Question regarding diy power supply

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ketem13
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Question regarding diy power supply

Post by ketem13 » Wed Oct 28, 2020 1:38 am

Hi,
I sew MFOS project for diy +-12v power supply .

I have at home an extra Doepfer 15v ac 2.5A power brick and I was wandering if I can use it with the above circuit ?

I do see the author mention its ok to use 15v ac, but he also mention not to exceed it. Also I don't know if 2.5A is to much ? or is it not really matter and the circuit will use as much Amper it can take ?

Thanks for clarifications!

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cygmu
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Re: Question regarding diy power supply

Post by cygmu » Wed Oct 28, 2020 1:59 am

The Doepfer brick will work fine with the MFOS wall wart supply. It was originally supplied as part of the Doepfer DIY PSU kit, which uses essentially the same circuit as the MFOS anyway.

As you guessed, the circuit won't take more current than it needs. The output voltage of the brick affects what the voltage regulators in the MFOS circuit have to do: the higher the output voltage, the more volts they have to drop and therefore the more power they dissipate. The regulators heat up as they dissipate power, so asking them to do too much will affect the performance of the circuit. But your setup should be fine.

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ketem13
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Re: Question regarding diy power supply

Post by ketem13 » Wed Oct 28, 2020 3:12 am

Good to hear!
I guess a heat sink will be a good thing to add

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ketem13
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Re: Question regarding diy power supply

Post by ketem13 » Thu Oct 29, 2020 2:47 am

Regarding the 15v ac 2.5A .
I read at MFOS site that the author say it is not recommended to use a wall-wart supply with a current output greater then 1A . why is that ?
Could I be sure it is fine using my 2.5A wall-wart supply ?

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ketem13
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Re: Question regarding diy power supply

Post by ketem13 » Thu Oct 29, 2020 4:07 pm

Sorry to write another message (third in a row) but there is a few things I try to understand better:

When comparing the MFOS power supply schematic with the one here (second schematic from top) there is one main difference I try to understand.

In the mfos schematic it seems 2nd AC is connected to ground while in the latter the 2nd AC is going through diode D2 (1n4004) to the negative voltage regulator.

If I use the same transformer ( 15v AC, the one you get in the doepfer diy kit) what is the difference between the two schematics?

Let's say I'm using 15v AC transformer ,the output from 1st AC +15v and the output from 2nd AC is -15v ?)
in mfos design the 2nd AC connected to ground. how come ?

Why there is a difference between the two circuits and how can I know what is better for my needs considering my transformer?

I know plenty of people are using both circuits so I guess both will be fine, but I try to understand the differences.

nigel
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Re: Question regarding diy power supply

Post by nigel » Thu Oct 29, 2020 10:27 pm

ketem13 wrote:
Thu Oct 29, 2020 4:07 pm
When comparing the MFOS power supply schematic with the one here (second schematic from top) there is one main difference I try to understand.

In the mfos schematic it seems 2nd AC is connected to ground while in the latter the 2nd AC is going through diode D2 (1n4004) to the negative voltage regulator.
That's because the "reverse engineering" of the frequency central circuit is wrong. The AC connections are actually the same as the MFOS circuit.

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ketem13
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Re: Question regarding diy power supply

Post by ketem13 » Fri Oct 30, 2020 1:04 am

nigel wrote:
Thu Oct 29, 2020 10:27 pm
ketem13 wrote:
Thu Oct 29, 2020 4:07 pm
When comparing the MFOS power supply schematic with the one here (second schematic from top) there is one main difference I try to understand.

In the mfos schematic it seems 2nd AC is connected to ground while in the latter the 2nd AC is going through diode D2 (1n4004) to the negative voltage regulator.
That's because the "reverse engineering" of the frequency central circuit is wrong. The AC connections are actually the same as the MFOS circuit.
Oh I see.. never believed all what you read/see on the internet :)

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