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HP Forum Archive 19

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HP-38E chips layout
Message #1 Posted by Alberto Fenini on 3 Dec 2009, 1:57 p.m.

Dear all,

I have received an HP38E which may be worth to restore, but it was in pieces when it came to me, and it is a "non soldered" one, does any one of you have a picture where I can see the chips layout ? Particulary, I need to see the orientation of the three small ICs, again, thanks in advance to everybody, take care all of you, Alberto

Re: HP-38E chips layout
Message #2 Posted by Vieira, Luiz C. (Brazil) on 3 Dec 2009, 2:50 p.m.,
in response to message #1 by Alberto Fenini

Ciao, Alberto;

I hope this picture helps you:

Details of the HP38E chips alignment

Although the unit is of the soldered type, position and alignment is the same. Because it is the E-series, the three 8-pin DIL chips (ROM and RAM) have all pins in common, meaning that there is no specific order for them. If it is a 38C, the upper-leftmost chip should be the RAM (continuous power supply).

Please, let us know if you succeed.

Luiz (Brazil)

Edited: 3 Dec 2009, 2:51 p.m.

Re: HP-38E restore project
Message #3 Posted by Alberto Fenini on 5 Dec 2009, 8:22 a.m.,
in response to message #2 by Vieira, Luiz C. (Brazil)

Thank you very much for the picture, it has been really useful, and may be could be of interest what I have done : as first step I have completely dissambled the unit, and with a soft iron brush (dremel) cleaned the pcb

to avoid any possible bad contact.
Then, with a light solution of warm water and Marseille soap the I have washed, rinsed and brushed (this time with a plastic brush) the keys and the skeleton

All the plastic items have been then polished with a teflon polisher

At this point, feeding power with cables, I have performed a self test, which proved that the contatc problems beetween pcb and ICs were fixed. However, the display has been soldered to the PCB, using a 16W solder wich has not melted the plastic foil.Display RED plastic was removed for separate polishing

Now comes the interestegin part, I have tried to restore the battery contacts at best, and your suggestion will be very helpful at this point.
I have drilled the old rivets, and separate the foil that hold the contacs, this has been cleaned till bringing the copper at view, and lightly soldered. Then, using some NICD Battery terminals (which I usually remove) I have cutted something close to old battery contacts, and I have soldered them from the battery caveau side. One more step, I have inserted a very small screew and soldered the backside. Finally, I have soldered the plastic foil for best contact

Last but not least, assembled back the unit, inserted a pack of fresh batteries and re-executed the self test.

How does it look ? Again, thank you very much to everybody and in this case to Vieira, Luiz C. (Brazil)! Take care Alberto

HP-38E restore project: CONGRATULATIONS!
Message #4 Posted by Vieira, Luiz C. (Brazil) on 5 Dec 2009, 8:51 a.m.,
in response to message #3 by Alberto Fenini

Beautiful! That's the least I can tell about!

I'm glad to know that your HP38E is working. This is the HP12C's platform, and if you actually know them both, the HP38E/C misses Bond and Depreciation. The HP38E/C actually offers storage arithmetic to registers R0 to R6 while the HP12C restricts it to R0 to R4. Some features are added, others are suppressed...

The solution for batteries' contacts is, at least, fancy! Both functional and brainy. In the picture below you can see I soldered two metal stripes in order to replace the original contacts (broken). Your solution is perfect.

The steel used in NiCad packs seems to be a very good solution because it is oxide resistant and is flexible enough. It's a pity it is not shaped accordingly, should be bent as you did.

What else to say? Just 'Thank you for allowing my posts to be useful'.

Best regards.

Luiz (Brazil)

Edited: 5 Dec 2009, 8:59 a.m.

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