Fried my PSU :(

MIDIbox SID
1

Well, in my attempts at being overly cautious, yet clumsy, I’m pretty sure I fried my PSU.

I was testing the voltages on the pins of the PSU, thinking I needed to make sure there was no issue with the PSU before hooking it up to my PCB. I think I must of slipped. At one point I heard a tiny little pop, but it was very tiny and I didn’t think anything of it. I suppose it was enough of a pop that I realized I didn’t know what I was doing well enough to try testing the PSU directly, though I thought I had covered all my bases.

I went ahead and tried the PSU with my PCB. Ok, not too smart after what had just happened, but at least the PCB wasn’t hurt. The 5V rail looked fine. The 9V rail barely had a volt or two on it. I hooked the PSU back up on my C64 and sure enough, the power light came on, but it didn’t have the juice to drive video.

*sigh*

I see three options:

  1. My PSU doesn’t seem to have screws, but I could try to crack this thing open and see if it’s a simple fuse replacement (if it was a blown fuse, I shouldn’t get ANYTHING on the 9V rail though, correct?)

  2. Buy a “new” PSU (I’ll be doing this anyway if I want to run my old C64 again :cry: )

  3. Try to run the entire thing off a 15V PSU using like Altitude explained on
    < base_url >/topic/16595-running-mb6582-off-a-single-12v-dc-supply/page view findpost p 146100?do=embed
    thread. I like this idea, and was planning on doing it once I got my MB-6582 working w/the C64 PSU. But, since I have no PSU to test with right now I’m not even 100% sure everything is set up correctly on the PSU. (I feel pretty confident that it is… everything that I’ve tested checks out and I’ve double and triple checked my connections)

Any thoughts from ye exalted enlightened ones? It would be much appreciated.

I know I’ve been posting a lot here… please pardon my noob-ulant exuberance.

Thanks,

Blatboy

2

Build a new modern safe one with lots of fuses and a crowbar circuit.

3

Yeah, I thought about that option too. Wind is out of my sails now and not feeling confident enough to build it… if I can’t even test it without frying it.

I do have a friend that I think will be willing to look over my shoulder if I go that route. I could start work on the control surface while waiting for parts to come in… hmmmm.

4

Hello.

Too bad you fried the brick. But I wouldn’t let that get to me if I were you :). They have a bad reputation of failing. Because it broke it doesn’t mean you did it ;). (personal crusade against c64 bricks :P)

If u don’t feel confident enough to build a modern one, you should look into the option on finding a psu kit or something. I have some designs, but no one ready for release yet, and I know many others are working on some designs too, so there might be a kit of some kind available specifically for the mb synths soon. But don’t go waiting for it though :wink:

5

Hey, don´t worry too much, better you fried your old PSU than it fries your SIDs @some later point in time :slight_smile:

Building a replacement unit is not so difficult… you can find many options and suggestions here on the forum, at the current point I also think Altitudes solution is the most elegant :wink:

Greets,

Peter

6

The US versions of the C64 PSU are all (all as far as I seen anyway, and I have had a dozen) encapsulated so you are pretty much SOL if you short it out and blow the internal fuse.

7

Yes, the euoropean versions have that “repair protection”, too :slight_smile:

You can open the psu case with some force somehow, which will be instantly rewarded with a fresh nose of 80s air (which was well concealed), ah nice, but then you see a dark gumball of epoxy and you´re out of options.

You can´t even reuse the case, because you hacked it open in the end, frustrated because the top would not come off :). It might be worth it, because of the 80s air, though :slight_smile:

8

.. because of the 80s air, though :slight_smile:

Ha! I call that “Roland Funk”, all the 80s x0x boxes i’ve worked on smell the same (stink actually) when you crack them open, I think its the conformal coating they used on the cellulose boards or the boards themselves that smell that way. I was considering bottling it and selling as a fragrance to DJs for a second.. :turned:

9

Ha! I’d buy that fragrance after thinking about it for a New York minute! :thumbsup: I used to call that sweet smell of groving up “Japanese factory air”. Had a Dx100 and a RZ-1 that smelled like hideous plastics way back…

10

Mmmmmm. Just recently opened my old RX17 to switch out the backup battery, and took a big hit o’ that 80’s polymer funk.

The early 90’s thing has a vibe too… I opened up a Mac Classic II for the first time recently and got a smell that reminded me of library back in my college days, mixed with old electronics. Kind of sick, didn’t seem healthy, yet loved every second of it… kind of like most the things I’m into… :wink:

I’ve got a “new” PSU on the way (thanks Altitude) and I’ll be able to get this tested and built. Next, I’ll either do a mod like Altitude’s or I’ll build a PSU. Thanks for your support.

11

What could be handy (if possible) is a crowbar protection box. Something you can use between the C64 PSU and your MB SID so if the PSU fails the thyristor blows the fuse in the box. It’s a little simpler than building the whole replacement PSU and it avoids messing with mains voltages.

12

I see no problem with that purely technical speaking, but I have several thoughts…

A crowbar is a over voltage protection device. It will trip the fuse when voltage rises above a certain set level, a referance voltage. Controlled either by a zener circuit or other slightly more advanced and accurate logical circuits like a comparator ic. There are also ICs made specifically for over/undervolt protection.

The thoughts are for: a crowbar circuit is usually not designed for negative voltages. And also, a over voltage protection isn’t the only protection a psu should have. It should also be protected from over current / short circuits. A modern vreg would handle all this in a good way. Also has nice features as thermal shutdown etc.

My point is, the transformer and smoothing caps and vreg are just a small part of a real PSU. There is at least as much design work and building with the rest compared to the very simple regulator circuits. So if u are gonna have a psu, u should not have to have a chain of boxes before the load.

Else, the argument for not messing with mains voltages.. yes mains voltages is bad if u don’t know what u are doing and if u don’t have a healthy amount of respect for it, it can easily kill you. And if construction is poor, u might end up with a fire.

I know how to handle mains voltage, and I have huge respect for it. And you should plain and simple not even think about touching the subject if u are not 100% sure u know the what’s and how’s here. So this is a good argument.

What I really suggest as an alternative, if u feel u can’t do the mains voltage dance, is to build a PSU that does everything except the transformation, and use a wallwart that has unregulated output ac.

But then again, that wouldn’t be a good solution either if u have a load tha requires for example 5 and 12v. This is all good when almost no current are drawn through the vregs, but as current rises, for example with a mb6582 with backlit lcd and tons of leds… When u run a 5v vreg and 12v vreg from the same voltage, wich is likely to he around 15vac, u will have to be very carefull to put a huge heatsink on that 5v vreg. Coz with much current, comes heat, and with heat comes instability in form of shutdowns etc.

So not to kill the initiative about a crowbar box, but imho I don’t think it will be as good as fairly good designed psu with everything included and with all modern components. I have worked on a modular psu design some time ago, and that also includes a crowbar module. My goal was to make a psu that could power all my mb stuff. And mostly for learning about psu design really… But my main argument is to be able to control every process of the psu.

But for those of you who swear to the brick supply, flemming can u hear me? Hehe, it is of course better with an insert crowbar than without.

I myself will never risk my sids on a bad PSU hehe.