Alchimie 0xb in Tain l’Hermitage (26) France

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Godzil
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Re: Alchimie 0xb in Tain l’Hermitage (26) France

Post by Godzil » Fri Nov 20, 2015 11:45 am

Yeah a generic switching power supply, not the worst I ever see, there are some basic things done quite correctly, My only concern is the lack of soldermask on the right side, just where there are the main voltage :D

Apart from that the creepage and clearance distances between main and output seems OK, so it's, I think reasonably safe

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Silicebit.
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Re: Alchimie 0xb in Tain l’Hermitage (26) France

Post by Silicebit. » Fri Nov 20, 2015 12:09 pm

I'm testing all controllers with a PSU as this:
Switching power supply.
Switching power supply.
5V 2.5Amp.
5V 2.5Amp.
PSU connectors.
PSU connectors.
No problems in testing, but I'm powering the Atmos with a independent PSU.
Oric user since 1984. YouTube

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Hialmar
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Re: Alchimie 0xb in Tain l’Hermitage (26) France

Post by Hialmar » Fri Nov 20, 2015 5:23 pm

If I power the Oric from my old 9V PSU, shouldn't I change the tension regulator in the Oric ?

Fabrice Francès told me something about the Oric regulator regulating from negative tensions while current ones regulate from positive tensions.

I'm unsure about all this as I'm dumb about electronics (you know I'm a software guy).
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Re: Alchimie 0xb in Tain l’Hermitage (26) France

Post by Godzil » Fri Nov 20, 2015 7:23 pm

Hialmar wrote:If I power the Oric from my old 9V PSU, shouldn't I change the tension regulator in the Oric ?

Fabrice Francès told me something about the Oric regulator regulating from negative tensions while current ones regulate from positive tensions.

I'm unsure about all this as I'm dumb about electronics (you know I'm a software guy).
Leave the 7905 as it is, this have nothing to do with the power supply you use.

Let's take a classic 7805:
LM7xxx.gif
LM7xxx.gif (5.73 KiB) Viewed 5709 times
The difference between the 7805 and 7905 is that the 7805 make sure that between the output pin and the gnd pin Vog there is a voltage of +5V. The 7905 will make sure that the Vog is -5V

As of course the Oric electronic need a positive voltage and not a negative one, that can't work this way. But if we take the Vgo (so ground to output) voltage, what we will get is a +5V, so what Tangerine has done is to put the GND line ot the 7905 to the "+X V" of the input power supply, and put the Input of the 7905 on the GND of the Power supply, and the Output on the Ground of the Oric.

What does that mean? simple, the +X V and +5V of the oric are in fact at the same voltage potential, so if you meadure the +5V line of the oric against the power supply ground, you will find +X V (9V in your case), and if you measure voltage between the ground of the power supply and the oric ground you will find +X-5V so for a 9V supply, 4V.

That's a big problem if your power supply is correctly isolated, it the ground is earthed, that will be a major problem, especially when connected to an earthed TV, worse, (or I hope they've done that..) but if you use the same supply to provide power to the Microdisc and a +XV for the oric via the power supply plug, that would also been a major issue as ground on both are not at the same potential.

As some official microdisc power supply had a power plug for the main oric, I hope that the microdisc main board wasn't supplyed in +5V and the the +9V and +12V were totally isolated, else it would be a real problem.

So, don't worry with the 7905 and you power supply, just make sure that your power supply is completely isolated from earth

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Re: Alchimie 0xb in Tain l’Hermitage (26) France

Post by Chema » Fri Nov 20, 2015 11:16 pm

It's just that you have to make sure the polarity is correct (center positive http://twilighte.oric.org/twinew/start.htm thopposite of the spectrum PSU) and that you configure the jumper in the controller so that it does not power the Oric through the expansion port.

That should suffice. But I usually plug both PSU on the same multiple plug base.

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