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#1 07-08-2022 00:02:55
- Alpha
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(Hover for details) - Registered: 05-08-2022
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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…

... 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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(Hover for details) - Registered: 05-08-2022
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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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(Hover for details) - Registered: 05-08-2022
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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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