Some HP parts inside

[Maximilian Hohmann]

Hello!

Recently I found this piece here missing from my collection (Aristo Unilog, ca. 1975 - non RPN...):



Unfortunately it does not work, even after replacing the slightly corroded battery connector. When moving the I/O switch, some digits of the display flash briefly, but this is all.

But inside, there is a display from HP, something that I don't see very often in non-HP calculators:





and some creative soldering as well (I have no idea what that potentiometer is needed for):



Any idea about repairing this calculator is certainly appreciated!

And in the same mail, I received this (inspired by the SR56 vs. HP25 thread http://www.hpmuseum.org/forum/thread-698...light=SR56 ) calculator, which has been missing from my collection so far. Works perfectly, even the original (!) battery can still hold a charge - not something any of my HP-25s is capable of...



As I own both now (the HP-25 and the SR56) I must say that the SR56 is overall the better calculator. But the Hp25 will always remain the one I would take to the solitary island!

Regards
Max

[HAL_2001]

Can't tell anything about SR56 but it's known for long that Ariosto's LED calculators featured HP display modules.

[Maximilian Hohmann]

Hello!

(11-16-2016 09:18 PM)HAL_2001 Wrote:  ... but it's known for long that Ariosto's LED calculators featured HP display modules.

Didn't know that! This one must be my first non-working Aristo calculator among 20 or so and therefore I never had to open one of them.

[PANAMATIK]

(11-16-2016 07:54 PM)Maximilian Hohmann Wrote:  Any idea about repairing this calculator is certainly appreciated!

The chip on the right certainly is a driver for the 9 digits. A similar transistor array could replace it. The chip on the left could be replaced by an 28-pin PIC like 16F1518 running a calculator software. Not impossible if you have some time to spend!

Bernhard

[Didier Lachieze]

The two chips may be the same as the one used in the Aristo M 76, if you have a spare one you can look inside and check for similarities.

[damaltor]

The right chip probably is a transistor array to drive the LEDs, as PANAMATIK already said. The potentiometer might set the brightness (= current flow) of the LEDs.