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mike <ham789@netzero.net>: Nov 05 04:44PM -0700 I have an HP Laserjet 4MP.   Something went haywire in the toner cartridge and dumped toner. I cleaned it out and replaced the toner cartridge and it sorta worked. Had some background artifacts, but I chalked that up to 20 year old toner cartridges.   A month later, I tried it and it had severe banding and the background was almost as dark as the print. Ran a dozen prints and it got a little better.   I pulled the toner cartridge out of a perfectly working Laserjet 4L and ran 8 successive prints in the 4MP. I put the toner back into the 4L and it still prints perfectly.   The following image represents 8 successive prints of the same page in the laserjet 4MP using the known-good toner cartridge.   http://i.imgur.com/dcuRRlW.jpg   It shows the first page and the left 400 pixels of the next 7 prints attached to the right to show the banding in the background.   There are artifacts from the aliasing in the scanner, jpg and the resampling to reduce the image size to something manageable to publish on the internet. The only intention is to show the background banding differences from print to print. Parts that are supposed to be black are deep black and clearly defined.   It's the background that is the issue. It's supposed to be white.   Note that the banding varies radically from print to print. If you look for bands that repeat at the circumferences of rollers in the print system, you can find some, but even those don't always repeat on the same page.   If I pull the toner mid-print, the background toner is definitely on the drum. It appears that the problem is NOT in the fuser or other rollers in the system. It happens inside the toner cartridge.   The only thing I can think of is that the power supply that charges the drum is defective and supplying insufficient voltage. The service manual is very detailed describing the process. There's a DC bias plus an AC component. But they stop short of describing the amplitudes of each. Seems to be about -500V from the rough graph. I could solder some wires on a toner cartridge and see what it looks like, but it would be nice to know what to expect. I don't know the current capacity (impedance) of the supply. Toner is likely conductive, but it doesn't look like toner got into the area of the power contacts. Anybody know what power waveforms/voltages to expect?   The thing is put together like a Chinese Jigsaw puzzle. The power supply is at the center. I don't have much hope of being able to run the supply disassembled. About all I can do is check caps for ESR and look for dirt or bad solder joints.   I like this printer. It does what I need and I have a lifetime supply of toner cartridges for it. I also have a LJ4L and a LJ4P. I'd buy an inexpensive color laser printer, but they all seem to have EXPENSIVE chipped toner cartridges that expire and refuse to print whether you used them or not. I don't print much. Inkjet is not an option. My inkjet plugged up a decade ago from non-use.   I understand that most of you would not waste time fixing it, but I have the time and the desire to learn about how it all works.   Anybody got ideas of what to try?   Thanks, mike

Jon Elson <elson@pico-systems.com>: Nov 05 09:26PM -0500 mike wrote:   > Laserjet 4L and ran 8 successive prints in the 4MP. > I put the toner back into the 4L and it still prints > perfectly.   A common problem on many of these printers is the wiper blade. it is a silicone elastomer that wipes excess toner that didn't transfer onto the page off the photoconductor drum. The blade gest a permanent set after sitting for a year or so, and won't remove toner effectively. I am not POSITIVE that is your problem, but it resembles what I've seen. I have a 5m that I think may use a similar print engine and cartridge. I buy NOS carts on eBay, and then generally have to replace the wiper blade. There are guys on eBay that will sell you a new blade. One way to check is look at the green photoconductor drum, you just have to pull back the protective cover. If it is strongly streaked with toner, then the wiper blade is not working. Or, look through the slot on top where the laser shines through, if there is any toner whatsoever there (it should be glassy clean and shiny) then the wiper is bad.   If you tear down the cartridge (which you have to do slightly to change the wiper blade) then inspect and clean the corona wires. if they get a bunch of toner on them, they either short out the HV power supply or just don't work.   The cart on the 5m has a cover on each end, held by 1 or 2 screws. After removeng them, there are two sections to the cart, held together by hinge pins. it is tricky to work the pins out, but when you do, the cart comes apart in two pieces. One is the toner applicator, VERY messy, keep from tilting it so the toner doesn't spill. The other part has the photoconductor and corona wires, and the wiper blade and spent toner bucket. When you get it apart, there are bearing pins in each end of the photoconductor, pull these out, the drum comes out, and you can change the wiper blade. Then, reassemble.   This all applies to the 5m cart, but I think the 4m either uses the same or a very similar cart.   Jon

N_Cook <diverse@tcp.co.uk>: Nov 06 03:53PM On 06/11/2016 02:26, Jon Elson wrote:   > This all applies to the 5m cart, but I think the 4m either uses the same or > a very similar cart.   > Jon   Is there charge neutralising linear lamp/s/LEDS for HP lasers, if so the cover glass could be dirty. Or problem with the reclaim/retraction (? I forget the term) "corona" voltage to assist in wiping the drum , not just the wiper blade to do that

N_Cook <diverse@tcp.co.uk>: Nov 06 12:19PM Erratic connection, not bad solder problem to pcb, internal failure probably loss of plating contact surface. Seems pointless trying to replace original dual concentric "socket", bound to be proprietary and so will also fail after warranty + 1 year. Some sort of polarised mateable line plug and socket with a well anchored stub of lead , soldered to the pcb inside, instead. The diverter switch in the socket just switches an LED on and off and has been defunct for ages anyway. So just 2 wire line connectors male and female for 20V ,3A. But what type of non bulky, hopefully side by side axial connections, ie not like 3.5mm (<3A anway) or dual concentric (no line sockets easily available). At the moment I'm thinking of moulding up my own connectors , as I cannot think of anything off the shelf. Using a pair of Q or Trident type sockets and pins, offset axially , to give the polarisation. Cosmetic appearance does not matter.

dansabrservices@yahoo.com: Nov 06 06:34AM -0800 I have replaced some of these in the past on a number of different laptops without any problem. I have not had a problem finding generic replacements either.   What laptop are you working on?   Dan

"Gareth Magennis" <soundserviceleeds@outlook.com>: Nov 05 10:53PM "Phil Allison" wrote in message news:148f351c-485f-42bf-a61b-82ec730ce66a@googlegroups.com...   Gareth Magennis wrote:   > Meanwhile, this link should supply some useful clues.   > http://www.tme.eu/en/Document/d3a1e827773837de0340fb075548fa6f/etd_29_16_10.pdf   > I'm pretty sure it has no gap.   ** There is one - it might be only a few thou of an inch, but it must be there or the whole thing would blow up.     > even with a core in several pieces, and measurable with a micrometer > without > having to reassemble.   ** This is NOT a SMPS transformer, it's a ferrite CHOKE that must pass a couple of amps of DC current. It simply HAS to have an air gap !!!     > yesterday showed it is not widely available in small amounts.   > Would you need to adjust the number of turns if you used solid copper > instead?     ** FFS, make your own stranded wire.   Dare to be great !!!!!!       > the second I have seen. The windings short together, and there is no > insulation or tape applied anywhere on the windings except the final outer > wrap.   ** Use higher temp wire, 220C stuff is readily available, the usual magnet wire is only rated at 120C at best.   Do not muck about: an active, high frequency, PFC choke is critical component.       .... Phil           It is becoming increasingly obvious to me that L9 in this design is ANYTHING BUT an inductor of the appropriate inductance and the required power handling for the job required.   It is clearly the Achilles heel of this particular design.   As such, I have given up any such silly idea as to how I might improve on it, as I am not qualified to do so.     Thanks,     Gareth.

Look165 <look165@numericable.fr>: Nov 06 09:51AM +0100 The trace of the inductor in the schematic means with a core.   No Litz wire, it is reserved for high frequency low intensity windinds.   SMPS works at "low frequency" (some 10 kHz).   If the core is ok, just unwind and rewind with a new wire.   Gareth Magennis a écrit :

gregory.beat@gmail.com: Nov 05 02:10PM -0700 Phillips Advance : Ballasts http://www.usa.lighting.philips.com/products/oem-components/fluorescent-ballasts.html   Their USA Corporate HQ are near O'Hare Airport (Chicago). Almost all of the Ace Hardware stores (especially the Industrial ones) in Chicago area (Ace HQ also) carry the Phillips ballasts or can order.   g. beat chicago

w9gb <gregory.beat@gmail.com>: Nov 05 07:48PM -0700 How to Buy: T8 and T12 LED Fluorescent Replacement Tubes Posted by EarthLED News on Jun 03, 2015   Choosing the right LED fluorescent replacement tubes can be confusing due to the myriad of product types and installation options. We at EarthLED.com have created this guide to assist in the process and help you make the right choice for your specific projects. https://www.earthled.com/blogs/light-2-0-the-earthled-blog-led-lighting-news-tips-reviews/33135492-how-to-buy-t8-and-t12-led-fluorescent-replacement-tubes   Currently, there are four types of options available in the market:   1.) Ballast Bypass or Direct Wire LED Fluorescent Replacement Tubes   2.) T8 Electronic Ballast Compatible LED Fluorescent Replacement Tubes   3.) Hybrid (T8 Electronic Ballast Compatible / T8 or T12 Ballast Bypass LED) Fluorescent Replacement Tubes   4.) Universal (T8 Electronic or T12 Magnetic) Ballast Compatible LED Fluorescent Replacement Tubes

Phil Allison <pallison49@gmail.com>: Nov 05 07:42PM -0700 N_Cook wrote: > actual circuit nodes on this amp and modelling the schematic I don't > know how much current is actually now or should be taken by the MJE340, > but something is not hunkey dorey.   ** I had a look at that schem and could see no sign of current sensing for the fan. The MJE340 is there to increase fan speed as the heatsink gets hotter.   IIRC, the 2W resistors are carbon composition types, which are notorious for increasing their value over time - but I have seen them do the reverse when subjected to excessive temps.   Famously in the ridiculously heavy Bose 1800 amplifer, where two 3kohm 2W composition types supplied current to the op-amp input stage.   http://i.imgur.com/ETpss.jpg   These resistors ran hot ( 1.6watts each) and the amp had no internal fan, so the insides got hot too. They steadily dropped value until one of the 16V zeners fried and went short. The amp then went full rail DC sending 80V into the speakers.   Fitting new zeners and changing the resistors to 4.7k, 5W wire wound made sure it never happened again.   In the examples I saw, the speakers were Bose 802s which had 4 amp fuses fitted on the back which saved the drivers.   http://www.timberridgestudios.com/bose802/PIC00054a.JPG     .... Phil

"Michael A. Terrell" <mike.terrell@earthlink.net>: Nov 05 06:54PM -0400 Phil Hobbs wrote:   > What I want for deer control is a robotically-aimed paintball gun. In > the winter the deer are harder to discourage, but frozen paintballs > would probably do it. ;)     How about using life sized scarecrow, with a leftover 'Hillary' Halloween mask? ;-)     -- Never piss off an Engineer!   They don't get mad.   They don't get even.   They go for over unity! ;-)

gregory.beat@gmail.com: Nov 05 02:04PM -0700 The Control Signal Corporation (CSC) of Denver, CO used this PROM (U1) in their model CWID-50B and -51B Automatic Station Identifiers with FCC licensed Land Mobile or Amateur Radio Repeaters. The PROM held the Morse Code (CW) message -- typically FCC license callsign. http://www.ti.com/lit/ds/symlink/jbp18s030.pdf   CSC CWID-50B : Owner's Manual http://www.repeater-builder.com/other-mfrs/pdfs/csc-cwid-50-51-identifiers.pdf   The original 16-pin TTL PROM (32 x 8) -- TBP18SA030 -- is obsolete (no longer production) and the 1970s programmers are rare to find. You can DIY Build an adapter to allow the usage of the more readily available 27Cxxx / 28Cxxx series EPROMS. The CSC CWID-50B manual walks you through what each bit on the PROM is used for.   gb

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