and well classified, spec'ed, and extremely finely organized for searching.?
I'd definitely go this route should I have to do it again.?
Radu.?


On Sat, May 4, 2024 at 2:29?AM Adrian Nicol via <Adrian=[email protected]> wrote:
In metric-land I got a bunch of 1mm ID 2mm OD watch stem seals, eBay or Amazon I seem to recall. That was about 10 years back on an 8566A - still working fine - done several other attenuators since.
However while they seem OK at the moment, nowadays having had cheap plumbing 'rubber' seals go gooey after about 5 years, I have little faith in unbranded stuff and I'll bet it's just a matter of time until they start to return to their original liquid hydrocarbon form.
Probably worth finding some of that size from a known (and trusted) manufacturer?

On 04/05/2024 00:08, Wallace Gasiewicz via wrote:

Does anyone know what size and where I could get "O" rings for my HP 8714 VNA.Attenuator??
One is not there and attenuator is not working properly.

wally KC9INK

 

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I think precision associates wanted somewhere between 30 and 40 cents each but I don’t recall the minimum order quantity.

About a year ago, they were around 1/3 of the price of apple rubber (NY).
 

I asked Precision for a quote, I guess we will see Monday.

Wally
 

PAI had a minimum order of 100, but when I went up to 500 they started to seem really worth it.? The worst thing about doing a bulk buy was having to count out all those little bags of 50 :^)? I've had no complaints since.
Dan
 

On Sat, May 4, 2024 at 08:51 AM, Radu Bogdan Dicher wrote:
I've used Amazon as source of o-rings when I repaired my 8657B. But to your pertinent point, I think I'd go McMaster-Carr or similar today:?.
McMaster-Carr is also my normal go-to for quality O-rings. I checked there, but they don't go as small as the 1 mm ID/2 mm OD that others called out. Buna-N is certainly the best choice of material.

I don't know about this application. Would the durometer (hardness) matter here? Buna-N O-rings can be bought in a range of durometers, where 70 is the norm, but harder and softer versions are available.

Try Apple Rubber. They have LOTs of choices in small sizes.?
 

Do these look correct???


https://www.ebay.com/itm/293851527865?itmmeta=01HX2WM6F270SAZY0X9KSYJH67&hash=item446aea7ab9:g:4NcAAOSwC7Vh1id6&itmprp=enc%3AAQAJAAAA4NyxuU3mlUEZV%2Bn9csEzewYdmbqpmPKU2zfXTNMFqmn8eaEDgCi3paQRuFWeIRfM%2FDoLlVjIxoJ%2FR0dl8MmaBF9jq3BOVXcW20QC4dgpmEEGmh3sQP%2FKY6GaYJNwisDDlQTrSR2GMhOtwoz5QboqhdRA9j45ejvMbJ86V21tFz3d2gJNUfYPaBpMGrUdCRVQLnB%2FqwIN7EQZAhaSXHi5ZNV--jLUlx1cBNT%2B0fVai4RYtWrI3BBxl0dkpZDeX0DQ1fCJpGK0SDf4xeXLO9VkA2xw6bRFIwty%2B4WpTsGf%2BvMW%7Ctkp%3ABk9SR9bn0NzoYw
 

I used these o-rings from 'The O-Ring Store' on the attenuator from the 8595E (a 33321 attenuator I think).

https://www.theoringstore.com/store/index.php?main_page=product_info&cPath=368_12_2185&products_id=43455
 

I Measured:

The Diameter of the pin itself to be 40 Thousands of an inch which is very close to ONE mm.
This corresponds to the ID of the O Ring
The OD is twice that so the Cross Section is .5 mm..? OD= 2XCS + ID

So I think VK2BEA is quite correct.

I do not have Metric measurement tools so I have to translate from the measurements on my English micrometers and calipers
 


McMaster-Carr is also my normal go-to for quality O-rings. I checked there, but they don't go as small as the 1 mm ID/2 mm OD that others called out.?

They do,?at least on the ID side. The smallest size on those McMaster-Carr o-rings is about .075mm ID, and the next one up is 1mm ID. ODs start a little larger?than 2mm. This is round rubber, it may not be extremely important for the OD to be exact to fractions of a mm.?
?
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McMaster doesn’t have quite the correct combination of size. You can get the exact size from Precison Associates or Apple Rubber.

The nominal size is 1mm ID cross section 0.6mm, BunaN medium hardness (70A durometer) - credit to Don Bitters for sharing the specifications numerous times.
 

I have used these. 0.5mm CS is standard.
 

Just to conclude. Repair is completed and the unit and attenuator? work just fine.
As per usual, it was not as easy as I thought it would be., but I did not loose any screws.

Thanks to all.

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