# Why is the ColecoVision AC adapter so big?

Why is it ColecoVision AC adapter so big? I never had seen someting like this in any console of the era or even after it. What are the design choices made by the designers? Was it to turn the project cost effective? Back in the 80’s, with the technology then available, can the designers had taken a more standardized aproach? Why no other console design follow this path?

Here is a link of a Youtube video from the AVGN making fun of this AC adapter size: https://youtu.be/rBMO8F1I-h4

• If you think it's too big, have a look inside and see how big the components are and whether there is much empty space or not. – Greg Hewgill Apr 18 '18 at 1:06
• Big power supply, or tiny hands? – Bruce Abbott Apr 18 '18 at 4:43
• Hardly too big saw bigger back in the day. This one seems to be more or less the same size of the ZX128-2 Power supply It is all the matter of how much power, filtering and cooling your device needs 50/60Hz metalic transformers where big in comparison to 40KHz ferrite switching we use today. But they lasted for decades have mine homemade for experiments and testing below my desk and it is still used/working after 20 years. Unlike the modern PSW in noisy environment they commonly last only ~2 years reliably – Spektre Apr 18 '18 at 7:45
• One would have to ask a product designer from Coleco. The size isn't much different from (say) the C64's brick of the same era. Perhaps the more appropriate question is why did they put the plug blades on the brick rather than having the brick in the middle of a cord like the C64's did? I think that is the bigger issue since the weight was a bit of a problem on horizontally oriented wall outlets (think: it was hanging sideways) – bjb Apr 18 '18 at 16:59
• Compared to my Amiga 600 power brick, it's a midget. – tofro May 9 '18 at 12:24

The ColecoVision power supply is a multiple-voltage supply producing regulated +5V, -5V, and +12V output. To provide these multiple voltages it needs a more complex transformer which takes up a large portion of the AC adapter seen in this repair video:

As the regulation is done inside the power supply and not in the ColecoVision itself additional components including a regulator and a heat sink have to be included. Take note of how large the heat sink is in that video in addition to the passive components within the walls of the heat sink.

In comparison most consumer electronics have the regulation handled inside the appliance and they expect unregulated DC output from the power supply. In that case all the power supply has to contain is a small transformer, bridge rectifier, and a few passive components so it can be much smaller. This is why your run-of-the-mill game console AC adapter is much more compact.

Even if a switching power supply was used it would still be fairly large due to the multiple tap transformer and the several switching circuits needed for each power rail. For this case you'd have more components (inductors, additional diodes, etc.) than in the linear design; the PCB would be more complex, more costly, and possibly larger than a linear design.

So linear versus switching power supply design has nothing to do with this. It's a complex power supply that was implemented fairly efficiently, and the only unusual aspect is that they didn't have a cord going from the wall socket to the AC adapter, and instead hung the entire thing off the wall.

• An equivalent switched mode power supply should be considerably smaller and lighter than a linear power supply. In an SMPS the transformer operates at a high frequency and can thus be much smaller than one operating at 50/60Hz. Also, SMPSs are more efficient so heat sinks can be smaller. – Glen Yates May 9 '18 at 15:54
• Could you back up any of these statements with evidence showing that this would have been a cost-effective and space-efficient design alternative using technology available at the time the Colecovision was developed? – user8526 May 11 '18 at 20:27
• Hmmm, the Atari PS also did +5/-5/12v and was a lot smaller. – Maury Markowitz Jan 15 at 19:09

As others have noted in the comments, apart from some guy ranting uncivilly about it, for it's era it's hardly special.

The general reason power supplies of the past were so much bigger than today's (apart from the devices they powered also being less power efficient than today's) is that they they are linear not switching designs, thus requiring bigger transformers and more thermal room.

• They where not so much less power efficient (for small powers like consoles) than switching supplies. The main problem is the number of screws needed in 50/60 Hz transformations is higher in comparison to switching PSW not to mention you got 2 windings instead of one. And lastly current running through the coil (defining the area of wires). So better formulation would be less volume efficient in my opinion. IIRC good metalic transformer has >90% efficiency while loaded (the good ones where even 95%) and switching ones are near 98% Of coarse this goes for indoor conditions – Spektre Apr 18 '18 at 8:00
• The inefficiency of metalic transformers (i think you refer to) is much much bigger when not loaded which is one of the main problems of energy loss while distribution (as the big transformers are connected to grid all the time) and outdoor environment adjusts design a bit too not in the favor. – Spektre Apr 18 '18 at 8:04
• The switching supplies of the era weren't small. E.g. Apple's i.ytimg.com/vi/tNIjMOF5sx4/maxresdefault.jpg or Acorn's retro-kit.co.uk/user/custom/Acorn/8bit/BBCMicroIss7/repairs/… . Both famous examples (in the former case because of Jobs' biography; in the latter because it is often reported as a matter of contention between Acorn and the BBC). – Tommy Apr 18 '18 at 11:44
• @Tommy - the Apple II power supply provides 38W, the BBC's 35W. Both provide >3 amps of output at each of several voltages. The Colecovision PSU supplies 9W, with <1 amp at each voltage produced. You'd expect a difference in scale between these devices. – Jules Apr 19 '18 at 14:19
• The term you are looking for is "turns". Any number of screws in a transformer, unless used to hold it together, is trouble :) – rackandboneman Apr 19 '18 at 15:11

As with most power supplies of the era, up to the early 90s, it is a linear supply. Linear supplies produce a fairly clean output that can be used directly by the computer, but need large transformers and produce a lot of heat. They are somewhat inefficient and generally only suitable for supplying a few tens of watts maximum.

Newer power supplies are switch mode. They use a switching regulator that is highly efficient and thus produces much less waste heat. That allows them to use far smaller housings, and also avoids the need for a large transformer.

These days such power supplies are mostly contained in a single chip, with only a handful of cheap external components. But back in the 80s and late 70s they had to be constructed from discrete parts and were difficult to design due to the lack of suitable switch transistors and test equipment. The technology simply didn't exist.

• Not all is positive with switching power supplies. They generate a lot more radio frequency interference than linear supplies do, especially if not well-designed. – Jim MacKenzie Apr 18 '18 at 13:17
• Very true. Particularly back in the 80s they were prone to that. Newer designs are much better, and operate at higher frequencies too which helps with both RF emissions and supply noise filtering. – user Apr 18 '18 at 14:02
• Typica (in 1980)l 60W DC linear supply weighed 21.5 lbs, 2.8 watts/lb; a laptop (in 2018) switching supply, 45W, weighs 0.35 lb so 127 W/lb – Whit3rd Apr 25 '18 at 7:37

The Coleco power supply is normally not wall mounted. That is only for dedicated countries. It was actually a clever design, in comparison to other gaming systems of it's time: by isolating the power to a single external housing the requirements for different countries could be easily met. Shielding etc. was also required, so having all combined in one "brick" simplifies the remaining system. The problem for the console was mainly having 3 different voltages for their subsystem: 12V for VDP, -5V for memory subsystem and 5V for Z80 and remaining logic.

Today, there are replacement power supplies for Coleco Vision. Since it is not rocket science to reproduce the unique connector from power supply to console the door to deliver alternate modern designs was opened nearly 5 years ago. With a retail price of about \$25 it is cheap, too.