Help with capacitor compatibility

[keelus]

Hello! I have a Macintosh Plus and as you recommended me, I'm gonna recap the analog board.
I'm trying to buy them in local shops (digikey,mouser, etc, have like +20€ shipping only, to Spain).
But I'm having some trouble finding some specific capacitors.

For some capacitors, can I buy them with slightly higher capacitance or/and voltage?
For example, I cannot find the C1 (3.9uF 25V) but yes the 4.7uF 50V.
Would that work / be effective?
Thanks.

 

[wottle]

My understanding is you want to ensure the capacitance is the same, but the voltage simply needs to be higher.

 

[JDW]

@keelus
My complete Mouser Cart is here, and my video is here. See the text description under the video on Youtube for lots more info! (For US Analog Boards only, not international.)

There is a cap kit for the International Analog Boards on Console5 here, but sadly, it doesn't include the RIFA caps.

 

[keelus]

@keelus
My complete Mouser Cart is here, and my video is here. See the text description under the video on Youtube for lots more info! (For US Analog Boards only, not international.)

There is a cap kit for the International Analog Boards on Console5 here, but sadly, it doesn't include the RIFA caps.

I watched your video to see how the process work and was super helpful! The thing is that I still don't understand very well the compatibilities. Can I ask, why, if the C1 is 3.9uF 25V, in your Mouser Cart you have one of 3.9uF 450V? Is that compatible? That higher voltage doesn't affect/it's ok? Thanks

 

[3lectr1c]

Yes, it should be. The voltage is the maximum that the capacitor can handle, running it at lower voltages will be fine for an electrolytic cap.

 

[keelus]

I understand! So, the capacitance MUST be the same? I cannot find 3.9uF ones.. the closest one are 4.7uF

 

[3lectr1c]

There is a 3.9uf capacitor linked in the mouser cart the JDW supplied, and yes, capacitance must be the same.

 

[keelus]

Yes, but to ship to spain, It has a base of 20€ shipment plus the capacitors I choose, I think it's pretty expensive

 

[3lectr1c]

Yikes. Yeah, that may be an issue. Not sure what I'd do about if no local places carry that value.

 

[JDW]

I watched your video to see how the process work and was super helpful! The thing is that I still don't understand very well the compatibilities. Can I ask, why, if the C1 is 3.9uF 25V, in your Mouser Cart you have one of 3.9uF 450V? Is that compatible? That higher voltage doesn't affect/it's ok? Thanks

My suggested replacement cap is a FILM type capacitor. Those almost always have very high voltage ratings. And that significantly higher voltage rating doesn't matter at all.

Most people who lack a schematic just need to recap based on the stock cap's marked voltage and buy the same or higher voltage rating. For example, if a stock cap is rated for 25V, but a 25V or 50V or higher replacement. In most cases, the higher the voltage the physically larger the cap, but in the case of film caps, it's not the same as with electrolytic caps. That's why a 400V film cap can fit into the slot we're talking about on the Analog Board.

But the reality is that it could be a 50V rated cap on a 5V line, which means you really don't even need a 50V rating. But the reason a 50V cap was chosen is due to a variety of factors, including part availability, capacitor ESR and so on.

When recapping, you need to be worried about voltage when you use Tantalum. Because if you have an operating voltage of 12V and you use a 16V rated SOLID Tantalum cap as a replacement, you will possibly have trouble down the line.

For all this and much more, please see my video on the topic here...

 

[JDW]

Yes, but to ship to spain, It has a base of 20€ shipment plus the capacitors I choose, I think it's pretty expensive

If price matters most to you, and if you prefer not to use my Mouser Cart, I do see that Console5 has a US edition Analog Board recap kit below, and it seems to include the RIFA caps too...

Macintosh 128K 512K Plus Analog PCB Cap Kit: 630-0102 661-0462

<p>High temp, electrolytic cap kit for the Macintosh 128K, 512K, and Plus Analog PCB.</p> <p>Features correct specialized low-impedance and Nichicon axial caps, and replacement X1 or X2 safety cap for C38.</p> <p>Some, but not all boards use RIFA Y-clas

console5.com

However, it seems to be backordered at the moment.

 

[keelus]

Hello! Finally I found a shop in my country where I could buy almost (not the C1) every capacitor of the analog board, along with the U3 octocoupler! Thanks for your help .