# Modifying my cheap Chinese power supplies...



## Big Monk

I have a number of these small and compact O’traki power supplies in both sizes:











They won’t win me any style points on TGP but they are pretty quiet and I like their size. Also, since I make my own boards out of wood, I like the mounting flanges.

The one thing that bugs me a bit is the combination of outlets on each. I really love the small one but it doesn’t have an 18 vDC output. I like the big one as well because of the 12 and 18 vDC outlets but it only has one 500 mA 9 vDC outlet.

I had a few spares so I cracked one open last night to see what was going on:









I reached out to the Amazon seller I buy them from last night. Basically told a little white lie about outputs on both sizes having failed on me and could I get a schematic.

I’d like to get an idea on what’s going on so I can maybe modify some of the outputs to better reflect what I want. Especially in the smaller size, which I’m using right now on my boards.

Can anyone make heads or tails of some of the components?


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## fig

You could trace it. If you can get a part # on these...





You could find the datasheet and possibly figure out what components to adjust in order to modify the output voltage for a particular port.

Edit: but....Ima go with @thewintersoldier on this one...


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## vigilante398

Pssh, why spend money when you can spend hours of frustration?  Realistically it should only be a few minutes though.

Can you read the part numbers on those 5-pin ICs? It's hard to read in the pictures with the lighting. Those are going to be the switching regulators for the outputs, and the resistors next to them (looks like 0603 package maybe?) are going to set the voltages. Like @fig says, using the datasheet you should be able to figure out which one is the feedback resistor and you can find the equation for what value to use to adjust the voltage and swap it.


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## Big Monk

thewintersoldier said:


> Buy an isolated one that has what you actually want.  The onespot or voodoo labs will last you years, be quieter (the above is basically a daisy chain) and give you the option to connect two outputs for higher voltage, power consumption and positive ground effects. You get what you pay for and as I alsways say... with quality you buy once cry once.



I'm with you 100%. I'm not looking to these as a permanent solution. I have my eye on the Strymon Ojai or the MXR Iso-Brick because of their small sizes and options.

This is simply an interesting experiment for the short term.


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## Big Monk

Here are closeup shots of the voltage regulators:





I'm assuming the SMD components circled below are fuses for thier respective taps. Is the black box circled a transformer?:


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## vigilante398

The smaller circled components are ferrite beads, just in-line filters for each tap, which give a degree of isolation aside from their filtering element.

The big black box is a power inductor used for the switch-mode power supply, the LM2956-ADJ. I found the datasheet, I'll take a look and see what resistor values you need to change for the voltage output.


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## fig

...or you could have all of us do this for you


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## Big Monk

fig said:


> ...or you could have all of us do this for you



Nah! Just needed a point in the right direction. Not used to SMD components so my eyes glazed over a bit. I have the data sheet pulled and was just looking over the calcs for resistor values on the output. 

I'll run some checks and see what voltages are coming out of the regulators and into the taps.


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## vigilante398

Mmkay, I think I got it. So looking at the spot you're zoomed in on, R4, R5, and R6 are the resistors that are setting the voltage. In this case R5 and R6 are in series.

R4 - 1k
R5 - 2k
R6 - 6.8k

In the feedback resistor setup of the datasheet R4 is your "R1" and R5+R6 is your "R2."

So based on the datasheet we see:

Vout = 1.23 ( 1 + R2/R1)

Which in this case means

Vout = 1.23 (1 + 8.8k/1k)
Vout = 1.23 (1 + 8.8)
Vout = 1.23 (9.8)
Vout = 12.054V

So this is the regulator for your 12V tap. Datasheets are neat


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## fig

No, I enjoy this stuff. Here's an idea as well.


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## fig

Oops, left out the idea part...anyway, you could make one port adjustable apparently..

Nice datasheeting @vigilante398 !


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## Big Monk

vigilante398 said:


> Mmkay, I think I got it. So looking at the spot you're zoomed in on, R4, R5, and R6 are the resistors that are setting the voltage. In this case R5 and R6 are in series.
> 
> R4 - 1k
> R5 - 2k
> R6 - 6.8k
> 
> So based on the datasheet we see:
> 
> Vout = 1.23 ( 1 + R2/R1)
> 
> Which in this case means
> 
> Vout = 1.23 (1 + 8.8k/1k)
> Vout = 1.23 (1 + 8.8)
> Vout = 1.23 (9.8)
> Vout = 12.054V
> 
> So this is the regulator for your 12V tap. Datasheets are neat



So basically un-modified voltage is being sent to the 12 vDC/100 mA tap. the 8 9 vDC taps must be dropped somehow from 12 vDC. And then the 12 vDC must get stepped up to 18 vDC for that tap.

My other goal would be to increase the current capacity on a few of the 9 vDC taps to accommodate more than one digital effect.


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## Big Monk

fig said:


> Oops, left out the idea part...anyway, you could make one port adjustable apparently..
> 
> Nice datasheeting @vigilante398 !



Me likey! This would be especially useful on the smaller 7 output unit, as I'd like the 12 vDC tap to be able to drop down to 9 vDC and up to 18 vDC.


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## fig

It's basically an array of DC buck converters...someone smack me if that's wrong.


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## vigilante398

Big Monk said:


> So basically un-modified voltage is being sent to the 12 vDC/100 mA tap. the 8 9 vDC taps must be dropped somehow from 12 vDC. And then the 12 vDC must get stepped up to 18 vDC for that tap.
> 
> My other goal would be to increase the current capacity on a few of the 9 vDC taps to accommodate more than one digital effect.


It's more likely that the 18V tap comes straight off the 18V input with a little filtering. I had a couple of these units, the wall wart they use is 18VDC. I would also bet that the 9V regulator also uses the 18V input directly, otherwise all the power would be coming from the 12V regulator and it would get bogged down.

Since the 9V taps are all off the same regulator the only thing really limiting the current output of each tap would be the filter of each one, so as long as you don't exceed the output of the regulator (3A) or the power of the wall wart (1A @ 18V = 18W) you should be able to exceed the stated 100mA output. The ferrite beads may be low rated, but if you jumper those then you're basically turning it into a real daisy chain with no isolation.


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## fig

Power filtering: That topic deserves a dedicated thread. I'm _currently _exploring this.


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## Big Monk

vigilante398 said:


> It's more likely that the 18V tap comes straight off the 18V input with a little filtering. I had a couple of these units, the wall wart they use is 18VDC. I would also bet that the 9V regulator also uses the 18V input directly, otherwise all the power would be coming from the 12V regulator and it would get bogged down.
> 
> Since the 9V taps are all off the same regulator the only thing really limiting the current output of each tap would be the filter of each one, so as long as you don't exceed the output of the regulator (3A) or the power of the wall wart (1A @ 18V = 18W) you should be able to exceed the stated 100mA output. The ferrite beads may be low rated, but if you jumper those then you're basically turning it into a real daisy chain with no isolation.



I was typing this when you responded! I forgot the input is 18 vDC off the wall wart. 

So let me see if I understand things so far:

1.) 18 vDC input is tapped directly with some filtering for the the 18 vDC output tap

2.) There is a dedicated regulator that steps down the 18 vDC to 12 vDC and supplies to the 12 vDC tap.

3.) There is a dedicated regulator that steps down the 18 vDC to 9 vDC and supplies to the 9 vDC taps.

4.) The maximum current output capacity is dictated by the capacity of the regulators

5.) One could technically increase the current capacity of the taps by increasing the maximum capacity of the wall-wart (as long as that does not exceed the maximum of the regulator with an adequate safety margin) and also increase the ratings of the ferrite beads to accommodate.


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## vigilante398

Oh the inductor. So in a SMPS you design for what you want it to do, not what it's capable of doing. The inductor they're using on the SMPS (black box marked 101) looks like the one I use on some of my pedals, which if true is a 100uH 2A inductor. If that's the case then you won't be able to exceed 2A and will likely be limited to around 1.8A because the inductor will saturate and you will have a bad time.

That being said if this regulator was 100% efficient (it's high efficiency, but nothing is 100%) you would still be limited to 2A @ 9V because of your 18W wall wart. If you find a different 18VDC supply to feed the box with you could suck a lot more current out of the ports.

So the current "limits" they print on the box seem to be lies, but there still are limits you need to be aware of.


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## vigilante398

Big Monk said:


> I was typing this when you responded! I forgot the input is 18 vDC off the wall wart.
> 
> So let me see if I understand things so far:
> 
> 1.) 18 vDC input is tapped directly with some filtering for the the 18 vDC output tap
> 
> 2.) There is a dedicated regulator that steps down the 18 vDC to 12 vDC and supplies to the 12 vDC tap.
> 
> 3.) There is a dedicated regulator that steps down the 18 vDC to 9 vDC and supplies to the 9 vDC taps.
> 
> 4.) The maximum current output capacity is dictated by the capacity of the regulators
> 
> 5.) One could technically increase the current capacity of the taps by increasing the maximum capacity of the wall-wart (as long as that does not exceed the maximum of the regulator with an adequate safety margin) and also increase the ratings of the ferrite beads to accommodate.


Lol and now I was typing when you replied  Correct on all counts.


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## Big Monk

thewintersoldier said:


> I'm waiting for the destruction of smd components and the new amazon order..



I have a bunch of these. I use one as a benchtop supply for testing and a few others are extras right now. I can sacrifice one for experimentation without losing sleep or having to make any late night emergency purchases!


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## fig

Big Monk said:


> I have a bunch of these. I use one as a benchtop supply for testing and a few others are extras right now. I can sacrifice one for experimentation without losing sleep or having to make any late night emergency purchases!


It's not like you tinker with just anything you happen to pick up.....right?


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## vigilante398

Big Monk said:


> I have a bunch of these. I use one as a benchtop supply for testing and a few others are extras right now. I can sacrifice one for experimentation without losing sleep or having to make any late night emergency purchases!


I think I still have one that hasn't been gutted. I wasn't using any of the other voltages, so I designed a drop-in board that had 10x 9V regulators so I could get an isolated 1.5A @ 9V out of every tap, so one of mine has that inside. Because tubes.


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## Big Monk

fig said:


> It's not like you tinker with just anything you happen to pick up.....right?



Yup! I'm just curious about how things work and this seemed so easy to tweak.


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## Big Monk

vigilante398 said:


> So the current "limits" they print on the box seem to be lies, but there still are limits you need to be aware of.



Interesting that you bring this up.

4-5 months back I bought a Mosky Iso-10 trying to have an all-in-one supply and solve some issues from digital noise from the Strymon pedals I own:



			https://www.amazon.com/Moskyaudio-ISO-10-Station-Isolated-Outputs/dp/B09BCK125L/ref=sr_1_35?keywords=Isolated+Power+Supply+for+Guitar+Effects&qid=1643210592&sr=8-35
		


Here I'm thinking "Wow! 7 300 mA/9v, 1 500 mA 9v and 2 adjustable 500 mA outs! Let's try it!" Never mind that the total output capacity, judging by the labels at least is 3,600 mA with a 2,500 mA wall-wart!

So I get it hooked up and the noise is gone. So it's definitely isolated. But I keep feeling a lot of heat on the chassis and a smell, not a burning smell per se, but the smell when electrical stuff is getting warm/kinda hot.

Keeps happening so I returned it. Obviously, in this case, the Mosky seemed to have overstated the current capacities of the taps where the O'traki supplies seem to understate them. 

I ended up hooking all the same pedals up to the O'traki before returning the Mosky and the noise was back but no overheating issues. Got a replacement for the Mosky and the same thing. Ended up returning that as well.


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## fig

thewintersoldier said:


> I modify all the kids stuff, pet toys and anything else in the house that runs on batters to run off and adapter with a 2.1mm jack. That's become my only use around the house anymore.


We're all tinkerers. That's how we ended up here, LOL


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## Big Monk

thewintersoldier said:


> I modify all the kids stuff, pet toys and anything else in the house that runs on batters to run off and adapter with a 2.1mm jack. That's become my only use around the house anymore.



I did this for the Christmas village about 5 years ago. Took an old Dewalt bit case and made a 6 output power supply with limiting resistors on Perfboard so that I did not have to turn the battery boxes for small street lamps, etc. off/on anymore.


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## Big Monk

If I get a service schematic by tomorrow for these from the seller, I'll post it here but i think there is enough info to start investigating some replacement parts.


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## finebyfine

man i just realized i should buy one like this and gut it for a power supply build. mine like this is probably less than an enclosure that would end up being an awkward size for a power supply anyway


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## Big Monk

For reference, here is the smaller of the 2 supplies:









This time we have a single regulator. 

So the 15 vDC is un-regulated but filtered off the incoming power feed, the 12 vDC tap is off the regulated output and I imagine the 9 vDC taps are stepped down in some way.


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## vigilante398

So based on the datasheet the output of that regulator is

Vout = 1.23 (1 + 6530/1000)
Vout = 9.26V

So that regulator is supplying the 9V, and it looks like there's a zener diode on the far right side of the board (conveniently close to the 12V output) that I'll bet they're using for the 12V. Zener regulation works fine for low current, but I definitely wouldn't push the output on that one much.


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## Big Monk

vigilante398 said:


> So based on the datasheet the output of that regulator is
> 
> Vout = 1.23 (1 + 6530/1000)
> Vout = 9.26V
> 
> So that regulator is supplying the 9V, and it looks like there's a zener diode on the far right side of the board (conveniently close to the 12V output) that I'll bet they're using for the 12V. Zener regulation works fine for low current, but I definitely wouldn't push the output on that one much.



The only effect I use 12 vDC for is my old Boss CS-2. I'd like that to be adjustable in a perfect world. 

Ideally on this smaller supply I'd want all the 9 vDC taps to be 300 mA and the 12 vDC tap to be adjustable from 9-18 vDC at 100 mA.


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## vigilante398

Big Monk said:


> The only effect I use 12 vDC for is my old Boss CS-2. I'd like that to be adjustable in a perfect world.
> 
> Ideally on this smaller supply I'd want all the 9 vDC taps to be 300 mA and the 12 vDC tap to be adjustable from 9-18 vDC at 100 mA.


Well we know the regulator is capable of 3A, so I would say you should be able to get 300mA per output no problem if you replace or jumper the ferrite beads for the 100mA ports (the three that say "010" on them) as long as your wall wart can handle it. Unfortunately the only way to get that 12V tap to be adjustable is to remove the zener and add a new regulator, like an LM317 with a pot for adjustment. You'll need to figure out where to put it though. To get up to 18V you'll either need a boost regulator or you'll need to start using an 18V wall wart instead of the 15V.


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## fig

Big Monk said:


> The only effect I use 12 vDC for is my old Boss CS-2. I'd like that to be adjustable in a perfect world.
> 
> Ideally on this smaller supply I'd want all the 9 vDC taps to be 300 mA and the 12 vDC tap to be adjustable from 9-18 vDC at 100 mA.


Question sir: If you have in mind what _ideally_ and _perfect _are, and should this endeavor not pan out, have you considered designing and building one custom to that criteria?


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## Big Monk

fig said:


> Question sir: If you have in mind what _ideally_ and _perfect _are, and should this endeavor not pan out, have you considered designing and building one custom to that criteria?



Sure. For the fun of it at the very least!

It shouldn't be too hard to design a board that will fit in these enclosures as well. I love a good project!


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## Big Monk

So I think I'm going to do the following to make the little power supplies a little more versatile:

1.) Run the supply off a larger 18 vDC/2A wall-wart. This should output 18 vDC from the 15 vDC port

2.) Change the Zener diode to accommodate this change and still output 12 vDC from the 12 vDC port.

3.) Rework the resistances off the regulator to still give me 9 vDC with an 18 vDC input

4.) Change the 100 mA ferrite beads for 300 mA.

Besides the $10 wall-wart, this should be about $1 in parts.


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## vigilante398

Big Monk said:


> So I think I'm going to do the following to make the little power supplies a little more versatile:
> 
> 1.) Run the supply off a larger 18 vDC/2A wall-wart. This should output 18 vDC from the 15 vDC port
> 
> 2.) Change the Zener diode to accommodate this change and still output 12 vDC from the 12 vDC port.
> 
> 3.) Rework the resistances off the regulator to still give me 9 vDC with an 18 vDC input
> 
> 4.) Change the 100 mA ferrite beads for 300 mA.
> 
> Besides the $10 wall-wart, this should be about $1 in parts.


2.  A 12V zener will give you 12V regardless of input, but it will decrease the amount of current you get out of it because you're dumping more voltage in the regulation. So you don't need to swap the zener, but you may want to get a higher power 12V zener if you're sticking with the zener.

3. You don't need to make any changes to the regulator. the output voltage is hard set independent of the input, so you'll get 9V regardless of the input. It will actually pull a little less current current from the 18V because of the efficiency of the regulator.


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## Harry Klippton




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## Big Monk

vigilante398 said:


> 2.  A 12V zener will give you 12V regardless of input, but it will decrease the amount of current you get out of it because you're dumping more voltage in the regulation. So you don't need to swap the zener, but you may want to get a higher power 12V zener if you're sticking with the zener.
> 
> 3. You don't need to make any changes to the regulator. the output voltage is hard set independent of the input, so you'll get 9V regardless of the input. It will actually pull a little less current current from the 18V because of the efficiency of the regulator.



Very nice.

When you say "pull a little less current", do you mean less available current for that tap(s)? Or less loss as a result of the higher voltage?

I'm thinking the minimization of I^2*R loss in my industry, i.e. sending power on 345 kV lines results in less loss as opposed to 13.2 kV, etc.


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## vigilante398

Big Monk said:


> Very nice.
> 
> When you say "pull a little less current", do you mean less available current for that tap(s)?


Nope, the same amount of current will be available on the regulator output, but the amount of current the 9V regulator pulls from the 18V input is decreased.

V_in * I_in = V_out * I_out + efficiency loss

so

18V * Input current = 9V * output current + efficiency loss

When input voltage goes up from 15V to 18V, your regulator isn't pulling as hard on the input.


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## vigilante398

Here's an example:

Let's say you have a 300mA load on your 9V regulator. The datasheet doesn't have the efficiency vs output load graph like I wanted to see, but let's assume 85% efficiency, which is a reasonable approximation for this thing.

With the stock power supply:

Vin = 15V
Vout = 9V
Iout = 0.3A

15V * I_in = 9 * 0.3 + loss
15V * I_in = 2.7 + loss

Loss with 85% efficiency of a 2.7W load is going to be 47.6mW, which gives us

15V * I_in = 3.176
I_in = 212mA

So let's look at the same thing with an 18V supply:

18 * I_in = 3.176
I_in = 176mA

Thanks for coming to my TED talk


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## Big Monk

vigilante398 said:


> Here's an example:
> 
> Let's say you have a 300mA load on your 9V regulator. The datasheet doesn't have the efficiency vs output load graph like I wanted to see, but let's assume 85% efficiency, which is a reasonable approximation for this thing.
> 
> With the stock power supply:
> 
> Vin = 15V
> Vout = 9V
> Iout = 0.3A
> 
> 15V * I_in = 9 * 0.3 + loss
> 15V * I_in = 2.7 + loss
> 
> Loss with 85% efficiency of a 2.7W load is going to be 47.6mW, which gives us
> 
> 15V * I_in = 3.176
> I_in = 212mA
> 
> So let's look at the same thing with an 18V supply:
> 
> 18 * I_in = 3.176
> I_in = 176mA
> 
> Thanks for coming to my TED talk



So for us Dummies out here, even on the 15 vDC supply, a 300 mA tap won’t yield 300 mA and when we step up the voltage of the supply, it yields even less.


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## vigilante398

Big Monk said:


> So for us Dummies out here, even on the 15 vDC supply, a 300 mA tap won’t yield 300 mA and when we step up the voltage of the supply, it yields even less.


Incorrect, you're looking at it backwards. I'm saying that when you're getting 300mA @ 9V to your pedals, you're only sucking 176mA @ 18V from your 18V wall wart.


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## vigilante398

I keep trying to find better ways to explain it but they feel convoluted, I really just need a big whiteboard and for you to come over so I can explain it in person


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## vigilante398

I think it helps to look at it in terms of power. Power = voltage * current. I'm going to pretend it's perfectly efficient for the sake of explanation.

input power (from the wall wart to the regulator) = output power (from the regulator to the pedals)

I'm going to stick with a 300mA @9V, so we know that our output power is 2.7W (9 * 0.3). Since they are equal, we know that input power is also 2.7W, regardless of what the input voltage is. The input voltage does not change the output power. So if input voltage is 15V, we know that input current is 2.7/15 = 180mA. We "gain energy" (for lack of a better expression) when we step down voltages so we only use 180mA @ 15V to generate 300mA @ 9V. If we increase the input voltage, the output power stays the same, which means the input power is still 2.7W, so the input current becomes 2.7/18 = 150mA.

That's all I've got, hopefully my ramblings make sense, but also let me know if they don't.


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## vigilante398

thewintersoldier said:


> View attachment 22127


IT'S NOT JUST A DAISY CHAIN, IT'S ART.


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## Big Monk

thewintersoldier said:


> View attachment 22127



This is why we needed IAIGF. A concentrated blasted of humorous and productive haterism.


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## Big Monk

vigilante398 said:


> I think it helps to look at it in terms of power. Power = voltage * current. I'm going to pretend it's perfectly efficient for the sake of explanation.
> 
> input power (from the wall wart to the regulator) = output power (from the regulator to the pedals)
> 
> I'm going to stick with a 300mA @9V, so we know that our output power is 2.7W (9 * 0.3). Since they are equal, we know that input power is also 2.7W, regardless of what the input voltage is. The input voltage does not change the output power. So if input voltage is 15V, we know that input current is 2.7/15 = 180mA. We "gain energy" (for lack of a better expression) when we step down voltages so we only use 180mA @ 15V to generate 300mA @ 9V. If we increase the input voltage, the output power stays the same, which means the input power is still 2.7W, so the input current becomes 2.7/18 = 150mA.
> 
> That's all I've got, hopefully my ramblings make sense, but also let me know if they don't.



This am the previous posts made major sense. 

Let me see if I can summarize in a sentence: switching from 15 vDC to 18 vDC supplies means the same current delivered to the taps but with less current drawn from the input to the regulator. 

Did I get it?


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## vigilante398

Big Monk said:


> This am the previous posts made major sense.
> 
> Let me see if I can summarize in a sentence: switching from 15 vDC to 18 vDC supplies means the same current delivered to the taps but with less current drawn from the input to the regulator.
> 
> Did I get it?


Yup, nailed it!


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## fig

cowabunga


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## lcipher3

box up some of these?


			Amazon.com
		


but why a switching regulator?  go for a linear (LM7809 or LM317 etc) or LDO (low drop out reguilator)?


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## Big Monk

lcipher3 said:


> box up some of these?
> 
> 
> Amazon.com
> 
> 
> 
> but why a switching regulator?  go for a linear (LM7809 or LM317 etc) or LDO (low drop out reguilator)?



I’m not building from scratch.


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## vigilante398

lcipher3 said:


> box up some of these?
> 
> 
> Amazon.com
> 
> 
> 
> but why a switching regulator?  go for a linear (LM7809 or LM317 etc) or LDO (low drop out reguilator)?


The rebuild I did of one of these bricks used 10x 7809 linear regulators, but switchers are better for efficiency and heat management, which is why they're so ubiquitous.


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## Harry Klippton

thewintersoldier said:


> View attachment 22127


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## Big Monk

Harry Klippton said:


> View attachment 22128



It works.

You bum. Only took 10 trys, 2 circuit boards and a gang of OG darlingtons but it works…😂

You and @thewintersoldier need to stop coming in half cocked. Make a new IAIGF already...😂


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## Big Monk

@vigilante398 

So jumpering where the 100 mA ferrite beads are gets me essentially unlimited current draw (depending on the pedal load) and so long as combined I don’t exceed the supply and regulator rating. 

What purpose do they have? It’s easy enough to get some 300 mA ones to match the other 9 vDC taps and just run an 18 vDC supply.


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## fig

noise filtering?


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## Big Monk

fig said:


> noise filtering?



I think that’s what we discussed earlier.

If that’s the case, I think replacing the 100 mA units with 300 mA is a cheap solution when co pared to just jumpering them.

So then all I’m going to do is swap 3 ferrite beads, grab a 12 v zener with a higher power rating then currently installed and grab an 18 vDC/2 A Wall wart from Amazon. 

This way I can have an 18 vDC tap, firm up the 12 vDC tap, and have 5 9 vDC/300 mA taps instead of 2 in case I run more than 2 high load digital pedals. 

Turns my $25 power supply into a $40 power supply but it will be an improved version.


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## fig

EMI suppression specifically.


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## Big Monk

thewintersoldier said:


> I can not believe we are on page 4 already...



C’mon!

Where is your curious spirit?! We just figure out how to make something cheap and available a little better! Well @vigilante398 did at least!

You elitist power supply snobs must be stopped…😂 (as I look at premium power supplies on Reverb…)


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## Big Monk

thewintersoldier said:


> View attachment 22135



I just GCF! Thank the sweet Jesus…


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## Stickman393

Man, monk-y, we gotta get you a transformer and a diode bridge and a big ol cap.

Then maybe add in a regulator, LC low pass filter, ferrite beads, more caps...

On second thought, mains voltage is dangerous.  I'd rather keep ya around.  Keep on fiddlin, bruh.


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## Big Monk

Stickman393 said:


> Man, monk-y, we gotta get you a transformer and a diode bridge and a big ol cap.
> 
> Then maybe add in a regulator, LC low pass filter, ferrite beads, more caps...
> 
> On second thought, mains voltage is dangerous.  I'd rather keep ya around.  Keep on fiddlin, bruh.



I just wanted to make this little thing a bit more versatile. It will only take a few small modifications to do that.


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## Big Monk

I’m going to try and pull some more LM2596 design documents and see if there are any small mods to improve noise rejection as well.


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## Big Monk

So, in the continuing saga of Derek doesn't know shit about power supply components, I give you today's "Dear @vigilante398" questions:

In reviewing the literature on noise and the LM2596 last night, the importance of low ESR electrolytic capacitors was continuously hammered upon. There is wild inconsistency even in the power supplies that I have in my possession. 

The 3 larger 10 output supplies represented a cross section of build methods. One has all low ESR electros, one has them on certain parts of the supply and one had none at all.

The 2 smaller supplies I am using on our boards here have no low ESR caps at all. This is an easy enough fix with a little trip top Mouser.

My real question centers around determining the frequency band of the supply noise I am getting and specifying the new ferrite beads to assist in killing some of this noise. Since ohmic impedance/resistance is frequency dependent for these beads, is it as simple as identifying the frequency band the noise "lives" in and use the data sheet to specify the ohmic impedance/resistance?


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## fig

Something something "-3dB cutoff frequency"

fc=1/2πRC something something


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## vigilante398

Big Monk said:


> So, in the continuing saga of Derek doesn't know shit about power supply components, I give you today's "Dear @vigilante398" questions:
> 
> In reviewing the literature on noise and the LM2596 last night, the importance of low ESR electrolytic capacitors was continuously hammered upon. There is wild inconsistency even in the power supplies that I have in my possession.
> 
> The 3 larger 10 output supplies represented a cross section of build methods. One has all low ESR electros, one has them on certain parts of the supply and one had none at all.
> 
> The 2 smaller supplies I am using on our boards here have no low ESR caps at all. This is an easy enough fix with a little trip top Mouser.
> 
> My real question centers around determining the frequency band of the supply noise I am getting and specifying the new ferrite beads to assist in killing some of this noise. Since ohmic impedance/resistance is frequency dependent for these beads, is it as simple as identifying the frequency band the noise "lives" in and use the data sheet to specify the ohmic impedance/resistance?


So looking at the datasheet you have a fixed switching frequency of 150kHz, which is pretty great. Obviously the higher you are above the audio spectrum (20Hz - 20kHz) the better, and the less likely you are to have audible noise leaking into your signal. But if you're looking to target the switching frequency for noise reduction, 150kHz is where it's going to be at. There are a few notes in the datasheet for reducing ripple (noise), but the summary is "garbage in, garbage out." The cleaner you scrub your input, the cleaner the output you'll get.

As far as low ESR caps, as long as you don't need a huge amount of capacitance, which you usually don't (except in very high current situations), MLCC are hard to beat for the price and I mostly rely on them for power supply filtering. 0805 are my favorite size, and I can get 0805 up to 10uF in voltages high enough to be useful, 1210 gives you even more options. Also for modding existing boards SMD caps are great because if you need more capacitance you can just keep stacking caps on top of each other


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## fig

Yep...that was the part I paraphrased


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## Big Monk

vigilante398 said:


> So looking at the datasheet you have a fixed switching frequency of 150kHz, which is pretty great. Obviously the higher you are above the audio spectrum (20Hz - 20kHz) the better, and the less likely you are to have audible noise leaking into your signal. But if you're looking to target the switching frequency for noise reduction, 150kHz is where it's going to be at. There are a few notes in the datasheet for reducing ripple (noise), but the summary is "garbage in, garbage out." The cleaner you scrub your input, the cleaner the output you'll get.
> 
> As far as low ESR caps, as long as you don't need a huge amount of capacitance, which you usually don't (except in very high current situations), MLCC are hard to beat for the price and I mostly rely on them for power supply filtering. 0805 are my favorite size, and I can get 0805 up to 10uF in voltages high enough to be useful, 1210 gives you even more options. Also for modding existing boards SMD caps are great because if you need more capacitance you can just keep stacking caps on top of each other



I found 2 sets of Low ESR electros that will work as far as size and value are concerned.

I think I may use these for the beads:



			https://www.mouser.com/ProductDetail/875-LI1806C151R-10
		


Another thing the data sheets and desgn docs point out is an output LC Filter can further reduce noise.


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## Big Monk

Well I have a mouser cart mostly populated. I just need to figure out the value for the current value for the new Zener.


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## vigilante398

Big Monk said:


> Well I have a mouser cart mostly populated. I just need to figure out the value for the current value for the new Zener.


If I had to guess (which I don't, but will anyway) it's probably 1/2W, which means if you're trying to come from an 18V supply and drop to 12V, you need 6V * output current, so a 1/2W zener will give you 83mA on the 12V line. I would suggest a 1W zener like this guy, that would give you just over 150mA on the 12V tap.



			https://www.mouser.com/ProductDetail/Taiwan-Semiconductor/ZM4742A-L0?qs=C%2F0tY%2F%2FqZe%2FAPIN826j%252BqA%3D%3D


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## Big Monk

vigilante398 said:


> If I had to guess (which I don't, but will anyway) it's probably 1/2W, which means if you're trying to come from an 18V supply and drop to 12V, you need 6V * output current, so a 1/2W zener will give you 83mA on the 12V line. I would suggest a 1W zener like this guy, that would give you just over 150mA on the 12V tap.
> 
> 
> 
> https://www.mouser.com/ProductDetail/Taiwan-Semiconductor/ZM4742A-L0?qs=C%2F0tY%2F%2FqZe%2FAPIN826j%252BqA%3D%3D



My man!

The 300 mA ferrite beads I picked out are a little narrower and taller than what’s installed now but the length is bang on so I’m not concerned. 

I’m also entertaining patching in an LC filter at the output like in the data sheets but I’ll do the easy modifications first.


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## Harry Klippton

Imagine if Derek bought one good power supply instead of the 5-9 chitauri power supplies he has now


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## Mentaltossflycoon

Harry Klippton said:


> Imagine if Derek bought one good power supply instead of the 5-9 chitauri power supplies he has now


Wait, is Thanos behind those things?


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## Big Monk

Harry Klippton said:


> Imagine if Derek bought one good power supply instead of the 5-9 chitauri power supplies he has now



If I got a full refund for all 5 I have in my possession, I still couldn’t buy a good power supply!

But yes, I agree. More of a cool experiment and excuse to learn about power supplies.


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## Harry Klippton

Mentaltossflycoon said:


> Wait, is Thanos behind those things?


Yeah


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## Big Monk

Harry Klippton said:


> Imagine if Derek bought one good power supply instead of the 5-9 chitauri power supplies he has now





thewintersoldier said:


> I quit reading this thread a page and a half ago and only wanted to see what will said. Did not disappoint.



You guys are no fun!


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## Big Monk

In spite of having my balls busted about this topic (those guys know I’m the sense of humor champion when it comes to good natured ribbing) I am still finding aspects of it that I’m curious about.

Case in point: @vigilante398 pointed out during the discussion on filtering and ferrite beads that the old adage “garbage in, garbage out” applies here. 

That got me thinking (Very dangerous. Can you smell the smoke?): part of my plan for the few small mods I plan to do was a new wall-wart that could deliver 2A instead of the 1A these ship with. Part of the reason was that if we tally the rated full load amperage of the power supply, it exceeds the 1A rating of the wall-wart supplying it by 100 mA. 

Now granted, there is safety margin inherently built in because most pedals you’d plug into a 9 vDC/100 mA aren’t actually drawing 100 mA. Yet I plan to modify the 100 mA taps with 300 mA ferrite beads to expand the capability of the taps themselves. 

So now I’m rambling. 

What I’m driving at is, and I think I’m understanding this correctly, that if we want to address the quality of the input power to the power supply itself, the quality of the wall-wart/inout power would be a good place to do so. 

So I’m thinking about the following:

1.) Start with a small enclosure like a 1590a

2.) Use a small step down transformer and rectifier to convert 120 vAC on the primary to 24 vDC on the secondary. 

3.) Use the same LM2596 regulator setup on a small board with all design document best practices and output LC filter to provide a nicely regulated 18 vDC on the output. 

4.) Feed this output to the power supply ensuring at least 2A available current.


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## vigilante398

Big Monk said:


> In spite of having my balls busted about this topic (those guys know I’m the sense of humor champion when it comes to good natured ribbing) I am still finding aspects of it that I’m curious about.
> 
> Case in point: @vigilante398 pointed out during the discussion on filtering and ferrite beads that the old adage “garbage in, garbage out” applies here.
> 
> That got me thinking (Very dangerous. Can you smell the smoke?): part of my plan for the few small mods I plan to do was a new wall-wart that could deliver 2A instead of the 1A these ship with. Part of the reason was that if we tally the rated full load amperage of the power supply, it exceeds the 1A rating of the wall-wart supplying it by 100 mA.
> 
> Now granted, there is safety margin inherently built in because most pedals you’d plug into a 9 vDC/100 mA aren’t actually drawing 100 mA. Yet I plan to modify the 100 mA taps with 300 mA ferrite beads to expand the capability of the taps themselves.
> 
> So now I’m rambling.
> 
> What I’m driving at is, and I think I’m understanding this correctly, that if we want to address the quality of the input power to the power supply itself, the quality of the wall-wart/inout power would be a good place to do so.
> 
> So I’m thinking about the following:
> 
> 1.) Start with a small enclosure like a 1590a
> 
> 2.) Use a small step down transformer and rectifier to convert 120 vAC on the primary to 24 vDC on the secondary.
> 
> 3.) Use the same LM2596 regulator setup on a small board with all design document best practices and output LC filter to provide a nicely regulated 18 vDC on the output.
> 
> 4.) Feed this output to the power supply ensuring at least 2A available current.


Finding a step down transformer with enough output current that still fits in a small box will be the hardest part there, but you're absolutely on the right track.


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## Big Monk

vigilante398 said:


> Finding a step down transformer with enough output current that still fits in a small box will be the hardest part there, but you're absolutely on the right track.



Yes. My Mouser, Jameco, and Digikey searches proved that!

I could also be a simple box that has the advanced filtering and a regulator providing clean 18 vDC to the main supply. Basically plug a 24 vDC/2A wall watt into this box and then I put the input to the supply. 

I ended up finding a True Tone CS7 last night for a good price but I’m still pursuing this, especially for my sons little board.


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## Big Monk

So I brought my laptop to the music store today when my Son was at his drum lesson and worked up a quick PCB for the regulated 18vDC patch box. 

It will fit in a 1590LB and I’m going to order 5 when I get the Fuzz 2022 board ordered.


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## Big Monk

So I’ve almost got my parts order ready. I’m going to mod on of the little supplies for my son’s board. 

Basically it will get some Low ESR caps all around, the taps will get new ferrite beads to bump the mA up and I’m going to use the 24 vDC wall wart into a clean 18 vDC regulator to feed the power in to the box. 

I’m also going to build a conversion box for my TrueTone CS7 so I can get an adjustable 9/12 vDC tap off the 18 vDC tap if I want for added versatility.


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## Big Monk

Here are a couple of boards i'm tacking onto the Fuzz 2022 order. They came out of the conversations here so this seemed like the right place to post them.

First is a LM2596 "Cleanup" box for my Chinese power supply experiments. Receives 24 vDC @ 2-3A and gives a clean 18 vDC supply to the Chinese units:






Next is a simple converter box for the 18 vDC/100 mA outlet on my CS7. Single DC input and 3 separate jacks for DC output. 78 series regulators allow me to use the 18 vDC tap to get 12 vDC or 9 vDC out depending on which jack I plug into. The 18 vDC output simply bypasses the regulator circuits:





Both will go in 1590A enclosures.


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