PAS3 power supply

I thought I posted this somewhere about 6 months ago but now I can't find it, and it's useful info I use almost every week trying to help someone,
so I'm posting this info here as a sticky so it's easy to find
If you do ANY mods to a PAS3 it's likely you'll need to make changes to the power supply

PAS3 power supply

Thanks for the article, very interesting.

As in ST70 there is a modification of the filter capacitor, placing one new 80-40-30 20uF, I would like to know whether PAS exists the possibility to replace the 20-20-10-30uF.

someone could easily replace the PAS3 quad cap, but for about $10 more you can replace it and the entire power supply with better parts!

Upgrading the PAS power supply is really pretty easy. The selenium rectifier and the old filament smoothing capacitors take up a lot more space than modern parts.

If you need more room, you can do as Frank Van Alstine does: mount the power transformer OUTSIDE the back panel where it will also have the benefit of open air to cool it. This also gets any potential hum fields from the transformer out where the steel chassis will shield them from the circuitry inside the unit...particularly important if you are using a different transformer that isn't totally encased in steel as is the original Dynaco. It doesn't look good, but who looks at the backside of your preamp, besides you? It does require clearance to the back of whatever cabinet you may want to use (if any) but if you are already intending to use super-size firehose-like interconnects, you'll need even more space than that!

tubes4hifi wrote:someone could easily replace the PAS3 quad cap, but for about $10 more you can replace it and the entire power supply with better parts!

I do not want to place a capacitor bottle, simply place a printed circuit board with 4 independent capacitors.
So wondering if it is possible to expand the capacity of said capacitors for better filtering.

Pillo69 wrote:

tubes4hifi wrote:someone could easily replace the PAS3 quad cap, but for about $10 more you can replace it and the entire power supply with better parts!

I do not want to place a capacitor bottle, simply place a printed circuit board with 4 independent capacitors.
So wondering if it is possible to expand the capacity of said capacitors for better filtering.

=============================================================

Yes.  Easily and frequently done with virtually all of the add-on power supply capacitor boards.

my standard power supply for the PAS3 has 266uF of B+ capacitance and 6600uF of filament capacitance,
compared to the original of 90uF and 4400uF
www.tubes4hifi.com/PAS3-CAT.htm

I got the information I wanted about the capacitors in SDS page Audio Labs
If anyone needs information click here.

http://www.quadesl.com/pdf/pas_capboard.pdf