Hamfest find today: HP59309A Clock

[BobVA]

(08-14-2016 03:35 AM)Adam Vaughn Wrote:  As for external power, there is indeed an internal socket for a 9V battery, though HP put all sorts of warnings around it saying something like a leaking battery installed in it would void the warranty (big stuff for a $995 device in 1976!). I'm pretty sure a simple/effective external backup could be made using a battery holder for six D cells wired to a BNC connector (pretty sure center pin is positive, though I have yet to verify this for myself). Anyway, here's a picture of my 59309A:

Thanks! Between being a clock, being made by HP and having LED's it's my perfect dust collector!

I actually tried to install a backup battery, but I don't think it's possible today. Modern 9v batteries seem to be too large to fit down through the aluminum bracket that's supposed to hold it in place and properly align with the connector on the motherboard. The back panel connector is probably the best bet.

I wonder if the previous owner of yours was running it solely off the backup power connector and not using the internal power supply? That would be a good reason to replace the push-to-read button with a toggle switch. (The display is always on if it's running off the internal line supply, so no need to push the button).
That's kind of an interesting idea though, for just using it as a desk clock (the HP-IB part won't work on backup power). Probably run much cooler, since it bypasses a lot of the linear power supply, particularly the toasty 5v regulator on the back panel.

I ordered a 0.25 ppm 10 MHz oscillator module so I'm hoping to put that and a backup supply in a small box to plug into the back panel. Fun toy!

Regards,
Bob