another psu question

[fadedpaper]

Hey all, I'm building the optimized psu and I can't seem to figure out if I can use the caps and rectifiers from the SID and Core modules to build it. I could be very wrong, but from what I've gathered I should be able to use these parts for the psu and leave them off their respective boards like this:

Core:            USE:

X1    ---->    X1

C5    ---->    PSU

C6    ---->    PSU

IC3  ---->    Left Out

C4    ---->    Left Out

C3    ---->    PSU

SID:            USE:

X1    ----->  Left Out

C9    ----->  Replaced by 2200uF/25V on PSU (left out of SID)

C10  ----->  PSU

Will that work? If I do it this way, what do I need to bridge besides the obvious 7805 on the Core? Do I need to bridge any of the places for the caps on the pcb itself?

[fadedpaper]

Let me rephrase that... To build the optimized psu, do I need extra caps and rectifiers? Or can I build it using only the parts that came in SmashTV's kits for Core and SID module, leaving them off the modules themselves?

[fadedpaper]

anyone?  ???

[stryd_one]

This is a good opportunity to mention a small gripe I have..... This is not just for you Jonny, this is for everyone:

X1, C5, C6, IC3, etc etc etc - If you've got all the part listings for all the schematics memorised, then I congratulate you! I, however, do not. These letters and numbers mean very very little to me, and I lack the time to look them up.

That's why I have not answered this post, or any others that asked the question in this cryptic manner ;)

Regardless, in this case at least, I think that the question will already have been answered - if the optimised PSU schematic has (for example) a 2200 cap, and says to take the cap off the core, then it's obvious that you can reuse it. If not, don't :)

[fadedpaper]

My bad... Still, I'm lost as hell. I tried building the OPSU but I've had no luck getting it to work. Now all I get is noise when I turn it on. If I listen really close, I can hear the little SID startup sound very faintly behind a wall of buzzing and noise.

Here's why I'm so confused and would really appreciate some help rather than just another "find it yourself" kind of answer. The writeup at  http://www.ucapps.de/mbhp_core.html  mentions the following:

"J2: When used as +5V input:  for supplying from J2 of another core module, or from an external stabilized Power Supply Unit (PSU). In both cases the voltage regulator (IC3) should not be connected, also the rest of the voltage stabilization circuit between J1 and J2 (X1, C5, C6) can be left out."

Ok... so bust out your schematic and you'll see that between J1 - J2 there's more than just X1, C5, and C6. There's 2 other capacitors in that chain. So that's where my confusion comes from. The writeup says to do 2 different things. Do I take off the whole "voltage stabilization circuit between J1 and J2?" or just the parts in parenthesis "(X1, C5, C6)" ? Also, does this apply to the SID module at all? I've read so many conflicting things as to how this is supposed to work, and obviously what I tried was a mish-mash of all of them, and it's not working. Seems like this should be so easy, but I can't find a solid answer anywhere.

[warland]

My suggestion is to build the SID modules including ALL PSU components as shown in the original SID schematic.

Build the optimised PSU as per the schematic without any modification at all.

On each core module leave out IC3 (7805 voltage regulator)and fit a bridge wire between pins 1 and 3 of this regulators PCB pads (the 2 outer ones), leave out X1, leave out C6 (330nF), leave out C4 (10uF) and in place of C5 (2200uF) fit a 1000uF/16v electrolytic capacitor.

A standard 78xxT series regulator is good for an output of 1 Amp. If fitted with a good heat sink this can rise to around 1.4 - 1.5 amps. If possible I would fit one of the 2 A rated 7805's if using in a system with multiple cores and sid's

Hope this is clear and helps.

[fadedpaper]

Wow, that was exactly what I needed to know. Thanks a ton warland!  :D Just ordered the parts so we'll see if I can finally get it right.

[warland]

glad to be of help.

As a matter of interest, the "ideal" filter capacitor value for placement after

a bridge rectifier can be determined from a simple calculation, C=(I*T)/E

where;

C = capacitor value

I = maximum current draw

T = half cycle time (8.33ms @ 60hz or 10ms @ 50hz)

E = the fall in voltage that will occur during one half cycle

The capacitor selected must have a voltage rating of at least 20% more than the expected

DC voltage output of the bridge rectifier. It is fine to go way over value (eg using a 100v

rated cap on a 12 supply) but never less, unless of course you dont mind your filter

cap going bang or shorting out!! The 20% allows for any fluctuation or spiking that may

occur. Most countries supply AC with a reasonably tight tolerance to the rated value but

in some circumstances this can vary considerably.