HP-67 tantalum capacitor: where to buy it?

[Archilog]

Hello,
It seems that I have to change this component because my HP writes but doesn't read cards.
HP-97 schematics didn't help so much because capacitance (6,8 uF) is mentionned but voltage is missing.
On the other site I found this:
TANTALUM CAPACITOR 6.8uF 6.3V M39003/01-2002 CSR13B685KL 5910-00-936-1331 5PCS
with the lowest voltage possible.

I am not an electronician, how to be sure that specifications are correct?
Furthermore this old component seems to be hard to find (I'm living in Brazil). OK, I own some old defective models (Comodore or so) I could canibalize, but researching for the good part should be tricky.

My HP-67 is from 1980 (edited), the component to replace is blue & red with two black little spots.

Thanks in advance.

[teenix]

(10-24-2018 10:16 PM)Archilog Wrote:  Hello,
It seems that I have to change this component because my HP writes but doesn't read cards.
HP-97 schematics didn't help so much because capacitance (6,8 uF) is mentionned but voltage is missing.

Thanks in advance.

I don't have a HP67 circuit, but probably similar.

I assume the capacitor in question is connected to R1/R2 near Q1 in HP97 card reader circuit.

This cap is connected to ground and Vss which is shown as +6.25V.

If this is the problem, then a 6.8uF 10V or 16V tantalum might be a better choice. These are commonly available from hobby or other electronic suppliers

cheers

Tony

[rprosperi]

(10-24-2018 10:16 PM)Archilog Wrote:  My HP-67 is from 2000, the component to replace is blue & red with two black little spots.

The HP-67 was discontinued in 1982. Perhaps you mean you obtained it in 2000?

[Archilog]

(10-25-2018 12:42 AM)rprosperi Wrote:  

(10-24-2018 10:16 PM)Archilog Wrote:  My HP-67 is from 2000, the component to replace is blue & red with two black little spots.

The HP-67 was discontinued in 1982. Perhaps you mean you obtained it in 2000?

Sorry, I mentally read '2000' in the serial number as year 2k. It is from 1980.

[Archilog]

(10-25-2018 12:22 AM)teenix Wrote:  

(10-24-2018 10:16 PM)Archilog Wrote:  Hello,
It seems that I have to change this component because my HP writes but doesn't read cards.
HP-97 schematics didn't help so much because capacitance (6,8 uF) is mentionned but voltage is missing.

Thanks in advance.

I don't have a HP67 circuit, but probably similar.

I assume the capacitor in question is connected to R1/R2 near Q1 in HP97 card reader circuit.

This cap is connected to ground and Vss which is shown as +6.25V.

If this is the problem, then a 6.8uF 10V or 16V tantalum might be a better choice. These are commonly available from hobby or other electronic suppliers

cheers

Tony

I thought the voltage was a problem, but if you say so...
Thank you, Tony.

[Paul Dale]

You are safe replacing a capacitor with a higher voltage one of the same capacitance.
Space won't always allow this but it's often worth going up one step voltage wise.


Pauli

[sasa]

(10-24-2018 10:16 PM)Archilog Wrote:  HP-97 schematics didn't help so much because capacitance (6,8 uF) is mentionned but voltage is missing.

Higher voltage does not matter at all, it matters minimum projected voltage (usually 30% higher than needed is fine) and capacity. You can think of voltage limit in capacitors as a safety valves - until some maximum projected value they will not blow up and will work properly.

Tantalum caps have quite good characteristic, except they have large tolerance of about 20%, i.e. value 6.8uF +/- 20% is in spec. The main problem with it is that can blow-up as firecracker if reverse polarity or apply higher voltage and catch fire. Nowadays there is quite good LOW and ULTRA LOW ESR electrolytic capacitors with high durability, which also may work correctly.

You can safely use any "tear drop" shaped tantalum capacitor you can found in any electronic shop, which have value of 6.8uF and voltage higher than that, you (i.e in some electronic service) can probably measure on board.

As Tony said, if on plus terminal voltage is +6.25V, safe voltage value for capacitor is 10, 16, 25... Notice that with higher voltage also increase physical size of the capacitor, then be sure there is enough space inside to be placed.

[Archilog]

Thank you everyone. I found a Mouser Elec. (https://br.mouser.com/Passive-Components...rs&FS=True) with a huge amount of tantalum capacitors to choose from, here in Brazil. I'll check the size.
Thank you again.

[Zaphod]

Check the auction site out for 182307853956 if you're in the UK
(No connection)

Select 6.8uF and 16V

5 for 99 pence

It doesn't have to be a tantalum, you could use a standard electrolytic cap of the same value.

As said, the rated voltage is immaterial broadly speaking (as long as the rating is higher or equal to the original it's fine)

But beware and ensure you get the cap the right way round , both types will explode if reverse biased (connected the wrong way round)