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Quadra 840AV video problem
- Thread starter Elv1s
- Start date
Daniël
Well-known member
Has the PCB been cleaned after recapping? Cap goop can cause all sorts of headaches if not cleaned off the board.
If this has been done and the board is clean, I'd suggest looking at the area of the board that deals with the video circuitry (basically the area around the VRAM slots).
Especially check the upper VRAM chips, which are right underneath a couple of caps, and whether the pins on the main graphics ASIC in the video circuitry (343S1103-A) are still solidly soldered down. Such QFP chips are not uncommon to have the solder joints on their chip legs fail. Use very fine tip tweezers, or something like a small needle, and only apply light pressure to check the solder joints.
If this has been done and the board is clean, I'd suggest looking at the area of the board that deals with the video circuitry (basically the area around the VRAM slots).
Especially check the upper VRAM chips, which are right underneath a couple of caps, and whether the pins on the main graphics ASIC in the video circuitry (343S1103-A) are still solidly soldered down. Such QFP chips are not uncommon to have the solder joints on their chip legs fail. Use very fine tip tweezers, or something like a small needle, and only apply light pressure to check the solder joints.
CRT is good, using on another comp.
VRAM slots is empty, have only the soldered on vram.
beachycove
Well-known member
The fact that the screen works on other computers does not in and of itself mean it will work with the 840av.
I’d make sure to try it with a monitor known to support sync on green, since the 840av is fussy about third party monitors, and that doesn’t look like an Apple-branded monitor to me. I say this because the only obvious alternative explanation I can think of is that the on-board vram is bad. That’s with me assuming that the logic board has been properly cleaned after recapping.
I’d make sure to try it with a monitor known to support sync on green, since the 840av is fussy about third party monitors, and that doesn’t look like an Apple-branded monitor to me. I say this because the only obvious alternative explanation I can think of is that the on-board vram is bad. That’s with me assuming that the logic board has been properly cleaned after recapping.
That monitor looks like it may be a performa plus display, but, that display was built by an OEM for, in addition to Apple, other OEMs like packard bell and I believe it may have sold separately.
If it is the Apple Performa Plus display, it should work fine with the 840av.
That said: the way the raster has expanded to fill the full visible area makes me think/agree something's wrong with the sync, so either this is the plain VGA version and the adapter isn't correctly syncing or the 840av doesn't realize this is a 640x480@67 monitor (again: if it is the performa plus display) and is trying to send it an incompatible signal.
If you have a VGA adapter and any other displays (maybe a 4:3 business LCD like a dell ultrasharp or p-series type of thing?) have you had a chance to try one of those on your 840?
This doesn't mean the vram isn't bad, but bad vram wouldn't on its own AFAIK cause a failed sync like this.
If it is the Apple Performa Plus display, it should work fine with the 840av.
That said: the way the raster has expanded to fill the full visible area makes me think/agree something's wrong with the sync, so either this is the plain VGA version and the adapter isn't correctly syncing or the 840av doesn't realize this is a 640x480@67 monitor (again: if it is the performa plus display) and is trying to send it an incompatible signal.
If you have a VGA adapter and any other displays (maybe a 4:3 business LCD like a dell ultrasharp or p-series type of thing?) have you had a chance to try one of those on your 840?
This doesn't mean the vram isn't bad, but bad vram wouldn't on its own AFAIK cause a failed sync like this.
croissantking
Well-known member
Another vote for possibly bad VRAM. I've seen an image similar to this on an LC475 with no VRAM installed.
Phipli
Well-known member
I'm not so sure it is VRAM. Like others have said, it isn't putting up bad data, it's... All over the place. It's more likely a bad trace or dry contact in the video circuit.
@croissantking no VRAM at all is a very extreme case to compare it with, given the chips are physically there, isn't it more likely an issue in the video circuit that impacts more broadly, than a VRAM specific fault that breaks all the VRAM (that's a lot of chips and traces to fail)?
@croissantking no VRAM at all is a very extreme case to compare it with, given the chips are physically there, isn't it more likely an issue in the video circuit that impacts more broadly, than a VRAM specific fault that breaks all the VRAM (that's a lot of chips and traces to fail)?
Last edited:
croissantking
Well-known member
Yes, I agree it maybe wasn’t a good comparison to make. Bad VRAM usually manifests as artifacts or other visual glitches but not digital snow.
croissantking
Well-known member
Could it be a bad chip, in that case? Your logic board looks clean.
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