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MB6582 PSU Caps


Shuriken
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I have my MB6582 almost finished. But still needed to sort out the PSU.

So i wanted to start soldering the components on it, but i ran into a bit of a problem. As suggested by the MB6582 surface partlist i ordered 2200uf 25V caps. Those are 7,5 RM with 1,0mm legs. But to my suprisse the mainboard has a big silkscreen but 5,0 RM 0,8mm position for both the caps.

As the rectified voltage goes way past 18 Volts i don't think its right to put in a 16Volt variant. But still dont understand why a 25V part is suggested as it wont fit the board...

Isn't this a bug or something which needs to be changed?

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Hi Shuriken,

I knew I'd seen something about this. From the FAQs on Wilba's docs: http://www.midibox.o...i/wilba_mb_6582

Is there any reason why 16-volt 2200uF caps cannot be used instead of 25-volt ones?

For the 5v supply: no. For the 9v AC after the bridge rectifier: not really. I was told once to expect up to 2x the voltage after the rectivier, i.e. if it's 9v AC, choose capacitor to handle 18v DC. It really doesn't go up that high I think, and caps rated to 15v should be enough.

As far as I remember I received a 25v version from SmashTv which fit perfectly.

Bye,

Hawkeye

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Hi Shuriken,

As far as I remember I received a 25v version from SmashTv which fit perfectly.

Bye,

Hawkeye

I found that post aswell and it says SmashTV delivered 16 Volt ones, not 25 Volt.

No. Like shoes, parts come in different sizes. You ordered the wrong ones.

You are right ofcourse. But i don't understand why the choice has been made for a niche part. The parts i found at Conrad and Reichelt are all RM 7,5 and have 0,8mm legs.

Edit: Puts foot in mouth :whistle:. It seems Conrad carries a Panasonic one which fits the bill . Part number: 422039 - 89 for anyone that needs it.

Edited by Shuriken
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I have my MB6582 almost finished. But still needed to sort out the PSU.

So i wanted to start soldering the components on it, but i ran into a bit of a problem. As suggested by the MB6582 surface partlist i ordered 2200uf 25V caps. Those are 7,5 RM with 1,0mm legs. But to my suprisse the mainboard has a big silkscreen but 5,0 RM 0,8mm position for both the caps.

As the rectified voltage goes way past 18 Volts i don't think its right to put in a 16Volt variant. But still dont understand why a 25V part is suggested as it wont fit the board...

Isn't this a bug or something which needs to be changed?

It's a bit of legacy and the fact that big electros come in different sizes depending on value, voltage rating AND some other magic factors like high temperature, low leakage etc.

The footprint on the PCB fit the 2200uF 16V caps I had in hand at the time of my prototype. AFAIK the rectified voltage does not go way past 18V, it is more like 11-15V under load. In addition, SmashTV assured me that the high-temp Xircon rated to 16V are safe to use. (Similarly, I "get away with" Xircon 2200uF 16V electros in sammichSID for the 9V regulation).

However, the original MIDIbox MIDIbox SID C64 optimized PSU schematic uses a 2200uF 25V for the 9V rectification and a 2200uF 16V on the 5V suppy (not that it's really required but doesn't hurt).

So you are right... the "25V" in the parts list was adopted from the schematic, but not what SmashTV supplies or what I have used in the past... so I changed it. I also saw your note, thanks!

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