Capacitor question for MB Sid module

[marcus77]

Hi there

I've got one short and simple question:

Does the 2200uF cap on the SID module require at least 25v as marked on the schematics or is it alright to use a 16v one?

Thanks for the help.

Marcus

[Wilba]

Are you're talking about C9 on the SID module schematic?

If you're using the "optimized" power supply that uses a C64 PSU and adds 9v and 5v together to get 14v DC, then yes, you would only need a 16v capacitor. FYI, you also would not need the rectifiers (X1) if using the "optimized" power supply, but you would have to add two bridges (it's pretty obvious where!).

I can't see any voltage rating on C9 in the schematic, and the quick view PCB shows it as only 1000uF/25v not 2200uF.... hmm... anyway, the rating of 25v is because if you supplied it with 15v AC, the peaks would be higher than 16v. If you're using 14v DC, then 16v caps are fine.

[marcus77]

Hmmm.. I'm getting a bit more confused..

Basically it is a question of parts for me because I got my main order to built the Sid and still it seems like I forgot to order some parts :(

If i would go for the "optimized" version of the C64 Psu, I would still need a 2200uF /25V for the PSU itself, which I don't have.Then also I noticed that the rectifier X1 on my Sid module is actually a B80 C 1500 instead of the B40C800 like on the schematics.

So now I ask myself two questions

1.If I build the optimized Psu, will it work with a B80C1500 or does it require the B40C800?

  (knowing that I won't need another rectifier on the Sid module)

2.Is the 2200uF behind the rectifier on the optimized Psu 25V or is 16V ok?

sorry for the mess but I'm quite new to electronic components

thanks for the help

 

[stryd_one]

http://www.datasheetcatalog.com/datasheets_pdf/B/4/0/C/B40C800.shtml and http://www.datasheetcatalog.com/datasheets_pdf/B/8/0/C/B80C1500.shtml

According to those, you've got a higher spec, it shouldn't be a problem. Might've cost a little more I suspect.

16V might be OK but if the design says 25 then I'd go 25... Not worth nuking your PIC to save a few cents on a cap huh.

[Wilba]

To explain a bit more...

The cap behind the 9v rectifier on the "optimised" PSU is 25v for the same reason as I said before, the peaks are higher than 9v, and there's some rule of thumb that says double that voltage and make sure the cap is rated for that, so use 25v instead of 16v cap.

The B80C1500 can handle 1500 milliamps, the B40C800 only 800 milliamps. Each SID will draw at most 40 milliamps of this (through its Vdd pin), so either is fine even up to eight SIDs.

[marcus77]

Ok.So far I understand the attributes of these parts.

But...

Suppose we use the "optimized" version of the PSU:

Which parts are then not anymore necessary on the Sid module and does the same count for the Core module?

Thanks for the much appreciated help

[Wilba]

For the SID, you CAN take off the rectifier (X1), bridge across it, ensuring the positive and negative rails are correct. In other words, J1 on the SID board is NO LONGER AN AC INPUT so you must take care which pins are +14v and ground. Optionally, you can do it like in my setup, where C9, C10 and the regulator (IC4) are next to the power supply circuit (aka. the "optimized" version) and I supply 9v to my SID boards instead (which don't have C9, C10 and IC4). But that's only worth doing if you have multiple SID PCBs.

For the Core, see the page on the Core module, read about port J2 used as a +5v input.

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. If the core module (and all connected modules to this branch) drains more than 100 mA, it's recommented to mount C5 directly to J2 (a small cable between the outer soldering pads of the left-out 7805 will do this).

[tos]

Sorry, this is a bit offtopic but wouldn't it be possible to feed the CORE with, let's say, 16V? I see that TS7805 can get up to 35V fed.