PSU Capacitors for Aleph
Salmacis,
This issue was covering in a previous thread.
However to answer your question yes the rifa are a very nice capacitors but you need to assess the maximum surge voltage and working voltage. (check the tech sheets on your caps)
For example you need to factor in the maxium mains voltage variations.
If the normal voltage under load is 45+- DC, then if the maximum peak increase on the mains was say say 10% then the dc voltage could be approaching the max operating voltage of your capacitors. (50 Volts)
You also need to add this the ripple voltage on top of the nominal dc voltage. I do not have the formulae handy for this.
The DC voltages need also to be calculated for the regulation of the transformer (no load vs full load) and allow for rectifier losses.
Typicially diode loss are 1.5 volts and assuming 3-4% regulation then this would give say 45 + 1.5 (for rectifier losses) =46.5 volts/1.414 =32.88 vac for the under load voltage of the transformer.
Yet another issue is the rating of the transformer, as a rule go for 2.7 times the maximum load, so for the Aleph use a 750 VA or preferable 900 va transformer.
So 35 volt AC secondaries may be a bit high for your 50 volt dc capacitors (ie 49 - 1.5 = 47.50 ) if we were to allow for 10% mains variations.
In my Aleph 2 project I am using plenty 15,000 uf 63 volt capacitors for safety and 900 va toroidals (33 + 33 volt ac secondaries)
Please do not however take my word for this and I suggest you check some good sites like Rod Elliotts DIY pages for a thorough analysis of power supply design.
best regards
macka
