My new(ish) HP-45

[jwhsu]

(01-14-2020 11:56 AM)Paul Dale Wrote:  Details of the crystal mod are linked from the museum front page.

I’m not sure you can get the required crystal without cannibalizing a broken HP55. There was a thread on this board about using a resonator/oscillator as a substitute with reasonable accuracy:

HP 45 oscillator

I did obtain one after contacting the OP several years ago. I don’t know if there are any left or if he is providing modules.

[teenix]

(01-14-2020 02:16 PM)rprosperi Wrote:  You stole my line - I was preparing to ask if the LED smelled minty fresh!

I'd also like to hear the technique you used for polishing with toothpaste and which brand had the right amount/type of fine abrasive; toothpaste ads for exotic flavors and vague guarantees to whiten are easy to find, but abrasion level specs. not so much.

I'm sorry, you can have it back :-)

I just dabbed a bit onto a cotton bud and rubbed it lightly on the surface.

I think all pastes have some sort of abrasive in them. I don't know if some brands advertised as tooth polish might be better or worse.

cheers

Tony

[teenix]

(01-14-2020 03:38 PM)jwhsu Wrote:  I’m not sure you can get the required crystal without cannibalizing a broken HP55. There was a thread on this board about using a resonator/oscillator as a substitute with reasonable accuracy:

HP 45 oscillator

I did obtain one after contacting the OP several years ago. I don’t know if there are any left or if he is providing modules.

I saw that, thankyou.

I wonder how the anode driver deals with a square wave clock signal when it is set up to accept an R/C or crystal input. I know modern microcontrollers can accept all manner of clock drivers but the inputs are user configurable.

cheers

Tony

[LEDfan]

It’s probably not the done thing to reply to such an old post, but I came across this thread when searching for some information on the HP-45.

I have been using a hairdryer successfully for a number of years to remove labels when repairing items that require it, using the same precautions as Geoff, low heat, ensuring that the heat source is continuously moving, ensuring that the case temperature does not get too hot.

On the other hand, I recently acquired a calculator for parts where a heat gun was used, damaging the case back. I guess what I am trying to say is don’t knock what works and use precautions.

I saw a neat label lift on a you tube short by Calculator Obsessed on an HP-45 earlier today (part of the inspiration to do a bit of reading on the HP-45). It just seemed to float away. Couldn’t see any static precautions though for the disassembly.

[LEDfan]

HP-45 Teardown YouTube short