Electrolytic Capacitors modern equivalents

[Silversdream]

I am restoring a Roberts R707 and note that the Electrolytics are 400 and 640uf
Struggling to find these valuers
Can i use close values or is there a supplier for out of date components ?

[paulsherwin]

Electrolytic values are rarely critical. Just use the next higher available value, in this case 470uF and 680uF.

[Silversdream]

Thanks Paul
I will purchase the higher values

[Bazz4CQJ]

Manufacturing tolerances on electrolytics are quite big. I find that most such caps measure at least 10% lower than labelled, sometimes more. As Paul says, rarely critical.

B

[factory]

The modern ones almost always seem to measure closer to the lower end of the tolerance (better manufacturing tolerance & cost cutting ?), when compared with older ones that are often marked -10/+50% tolerance and measure higher.

David

[David G4EBT]

Originally Posted by Silversdream

I am restoring a Roberts R707 and note that the Electrolytics are 400 and 640uf
Struggling to find these values
Can I use close values or is there a supplier for out of date components ?

While you're at it, you might wish to also replace C42, 250uF (use 220uF), which is across the 12 V supply.

It won't do any harm if you don't, but if it's leaky (in the electrical sense) it will pass DC current, increase the drain on the battery and shorten the battery life. If very leaky, it will act as a low value resistor and the current drain might be sufficient to lower the voltage. The 707 is now more than fifty years old, and the electrolytics have had a good life, no doubt well beyond the maker's (Philips?) 'mean time before failure' specification.

You can of course lift one end of each capacitor, insert a meter on the mA range to see if the capacitor is passing DC, but in the time it takes to do that, you can have it out and replaced. Some may disagree, but to my mind, for the little bit of trouble and expense involved it's worth the effort to give the radio a new lease of life.

Good luck with the restoration.

[Silversdream]

Thanks for the advice David
I will change all the Electrolytics
Would you change anything else ?

[David G4EBT]

Originally Posted by Silversdream

Thanks for the advice David
I will change all the Electrolytics
Would you change anything else ?

No. If the radio is working, I’d just change the electrolytics one at a time, testing after each one, so if by chance the radio stops working, you don’t have to recheck all your work - just the last thing you did. (No doubt there are other forum members who have restored R707s who may care to comment).

Good luck with it.