Adding a crystal to my HP-45

[Dan W]

I might be some years behind the times, and the last on the planet to perform this mod, but I'd like to add a crystal to my HP-45. Anyone know where I can find a 784 kHz crystal?

Thanks, -- Dan

[Gerson W. Barbosa]

Quote:

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I might be some years behind the times, and the last on the planet to perform this mod,

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You can bet you are not the last one! I have a good-looking HP-45. I like neither the initial FIX 2 display mode nor the automatic changing to SCI mode but I like the timer feature and might try the mod myself. I hope the crystal can be found in any electronic warehouse. Crystals can be found in cheap digital clocks or clock-calculators made in China (I don't know what their typical frequencies are). I was not intending to open mine, but since one of the decimal points don't light up I might check it out.

Regards,

Gerson.

[Dan W]

I've checked the usual sources: Digikey, Mouser, Jameco, All Electronics, but no luck. You might be on to something - taking apart some cheap device - but what else might use this frequency?

[Richard Ottosen]

I also looked in Digi-Key and Mouser. The closest I came was some ceramic resonators at 800 KHz. These would most likely run the calculator correctly, however, this frequency is not accurate enough for time keeping.

None of the programmable crystal oscillators I looked at were specicfied for less than 1 MHz.

Another possibility is to run a crystal at an overtone. I saw some 153 KHz crystals. If you ran one of these at the 5th (4th?) overtone then you would get 765 KHz. Again, the calculator would work but not for time keeping.

-- Richard

[Monte Dalrymple]

Watches use 32.768KHz.

[John Limpert]

I would go to a vendor like International Crystal Manufacturing Company (http://www.icmfg.com). I've used them when I needed crystals for amateur radio equipment. The problem is providing all of the specifications needed for them to make your crystal. Besides frequency, they need to know the cut, package, fundamental or overtone, accuracy, and probably other things that I don't remember.

[Steve Borowsky]

I may have a couple of 786kHz crystals. I'll have to verify they're working though. Let me know if you're interested.

[Dan W]

Yes I would be interested. Send a note to Revolvr at cox dot net