Hey Luiz ... electrolytic spice caps


Hey Luiz,

In your "jumper" picture for spice, there are two electrolytic capacitors (like in a 34C power supply board).

Have you ever taken time to replace those ?
It seems to me that electrolytics dry out.

Would you agree that changing them to dipped-tantalum capacitors might be wise ? Then they do not degrade with time .

They had some oddball value, 22 uF and 10V or so.
It was a little hard to find, so I was going to order some tantalums probably 22uF and 16V soon. Then I can change them if I work on such a calculator in future.

What do you think ?


Hello, Norm;

thank you for your question... Hey, you're the "analog guy"... I'd probably ask you about electrolytic caps 8^).

I'd replace them, you bet. Did you read Ellis' post about electrolytic aluminun/tantalum capacitors? It's a "must read", believe me, I recomend. If I am not wrong, Ellis once mentioned that he worked with components technology, as his posts are full of technological information. The way you, Norm, most like to read and post, as well.

There is one thing that scares me about electrolytic tantalum capacitors: if they are overloaded (excessive voltage), their BANG! is too noisy... One other thing: at least where I live, a small 150,000 inhabitants citty where RPN and HP are fairly "unknown", tantalum capacitors are rare. Only a few dealers "have heard about them". I must search in some electronic junk I have at home to find replacements. Oh, yes, in time: I'm lucky having a capacitance metter and sometimes some "capacitor codes" are way beyond my understanding. Any clues?

Best regards, Norm.

Luiz C, Vieira - Brazil

Edited: 19 June 2003, 1:56 p.m.


Hi Luiz,

I was thinking of ordering a bag of 100 tantalum caps.

Since you need some, I will do that, eventually.

Then i will send 2 dozen your way.

Not sure when, sometimes these things take awhile.

I need more than one item, for placing my order with
the parts distributor.

- Norm


Here's one paragraph from my 34C report:

I traced out a schematic of the solderless unit including the power supply and compared the two units. I noticed two differences in the power supplies: The newer unit has a 10K resistor instead of a diode to provide the standby power from the battery - I imagine that keeps the memory alive with a lower battery voltage - also, the capacitor that holds some charge for the standby power when the battery is out is 22 mf in the older unit and 33 mf in the newer one.

The 33 mf cap is black, has a rectangular cross section, the only markings are "336" and a red dot to indicate the positive lead. I am inferring this means 33 mf, don't know what the voltage rating is. The fact that it is rectangular might mean that it is a tantalum cap - wet slug vs. rolled aluminum foil, so it can use the rectangular shape for higher density. I think space, especially height above the PCB, is very limited on the power supply module. But for what it's worth, my newer unit seems to have no trouble remembering when I take the battery out for considerably longer than the time required to put in a new one (I'm using one battery pack between both calculators). The other two electrolytic caps are 22 mf in the newer calculator.

If I am not wrong, Ellis once mentioned that he worked with components technology, as his posts are full of technological information.

Luiz is overstating my experience, I started as an electronics hobbyist and have worked as a technician, manufacturing engineer, diagnostic software engineer, and even spent a little time as a design engineer, and now I'm back to being a hobbyist. I try to share the things I've learned when they might shed some light on issues that arise here in the Forum.



I try to share the things I've learned when they might shed some light on issues that arise here in the Forum.

For this and much more, I (and I believe others, too) am humbly thanked, Ellis. Your shared knowledge, along with other contributors', helped me many times.

Let's face it: this forum RULES!

Luiz C. Vieira - Brazil


I've just finished going over my 34C schematic (you'll see what I mean!) and I realize I was mistaken about the location of the 33 mf cap in my newer calculator. It's not across the battery but rather it is the filter cap for the voltage regulated supply. But both of my units remember their settings (no PR ERROR, anyway) a lot longer than it takes to change the battery.

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