Videopac+ G7400 PSU

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qq1975b
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Re: Videopac+ G7400 PSU

Post by qq1975b » Sun Jan 03, 2021 7:46 pm

I will see if I can load it with a game.

Maximilian wrote:
Sun Jan 03, 2021 7:14 pm
IMHO:
I dont know the Videopac machines but lets take a look.
Testing this without a load is meaningless, but to use your Videopac as a load is a gamble ofcourse.
Also I would not test the PSU without load as I have seen some (bad) PSU's go up in smoke because of that.

Finding a compatile load is going to be an issue, it looks like the 12V is only using 70ma and the 5V could be up to ~1a?
(2 big ass 5V fans and a teensy 12V fan?)

If you are within ~8% of 5V and 12V under load you will probably be ok.
For example:
Measured under load: The pal video encoder that uses 12V can handle a minimum of 10,8v(-10%) and a maximum of 13.2v (+10%)
(the closer to 12V you are the better.)

The other PSU with 6,5V on the 5V rail is probably dangerous and probably needs a recap at the minimum.

Maximilian
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Re: Videopac+ G7400 PSU

Post by Maximilian » Sun Jan 03, 2021 8:51 pm

Testing a PSU without a load is considerd without the Videopac mainboard connected, this has nothing to do with a game cartridge being connected or not!

If the voltages are more than 10% higher than 5V and 12V with the mainboard connected then shut it down or you will most probably damage the mortherboard.

Maximilian
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Re: Videopac+ G7400 PSU

Post by Maximilian » Sun Jan 03, 2021 8:51 pm

P.s. where are you from?

qq1975b
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Re: Videopac+ G7400 PSU

Post by qq1975b » Sun Jan 03, 2021 9:34 pm

Maximilian wrote:
Sun Jan 03, 2021 8:51 pm
Testing a PSU without a load is considerd without the Videopac mainboard connected, this has nothing to do with a game cartridge being connected or not!

If the voltages are more than 10% higher than 5V and 12V with the mainboard connected then shut it down or you will most probably damage the mortherboard.


Ok. I will first replace that 220uf cap that looks bad although it is new and then I will attach the PSU to the motherboard again and get the readings again.

I am from Barcelona.

Maximilian
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Re: Videopac+ G7400 PSU

Post by Maximilian » Sun Jan 03, 2021 10:07 pm

As you have also posted to a Dutch forum I hoped you would be near to the Netherlands, that would make it a lot easyér as some things seem to get lost in the translation.

As stated before you would be better of connecting another suitable load(not the Videopac mainboard) to the PSU while testing.

qq1975b
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Re: Videopac+ G7400 PSU

Post by qq1975b » Sun Jan 03, 2021 11:52 pm

Maximilian wrote:
Sun Jan 03, 2021 10:07 pm
As you have also posted to a Dutch forum I hoped you would be near to the Netherlands, that would make it a lot easyér as some things seem to get lost in the translation.
Yes, on a Videopac forum but it isn’t very active and the problem is about the PSU.
Maximilian wrote:
Sun Jan 03, 2021 10:07 pm
As stated before you would be better of connecting another suitable load(not the Videopac mainboard) to the PSU while testing.
Ops! Yes...I didn’t understand it. I have 5v and 12v fans, so I will try with those.

Thank you

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Re: Videopac+ G7400 PSU

Post by rubber_jonnie » Mon Jan 04, 2021 12:09 am

@Maximilian Nice idea to use fans for load, like it :)
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Maximilian
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Re: Videopac+ G7400 PSU

Post by Maximilian » Mon Jan 04, 2021 9:44 am

For the load:
Aim for at least 400mA for 5V.
And at most 100mA for 12V.
Make sure you have a good connection between the fans and the PSU.

Most people do not have a lot of high wattage resistors lying around, but for some reason most of the retro guys cannot through away a fan :D
(I thought about HDD's and Cdrom drives first, but they have a to high 12V current)

qq1975b
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Re: Videopac+ G7400 PSU

Post by qq1975b » Mon Jan 04, 2021 12:17 pm

So here are the news:

I have attached 3 little 12v fan and 3 little 5v fans.

On the psu with replaced caps the 12v fans work and the 5V fans don’t. Without them it shows 4.9V though.with them the 5V shows 1,65V and the 12V’s shows 13v then 21 then 27 and 13 again,....

On the old PSU all of them work. 5.16V and 10,62V.

Maximilian
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Re: Videopac+ G7400 PSU

Post by Maximilian » Tue Jan 05, 2021 12:20 am

What are the voltages and the current of the used fans for 5V and 12v?
(see the labels on the individual fans)
As said the 12V can probably only handle 100mA so 3 fans is probably way to much.

Also if you are using fans with 3 wires, only use the red and the black wire,
leave the yellow one alone as it is for sensing speed only.

At this time there have been a few things that have gone wrong, it seems that it would
be a good idea for you to get into contact with someone who can assist you locally who
has a deeper understanding of electronics before (any more) damage occurs.

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