Fix HL-5470DW Laser Printer with B512342-5 controller

This is a nice 600DPI PostScript laser printer from 2012- 10 years ago. 
* WIFI can be joined, USB recognizes its name on a MAC computer, Also Linux
Ethernet Cable registers on the 16 character LCD screen as Connected, With Address.
* Self-test Printing works fine from front panel delivering a nice report
BUT– It refuses to print through any interface  No BUSY light or anything
Bit o’ Research shows it has a primary circuit board to manage all this, I have to guess that’s (ir)responsible for this Problem.
I did spend some time monkeying around with the cursor keys and LCD display to reset the ROM, reset factory defaults et cetera et cetera… To No Avail.
Looking back now I might have considered trying to upgrade the firmware to see if that made any difference – I doubt it but only realised a firmware upgrade was available after replacing the motherboard. “maybe try that next time Paule”

My subjective impression was that there was no association between the printing part of the machinery and the outside interfaces.
I took the side panels off the checked the many cable connections for loose fit, burned chips, etc. and All seemed fine.
Nowthen– Curiosity aside, what is it worth spending to fix this? Surprised to learn on Ebay that these things come in at least $150+shipping. 
Refurb Toner Cartridges, if needed,  are not prohibitive– $17.00
Found a free return refurbished spare controller board on eBay (warranted) for $40- the upper limit of what seemed worthwhile.. 
the part happened to be labelled: 
I did find a dealership service manual online with excruciating detail about screw torques, Wire color coding, even a section on attaching a debugging port to the main circuit. 
Interesting: But Helpful?
Nothing of the surface mounted components would I try replacing. I have had dismal failure own that front, before….
Why look for Problems one has no direct solution for?

First thing to do was a Google Image Search for the card ID: to see whereabouts this thing shows up- Well several versions did show up- the -5 suffix is some kind of versioning because lower numbered revisions actually used some real estate on board for a Centronix Parallel Port- My circuit board only had the solder pads for that, But with USB and Networking, who needs parallel? It woudl have been easy to cut the case to match but… No, Paule.
Yes, by 2012 that was all Over, but the design obviously went further back.

Cuts a long story Short- 
– Before removing a circuit board I always label it OLD with a Sharpie
– The NEW or rather Refurbished one was so very similar I knew I was likely to screw up!
– Several zoomed photos to show plug color, location and wiring, though in this case nothing could be mis matched.
– two ribbon connecters made me think they might be the type that has a ‘captive’ clasp on the plug. The ribbon had a hard blue plastic card end-backing it seems in order to allow push and pull insertion and removal (AKA: Interference Fit) without whacking the cable.
– I usually pop out the white connectors with a screwdriver blade prying each side in turn Could fin no ‘retainer’ — some such plugs have a tint patch that needs to be pushed to release the connector. Not these.

Alright so the Printer is back together- It DOES take some puzzling to do this, but it’s OK.
On power the LCD showed ready but griped about the Electrostatic Drum being ‘End of Life’ which it never said before. I think this was an ‘ancestral memory’ of the Printer it came from. My Guess: That whoever recycled the printer this board came from gave up ion that Message on seeing the Brother price for a Fuser/Elctrostatic Toner unit was $80-$90
NOT worth it fro them! the LCD does allow resetting this to 0, and No More COmplaints

The former Page Count had been 80,000, it now dropped to 55,000 as the NVRAM on the board ‘remembers’ its old life

Also, the serial number label on back of this printer is now WRONG

Stats page
Stats page

and YES it DID take a Firmware Upgrade to 1.25- Wish I had tried this first with the Old Board though I suspect it was un revivable. AQt 10 years old it seems Brother is still happily supporting these units, and even successfully upgrade the Forward from a very modern MacBook M1!- also the Printer Preferences Found and Used this printer without further intervention

I. can see the high price of this laser printer comes from its ability to handle Postscript, lots of internal fonts an compatibility with several other Printer Standards from HP (Laserjet) its ability to be used in Windows Workgroups etc. It dod NOT seem to have AFP (Apple Networking) however.. 

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