Atmos powered SCART lead question

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kppot
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Atmos powered SCART lead question

Post by kppot »

Hello

This is a bit weird. I have Atmos and powered SCART cable. While I was on CRT it wasn't necessary to feed the power, as my old telly was happy. When I moved to LCD panel I need to feed +9v from the battery.
4F0992D0-FE8A-4FF8-B027-4DADC1F5562F.JPG
It is generally okay but one I forgot to remove the battery and it was drained completely.

So I convert it to PSU powered lead.
4CBF3AC8-45C5-492C-9DD6-397CCCB93578.JPG
Now I have a problem - being powered from 9v battery is okay.
But being powered from PSU - I got the TV picture, but the machine is hangs on reset, it does not boot.
9A59EFDC-DF3A-4B2C-B920-EAD168C873ED.JPG
My guess would be the PSU provides not enough power, but it produces 2.5A in fact :shock:

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kppot
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Re: Atmos powered SCART lead question

Post by kppot »

With no power from PSU (or battery) I got no picture (I have ghostly black white one) - this is where I have no question, as this telly needs power on 16 pin to select Scart input.
AD9F4F1F-F26E-45D2-8BD8-16EA85697CC5.JPG

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iss
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Re: Atmos powered SCART lead question

Post by iss »

Do you use one PSU to power the Oric and the SCART?
If so, stop doing it because this can be dangerous for Oric and/or LCD.
Draw simple sketch with wiring to see what can be potential problem.

If your LCD TV has an USB input - you can use it with old USB cable to get 5V and "self"-power the SCART - in most cases 5V are enough (instead of 9V).

EDIT: Here is my cable:
20210417_002453.jpg
and the connection sketch (R ~100 Ohms is advised for any case):
sketch.jpg
sketch.jpg (7.8 KiB) Viewed 522 times

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kppot
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Re: Atmos powered SCART lead question

Post by kppot »

iss wrote:
Fri Apr 16, 2021 10:16 pm
Do you use one PSU to power the Oric and the SCART?
Yeah, as some youtube guys suggested, but I always wondered if it that safe.
So now I am using one more external 5v PSU and everything looks fine!
Thanks for poking me on FB as I was really impatient to spend another night with Oric games!
F6D3737B-60FD-4C56-A248-7F1C74FA458C.JPG
Kids, do not use that suggested way of feeding 9V from PCU to Oric and to Scart at the same time!
Note to self - do not forget to solder that USB lead, really nice!

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iss
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Re: Atmos powered SCART lead question

Post by iss »

Cool!
Actually the idea for the USB was to not use second PSU but to plug the USB in the TV's input for USB-stick (for direct media playback).
But of course this is valid only if the TV has such connector.

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kenneth
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Re: Atmos powered SCART lead question

Post by kenneth »

If we consider that the Oric's ground is the referential, the psu produces -4v and +5v: the total voltage is 9v, then it is dangerous to connects the both wires like an independant power supply, it will produce a shortcut. However, if only one wire (+5v) is used to feed the Scart plug, that could work correctly, we can add a capacitor pump inside the Scart shell to obtain 9v. I think that the Retroshack's cord use this way to work.

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