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#1 07-08-2022 00:02:55

Alpha
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Completely dead NewBrain AD, problem with voltages.

Hi all.

I decided, after a long long time to repair my completely dead NewBrain AD. First of all I did full recap to every board, plus PSU. When I got this, it was already dead from previous owner.

Looking at this picture from the internet…


https://i.postimg.cc/wM5v48np/658-B7652-CF2-C-433-B-9-D11-00-C8-E17463-CB.jpg


... i realize that i have way wrong voltages.

The -5 volt are ok, as I got -5,3 volts.
The 12 volts, is 3,2 volts in my board.
And the 5 volts is 1,2 volts in my board.

Checked my power supply before I connect it, and all values are ok for PSU. But to be honest with no load.

Any help is more than welcome!

Thanks.

Last edited by Alpha (07-08-2022 00:20:41)

 

#2 09-08-2022 07:32:28

Alpha
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Re: Completely dead NewBrain AD, problem with voltages.

First of all the PSU even if produced the 6.5 volt when i plugged it to Computer dropped down to 1.2 volts. I thought that maybe is a sort somewhere in NewBrain but was just the PSU. Test it 12 volt 21w bulb and can’t handle it. So i use a pc PSU to be able to test my NewBrain.

All voltage now are ok, only the 5 volts it is 4.7 volts. I don’t think it is a problem.

NewBrain power up with VFD post unknown symbol’s, some flashing.

I check all paper flat cables for connectivity board to board and looks ok. I desolder all memory’s and tested and also looks ok. Z80 cpu is in working condition cause I test it too. Also I missing video signal.

That’s so far.

 

#3 12-08-2022 08:20:07

Alpha
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Re: Completely dead NewBrain AD, problem with voltages.

Can anyone please post here the voltages from the power transistor 2N5193 pins? The left one, the one for the 12 volts. All 3 voltages please. On (E) (C) & (B).

Thank you

Last edited by Alpha (12-08-2022 08:20:55)

 
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