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C128 Power Supply Connector Question


SIDsyndrome
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Hi -

I found some helpful info regarding the compatibility of C128 power supplies with the MIDIbox SID in some old posts, and since that's all I've got, I'm glad I can use it.  Tonight I split apart the 5 pin square connector from the C128 and found the following:

( background info on connector/pin-out here: http://pinouts.ru/Power/c128power_pinout.shtml )

Inside - -

Pin 1:  Yellow AND Brown lead*

Pin 2:  Nothing

Pin 3:  Red lead

Pin 4:  White lead*

Pin 5:  Black lead

*there is a ceramic capacitor soldered to pins 1 and 4 that is marked 104 Y5T

Additionally, there is a silver braided shield around the 5 leads which was soldered to a clip that attached to half of the housing for the square socket. 

Basically, my intention is to use a 4 pin XLR to replace the obsolete 5 pin square connector because they are sturdy and additionally I can get a nice panel mount jack.  My (newb) questions about doing this are:

-Do I need to put a capacitor between the ground and the 5V DC?  Is 100 nF the correct value or am I reading that wrong?

-Do need to solder the silver braided shield to the XLR connector somehow?  What is necessary and what are the smart ways to go about doing this?

-A friend of mine mentioned that the 9V AC maybe different from each other - one hot, one neutral or something like that.  Does it matter which one connects to which of the 9V AC pins of the SIL header on the circuit board (MB-6582 by wilba) ?

Thanks so much for helping.

-S

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-Do I need to put a capacitor between the ground and the 5V DC?

Need? No. I would though, for the primary reason that if you're cloning something you clone it ;) (anyway I guess it's a bypass cap and that's good)

  Is 100 nF the correct value or am I reading that wrong?

Guess so: http://www.muzique.com/schem/caps.htm Google is good :)

-Do need to solder the silver braided shield to the XLR connector somehow?  What is necessary and what are the smart ways to go about doing this?

Hey, you chose the XLR connector, you tell me! :D I would find a way to connect the cable shield, if that's what the original does. (clone, blah blah)

-A friend of mine mentioned that the 9V AC maybe different from each other - one hot, one neutral or something like that.  Does it matter which one connects to which of the 9V AC pins of the SIL header on the circuit board (MB-6582 by wilba) ?

I don't think it matters in this case, the rectifier will take care of it anyway....

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Basically, my intention is to use a 4 pin XLR to replace the obsolete 5 pin square connector because they are sturdy and additionally I can get a nice panel mount jack.  My (newb) questions about doing this are:

I suggest using a 7-pin DIN plug and matching panel mount socket - these are fairly easy to find (it's only the PCB-mounted 7-pin DIN socket that is hard to find). Then wire it like a normal C64 PSU plug - that way you can be sort of compatible if you need to change PSUs later. Plus I think XLR plugs/sockets are much more expensive.

But it's just a suggestion - there's nothing wrong with your idea.

-A friend of mine mentioned that the 9V AC maybe different from each other - one hot, one neutral or something like that.  Does it matter which one connects to which of the 9V AC pins of the SIL header on the circuit board (MB-6582 by wilba) ?

I don't think so. I would assume this PSU is much like the C64 one - the transformer has two 9V AC secondary coils, one is rectified and regulated to 5V, the other goes straight to the plug, which can then be rectified and regulated on the MB-6582 PCB. You should have no trouble connecting this to the J1A header, but I would advise using a polarized header and connector so you never accidentally swap 5V/ground.

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I suggest using a 7-pin DIN plug and matching panel mount socket - these are fairly easy to find (it's only the PCB-mounted 7-pin DIN socket that is hard to find). Then wire it like a normal C64 PSU plug - that way you can be sort of compatible if you need to change PSUs later. Plus I think XLR plugs/sockets are much more expensive.

But it's just a suggestion - there's nothing wrong with your idea.

I was thinking about doing that for my PSU. It won't be C64 compatible (it will output  9v and 5v DC), but means I can use a, more or less, standard plug (at least for MidiBox SID projects). I haven't looked, but I think that might make it easier to use with the MB6582 if I did that as well? The only concern I have is the cabling. Do they make premade 7-in DIN cables? Since it's pushing power, it seems like this might need to be heavier duty than, say, a MIDI cable.

I figured since XLR cables seem pretty hefty and can be easily had, this might be a good option. You're right, though, they connections are noticeably more expensive.

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It might make it easier to use for the MB-6582 PCB, because you could use a PCB-mount 7-pin DIN socket, and then make some changes to the board, like bridge across the bridge rectifier pins. My previous suggestion was to add a DIN plug to the existing C128 PSU cable. For your idea, you can buy just the DIN plug and use whatever cable you like. The DIN plug/socket can certainly handle 2 amp loads.

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Yep, that was my plan. Specifically, I want to use PSU Option D. I haven't decided yet if I'm going to put mine in a PacTech case or use a C64 case. If I do the latter, it may not matter all that much since I might have to mount the power socket elsewhere. Where the socket used to go on the C64 would make sense, of course, that WAS a DIN socket anyway so I guess that would make sense.

My only big concern with that is getting the cables. Thumbing through some catalogs, it looks like there are multi-conductor cables that would easily work - just not sure I'm confident enough terminating the cables with DIN plugs :)

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Actually, if I can throw a follow-up question out there. If I make my own DIN cable, are there any recommendations on the type of cable to use in between? I was thinking a 3-conductor 18AWG cable. Would a shielded cable be better (and should the shield be connected to GND or not?). Doing a bit of research, it seems like wiring it up to the DIN adapter should be easy enough - looks like I have the option to solder or crimp. Thoughts?

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