Commodore PSUs, voltage regulation, connectors et al

Disk drives, Monitors, SuperCPU etc.
Stealth
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Commodore PSUs, voltage regulation, connectors et al

Post by Stealth » Mon Apr 03, 2017 9:07 am

I know there's already an active thread on PSU certification, but I didn't want to hijack it with this (rather) simpler batch of questions. Along with my other areas of research (rolling my own cables, making an H2Obsession-like powered RGBI-to-RGBA converter etc.) I'm looking into maybe making a universal power brick for my peripherals.

I recall reading everywhere that the C64 used a linear voltage that was prone to failure (I had one go bust some 17 years back, thankfully it didn't pull the 64 with it), while the C128 used an SMPS. I know this obviously only refers to the DC part - the 9V AC was derived from a transformer.

This got me thinking - is there any inherent reason why I wouldn't be able to make an SMPS power brick for the 64, and maybe even make a sort-of universal PSU for a few 64s and peripherals? I know some had converted C128 PSUs for a C64 by means of an adapter (since it has all the same pins, effectively), but is there any real reason to insist on a linear transformer design, especially since the lot would require +5VDC, +12VDC (FDDs and all) and 9VAC?

Since I'm okay with understanding electronics, but not so much with designing them, a friend of mine sent me this as an idea:

Image

Basically a transformer to handle 9VAC, an SMPS 220VAC-to-12VDC and a 12VDC-to-5VDC step-down to give me all the required voltages, plus a few fuses not drawn here. (Now that I look at it, it's also missing the 64 Saver circuit, but I have that stored elsewhere).

Does this look like a feasible design? Is there a simpler or more reliable way to do it?

Finally, how would I go about finding a C128 power plug? For most cables there's no issue - the C64 power cable is a DIN-45329, the 1541 power cable is a DIN-4 (standard), whatever I will use for a display converter can also go off 5 or 12V, but does anyone know a good source to get a couple of C128 power plugs (square DINs)? All I've seen are discontinued product numbers - looks like even the A/V DIN-41524 is easier to get, and that's a quirky standard to say the least!



Ready.
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Re: Commodore PSUs, voltage regulation, connectors et al

Post by Ready. » Mon Apr 03, 2017 11:40 am

Hi Stealth,
the schematic you provided will basically provide the needed function to run a c64/128 and a drive 1541-II.
But the design I had in mind was to use DC-DC converters and avoid AC-DC ones. This because AC-DC have much higher voltage inside since it rectifies 220VAC, which means having around 310VDC. Also you must be sure to have a proper AC-DC converter with correct safety measures, like double insulation in the high frequency transformer to avoid that a failure puts the input voltage to the output. So surely avoid all cheap and low quality chinese stuff.
My choice is to use a good transformer with double insulation and design all my circuits on the low voltage side. This allows me even to use cheap components since a failure will not cause harm, but also use a safety monitoring system to check for failures. Check my blog here:
http://danieleredivo78.wixsite.com/c64psu
This is the schematic I use (below version is a bit obsolete now):
https://ibb.co/dZaQ6F
Even if I used cheap DC-DC converters, so far not one PSU of the ones I use to run my commodore equipment has failed and I also got good results electrical wise, like voltage stability and ripple.

About the C128 plug I manage to find a small stock in a shop where I live. We live close to each other, should you pass through Trieste, just let me know.

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Re: Commodore PSUs, voltage regulation, connectors et al

Post by Ready. » Mon Apr 03, 2017 11:47 am

while I am working on a version with separate AC-AC converter as separate box, I am also going forward with a version as described in my blog as a per assembled kit, so that the user would have to assemble the high voltage part by insertion of the transformer in the box following very easy steps, no soldering and just plugging in faston connectors, tighten a few screws and plastic strips. I am updating the current PCB layout to allow more room for the high voltage part, so that I can insert a plexiglass screen to ensure full separation between high voltage and low voltage. The transformer is CE certified (produced by http://www.botter.com/ ) and the assembly will be done by the end user.

Stealth
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Re: Commodore PSUs, voltage regulation, connectors et al

Post by Stealth » Mon Apr 03, 2017 12:33 pm

Thanks for the feedback, I've been wondering about the sanity of using an AC-DC converter, good to know there's another way to go about it! I haven't seen your blog before, it's going on the reading list ASAP.

As for the C128 plug, you're right, Trieste isn't that far off from me. We'll be in touch.

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Re: Commodore PSUs, voltage regulation, connectors et al

Post by Ready. » Mon Apr 03, 2017 12:50 pm

I might bring a few C128 connectors with me during vacation this summer, then. If you come by the coast ;)

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Re: Commodore PSUs, voltage regulation, connectors et al

Post by eslapion » Tue Apr 04, 2017 12:57 am

Just a little side note here: the 1581 uses the same power supply as the 1541-II.

Also, since internally the 1541 has a 12V/5V psu, it is quite easy to mod one to use the same PSU as the 1541-II/1581. I did it and it reduces considerably the amount of heat produced by the drive.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

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Re: Commodore PSUs, voltage regulation, connectors et al

Post by Stealth » Tue Apr 04, 2017 12:24 pm

If I got it right, here's the division:

Internal PSU
  • 1541
  • 1541C
  • 1571
External brick
  • 1541-II
  • 1581
All of them require +5VDC for the logic board and +12VDC for the drive assembly.

The only type I'd ever owned was a 1541-II, so if I ever get my hands on anything that's not it, that'll make adapting them a cinch.

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Re: Commodore PSUs, voltage regulation, connectors et al

Post by eslapion » Tue Apr 04, 2017 4:28 pm

Stealth wrote:
Tue Apr 04, 2017 12:24 pm
All of them require +5VDC for the logic board and +12VDC for the drive assembly.
I don't know about the other drives because they use some sort of hybrid module but the VIC-1540, VIC-1541 and 1541 all require 12Vdc for the video amplifier stage used for reading diskettes.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

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