Yes, pretty broad peaks, which might explain why Nikon LED scanners have bit higher saturation and a bit better colour accuracy in raw scans.
Which is in line with what I suggested before; broad peaks, centered around the wavelengths I mentioned earlier. Apparently, the overlap isn't problematic enough even with a white light source (CFL).
Yes, see what the continuinity testing gives. I'm interested whether you can verify that C42 connects to both pins 20 & 21 on the ADC chip. If so, it would be worthwhile replacing it with a new one and see if that improves matters. It's a good lead.
I would need to make some specific measurements with the scanner, but if I set the backlight to match the colour filters of the CCD, I should be able to get a pretty good result. (like Nikon Coolscans or Frontier SP3000) The current CCFL backlight suffer from significant spectral problems, and require too much correction with IT8 calibration and R-G-B analogue gain settings. A backlight that can be adjusted per colour channel would open up a lot of possibilities, especially for negatives.A lot depends also on signal processing; this is pertinent in your digital camera example.
Spectral sensitivity of the sensor is just one aspect and by itself, it doesn't say all that much.
Sony ILX739KA.
The author of this article once commented that Minolta 5400 and Canon FS4000US share the same CCD.
Thank you all, these are useful results!Interesting. I can't find a datasheet for that one, but I suspect the ILX734KA is related and that one has the following spectral sensitivities:
Ok, I think we have our breakthrough here. There is continuity between C42 and pin 20 and 21. I think we can safely assume we have a very likely culprit to this infamous zigzag plague.
I mean, same symptoms as Coolscans, same ADC, same electrolytic connected to the same pins... Okham's razor and all that. I might order a few caps and learn how to solder SMD's. Shouldn't be THAT hard, right ? My soldering skills aren't that good but it may be worth the calculated risk.
I removed the PCB and it is incomprehensible to me how such old microscopic LEDs can give enough light.
I just received a very dense led strip with reasonable CRI. I am simpy going to try to swap the CCFL tube for it and see where that takes me.
That made absolutely no difference
I bought a backlight unit of a Coolscan 5000ED scanner. Hopefully it will fit the Minolta 5400 with a little modification.
The optics are good, I hope to get a homogeneous light source. I removed the PCB and it is incomprehensible to me how such old microscopic LEDs can give enough light. Unfortunately I cannot identify them, maybe they could be replaced with Cree XE-Gs.
Or maybe just try to find the appropriate CFL tube as a snap-in replacement in the hopes of getting a few more years of good use out of the scanner. That would be by far the easiest and most dependable solution.
Yes, but the chips are only ~0.3x0.3mm, and the light emitting area is even smaller for the green and blue LEDs. These are from 2001. I looked at it under a microscope at 40x magnification. Perhaps the spectral distribution also helps efficiency.Firstly, LEDs are really, really small. What makes them 'big' is the substrate they're on and the package they're in, which is there for optical, mechanical and thermal reasons. The actual LED die is tiny, as shown in your photos. Secondly, the reason that unit is so efficient is because it's a condensor design that makes very efficient use of the radiant power of the LEDs - nothing is wasted. Conceptually it's similar to a condenser enlarger.
The original heat dissipation is brilliant, but fortunately I can fit a larger heatsink in the other side. (see pic) I need a copper based PCB and a heat sink or maybe a heat pipe.The LEDs in this case are a custom assembly made specifically for this application. You could try to kludge CREEs in there, but thermal considerations may make things a little complicated. Note how the thermal arrangement is in the module you posted: the actual LEDs are on a gold-plated copper structure that also acts as the anode or cathode. Note how there's only green solder masking applied in places where it's strictly necessary so that the traces can radiate heat away from the module. Then, most importantly, the LED assembly is mounted on a relatively beefy chunk of aluminum which acts as a heat sink as well as a mechanical base for the prism and the diffuser.
Yes, I will need an external power supply because the ccfl use an inverter.Instead of trying to fit other LEDs into this (which will never be a snap-in replacement anyway), I'd just use it as-is. However, if your 5400 came with original CFL light, I don't think there'll be LED drivers in there, so you'd have to add a LED power supply and constant current driver for these LEDs as well.
There are 8 LEDs in total, green, blue, red and IR. The red and IR are clearly distinguishable. Unfortunately I don't have any documentation for it. I'm trying to find the opening voltage with a regulated DC power supply, but I don't know how far I can go. Another problem is that in the original circuit, each LED had a different resistance, so the colours were balanced.Keep in mind you have two pairs of two LEDs in parallel there and one string of four LEDs. I suspect the 4-LED array is the green array and the others are red (easily identifiable) and blue. Drive current will have to be guessed unless you can find specifications or an annotated schematic or LED driver used in the Coolscan this module is intended for.
If it's not optically perfect, I can always try with the grain dissolver, and increase the illumination. But I'm really curious about the collimated light of the condenser lens. Yes, it's a harder light with additional problems.There's no guarantee that the light source will physically fit and project the correct beam angle in the Minolta scanner. You'll have to try and luck out with that.
I'm sorry it didn't work out. Thank you for trying.Yeah. Seems like a complicated way to achieve your goal.
I just received a very dense led strip with reasonable CRI. I am simpy going to try to swap the CCFL tube for it and see where that takes me.
I thought about the transparent condenser but I am going to trust the pseudo scanhencer already present in the 5400 to tame the light a bit and make it even. It's not very ambitious I am effraid.
On the recapping front. I actually learned soldering, bought for 200 euros worth of magnifier, soldering stations, test PCB to train, the whole nine yards. I recapped in a very ugly way but hey, it works, the C42 capacitor. aaaaaaaand.... That made absolutely no difference
But I did it with a clean iteration of the scanner. Meaning the zigzag effect was very feint. So I took another ccd unit laying around that I knew was terrible. I made some test scans. Recapped it, and swapped the whole ccd unit into the working scanner. It still looked like utter shit. No difference at all.
My take is that it's a lot more complicated than I thought, and out of my paygrade. But hey at least I can solder now.
Yes, but the chips are only ~0.3x0.3mm
There are 8 LEDs in total, green, blue, red and IR
I'm trying to find the opening voltage with a regulated DC power supply, but I don't know how far I can go. Another problem is that in the original circuit, each LED had a different resistance, so the colours were balanced.
a small 110VAC to 12VDC to convert the CCFL power supply wiring to 12V DC
I wouldn't recommend that. You could try, but don't freak out if it doesn't work. The risks include damage to either of the power supplies.
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