HP/Agilent 8644A/B difference

[tkamiya]

Hello.  I'm a first timer here.  So, HELLO!

I went crazy on eBay and purchased 3 RF generators.  Two HP8644A with Oven controlled Xtal oscillator and One Agilent 8644B with no options. 

Other than name plate and the fact B has low phase noise option (mode 3) standard, one is optioned to 2GHz and others just 1GHz, what are the differences?  They look identical and seems to work identical to me.  Also, where IS the NiCad batteries?  From forum searches, there are Nicads somewhere and holds self-calibration data.  I'm pretty sure they are dead by now, so I'd like to replace them.  I opened the top side and looked around and I found none.  I'm pretty sure bottom is just a backplane?

Thank you very much.

[OH7MHL]

Hi,

Nice pile of generators, congrats!

NiCad battery is located in DCU unit (slot A16).

I replaced that with bigger NiMh type.

In 8644b version there is a electrtonic attenuator (PIN-diodes) and A-version include traditional resistive attenuator network with relays.

Here you can download all availabe 8644x documents:
https://www.keysight.com/en/pd-1000002189%3Aepsg%3Apro-pn-8644B/high-performance-signal-generator-1-ghz-or-2-ghz?cc=FI&lc=fin&lsrch=true&searchT=8644B

I have to say that 8644b is very good RF generator for my purposes.

[tkamiya]

Thanks for that. 

A pile is right.  Very heavy pile indeed....  I've located the battery.  I, too, would like to use something other than Nicd but NiMH uses different charging scheme.  Have you had any issues?  Otherwise, there is plenty of space in that area, so I'll just use cordless phone batteries.

[OH7MHL]

Yes that charging cheme difference was one concerrn but so far I did not found any problem with that.

[tkamiya]

I've decided to go with NiMH.  I got 3.6v 80mAH version.  I'm thinking with such small amount of charging and draining, I shouldn't encounter issues.  I'll do one at a time just to make sure.

Thanks.

[beanflying]

Just watch out for the NiMh self discharge issues, I am dealing with a dead rom for someone currently after she didn't use her controller for a while. Nicads are better on that account and LiPo's better again.

[OH7MHL]

NiMh self discharge issues can be avoid by using Low Discharge Cells but I think that availability is zero in that size. But there is plenty of room for own build 3 x 1.2V NiMh LSD stack.
I would not use LiPo in that device without proper charger.
When  I bought my 8644B that battery was totallly dead. Only drawback was long self calibration routine in every time when switched on.