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Sourcing a toroid transformer for psu


mazatta
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I am looking at building a psu based off of NorthernLightX's schematic, but I am having difficulty tracking down an appropriate toroid transformer that will run on 110v and not break the bank. The only thing I could find so far that comes close to the 220v RKT 5012 used in the schematic and costs the least isthis one from DigiKey (amps seem too high though?)

I have found manufacturers that specialize in these types of transformers, but they are at least twice the price of the one linked to above. Ebay doesn't seem to turn up anything useful either.

The reason that I am building a psu, rather than repurposing something else (e.g. Amiga 500 psu), is that I want to build a MBFM and I don't want to use something that's 20+ years old. Has anyone in North America had success sourcing a transformer and/or building this psu?

I appreciate any and all feedback!

-Colin

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50VA means >2A per rail. That's a lot. That's way too much for an mbFM. You won't need more than a few mA per rail as the only thing the +-12V supply is driving is a bunch of TL074. So to be on the safe side and have more than enough reserves let's say 300mA so a 300mA * 12V * 2 = 7.2VA toroid will do.

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50VA means >2A per rail. That's a lot. That's way too much for an mbFM. You won't need more than a few mA per rail as the only thing the +-12V supply is driving is a bunch of TL074. So to be on the safe side and have more than enough reserves let's say 300mA so a 300mA * 12V * 2 = 7.2VA toroid will do.

But if you want to use the transformer for 5V too according to http://www.midibox.org/dokuwiki/doku.php?id=northernlightx ?

I plan to use this schematic for my MB6582 (allong with AOUT_NG and SSM2044s) too, how much juice do you think is necessary for that?

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Look at the schems of the modules, get out the datasheets, check for max current draw of the active components, sum them all up, add a good bit for good measure, get back to us with the results :)

Sounds like a good exercise.

Edit: Had a quick look and including SIDs, PICs, LCD, LEDs and shift regs. I sum up the max to allmost 30 W. The specs of the C64 PSU seems to be 40W. Most of the current is off course drawn by the 5V rail, so it might make sence to use a separate transformer for the 5V rail...

Edited by strophlex
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mazatta: Sorry for hijacking the thread. I still propose the 25VA transformer if you are going to use it for all voltages, -12, +12 and +5V. It is more than you need like Nils says, but unless you are short on space I don't see a problem.

Nils: I messured the current draw of the 5V rail of my MB6582 when it was idle. I was exactly 1A. I guess 2A should be more than enough for any situation. 10VA that is.

Edited by strophlex
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Hi,

I am also looking for a replacement for the C64 PSU. I have been enjoying my brand new mb6582 for a month and then the PSU died in a white smoke final breath...

I would not normally look into building my own as I do not know anything about PSU design but I can't find a linear +9/+5V that would suit. I am now considering building NorthenLightFX PSU for a replacement.

I am wondering if I can jump to building straightaway or if I should get math & electrical knowledge before I start. Any thought ?

Also is it possible to customize the design just by deleting and copying/pasting power lines behind the bridge rectifier ? In order to get 2 x 9V and 2 x 5V from the secondaries. That would make a single PSU with two blocks of 2x5V, 2x9V outputs, each block supplying 2A. This seems too easy, so I guess the answer is no. :)

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Hi,

I am also looking for a replacement for the C64 PSU. I have been enjoying my brand new mb6582 for a month and then the PSU died in a white smoke final breath...

I would not normally look into building my own as I do not know anything about PSU design but I can't find a linear +9/+5V that would suit. I am now considering building NorthenLightFX PSU for a replacement.

I am wondering if I can jump to building straightaway or if I should get math & electrical knowledge before I start. Any thought ?

Also is it possible to customize the design just by deleting and copying/pasting power lines behind the bridge rectifier ? In order to get 2 x 9V and 2 x 5V from the secondaries. That would make a single PSU with two blocks of 2x5V, 2x9V outputs, each block supplying 2A. This seems too easy, so I guess the answer is no. :)

If I understand you right, I'd say it's not that easy. But still you can stick with standard values as long as voltage rating of caps and current rating of transformers and regulators are high enough. To make a PSU with several different output voltages you'd normally have a transformere with several taps or several transformers because if you feed a regulator a voltage far above the output allot of heat will be produced. The NorthenLigthsFX PSU remedy this with the voltage dividing resistors (the high power ones) so that only part of the voltage is applisd to the regulator. If you didn't see these before:

http://www.avishowtech.com/mbhp/ps/

http://www.midibox.org/dokuwiki/doku.php?id=bipolar_12v_psu

Edited by strophlex
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Thanks four your reply, I had a double winding (see pic (no those are not butts ...)) transformer in mind when writing the previous post. I plan to use a R-core transformer. So it would have 2 bridge rectifiers.

What voltage ratings? 2x6V? Then you could use the one tap for regulated 5v and both for regulated 9v. However, you will need a 6(V)*2(taps)*2(A) = 24 VA transformer. I the beginning of this thread I mentioned a 25VA transformer at mouser. That could be something.

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What voltage ratings? 2x6V? Then you could use the one tap for regulated 5v and both for regulated 9v. However, you will need a 6(V)*2(taps)*2(A) = 24 VA transformer. I the beginning of this thread I mentioned a 25VA transformer at mouser. That could be something.

I was thinking of 12(V)*2(taps)*2(A) = 50 VA (as of the original NorthenLightFX proposal) in order to get 2(taps)*(2*+5VDC, 2*+9VDC) from the secondaries. I am not planning on using every output at once. Just to have mb6582 on one tap and 2*SEQ v4 on the other. The idea is to design the psu to be reusable.

Am I on the right track or did I miss it completly ? :)

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I was thinking of 12(V)*2(taps)*2(A) = 50 VA (as of the original NorthenLightFX proposal) in order to get 2(taps)*(2*+5VDC, 2*+9VDC) from the secondaries. I am not planning on using every output at once. Just to have mb6582 on one tap and 2*SEQ v4 on the other. The idea is to design the psu to be reusable.

Am I on the right track or did I miss it completly ? :)

I think you are on the right track. I am not an expert either.

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