[PlanetCCRMA] ardour timing out )

Tracey Hytry shakti@bayarea.net
Mon Oct 25 19:47:02 2004

Sigh, I've been too busy to read my email.

I posted a long time ago somewhere about those caps and about what they are doing.  As far as I can remember those are not filter caps in the regular power supply sense. They are part of a voltage doubler at the input used to create the analog power supply rails along with the 5 volts logic supply.  
I would suggest going for a higher voltage rating on the caps before thinking that a higher capacity would help. When we repaired the 1010 we have, we pretty much figured out the power supply and tried to fix it so it stayed fixed.

This is all from memory, but I do remember that it gets real hot in that area from the voltage regulators; which is real hard on the caps as it can dry them out.  Also, they do seem to have been a little under voltage for the application.  The first of the caps if I remember has a very hig ripple current through it because it's _not_ really a filter cap,  it's more like the type of capacitor you'd see in a speaker cross over(except in this power settup a polarized cap will work).

My suggestion is to replace those 2 on input to the power supply with something slighty larger in capacity, but as large as will physically fit in voltage rating.  Try to get capacitors that are rated for long life and heat if you can.

Also, try to find a way to keep the heat down on that end of the unit.  My final solution was to mount a standard 12 volt computer power supply fan at the back of the rack and aim it at the hot side of the delta.  I used a small plugin transformer that was rated at 6 or 8 volts to power the fan at a low speed which kept it very quiet.  This also cooled down a couple of other things that were mounted under the 1010.

As an aside, the components in the rest of the rack unit seem to be of a good quality, and the design seems very good.  When the 1010 first showed problems one of the sides of the analog supply was only about a third of what it was suppose to be and had a lot of ripple on it.  Even under these conditions there was no power supply noise present at the outputs. The power supply noise rejection is excelent.

Who ever designed the power supply itself should be fired!

Tracey :)