Optimized PSU Voltage to SID Module Question

[frailn]

I just finished building an Optimized PSU for the MBSID. I'm getting 5V on the LED line, 5V on the line to the Core. But, on the 14V line to the SID, I'm actually getting 16V. I'm thinking that once the line gets to the 7809 on the SID module, it will regulate down to 9V, anyways, so this shouldn't be a problem (using 6582A SID from Wilba). Can someone confirm that for me before I start building SID modules and connect power? Thanks!

[SLP]

I'm thinking that once the line gets to the 7809 on the SID module, it will regulate down to 9V, anyways, so this shouldn't be a problem

that's correct. But I think that the 16V will drop to 14V as soon as there's some load hanging on it.

But take care of the electrolytic capacitors. AFAIK the ones used in your project are rated at 16V maximum (but I'm not sure about that), so take care. If you exceed the maximum voltage (or connect them with the wrong polarisation) electrolytic capacitors will explode! And you don't want that those toxic and highly corrosive acids in your face/eyes.

And of course tha bang wil be pretty loud.

matthias

[frailn]

Thanks!

AFAIK the ones used in your project are rated at 16V maximum (but I'm not sure about that), so take care.

I think I'll swap my 2200uf 16V capacitors that came in Smash's SID kit for 25V just to be safe.

[SLP]

just try to put a resistor in series with your PSU:

+16V------R-----GND

Then measure again. I think the voltage should drop.

[frailn]

Well, I went back to remeasure the voltage and now I'm putting out 5V on the 14V line out. Back to the troubleshooting! I'm sure I have a short or bad solder somewhere on this stripboard...thanks for the help, I'll try a resistor after I figure out the problem on my 14V line.

[M.U.L.E.]

Hi Frailn,

In case you haven't solved this issue yet, you may want to check your C-64 power supply for a blown fuse internally.  I have two C-64 supplies that were acting the exact same way, with and output of 5v on the 14v line (testing from the optimized psu circuit ground and 14v points) - hopefully you have the type of supply that has four screws in the bottom, you can just back those out and check the fuses to see if they are blown.  In my case only one of the two were blown.  If you do not have a supply with screws, it's most likely much heavier, and completely encased internally with epoxy, which should make for a fun time to get to the fuses.  I vaguely recall seeing a post where someone did this though.  I did find these posts as well:

http://www.midibox.org/forum/index.php/topic,8164.0.html

http://www.midibox.org/forum/index.php/topic,9351.0.html

I'm sure there are more about repairing that I'm missing.  If it is the fuse issue, then something may be wired wrong on the psu circuit that's blowing that fuse, so if you replace the fuse and the same thing happens check the fuse again.  I'm guessing you already solved this issue though, just thought I'd add this in case someone came across with a similar problem.

Here are a few pics of my two supplies, one fixed, one bricked.

[frailn]

Thanks for the info!

My PSU is actually a third-party generic brand, not the official Commodore version. I checked the fuse and it was fine. Then, I plugged it into a C64 and tested the voltages on the power port, from inside the case, and the voltages are fine (5v and 9v). The builder of this PSU might have got the pin out wrong? But, I don't think so, since I'm able to fire up a C64 and use it normally. I think my issue is just that I'm OPSU building-challenged! But, I'll double check the voltages again against the pin-out of the OPSU schematic and see if I missed something.

I ended up rebuilding an OPSU using a C64 disk drive power supply, and I've managed to get it to send the right voltages to the SID and Core modules and operate a one-SID synth with no issues. However, I do want to get an OPSU working correctly with a regular C64 power supply so that I can add more SID modules in the future....

This is good info. Maybe should add to an OPSU page in the WIKI!

[M.U.L.E.]

I'm curious what your power supply looks like, I have one non official 64 supply made by Tenex that works great.  It's a funny story too, I got it by what must have been a blessing from the gods - I was browsing around my local craigslist and decided to check the "free" section, I never checked it and wondered what was in there.  The third newest listing read "Huge lot of Commodore 64 hardware and related, on curb MUST TAKE ALL" - the posting was very specific, it had the address and the terms were "if you show up you must take everything, no picking through.  Also DO NOT COME UP TO THE HOUSE, do not knock on the door.  Do not reply to this ad.  Thank you."

It was a crazy amount of stuff, no less than 15 c-64's, several monitors, stacks of disk drives, power supplies, the list goes on and on.  It appears it was from someone who ran a commodore club back in the day, who went by the name ''The Wyoming Unicorn'.  I drive a newerish chevy imapala, and it was full to the gills, trunk and all - once the last item went in I had barely enough room to steer!

Had to share that, it was like finding a bar of solid gold at the time.

Oh yeah, we were talking about power supplies  :)  Here's a pic of that third party one I had in the bunch: