EEVblog 1459 - Is it worth PARTS SALVAGING an Inkjet Printer/Scanner? - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: February 22, 2022, 11:32:30 pm
content: Is it worth salvaging parts from a consumer HP office Inkjet Printer/Scanner from the dumpster?Scrapping a dumpster laser printer for parts:

author: SeanB
author_rank: Super Contributor
timestamp: February 23, 2022, 05:35:02 am
content: Funny enough took one apart yesterday, just to get rid of it. About the only parts in it to keep is the 24VDC power supply, and the silicone tubing for the head suction pump, as that is a useful source of sleeving. Rest was plastic, and the motors and the only bit of steel went right into the scrap metal pile. No sensor in the spittoon, there is a counter in the main board processor that stores the number of cleaning cycles, and with every power on cycle it does a clean, and again every few hundred pages. Most of the ink in your cartridges will end up in that spittoon sponge, not on the paper.Power supply has sleep mode, 12V in standby, to keep the CPU alive using one of the DC DC converters on the main board, and when it is powered up it produces 36V to run all the motors and the print head, motors all being run off 24VDC, and the print head using 36V to drive the silicon heaters in the head. Normally sleep is simply a single transistor that is used to shunt a second resistor across the feedback of the TL431, so it regulates at 12V , or simply puts a 12V zener diode in the circuit instead of the TL431, so the feedback led is running to keep the power supply at 12V, generally in hiccup mode.

author: WannesS
author_rank: Newbie
timestamp: February 23, 2022, 08:37:24 am
content: With the separate power supply you could have probably replaced that and maybe have a working printer

author: SeanB
author_rank: Super Contributor
timestamp: February 23, 2022, 04:12:50 pm
content: Power supply is only separate so that the manufacturer saves money on compliance, needing only a single approval for power supply design, the rest of the changes only being to the outer case plastic, inner stays the same. Note the power supply has all the certifications stamps on it, not the printer, and that same power supply is used in a whole range of printers as well, yet they only have the single compliance cert for perhaps 30 different models, which they otherwise would have to submit each as separate.

author: ggchab
author_rank: Frequent Contributor
timestamp: February 23, 2022, 05:20:17 pm
content: Didn't you forget the automatic sheet feeder? Maybe another motor

author: tigrou
author_rank: Regular Contributor
timestamp: February 23, 2022, 10:34:52 pm
content: It has already been said by someone in the comment but the opto at 7:35 is actually a transformer.Here is how it looks like inside. Amazing.

author: MrMobodies
author_rank: Super Contributor
timestamp: February 24, 2022, 04:24:07 am
content: I'd like to see you open and test that power supply see if that is the source of failure.I was hoping you would have got that printer powered up before going medieval on it but then when I saw where the power supply which was underneath everything I could see that it was not pratical.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 24, 2022, 05:06:38 am
content: Totally agree with the value for salvage, but the disdain for the molded scanner mechanism seems off base to me. Likely to be as or more accurate than rubber belts. Same sort of thing on the paper feed position encoder. I was working on one project and looked at quite a few traditional position encoders. They were rock solid, bulky and expensive. That HP sensor was more compact, more accurate and two orders of magnitude less expensive and as far as we could tell just as reliable in a clean environment. The only drawback was lack of environmental sealing. Which didn't matter since our application operated in a sealed environment.Actually there was one other drawback, which we could live with. The expensive guys were happy to talk to you about custom configurations for an upfront fee and increase unit cost. The HP sensor was what it was. No modifications allowed. Even in the boxes they were delivered in (which incidentally set the minimum order quantity). They weren't at all interested in disturbing their line to add a few hundredths of a percent to their production volume.

author: jonovid
author_rank: Super Contributor
timestamp: February 24, 2022, 09:39:59 am
content: the 6 pin optointerrupers are unique, very precise to less then 0.1mmI would cut the big pcb in to beer coaster sized bits and dip them in to the solder pot and pick offanything interesting. inductors the odd crystal. for the used parts bin if you got one.warning! cooking pcb,s -very smelly, do it outdoors.