HP-34C LED display



One of the segments in my HP-34C LED display no longer illuminates. I removed and tested the LED display and found that the segement of the last digit on the right hand side was still not illuminating, hence, this confirmed that the problem lay with the LED display and not the HP-34C drive electronics.

Would someone have a spare LED display or know if HP or another manufacturer can supply a compatible LED display that I could purchase.

I realy love this machine and would like to get it working again. Any help would be greatly appreciated.

Thank you, & Best Regards



I had a wee search through the archive but didn't find any messages regarding a single segment failure in the LED display of a HP-34C. Most display failures were contact related.

Best Regards


I don't know of other manufacturer's replacement for this display, but you can use the display from any other Spice series calculator. They all used the same part for the display and you can often get a poor quality 33E or 38C/E for not too much on ebay.


The display isn't corroded in some way due to battery leakage? I have 2 "dead" spices with great corrosion, in one of the displays the silicon chips simply disapeared! Anyway, DO NOT try to open the plastic lens to do anything, you'll ruin the rest of it (I have some bad experiences with cleaning of old NOVUS LED displays... now they have several missing segments...)

Good luck!




Thanks Katie, I like the suggestion that I could purchase a Spice series HP, in poor condition, for its LED display. This was also suggested by Viktor T. Toth.

I will do the above, but please contact me if anyone has a spare LED display.

Thankyou & Best Regards


This is a very common fault in Spice series displays. Your only source of another one is another machine. You may have to go through a couple of "bad" machines to find a good one.


Hi Dave,

Thats unfortunate that I may have to purchase more than one machine before I find one with a functional LED display.

Have you experienced this type of problem with a spice LED display?

Thats life!

Thanks & Best Regards


I have over a dozen bad Spice displays...


Hi Dave,

Do you think the source of the bad displays in the spice series may be due to electrlyte (or whatever) leaking on to the LED display below?

Best Regards


Some of the faults are obviously caused by corrosion. Many others just seem to be normal LED faults such as bad bond wires or bad LED's. LED displays were a fairly new technology at the time and there was a learning curve to overcome in their mass production. The chip-on-board displays in the Woodstock and Spice machines seem rather prone to random display faults.


Hi, Imram;

keep in mind that there are two "spice spieces": one with soldered IC's AND LED assembly, and another one built as a "sandwich", where IC's terminals are pressed to a flex circuit. As you have already opened your 34C (great calculator!) you may tell which one is yours.

I replaced a corroded (as Nelson mentioned; by leakage, no hope for them...) LED assembly in one solderless spice for another one removed from a soldered unit. It seems to me that they are electrically equivalent, but I'd like to know from other contributors, please, if there is any sort of limitation or incompatibility. At least for it worked pretty fine, but you must clean the LED assembly terminals in a way you do not experience bad contact further problems. Don't use any sort of scrapper or sand paper, instead carefully use alcohol to remove soldering flux and after that, apply some metal polisher to obtain a smooth, regular surface, better for contact with pressure; remember cleanning it well after this. If yours is a soldered unit and you are going to use a LED assembly from a solderless one, you'll just have to solder it in place. JUST be carefull aligning it well, if so.

My 2ยข.

Luiz (Brazil)


As far as I know, the solderless and soldered Spices (of the same model, of course) are electically identical, and the display, ICs, etc will interchange between them. I've never had any problems doing this.

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