HP 8644A/B internal battery

[Roy Mercer]

Does anyone know if the HP 8644A/B RF signal generator has an internal battery that holds important calibration data? I want to buy one of these. However if there is a battery holding important data that I can't replace, I don't want to risk it.

[siggi]

I believe the only battery in these is a NiCAD, that's used only to store self-calibration data. This is certainly the way my HP8643A works, if it's left unplugged from the mains for an extended time, it barks a "calibrating" message at me on the next power up. This takes on the order of 10 minutes or so, after which the instrument looks to be in calibration as well as I can measure.

[Roy Mercer]

So you believe that if this battery is replaced the entire unit will not need fully calibrated? Thank you for taking the time.

[Roy Mercer]

After re-reading your reply I realize that is exactly what you meant. When left unplugged the internal NiCAD battery dies causing the unit to do perform some kind of auto cal. Based off this I think i'll take my chances again. Thanks!

[siggi]

After re-reading your reply I realize that is exactly what you meant. When left unplugged the internal NiCAD battery dies causing the unit to do perform some kind of auto cal. Based off this I think i'll take my chances again. Thanks!

Yes, sorry if that was unclear.

Incidentally, my 8643A came to me in "doesn't power up state", with the PSU in tick-tick mode. The first fault was easily isolated to a module by disconnecting them one by one. Turned out a SMD tantalum capacitor was making like a short on the + or -15V rail. After that she came alive but threw calibration errors after power up. The displayed error was quite accurate and descriptive, as it was complaining of a low 5V rail. These instruments are wired for quite extensive self-testing, and the 5V rail was indeed *just* out of spec.
Re-capping the PSU brought everything back into spec (as near as I or the instrument itself can measure).
 
Artek Manuals have the CLIP, in an excellent scan, although didn't cover the switch-mode PSUs on mine. I believe the 8643A is the only one of the family that has a switch-mode PSU, the others are all linear.

[Roy Mercer]

No sir, you were quite clear. That was my fault for not paying close attention.

How interesting. I had not known of the 86443 until now. I see it has higher phase noise and a solid state attenuator. I wonder if the SMPS is the reason for the higher phase noise. Even though phase noise is higher it's still plenty low for anything I would need. The specs on these things are "out of this world" good.

Thank you for the manual tip. I downloaded one elsewhere but the search function in adobe would not work well. I'll head over there in a bit.

Are you aware of a way to know what year a unit was built? Or what years certain models were sold?

[siggi]

I see it has higher phase noise and a solid state attenuator. I wonder if the SMPS is the reason for the higher phase noise.

Yes, I believe the 8643 is the "budget" generator of the family, and the switcher is almost certainly lower cost and higher noise than a linear hunk'o'metal supply.

Are you aware of a way to know what year a unit was built? Or what years certain models were sold?

Mine has a 33X serial, so built in 93.

You probably know this already, but these things are huge and heavy. I measure 23 inches of depth just for the case. The power supply cowling and front panel knobs then add at least another inch.



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[Roy Mercer]

Ye sir I sure do.  Thank you for pointing that out in case I wasn't aware. I have an HP 5371A and the weight and dimensions are quite close.

[grifftech]

I suggest that you replace the battery to save you 10 minuets every time you plug it in.