[repaired] HP 8445B input connectors replacement [+ a peek inside]

[ThomasHPL]

Hello to everyone in this lovely forum,

I just got a new beauty in my lab, a really nice HP 141T +8555A and 8552B. I also got an8445B automatic preselector with it, but the two N-type connectors are kind of broken.
Has anyone in here already found a fitting replacement for those?

I checked on mouser, and this looks like a potential replacement, but is only specified for 12.6GHz, and is almost half the price I paid for the whole deal!
https://www.mouser.be/ProductDetail/Amphenol-RF/901-295?qs=sGAEpiMZZMvlX3nhDDO4AGs0nx9o%252BG3LTYCYhl%252BPfJk%3D

I'm also attaching a picture of the inside for the RF lovers

[tkamiya]

They are plentiful on eBay.  I have a few here, too.  Be warned, they are relatively expensive at around 50 dollars....  HP has/had a tendency to use N connector beyond official specification.  I have a several stuff N is used up to 26.5GHz.  Some say they are specially made, but I found HP forum comment where HP official is explaining the discrepancy is within specification and admit that part is used beyond it's official limit.

https://www.ebay.com/itm/Hp-Agilent-Keysight-Type-N-f-to-SMA-f-Adapter-08341-60001-Mount/263901942200?hash=item3d71c811b8:g:XEUAAOSwpspbiCPc

[jfphp]

HP used a special N connector called N Precision : the tolerances are tighter and have nothing to do with a common N connector. The limits on a N gauge are very special and, for example, a Weinschell N gauge has quite different limits on its dial comparing to a HP one (in some cases mating a Weinschell N connector with a precision HP will detroy one of the connectors). In the male HP precision the cylinder around the male pin is without the common 4 slots. Gauging the N connectors of all of the 848XX power heads gives the same value of recession of the central pin within 1/100 of an inch...
N precision is usable to 22 Ghz but above there is a waveguide effect about 23 GHz  and it is used well beyond to 26.5 Ghz on the 8562X and 8563X SA with a degradation in flatness response (8566B can go to 24 Ghz but it is not specfied above 22 Ghz)

[tkamiya]

Here's the discussion I mentioned

https://community.keysight.com/thread/7095

HP rep initially says there is something special about the connector but reverses his statement later on the thread.  I wonder though, if there is something special about the connector, and worse, if connecting an N connector to an N connector end up in destroying one or the other, can it be truly called an "N" connector?  It kind of defeats the purpose of being a standard.

Mating precision to non precision is not desirable but it shouldn't end up in destruction....

[ThomasHPL]

Thank you for the very interestings precisions !
I found pictures of male type N connectors without slots on the cylindre around male pin.
However a document from Berkeley mention a slotless female contact for the HP precision N connectors.
https://www.google.be/url?sa=t&source=web&rct=j&url=https://people.eecs.berkeley.edu/~aflynn/Cory111Lab/AGILENT_PRECISION_RF_CONNECTOR_FAQ.doc&ved=2ahUKEwits_Gjy6HnAhXOZlAKHePFBm4QFjAQegQIAhAB&usg=AOvVaw2B72PoIflJVRTlUCiN2F8L

By the way, a member of the forum, mikepi, offered to send me a couple of original HP connectors he had in stock, many thanks to him!  This forum's community is awesome!

[jfphp]

HP Precision :                                                  Weinschell

Male recession
0.207----0.210                                                 0.218---0.228

Female protusion
0.204---0.207                                                   0.192---0.202

Gap between 0.000---0.006                               

Ordinary military N connectors have much larger dimensional specs, therefore always gauging connectors before use...

[ThomasHPL]

I just received the package from user mikepi (he sent me two original HP connectors!)

Thanks again to him, they are perfect on my HP 8445B