Looking for info on custom N64 power supply caps

[Dopy25]

So I have a non working N64 PSU that I wanted to put more modern components into and use a 12v switching PSU to plug in.

I think it looks pretty good from the outside but I am having trouble with the circuit.

I have my 12v in and my 3.3v buck converter soldered in on perf board for mounting.

The trouble I am having is that I can't find the right info I need for the capacitors and fuses.

I understand that I can reuse the caps from the N64 PSU and they don't seem to be bad but I am not opposed to new ones since my goal is modern components. The other issue is that since it did not work, I am not sure what is bad inside. 

 

The problem is that when I first started, I didn't think about caps or fuses. I have watched a few videos that show various mods, but the first one I watched had no fuses or caps so I didn't think I would need anything. It wasn't until I read about a few other mods that I saw filters and fuses. After that I notice in the original video I watched, the OP stated he added fuses later. I will admit, I am not familiar with what caps do in a power circuit so I have no idea how they are wired. In the video mods I have done, the capacitor serves as a filter so it is in line with the output. But from what I have read, power circuits go to ground through the cap, is that right?

 

I know I should have a capacitor and a fuse on each line but I can't figure out the uF to use, the polarity, and where it fits in the circuit.

 

I have a rough schematic attached if anyone can help me out.

 

Do I add a 220 uF cap in line on the 12v line, or positive leg to line in and negative leg to ground? Same question for the 3.3v line with a 470uF cap. Other sources also identify a 0.8 fast blow fuse but I wouldn't know where that goes either. I assume that one is in line on each 12v & 3.3v lines, but does it go before or after the cap?

 

I have to figure the voltage on the caps doesn't matter as long as it is higher than the source voltage, right?

 

The PSU these came out of is the far less common LSEP01106 so all of the parts inside seem different that the others. I also cannot find a schematic to tell me the parts, or what the heck fuses were in it to begin with.

 

Any help or advice is appreciated.

 

[Dopy25]

Oops. Past my edit time. So it looks like the caps should be about double the voltage to work effectively. So I should use a 6.3v 470uF cap on the 3.3v line, and a 25v 220uF cap on the 12v line. Is that right? I think I found my answer about caps and grounds as well. I still am unsure where the fuses go, or what the even are.

 

Has anyone here done anything like this?

 

Sorry for the early bump. I would have edited my post but I past the time limit.

[Dopy25]

Ok I figured out the caps thing. Now I am looking at fuses. Some information says .8a fuse but various listings online for ebay and even console5 have a 2.5a AND a 5a fuse for the N64 PSU. The issue I am having is still that I have an uncommon PSU so it is poorly documented. I have 2.5a and 5a fuses just like the ones on console5.

 

Can anyone advise on whether or not a 2.5a or 5a fuse on a 3.3v or 12v line would be too high? I am thinking a 2.5a on the 3.3v line and the 5a on the 12v line would be good if that is the case. Am I reading that right? Or should I put a 5a fuse on both? The buck converter is dropping the 12v to 3.3v but the amperage would increase if I understand correctly, therefore outputting somewhere over 10a. Right? Is the fuse there to blow if more than 5 amps (or 2.5a) are pulled or if more than 5 amps (or 2.5a) are sent over the 3.3v line?

[+Stephen Moss]

People may be able to help more if they know what circuit you were following and/or which buck converter IC you were using.

 

I know you said you have the caps sorted but just in case...

For Cap voltage anything more that the expected voltage across them is good (less and they won't last long), double will give you plenty of overhead but if you are limited for space you might have to go with a voltage a little lower than double (physically smaller).

Caps are short circuit to AC but open to DC, unless there is specific reason for them to be connected otherwise always connect caps between the supply voltage and GND.

If the capacitor on the supply output is for smoothing then they should definitely go to GND. Generally the larger the capacitor the more smoothing you get and the larger the current draw the larger the capacitor you need. I am not sure where you got the current values mentioned from and if you search the web I am sure you will find the correct calculations for determining the correct capacitor values for the applicable switching frequency and current draw.

 

However, if the caps are for filtering then a 0.1uF disc to ground may help but you may need to research passive low pass filters to cut out all the switching noise from the buck regulator output (if filtering is not built in to it) otherwise you may find the switching noise creates noticeable interference on the audio and/or video.  

 

AS for the fuses, if I understand your diagram correctly then I would place...

a) One fuse between the output of your 12V 3 A switching supply and the power connector 12V in line

b) One fuse between the output of your 12V 3 A switching supply and the Buck converter input and 

c) One immediately after the output of your Buck circuit.

 

7 hours ago, Dopy25 said:

Is the fuse there to blow if more than 5 amps (or 2.5a) are pulled or if more than 5 amps (or 2.5a) are sent over the 3.3v line?

Those are the same thing, a 5A supply will not put 5A down the power rail regardless, it will only do so if the connected circuit pulls that much current from it.

 

If a power supply can supply 5A but the connected circuit only draws 1 amp then a 1 amp fuse should be used, because if a problem arises with the circuit the fuse will blow at around 1.5A both protecting the power supply and limiting the amount of damage done to the circuit keeping it repairable. Whereas if you were to use a 5A fuse, it would not blow until 6A of current are being drawn, it may just be enough to project the supply but the circuit would be very crispy and possibly damaged beyond repair.

  

If nobody knows the correct fuse sizes and you cannot find an schematic which shows them, you will need to use a multi-meter it to measure the current being drawn, that will indicate what size fuse you need.

[Dopy25]

I see how that makes sense. My apologies. That's what I get for not knowing much about a power circuit. I figured going in was all the same and 12v was 12v. I'll provide pictures and links if it helps.

 

Here is the circuit I'm working on. It's not complete but I have the in and out as well as the n64 port mounted. The grounds for the buck are just for mounting. They're not directly connected to each other on the board. I soldered them to keep it all together so nothing has the chance of touching when I close it up.

 

 

here are images of the caps that came off my board.

 

and here are what I thought were fuses but I don't think so any more. I found other info saying the fuses were different but once again this PSU is apparently uncommon so I'm still not sure.

 

This is the exact buck I'm using. I bought a few from Amazon last year and had extras:

 

https://www.amazon.com/dp/B00LOG4XC0/ref=cm_sw_r_apan_glt_fabc_CGMNZDZHH7Y6CNKP4Y3B?_encoding=UTF8&psc=1

 

So what I'm understanding is that I should have a fuse from the 12v in before the buck, and one after?

 

This buck has reverse polarity protection. It just won't work reversed, but that would only protect the 3.3v line as the 12 would be direct from the switching supply, right? Is that why I should have one before and after?

 

Size isn't really an issue. I'm using the n64 PSU enclosure and there is plenty of room to use an external 12v switching supply. The other links and videos I saw have it built inside with the 12v and the buck in the same enclosure. I'm looking up plug in a 12v supply from the outside and only convert down the 3.3v. That leaves plenty of room for me.

 

Here are some of the links I've reviewed for this project:

 

Sorry for the imbedded link for reddit^ it won't let me undo or delete on mobile.

 

Here is one of the videos I watched.

https://youtu.be/-WgtZ_stU9Q

 

The information about the caps was found in the comments. The dude in the video mentions caps but only their uF value and not their voltage.

He also says use the fuses from the old PSU but once again, I have an uncommon one and honestly I don't think there are fuses for 12v and 3.3v. I THINK there is only one before the 3.3v line but I can't tell if that's what it is. I'll add an image of that one soon.

 

Thanks for the information, Stephen. It's helped me understand even a little more than I did. Which is very helpful. 

[+Stephen Moss]

First, if that Amazon link is correct the reviews are not good and strongly suggest the the input voltage is the same as the output voltage, also the general description indicates that the output voltage is 1.25-36V which both explains the present pot (blue component with screw on) and why there is no thread lock on it to prevent adjustment.

Obviously, I have no idea what the reviews were trying to do but as it the output is adjustable I strongly recommend measuring it (and adjusting as necessary) if you have not already done so before connecting it to your console to prevent potentially damaging the console if the output is initially set higher than 3.3V.

 

Second, the DC-DC converter used in the linked videos is a different type, it has a fixed output and look like it would have the necessary filtering and smoothing built in.

 

Third, the items you think are fuses have a resistance values (0.22 & 22 Ohms) printed on them. Although it is not impossible to use resistors as fuses by relying on them burning out to protect the circuit, I may be wrong but I don't think these are fuse resistors as there resistance values, wattage (going by size) as the maths does not appear to support that. 

 

4th, between the linked video and image posting in the Redit link I have surmised the following...

1) The 220uF cap on the 12V and 470uF cap on 3.3V line are for smoothing the DC voltage, not for filtering any switching noise. If you want to use any of the caps you provided images for in place of those use the two 680uF, put the 10V one on the 3.3V line and the 35V on the 12V line.

2) The Redit pic shows two fuses, it looks like one is on the 12V line to the Connector (after the 12V connection to the DC-DC converter) which protects the the 12V circuity and one on the 3.3V output of the DC-DC converter protecting the 3.3V circuity. That makes sense, although as I stated previously I would also put one between the 12V supply so that you have...

 

Fuse 1) 12V DC to Input of DC -DC converter - if this blows then you have a problem with the DC-DC converter and 12V supply should be protected from that.

Fuse 2) 12V to 12V pin of Connector - if this blows then you have a problem with the 12V circuitry in the console and 12V supply should be protected from that.

Fuse 3) 3.3V to 3.3V pin of Connector - if this blows then you have a problem with the 3.3V circuitry in the console and the DC-DC should be protected from that.

 

You could do away with fuse 1 and connect both the input of the DC-DC converter and the connector 12V to the output side of the 12V fuse but the three fuse method is better,

 

If using a traditional fuse I would go for 20mmx5mm or 32x6.3mm (1/14" x 1/4") glass because you can often visually see that they have blown without using a multi-meter (break in wire, or glass blackened/spattered with metal). Fast blow (F) may be sufficient, although if using those 680uF caps instead of the 220 & 470uF caps suggested by the sources you quoted as extra smoothing then Anti-Surge(T) may be better, the extra in rush current of the larger caps will probably be OK for fast blow, but going anti-surge will remove the possibility of the inrush blowing the fuses.

 

The rated current on fuses is the hold current, the blow current of often much higher so for values I would suggest...

Fuse 1) Not entirely sure what he correct value is for this, it really depends on knowing input to output current ratio, but as we do not know that and as you will need a multi-meter to set the output voltage of your DC-DC converter the you can simply measure it to determine the required value. If you are lucky it will be close enough to the value of either Fuse 2 or two of Fuse 2 wired in parallel (not tried it but I think it should work) to create 1.5A/2A option.

It cannot be greater than 2A otherwise you will overload your 12V @ 3A supply, if you use parallel fuses instead of buying an extra one of the correct value then always replace them in pairs even if just one appears blown. 

Fuse 2) The moulding on the case indicates 0.8A (800mA), if you can find that then use it otherwise the closest will probably be 750mA or 1A. Given those options I personally would try 750mA first, I expect it will hold (but may be a little stressed & occasionally fail through fatigue) and is a little safer that using the larger 1A, but if it blows frequently then swap to 1A. Alternative you could just go for the 1A from the get go.

Fuse 3) The moulding on the case indicates 2.7A, if you can find that then use it but your likely available options will be either 2.5A or 3A. Given those options I would try the smaller one first for the same reasons given for fuse 2.

 

Finally, are you sure you have wired everything up correctly? The reason I ask are...

a) You appear to be using Black wires for the 12V & 3.3V supply and Red wires for GND, traditionally those colours are reversed. 

b) Your Red GND connection from the DC-DC converter appears to be connected to the positive side of the capacitor instead of the negative side (stripe down side is usually negative unless indicated otherwise).

       

[Dopy25]

6 hours ago, Stephen Moss said:

First, if that Amazon link is correct the reviews are not good and strongly suggest the the input voltage is the same as the output voltage, also the general description indicates that the output voltage is 1.25-36V which both explains the present pot (blue component with screw on) and why there is no thread lock on it to prevent adjustment.

Obviously, I have no idea what the reviews were trying to do but as it the output is adjustable I strongly recommend measuring it (and adjusting as necessary) if you have not already done so before connecting it to your console to prevent potentially damaging the console if the output is initially set higher than 3.3V.

The reviews on amazon are not accurate. Those reviewers either turned the pot the wrong way, or did not turn it enough. The ones I have did default to no change when powered, but after enough turns on the adjustment it dropped every time. I have a few of these in use. One for 10v output and one for.. actually I can't remember what I used the other one for but I know I've used 2 so far and this is the third. All have adjuste4d exactly where I needed and have not changed since. It does not take little turns to adjust. It takes a good whole turn or more to drop 1V.

 

I did adjust and measure, multiple times just to make sure. Thank you.

 

6 hours ago, Stephen Moss said:

Second, the DC-DC converter used in the linked videos is a different type, it has a fixed output and look like it would have the necessary filtering and smoothing built in.

I noticed those were one output only but the comments mention the possibility of using a buck in place. I also saw one other video titled "ultimate PSU" or something. Dude used a buck and a 12v input in the same manner but his had no caps or fuses. He did mention in the comments that he planned on adding them. Didn't really help for the video though so I don't know.

 

6 hours ago, Stephen Moss said:

Third, the items you think are fuses have a resistance values (0.22 & 22 Ohms) printed on them. Although it is not impossible to use resistors as fuses by relying on them burning out to protect the circuit, I may be wrong but I don't think these are fuse resistors as there resistance values, wattage (going by size) as the maths does not appear to support that. 

This is also why I figured they weren't fuses after I pulled them off.

 

6 hours ago, Stephen Moss said:

4th, between the linked video and image posting in the Redit link I have surmised the following...

1) The 220uF cap on the 12V and 470uF cap on 3.3V line are for smoothing the DC voltage, not for filtering any switching noise. If you want to use any of the caps you provided images for in place of those use the two 680uF, put the 10V one on the 3.3V line and the 35V on the 12V line.

That makes perfect sense! Thank you!

 

6 hours ago, Stephen Moss said:

2) The Redit pic shows two fuses, it looks like one is on the 12V line to the Connector (after the 12V connection to the DC-DC converter) which protects the the 12V circuity and one on the 3.3V output of the DC-DC converter protecting the 3.3V circuity. That makes sense, although as I stated previously I would also put one between the 12V supply so that you have...

 

Fuse 1) 12V DC to Input of DC -DC converter - if this blows then you have a problem with the DC-DC converter and 12V supply should be protected from that.

Fuse 2) 12V to 12V pin of Connector - if this blows then you have a problem with the 12V circuitry in the console and 12V supply should be protected from that.

Fuse 3) 3.3V to 3.3V pin of Connector - if this blows then you have a problem with the 3.3V circuitry in the console and the DC-DC should be protected from that.

 

You could do away with fuse 1 and connect both the input of the DC-DC converter and the connector 12V to the output side of the 12V fuse but the three fuse method is better,

 

If using a traditional fuse I would go for 20mmx5mm or 32x6.3mm (1/14" x 1/4") glass because you can often visually see that they have blown without using a multi-meter (break in wire, or glass blackened/spattered with metal). Fast blow (F) may be sufficient, although if using those 680uF caps instead of the 220 & 470uF caps suggested by the sources you quoted as extra smoothing then Anti-Surge(T) may be better, the extra in rush current of the larger caps will probably be OK for fast blow, but going anti-surge will remove the possibility of the inrush blowing the fuses.

 

The rated current on fuses is the hold current, the blow current of often much higher so for values I would suggest...

Fuse 1) Not entirely sure what he correct value is for this, it really depends on knowing input to output current ratio, but as we do not know that and as you will need a multi-meter to set the output voltage of your DC-DC converter the you can simply measure it to determine the required value. If you are lucky it will be close enough to the value of either Fuse 2 or two of Fuse 2 wired in parallel (not tried it but I think it should work) to create 1.5A/2A option.

It cannot be greater than 2A otherwise you will overload your 12V @ 3A supply, if you use parallel fuses instead of buying an extra one of the correct value then always replace them in pairs even if just one appears blown. 

Fuse 2) The moulding on the case indicates 0.8A (800mA), if you can find that then use it otherwise the closest will probably be 750mA or 1A. Given those options I personally would try 750mA first, I expect it will hold (but may be a little stressed & occasionally fail through fatigue) and is a little safer that using the larger 1A, but if it blows frequently then swap to 1A. Alternative you could just go for the 1A from the get go.

Fuse 3) The moulding on the case indicates 2.7A, if you can find that then use it but your likely available options will be either 2.5A or 3A. Given those options I would try the smaller one first for the same reasons given for fuse 2.

That's a lot of helpful information and I will follow your suggestions. Thanks again! 

 

6 hours ago, Stephen Moss said:

Finally, are you sure you have wired everything up correctly? The reason I ask are...

a) You appear to be using Black wires for the 12V & 3.3V supply and Red wires for GND, traditionally those colours are reversed. 

b) Your Red GND connection from the DC-DC converter appears to be connected to the positive side of the capacitor instead of the negative side (stripe down side is usually negative unless indicated otherwise).

I appreciate your attention to detail but yes, I am sure I used the red only for the positive lines, and the red black for the ground lines. I would have used other wires but I ran out of thicker gauge wire and the excess from the 12V DC input plug I used was the right length and I figured keeping the same gauge across the board was best. My image may be blurry because on one of the lines, the black stripe faces down. In retrospect, I should have faced it up, but this is going to be for my own N64 so I don't plan on putting in in the wild. If anyone ever opens it up they may have a "WTH" moment anyway as I broke the tabs holding the stupid N64 connector in place so I had to gorilla glue it in to the PSU housing.

 

The biggest thing is that I will look into finding the right fuses.

 

I was able to put it all together and use the actual 5a fuse found in the PSU (I did not get an image of it again) for the 3.3V line and I used a 2.5a fuse on the 12V line. I did not have extra 5a fuses, they were 1.5a and 2.5a for SNES and I think Dreamcast. I can't remember why I bought them. One for sure was the SNES.

 

I used the 2700uF 16V and the 680uF 10V in series. I read this is an acceptable way to get the desired capacitance. I also used a 220uF that I had extra. I like your suggestion better than with the 680 on each line though so I will be changing it soon.

 

It worked but oddly intermittently but I think that ended up being the video cable I was using. For some reason, the connections were breaking. I didn't realize this until after messing with the PSU a bunch. I realized it was still outputting the desired 12 and 3.3v so I wiggled the video cables and it flashed on screen. At that point, I swapped the cable out for an S-video one I made and had no issues.

 

I did all this because I have been researching since I posted the original. I figured I could learn something in the meantime.

 

Again, thank you for the information. It is way more than I had to begin with. I will post back once I swap out those caps and fuses.