exxos's Atari, Amiga & retro forum

Hello all I am new to Exxos forum and electronics but I have a couple of questions.

I really need some advice, my DVE DSP-508A psu and have read the Exxos guide but I am a little unsure about voltages and capacitance? Exxos recommends the following?

330uF 35V = 378uF (replacement 680uF 25V EEUFM1E681 )
330uF 35V = 355uF (replacement 680uF 25V EEUFM1E681 )
330uF 35V = 376uF (replacement 680uF 25V EEUFM1E681 )
2200uF 16V = 2330uF (replacement 16V 4700UF EEUFR1C472 )
2200uF 16V = 2310uF (replacement 16V 4700UF EEUFR1C472 )
47uF 250V = 48.2uF (replacement 250V 47UF EEUEE2E470 )
47uF 250V = 48.6uF (replacement 250V 47UF EEUEE2E470 )

I'm not saying I now better, what I know could be written on the back of a postage stamp :) but I thought the rule when replacing capacitors was the voltage needs to be the same or greater but capacitance and polarity must stay the same?

Regards

The "rule" is generally correct, but it also is incorrect as ESR ratings can come into play. Some older circuits would malfunction if replacing a old 25V 1,000uF with a modern one for example. So the rule is very generalized. Rule should be "<insert rule here> - unless exxos says otherwise" :lol:

I use higher value capacitors because they reduce ripple on a lot of PSU's and give better performance. I have tested the values out thoroughly for some months before selling kits of anything. So I know they work and improve the circuit. This also doesn't mean you can simple place higher values into any circuit and it will be better either.

For example, the ripple filters on the PSUs are terrible, LC filters, don't get me started on cheap inductors! Generally higher L or C lowers the filter frequency and filters out more HF content. Under load the inductors value drops and the frequency filter becomes less effective, to compensate you need a higher value capacitor. Higher value capacitors with better ESR also help ripple voltages. But of course you need to make sure the feedback loops don't screw up and you don't hit overcurrent protections either..

Some people think I just take a PSU and change one for 4,700 from 2,200 with no real reason, but I actually put in a lot of work into it all.. hence my website which basically gives a summary of it all. I do try to explain things simple as possible, but generally seem to fail at it I think :roll:

Voltages is another matter. I get asked constantly that they took out a 25V cap, and I sell 16V in my kits, and yet the same PSU can have 16V or 25V caps fitted. So you can't always exactly go with what is in any particular PSU. Also compromises have to be made over physical size vs ratings... Can actually get pretty complicated.

You could just simply get a kit from my store..

https://www.exxosforum.co.uk/atari/store2/#0028