optimized psu: 2 questions

[mat_s]

hi,

2 things i did not really understand about the optimized psu ( http://www.ucapps.de/mbhp/mbhp_8xsid_c64_psu_optimized.pdf )

1:

(3) the 7805 regulators of the core modules have been removed. The Input/Output line

of this IC has been shortened so that C5 of the core module (ca. 1000 uF is ok)

is directly connected to the +5V input

(ca. 1000 uF is ok) -> not sure what that means ? is it that C5 (originally 2200uF/16v ) should (or can) be replaced by one 1000uF ?

2:

(5) the additional cap at the last SID module reduces high frequency digital noise

i guess this cap is needed for a sidV2 even with only 1 core+ 2 sid ?

is there some names for the reason of having this capacitor or for the technique used there ? i would fancy to google some explanations but not sure what to search for...

actually i had forgotten about these caps (and they are rather bulky). fortunately i think i have the space to solder them underneath both J2 of the SID.

thanks :)

[Sasha]

(ca. 1000 uF is ok) -> not sure what that means ? is it that C5 (originally 2200uF/16v ) should (or can) be replaced by one 1000uF ?

If you alreay soldered 2200uF you can leave it on, if not 1000uF is enough.

i guess this cap is needed for a sidV2 even with only 1 core+ 2 sid ?

is there some names for the reason of having this capacitor or for the technique used there ? i would fancy to google some explanations but not sure what to search for...

actually i had forgotten about these caps (and they are rather bulky). fortunately i think i have the space to solder them underneath both J2 of the SID.

It has nothing to do with SID versions. If you have that space I advise you to add it. Check if you can find some smaller size caps. Maybe you have the one rated 25V, 35V...? Sizes varies from manufacturer to manufacturer, so if you really battle with space try to find some smaller one rated 16V.

[mat_s]

thanks for the quick answer!

It has nothing to do with SID versions.

yep i had realized that. i was wondering if it had to do with the fact of having several SID chained together at the power input (which i don't have in this setup).

i am still curious about the theory behind this capacitor at the sid power input, if somebody has a link or keywords i could google, that would be great!

[Wilba]

i guess this cap is needed for a sidV2 even with only 1 core+ 2 sid ?

is there some names for the reason of having this capacitor or for the technique used there ? i would fancy to google some explanations but not sure what to search for...

actually i had forgotten about these caps (and they are rather bulky). fortunately i think i have the space to solder them underneath both J2 of the SID.

You could try a tantalum capacitor, these are much smaller but (from what I heard) can have the same effect of suppressing noise and smoothing out ripples.

The problem is mainly that there's a shared 5v supply to the shift registers also. If you were able to have separate 5v and ground supplies to the SIDs and shift registers, this would have the same effect of reducing digital noise.

[mat_s]

thx for the explanation!