Commodore 128D to C64 PSU Mod

Forgot to turn on notification, thanks for reminding me Heather.

I want to begin by saying it's a beautiful PSU, wish I had one myself.

I meant that if you have a PSU that can give a lot more Amperes than your C64 need it can be a good idea to fuse the 5V line and 9VAC line with appropriate size fuses.

Should there be a short I'm sure a 5V 6A PSU will damage more than a 1.5A or a 6A fused with 2A. So my suggestion was really that as you have two outputs it could be an idea to put fuses on the each of the 5V lines and possibly also the 9VAC if you want to have damage control and also allow unit number 2 to keep running even if unit number 1 shorts out. Fuse would burn at a lower Ampere and wouldn't take the whole PSU with it.

It's possible there's already fuses here and there and built in protection. ;-)

Regarding the LED, if you decide to make another one some kind of panel mount without the screws could look nicer. If you use the rectangular kind it would look nice to have it flush to the metal - kind of like the C64C LED (which is slightly recessed). But I guess you already explained that. ;-)

Maybe:
141129.jpg

or...
http://www.oznium.com/led-indicator-light
4pgs.jpg
 
Ah! I see what you are talking about now with the fuses. I believe the panel mount fuses that I put on the back fulfill the fuse needs. I know one of the fuses is for the 5V output because I have one that I tested that keeps blowing that fuse as soon as it's plugged in. The other fuse covers either the 9VAC output or the 12VDC. I'll have to look to verify which it is. I should put another fuse in to cover whichever one is not currently fused.

I think retrofitting this one with separate fuses for each output port might be a bit of a pain so I probably won't do that. Still, I really like the idea and will incorporate that into the next one. :D

The first panel mount LED is the exact one I bought for this project but I couldn't for the life of me remember where I had put them. I recently found the Radio Shack bag that still had them along with the receipt. It fell behind a bookcase. :picard The next PSU will definitely contain that LED!

Thank you again!!!

Heather
 
Heather,

What tools did you use to cut the holes in the case for the powerswitch and 110v power cord? Also did you just drill holes for the fan? I am assuming the case is metal and not plastic.
 
The case is metal and is already vented on both sides so I simply drilled the holes for the screws to attach the fan over the vents on one side. All the round holes were done with a standard drill using whatever bit best fit the size of the component. I had to drill the two holes for the DIN connectors using a larger bit than I had, so I brought it to work and used the larger drills that we have there.

Both the power switch and 110V socket were cut out using a Dremel. Just measure and draw the holes on the case then take your time cutting them out. You should also cut on the inside of the case since you may get scuff marks outside the cutting area, which you don't want on the outside of your case.

Please let me know if you have any more questions.

Thanks,

Heather
 
Just a quick update on slowing down the fan. A Lemon64 member, Eslapion, suggested using diodes to drop the 12VDC power going to the fan to a lower voltage. I used six 1N4001 diodes to drop the voltage from 12VDC to 9.63VDC without load and 7.36VDC under the fan's load. The fan, while not totally quiet, is a lot more bearable in a quiet room.
icon_smile.gif


My only concern was the possibility of heat build-up in the diodes themselves. Fortunately, that is not an issue.

Now I'm ready to finish modding my second PSU. This next one will be a little different than the one in this thread because I'll be making some changes based on what I learned during this build. Still, this one is a great PSU for my C64. :D

Heather

 
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SkydivinGirl said:
Just a quick update on slowing down the fan. A Lemon64 member, Eslapion, suggested using diodes to drop the 12VDC power going to the fan to a lower voltage. I used six 1N4001 diodes to drop the voltage from 12VDC to 9.63VDC without load and 7.36VDC under the fan's load. The fan, while not totally quiet, is a lot more bearable in a quiet room.
icon_smile.gif


My only concern was the possibility of heat build-up in the diodes themselves. Fortunately, that is not an issue.

Now I'm ready to finish modding my second PSU. This next one will be a little different than the one in this thread because I'll be making some changes based on what I learned during this build. Still, this one is a great PSU for my C64. :D

Heather
Click to expand...

Why didn't you just use a resistor to drop the voltage instead of a whole load of diodes?

Bryce.
 
Bryce said:
SkydivinGirl said:
Just a quick update on slowing down the fan. A Lemon64 member, Eslapion, suggested using diodes to drop the 12VDC power going to the fan to a lower voltage. I used six 1N4001 diodes to drop the voltage from 12VDC to 9.63VDC without load and 7.36VDC under the fan's load. The fan, while not totally quiet, is a lot more bearable in a quiet room.
icon_smile.gif


My only concern was the possibility of heat build-up in the diodes themselves. Fortunately, that is not an issue.

Now I'm ready to finish modding my second PSU. This next one will be a little different than the one in this thread because I'll be making some changes based on what I learned during this build. Still, this one is a great PSU for my C64. :D

Heather
Click to expand...

Why didn't you just use a resistor to drop the voltage instead of a whole load of diodes?

Bryce.
Click to expand...


or a 12 volt speed adjustable fan.
 
Bryce said:
Why didn't you just use a resistor to drop the voltage instead of a whole load of diodes?
Click to expand...

Or just connect it between +5V and +12V which results in +7V. As long as there is load on the 5V line it will work fine and will be the most efficient solution.
 
Putting a fan between 12V and 5V can add a lot of noise to the 5V rail. I wouldn't recommend it for systems that don't have a very good regulator AFTER the fan.

Bryce.
 
Everyone,

I had at first thought I was going use a resistor to drop the voltage down in order to slow down the fan so it would not be so loud. However, eslapion on Lemon64 offered up both the diode solution as well as connecting the fan between the 12V+ and 5V+ rails. After discussing the pros and cons of all three options, I went with the diode solution.

The reason I went with the diode solution over the resistor solution was mostly because I wanted to learn how it worked compared to how a resistor worked. I could also fine tune the diode version by adding or removing a diode. I did not choose the 12V+ and 5V+ solution because I was told that I would need to always have a load on the 5V rail, which might not always happen if I want to turn off the computer from its switch.

I didn't go with a variable speed fan because I already bought this one and didn't want to just toss it to the side since it fits the case so well. :)

Any of the suggested solutions would have worked, but the diodes seemed the best for me in my particular situation. I'll probably try the resistor version on the next one just to see how warm the resistor gets compared to the diodes. And before you ask about the variable speed fan, I had ordered two of the fan that I used in this project.

If you're bored, you can read through the posts about the different methods I discussed with eslapion in the following thread:

http://www.lemon64.com/forum/viewtopic.php?t=50577

I'll post pictures of the next PSU when I have it completed. It won't physically look much different from this one except that I am going to try to make it more modular so the main board can be removed in case repairs need to be made at any point.

Thanks guys!

Heather
 
couldnt you of done this with a zener diode heather?

what was you looking for 7 volts?

you know heather,i like options.:D
 
Diodes are a good solution, and I've used that method several times in the past. Compared to a resistor, you distribute the heat across many components which might be good.

If the fan has trouble starting since you want to run it at low RPMs, the diode solution will often also be better since it can provide a higher voltage during startup where the fan draws the most current.

Effectively this mean you can lower the speed a little more using diodes than what is possible with a resistor.

roy_bates said:
couldnt you of done this with a zener diode heather?
what was you looking for 7 volts?
Click to expand...
A ~5V zener diode might have worked in theory, but you'd need one that can handle the power, not the typical small zeners.
 
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I don't have any experience using zener diodes so I didn't think about that as an option. The fan I have is rated down to 7V but I was able to drop it lower than that with an additional diode and the fan still didn't have any trouble starting. That sounds like it supports what demolition said about the higher voltage during startup when using diodes. :)

This discussion is why I like hearing about all the possibly options. It lets me learn quite a bit and I enjoy that about as much as actually getting it working!

Heather
 
demolition said:
Diodes are a good solution, and I've used that method several times in the past. Compared to a resistor, you distribute the heat across many components which might be good.

If the fan has trouble starting since you want to run it at low RPMs, the diode solution will often also be better since it can provide a higher voltage during startup where the fan draws the most current.

Effectively this mean you can lower the speed a little more using diodes than what is possible with a resistor.

roy_bates said:
couldnt you of done this with a zener diode heather?
what was you looking for 7 volts?
Click to expand...
A ~5V zener diode might have worked in theory, but you'd need one that can handle the power, not the typical small zeners.
Click to expand...


yeah mate i know,but you can get these in different power ratings.
 
The thread is a little old now but wanted to update how on my version of this went.

I made three of them based on Skydivinggirl's post. Cheaper design as I did not add the connections for the fuses. I figured if they were blown out I could just open the case. New capacitors were added to two of them. Not very pretty job on my end.

I originally made them with the fan and only the cable for the 64 power.

I have modified them further to add a fan cover. (Cut the vent slits to have better air flow. I have also added the 6 diodes to slow down the fan.

Lastly I have added leads to and din plugs to power a 1541-II drive using the 12v and 5v lines.

So I ended up with:

1. Powers the 64 breadbin/REU/Swiftlink and 41-II
2. Powers the Plus4 and 41-II
3. Sits at the workbench for testing other 64's / 41-II.

If I decided to order another case and transformer I can make one more with the parts I have.

For me the hardest part of doing this mod is the case. Not a fun thing to cut into. It is also the most expensive part of the kit. I wish I could find a smaller case that would still fit it and be easier to work with.
 
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Thanks for the update! It sounds like you've got some good options now. I'd love to see some pictures of your builds. :)

I totally agree that modifying the case is the biggest pain with this build. I am about halfway through my second build but I was put off by having to work on the case again. I'll finish the second one at some point and then possibly do a third so I have some spares. :thumbsup:

Heather
 
Nice to see things are still being built here. Seems lemon64.com is down at the moment so I couldn't check the diode-discussion there.

In my Amiga 2000 I long ago put a resistor on the fan, largest one that allowed it to start with no problems and then one of those bimetall temperature sensors that close when a certain temperature is reached. That shorts the resistor and sets the fan to full (normal) speed. Has been working pretty well for 15+ years.

There must be all kinds of "in between" fan controllers you can buy that increase/slow down the fan along a nice straight curve for "stepless" change of rpm.

I haven't checked the details but here's an example:
http://www.ebay.com/itm/350913778292
 
Thanks for the link. I'd be interested to see what they are doing within that speed controller to control the speed of the fan. :)

I really liked the diode solution because it didn't seem to come with any detrimental heat effects through the diode chain, even after running for quite some time. Fortunately, I can continue to look at the alternatives and easily change out the diode fix with something else. I'm mostly just happy that I'm no longer using the original C64 power bricks! :thumbsup:

Heather
 
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