Replacement power supply (any interest?)

Started by Arcade, October 03, 2014, 07:23:30 AM

Previous topic - Next topic


Hey everyone.

I decided to make a drop-in replacement for the 'tetris block' type power supplies.  There's not a lot to it-- a modern 12VDC switching supply acts as the primary converter, then an on-board PicoATX supply handles the switched power rails and final power conversion.  The idea is just that you would take your existing supply, remove the wire harness from it (solder it in place on the new board) and drop the whole thing back inside the metal case with the existing fan, switch, cord, etc.

Anyway, I still need to do some testing on it, but I thought I'd post a picture and see if there's any interest and if I should make more than just the ones I need.



Hi Arcade,

Great project ! Sure there will be interests !  :)

Few questions :
- What's the maximum power delivery of the main switching PSU ?
- As you plan to use the original power cord, I guess it's 110 VAC only ?

Keep up the good work !


That's really excellent, and sort of makes me regret throwing out all my original PSU shells when I put ATX power supplies inside.  =D


Yeah same here, wish I knew about this a few days ago!


To me it would depend on the cost...  A pico psu + external supply is about $70 or so for 120 watts  so if the cost of this exceeds that cost by much it would be hard for me personally to justify it.  For a lot of people though it would be a simpler solution.


It's a universal input supply (~90-260VAC @ 43-64Hz), so pretty much whatever type of AC mains you can get the plug to go in to, it should work. ;-)

The primary DC stage should be good for ~65W with the fan in the x68000 PSU keeping it cool.   (I need to test some other systems, but on a XVI with HD + keyboard + maximum RAM expansion + MIDI + playing a game with internal speaker on, the peak draw on the AC side was ~55W (when the HD and floppies first spin up) with the 'running' numbers closer to ~47W or so.  That's ignoring any potential difference in efficiency... I'm not sure what the efficiency of the OEM supply is.  The PicoATX converters must be pretty efficient-- there's not enough mass or heatsink on them to dissipate much in the line of conversion losses!)   It'll be interesting to see the total power dissipation in the exact same system/configuration with the 'new' supply.  (That'll say whether it's more or less efficient end to end than the OEM version.)

Without the HD spinning the number comes down ~4W or so which buys quite a bit of operating margin and the floppies spinning take a lot too.  A non-HD system that's not running the floppies and doesn't have a full expansion bay is probably under ~40W average operating consumption.

These prototype boards are just on 1oz copper PCB's, so I'll get it hooked up and running and watch it with the thermal camera to see if anything's getting stressed.  For production I used design rules so I can order ~3oz copper clad to handle higher current if anything on my part of the design heats up.  (1oz is just the 'standard' low-cost prototype PCB's-- I didn't want to spend $100's extra to get 3oz on the prototypes.)

Price wise I'd need to be right around ~$80 USD (basically everything in the picture except the aluminum frame).  That's the downside with the pre-built power modules-- kinda expensive, but they're tried and true designs and make for a quick implementation!  Another possibility is to leave the 12V module unpopulated and use an external 12V brick supply which would lower the cost and keep heat out of the case as well while preserving the original form-factor.  That would be more like ~$55.



That's really nice piece of hardware. Looks clean, feels more authentic. Original power cord and that's it. Nice, nice.
ATX begone!

Now the question that goes against "authentic" and it's probably too large anyway :)
Would it fit inside the first x68000 model? horizontally instead of vertically maybe?


It should fit OK inside the original models PSU.  Only trouble there might be ventilation since the original model fans arent directly on the psu case.


So, 65W. Looks like suitable for XVI model or compact ; not sure for post ACE ones.
I'm also pico-itx PSU modded on a SUPER and ACE models, and I burnt a 90W (rated) external power brick while using it on my SUPER with an hard drive and my ERSA board. However, I'm still not sure of what happend exactly, the power brick itself could be the culprit (was a cheap one). One component on the hard drive totally melt (look likes a power mosfet or motor driver), one floppy drive and the SUPER seems dead now.
I'm now using a 120W with a fan for about a year now : no problems yet !

As for original CZ600, 65W is probably not enough.

That's ignoring any potential difference in efficiency... I'm not sure what the efficiency of the OEM supply is.
This made me smile a bit ! High effiency SMPS was pretty new during x68000 times and was greatly improved since 2000's. I can't tell, I'm not very well equipped for high voltages and power measurements. However, all heating elements are in contact directly to the aluminium case and a fan was necessary. I wouldn't be surprised of a 70% or less in efficiency...

Sure your solution is far better ! The first PSU stage is small, and well placed for cooling.


Yeah, agreed on the efficiency of the early 80's SMPS solutions.  Anyone here able to read the Japanese text on the bottom of the tower that talks about power?  There's two numbers, one that I assume is the 'average' power consumption and another that I assume is 'maximum'?  I noticed on the Expert the numbers were like ~38W/81W, the Ace was ~44W/99W and the XVI was ~47W/99W (those could be wrong-- just going from memory there).  The original CZ600's say 44W/75W, IIRC.

This 12V supply I have in the design now is a "cost effective" one-- I figure it'll be fine for a typical CF setup with memory and MIDI cards with some room to spare.  You can get higher efficiency models (I see one that's claimed >87%) that supply more current in the same form factor with the same cooling.  The "ECS130US12" is a nominal 100W convection cooled and 130W w/ 10CFM of airflow.  It's the same standard form-factor (2"x4"), just more expensive and probably not worth the expense if you don't need it.  (eg, no sense in paying extra for power you won't use) 

On the upside, all these modern SMPSs have standard over-current foldback and thermal protection, so in theory everything should gracefully shut down if there was a short or something happened to draw too much power and get too hot.

On the original model x68000's the power supply is physically much larger (and doesn't have the funky zig-zag shape), so I could do the same thing there (replacement board using existing metal) and use a 3"x5" supply which is much easier to get in higher power densities.


 Hi Guys !

If anyone is interested, here is the power consumption chart for almost every model:

X68000 Product Catalog

Keep the scene alive !
X68000 personal computer is called, "X68K" or "no good good" is called, is the PC that are loved by many people today.


Thanks for the link, Eidis!

I'll try to get some testing done this weekend.  The 'wildcard' of course being that the published power consumption numbers are entirely dependent on the efficiency of the OEM supply.  ("40W" consumption on the AC side if the supply is only 70% efficient might only be delivering ~28W on the DC outputs.  So a modern "35W" supply with >80% efficiency could provide the same usable power, just with ~12% less losses.)


 Hi Arcade !

I have a power meter buster and in the name of science and curiosity was tempted to know how much power my ACE-HD with Yamaha V769970, CF card reader and SH-6BE-2/4M-1 RAM expansion and a stock PSU draws.

Here are the results:

~58W at cold boot
~52W when both floppies are running
~45W when only CF card running

Keep the scene alive !
X68000 personal computer is called, "X68K" or "no good good" is called, is the PC that are loved by many people today.


Thanks for the numbers!  That's in the same ballpark as the XVI I checked out.  I'm pretty sure the 65W first stage will be fine (it's 65W continuous but will go higher for short periods of time-- I'm thinking the initial inrush and drive accesses will be OK), but if it's undermatched I can drop in an 80-100W module instead.  Just trying to keep the costs as low as possible for starters... ;-)


October 05, 2014, 03:54:47 PM #14 Last Edit: October 05, 2014, 04:11:40 PM by eidis
 Hi Arcade !

Sometime ago I experimented with Micro-ITX cases which had external power supply. The maximum total power consumption values were calculated for all components and a PSU with slightly higher rating was chosen. However, the PC was crashing and behaving unstable when at full load and a slightly higher spec PSU cured the problem. I have a gut feeling that 100W would be the best and most reliable choice.

Update: Here are the specs which are written on the ACE-HD

Rated voltage 100V
Rated Frequency 50 / 60HZ
Rated power consumption 55W (100W maximum)

Keep the scene alive !
X68000 personal computer is called, "X68K" or "no good good" is called, is the PC that are loved by many people today.


Quote from: eidis on October 05, 2014, 03:54:47 PM
> I have a gut feeling that 100W would be the best and most reliable choice.

Overkill is almost always 'safest' in power supplies, but a 100W 12V brick in a 4"x2" form factor is more than twice the price of a 65W...  So there's no free lunch. ;-)

On the other hand, the difference between modern computer designs and the x68000's are pretty extreme-- a ~16Mhz 16 bit bus CPU with 5V signal levels has a LOT more operating margin than a multi-gigahertz 32/64 bit CPU with 1.5V DDR3 memory.  (+/-10% supply on 5V is a full volt of swing, while the same tolerance on a 1.5V rail is only 300mV)

Anyway, it's pretty easy to see if a power supply is getting stressed or not.  Observing the output voltages under 'worse case' conditions (low line voltage, high transient output currents) will either result in voltage dips (poor regulation) or excessive heating (or both), so I think some empirical tests will be educational.

At any rate-- a bigger 12V 'brick' can always be dropped in if someone needed a 'super' version of the supply.  I just couldn't hit an $80 price point and include a 100W+ 12V supply.  It'd be more like ~$110.

I'm going to do some tests today, so I'll post any interesting findings here. ;-)



Any news on this?

Looks like a great idea  8)


I am interested on this power supply, but no more news since october 2014... sorry for the long time bump, but I had to know, is this project still alive?

From Mexico City... Amigo-Mexicano!
Also known as: "compil3r" ||