Broken HSYNC (probably short circuited it or something)

Discussion of programming and development for the original Game Boy and Game Boy Color.
lidnariq
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Re: Broken HSYNC (probably short circuited it or something)

Post by lidnariq » Wed Nov 01, 2017 12:59 pm

You can get the regulated +5V from the DMG CPU, or the RAMs, or the link port, or the link port protection diodes.

Probably other places too, but those are the first ones that stick out for me on Jeff Frohwein's schematic.

zerowalker
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Re: Broken HSYNC (probably short circuited it or something)

Post by zerowalker » Wed Nov 01, 2017 1:23 pm

Hmm looking at the schematics, how would i know where it's actually on the board.

Are the Link port pins here: https://abload.de/img/gameboy_innen_img_0179su73.jpg ?

lidnariq
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Re: Broken HSYNC (probably short circuited it or something)

Post by lidnariq » Wed Nov 01, 2017 1:28 pm

Yes.

It's also on the LCD connector ("VCC")

zerowalker
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Re: Broken HSYNC (probably short circuited it or something)

Post by zerowalker » Wed Nov 01, 2017 2:02 pm

Okay connected HSYNC to the VCC on the Link connector (Pin 1, opposite of Ground i hope).

Then i check with the multimeter on each side of the resistor, i get no DC voltage, and AC (set on 200) get about 09.1, i guess that's a good thing?

EDIT:

or wait, maybe i was supposed to check between HSYNC and Ground lol xd

EDIT 2:

Here's a shot: https://abload.de/img/img_75031ots20.jpg

lidnariq
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Re: Broken HSYNC (probably short circuited it or something)

Post by lidnariq » Wed Nov 01, 2017 3:29 pm

That looks plausible?

zerowalker
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Re: Broken HSYNC (probably short circuited it or something)

Post by zerowalker » Wed Nov 01, 2017 3:33 pm

Was i supposed to check VAC between the resistors ends, cause if not and it was supposed to be from HSYNC side to Ground, then sadly it's 0 on DC and AC:(

lidnariq
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Location: Seattle

Re: Broken HSYNC (probably short circuited it or something)

Post by lidnariq » Wed Nov 01, 2017 3:45 pm

0VDC and 0VAC from the pin to ground after you added the resistor to +5V?

But ... you also said the voltage just across the resistor was also 0VDC? You must have wired that somehow wrong.

zerowalker
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Re: Broken HSYNC (probably short circuited it or something)

Post by zerowalker » Wed Nov 01, 2017 3:51 pm

Yeah it's 0 on both voltages from pin to ground.

And there's no DC voltage if i touch each end of the resistor either, but there's a AC voltage.


Will recheck so i am not lying lol


EDIT:

Okay was lying haha, there is about 4.57 DC voltage across the resistor,
no clue why i didn't get that before, must have done something wrong and though i did it.

EDIT 2:

But confirmed that Pin to Ground is Always 0.

lidnariq
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Location: Seattle

Re: Broken HSYNC (probably short circuited it or something)

Post by lidnariq » Wed Nov 01, 2017 3:56 pm

I think that sounds promising? this logic analyzer trace shows that HSYNC is low for ≈90% of the time, so getting 4.5Vdc on average and any non-0 Vac would be not inconsistent...

Do you get a valid signal if you measure the HSYNC pin with the logic analyzer now that the resistor's in place?

zerowalker
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Re: Broken HSYNC (probably short circuited it or something)

Post by zerowalker » Wed Nov 01, 2017 4:02 pm

Tried connecting from the Resistor (Pin side), but nothing comes up in the Logic Analyzer, with or without ground connected to it.
Can also note that the LCD itself doesn't work as before either.

lidnariq
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Location: Seattle

Re: Broken HSYNC (probably short circuited it or something)

Post by lidnariq » Wed Nov 01, 2017 4:04 pm

This is the kind of situation I'd love to have an oscilloscope for. Even a crappy one...

You could try decreasing the resistor. Strict lower bound is 3kΩ, and I'd be uncomfortable below 10kΩ.

zerowalker
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Re: Broken HSYNC (probably short circuited it or something)

Post by zerowalker » Wed Nov 01, 2017 4:20 pm

Hmm, doesn't seem to yield any difference on the LCD at 50k, 20k, 10k etc:(

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