C64 PSU Pinout Problem (affects MB-6582 base PCB)

[Wilba]

jimp discovered his two C64 PSUs do not have all 7 pins in the plug, only the 4 required (9v AC, 9v AC, +5v, Gnd) and actually have the +5v pin in a different position to my PSU, TK's diagram of using a C64 PSU (http://www.ucapps.de/mbhp/mbhp_4xsid_c64_psu_optimized.pdf) and unfortunately the socket pin used on the MB-6582 Base PCB.

As can be seen in these references:

  http://www.hardwarebook.info/C64_Power_Supply

  http://personalpages.tds.net/~rcarlsen/cbm/pinouts.txt

Pin 5 is shown with +5v to be connected always, with pin 4 either not connected or the same +5v. jimp's C64 PSU only has pin 5 and not pin 4. But on my PSU, pin 4 has +5v and pin 5 has nothing, and this matches TK's diagram of which pin has the +5v, and so naturally I designed the MB-6582 base PCB to match. This means jimp's PSUs (and maybe others!) won't work with the MB-6582 base PCB without a little "fix"  :-[

This is just a warning to people who are starting to solder/use their PCBs that you should check the expected voltages are coming out of your PSU. I've been too busy to write up the complete construction guide including things to test like this...  ::)

You should be fairly safe to solder a thick insulated wire between pins 4 and 5 of the power socket on the base PCB, to get +5v from pin 5 across to pin 4 and the rest of the PCB. But don't do this unless you fully understand why you are doing this - I'd like to get some more info before I publish this as an official "everyone do this" fix.

Pin 4 and 5 are the two pins closest and on either side of the pin in the middle.

Quick hacky diagram until I do something better (bottom of PCB shown):

[tt]

O    O    O

  O-------O

O          O

[/tt]

I'd like to know which PSUs are affected. Is this a Europe/Australia vs. U.S.A. thing? Or a 220v vs. 110v thing? Why does my PSU have +5v only on the optional +5v pin and nothing on the always +5v pin (according to the pinout diagrams)? Did TK draw that diagram because his PSU and many other "Eurpoean" ones are the same as mine? Or does his have +5v on both pins 4 and 5 and just happened to choose pin 4?

[seppoman]

Hi Wilba,

once I also had a C64 PSU with "wrong" 5V pin - all PSUs I´ve seen were european 220V versions, so this is not the distinguishing factor.

Seppoman

[Renze]

Hello,

Thanks for the tip. I'm a beginner and about to start building the Midibox Sid. I had already noticed my PSU was missing some pins, and at first I thought it was broken. But the C64 did power up, and as I can see now it does have all the necessary voltages and ground. I think I understand the workaround you mentioned. My PSU plug only has pins 2, 5, 6 and 7.

edit: my PSU is a European 220V which came from Germany.

[nebula]

I just looked at the way the jack is wired on a C64 main board.  The 2 pins are connected together - so no matter what, bridging those 2 pins should never cause a problem, and will probably ensure compatibility with C64 power supplies worldwide.

[Wilba]

Yes, I agree, which is why a track was put in Base PCB Revision 2 to bridge these two pins.

For people fixing up their Revision 1 boards, a cut resistor lead is sufficient to bridge these two pins.

If you want a cut resistor lead, I have plenty to give away absolutely free, but you have to pay AU$2 postage.  ;D

[dj3nk]

If you want a cut resistor lead, I have plenty to give away absolutely free, but you have to pay AU$2 postage.  ;D

Take 2 cent for each. ;)

[/tilted/]

If Wilba runs out of these cut resistor leads, let me know. I've got heaps, too.

Edit: if demand proves high enough, maybe we should do a bulk order? ::)

[nebula]

Thanks! 

Can I make my own?  If so, what value of resistor should I cut the leads from?

[bugfight]

for audiophile quality, you must harvest cut resistor leads only from 0 ohm resistors!

measure them first to make sure they are not counterfeit...

[nebula]

for audiophile quality, you must harvest cut resistor leads only from 0 ohm resistors!

measure them first to make sure they are not counterfeit...

Thanks.  I think I still have a few 0 ohm, metal oxide, 1% tolerance.  I'll have to check.

</flogging>

[bugfight]

...Thanks.  I think I still have a few 0 ohm, metal oxide, 1% tolerance.  I'll have to check...

ok, but remember if you use tubes that carbon composition 0 ohm resistors sound warmer.  and if you can't get those in better than 1% tolerance, just measure each one and make sure it is closer than 1% of 0 ohms,

(i prefer to be within 0.001% of 0, but that's too perfectionist for most folks)

[pkniffer]

is one able to convert a 220 v ps to 110v?

[/tilted/]

ok, but remember if you use tubes that carbon composition 0 ohm resistors sound warmer.  and if you can't get those in better than 1% tolerance, just measure each one and make sure it is closer than 1% of 0 ohms,

(i prefer to be within 0.001% of 0, but that's too perfectionist for most folks)

I usually buy really low spec 0 ohm resistors. I find that even the 20% tolerance types are still pretty good.

But you still need to measure them. If you get a 20% tolerance 0 ohm which is 20% under, you're in big trouble. I think they call these "batteries".

[nebula]

is one able to convert a 220 v ps to 110v?

That wouldn't really be practical. You should use the appropriate p/s for your country ... either will work for mb-sid with optimized power supply circuit (or mb-6582)

[Foona]

Iv'e read through this post and it seems that this forum

seriously needs a psychologist.  :)

[Doug Wellington]

Iv'e read through this post and it seems that this forum seriously needs a psychologist.  :)

Ah, so...  I'm glad you are self confident enough to assert yourself in such a non-threatening manner.  And how does that make the rest of you feel?

;D

[Foona]

..well...after joining this fine forum, i might soon be in need of a psychologist myself  ;)