Certified idea for a repairable heavy duty power supply

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Ready.
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Certified idea for a repairable heavy duty power supply

Post by Ready. » Wed Mar 29, 2017 2:48 pm

I have thought several ways to provide a new PSU to the Commodore community, but I've always got stuck on one point: certification. Selling non certified stuff puts the seller in a liable position in case anything bad should happen. There are several types of certification, but my biggest concern is with the high voltage part (>50Vac). Of course also the low voltage part should go under several certification checks, like RF radiations, RoHS,.... but actually the certification is never invoked until anything bad happens and with low voltage it is rare that something bad can happen. This is how I guess most of our beloved expansion cards (1541Ultimate, Chameleon, SD2IEC stuff, C64R...) are sold, i.e. without certification.
So the step for selling a new PSU without too much risk, would be to certify the high voltage part. But in order to have a certified product it's not sufficient that all its components are certified: the whole assembly must be certified. Technically I could take an AC/DC converter and put it in an enclosure which blocks the heat dissipation and it could catch on fire: surely this type of assembly would not pass certification tests even if inner parts are certified!
So the idea is to take an AC/AC converter to produce a 9Vac and something like 20Vac (suitable as input for a DC/DC converter). This AC/AC psu should come in a separate box, so the user may just connect to it a second box in which there would be all the necessary stuff to convert 20Vac into 5Vdc and/or 12Vdc. 9Vac would be passed through as it is, maybe a fuse or filter.
Now the problem regards just the AC/AC part: we need that to be certified. If we succeed on that we are done.

Good news is that I found an Italian supplier who could supply CE certified AC/AC PSUs with custom outputs (9Vac and 20Vac are fine!). The design would be based on a double secondary transformer with double insulation (thus no grounding needed). The final user should not open this PSU but just connect the low voltage box to the screw terminals of the AC/AC psu.
The supplier can add PTC self resettable fuse to the primary of the transformer. Unfortunately they cannot add power switch, EMI filter and surge protection, but I guess these could be added to each secondary output of the transformer inside the low voltage box. Of course adding them to the primary would be much handier. From my experience EMI filter is necessary to keep out dirt from the C64 when you turn ON/OFF other stuff in your house. Without EMI filter these disturbances can be seen in the video output for example.

Price of this AC/AC psu? I would say around 20 euro (including taxes), maybe a bit more due to shipping costs depending on location in the world.
Another good thing I see in this is serviceability. The transformer very seldom fails, so one could just replace the low voltage part when it fails with little cost.

If there is interest in this, my plan is to buy 1 piece of this AC/AC psu and test it with my Commodore equipment. I have oscilloscope also.
Here's my PSU project development, which cannot be sold as is due to the uncertified high voltage assembly:
http://danieleredivo78.wixsite.com/c64psu

Any feedback is welcome.



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eslapion
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Re: Certified idea for a repairable heavy duty power supply

Post by eslapion » Wed Mar 29, 2017 4:21 pm

Ready. wrote:
Wed Mar 29, 2017 2:48 pm
Good news is that I found an Italian supplier who could supply CE certified AC/AC PSUs with custom outputs (9Vac and 20Vac are fine!). The design would be based on a double secondary transformer with double insulation (thus no grounding needed). The final user should not open this PSU but just connect the low voltage box to the screw terminals of the AC/AC psu.
The supplier can add PTC self resettable fuse to the primary of the transformer. Unfortunately they cannot add power switch, EMI filter and surge protection, but I guess these could be added to each secondary output of the transformer inside the low voltage box. Of course adding them to the primary would be much handier. From my experience EMI filter is necessary to keep out dirt from the C64 when you turn ON/OFF other stuff in your house. Without EMI filter these disturbances can be seen in the video output for example.

Price of this AC/AC psu? I would say around 20 euro (including taxes), maybe a bit more due to shipping costs depending on location in the world.
Another good thing I see in this is serviceability. The transformer very seldom fails, so one could just replace the low voltage part when it fails with little cost.
Any image or links ?

IMHO, when you have a good transformer handle the mains, EMI filter and surge protection is not so important. The high inductance of a 50/60Hz transformer is a large filter in itself.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

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Re: Certified idea for a repairable heavy duty power supply

Post by Ready. » Wed Mar 29, 2017 4:37 pm

This is the link to their web site:
http://www.adigesrl.it/product_lang-1-proId-66.html

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Re: Certified idea for a repairable heavy duty power supply

Post by Ready. » Wed Mar 29, 2017 4:41 pm

this is a test I made with my self built PSU of switching on the C64 with PSU switch.
Without C-L-C filter bewteen switch and primary of transformer:
https://ibb.co/mU20ov
With C-L-C filter bewteen switch and primary of transformer:
https://ibb.co/f7AQMF
that's why I thought C-L-C filter is necessary.

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Re: Certified idea for a repairable heavy duty power supply

Post by Zippy Zapp » Wed Mar 29, 2017 5:01 pm

Jim Brain was working on a new power supply, I think with Bil Herd. I don't think anything ever came of it, which is a shame. His design was to use one external power supply to generate the needed AC and DC voltages. Here is a link:

https://www.youtube.com/watch?v=yszGYBzxUDA

I have thought about contacting him to see what the status is but my brain cells seem to be not reminding me of things lately... ;-)
Commodore - Changing the world 8 bits at a time.

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eslapion
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Re: Certified idea for a repairable heavy duty power supply

Post by eslapion » Wed Mar 29, 2017 5:30 pm

Ready. wrote:
Wed Mar 29, 2017 4:41 pm
this is a test I made with my self built PSU of switching on the C64 with PSU switch.
Without C-L-C filter bewteen switch and primary of transformer:
https://ibb.co/mU20ov
With C-L-C filter bewteen switch and primary of transformer:
https://ibb.co/f7AQMF
that's why I thought C-L-C filter is necessary.
Good point. What does it look like on the secondary ? Does the transformer filter that out, or part of it ?
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

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Re: Certified idea for a repairable heavy duty power supply

Post by Ready. » Wed Mar 29, 2017 6:23 pm

The measurements are from the inside of the c64, so it IS taken on the secondary.

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eslapion
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Re: Certified idea for a repairable heavy duty power supply

Post by eslapion » Wed Mar 29, 2017 10:00 pm

Ready. wrote:
Wed Mar 29, 2017 6:23 pm
The measurements are from the inside of the c64, so it IS taken on the secondary.
The original C64 power supply was expected to remain powered at all times and so, neither it nor the C128 PSU are equipped with switches. It was expected the power would be switched on the low voltage side.

Does that make a difference on your opinion ? Possible impacts ?

Could the suggested C-L-C filter be placed on the low voltage side and provide the desired results ?
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

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Re: Certified idea for a repairable heavy duty power supply

Post by Ready. » Wed Mar 29, 2017 10:30 pm

Surely it would provide same results on secondary side, it will still create a path to dissipate High frequences, but on the secondary you need 2 filters, one per each secondary winding. So on the High voltage in more practical.

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Re: Certified idea for a repairable heavy duty power supply

Post by Oge_user » Sun Apr 16, 2017 12:06 pm

Ready. wrote:
Wed Mar 29, 2017 4:41 pm
this is a test I made with my self built PSU of switching on the C64 with PSU switch.
Without C-L-C filter bewteen switch and primary of transformer:
https://ibb.co/mU20ov
With C-L-C filter bewteen switch and primary of transformer:
https://ibb.co/f7AQMF
that's why I thought C-L-C filter is necessary.
This is a huge improvement. I'd guess that even a simple "C Filter" on the secondary side would help smoothing the AC current.

I recall proposing a MKT capacitor for filtering of RF/HF frequencies (which will benefit VRs placed into the C64s, thus resulting voltage going onto both VIC-II and SID) and being accused that it was a Snake-Oil-Feature.
From my experience EMI filter is necessary to keep out dirt from the C64 when you turn ON/OFF other stuff in your house. Without EMI filter these disturbances can be seen in the video output for example.
This is true.

I'm really glad that someone showed that filtering makes a difference.
Image

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