LaserJet 4240n/4250/4350
PARTS CATALOG

The particular model number of the printer (4240n, 4250n, 4350n) and associated printing performance is determined by programming codes stored in both the formatter board and the DC controller board. The model information was initially set by HP at the factory, but that information can be changed in various ways. Under certain circumstances repair technicians have accidentally changed the printer model setting resulting in upgrades or downgrades to the performance. The Printer Works can correct those problems.

The model information as stored in the DC controller settings are usually the master settings. Formatters look to the DC controller to determine which model printer they are connected to. Given that the DC controller usually plays the role of model master, if the DC controller is changed, then the model of the printer will be changed to whatever model the DC controller was previously set to be. So installation of DC controller with the settings of a 4350n printer into a 4250n printer will result in upgrading the 4250n into the faster 4350n model. Conversely, installation of a DC controller from slower 4250n into the faster 4350n will downgrade the 4350n to become the slower 4250n model. These changes also apply to the value-priced 4240n model.

Usually, DC controllers sold by both HP and The Printer Works are always programmed to be “blank” and do not have any model information stored inside the non-volatile memory. Using blank DC controllers will not change the model inadvertently. When the DC controller has not been programmed for a particular model, then it can not take on the role of being the master of the model determination. A blank DC controller will determine the model information by getting the settings from the formatter board that it is connected to. This cleaver software system created by HP also creates pathways that can be used by informed technicians to make printer model changes. However, if the model changes are done unwittingly by swapping used boards between different models, then unwanted model changes with associated performance upgrades or downgrades can result.

The model determination system works just fine in the ideal world where repair technicians only install properly programmed replaced parts purchased from HP, or from other sources like The Printer Works that provides the replacement parts configured the same way the factory provides them. To avoid model changing problems, formatter boards sold by HP, and by The Printer Works, Inc. are normally always set to be “blank” with respect to model information – unless the customer has requested a special version by special order. This allows parts suppliers to only stock only one type of DC controller, and only two types of formatter boards (network and non-network) to support all of the different models in the field.

However, we realize that in the real world people often trouble shoot printers by swapping parts from different used machines. Unwanted model changes often result when this is done. Models changes have also happened by memory failure in the printer. Customers have reported model changes to us after having lightning strikes in the area. Therefore, by special request we are willing to supply pre-programmed boards, ready to correct any problem situation that might have resulted from board changing sequences, or other hardware, and printer memory failures that have resulted in undesirable results.

The model determination system described above is not unique to the 4240n, 4250, 4250n, 4250tn, 4250dtn, 4350, 4350n, 4350tn, 4350dtn series of printers. The same sort of code-based model determination methods have also been employed by HP in the 2420, 2420d, 2430, 2430n, 2430tn, 2430dtn series of LaserJet printers, as well as the Color LaserJet 3600, 3600n, and 3800n printers.

Although The Printer Works’ standard stocking unit items are all pre-programmed to be the same as new boards from HP, The Printer Works can provide whatever replacement boards and programming services are needed to solve the model setting problems that may have resulted from board swapping or hardware failure. Consult with our sales department for special-order, pre-programmed versions.

For the purposes of recovering inadvertently lost model settings, boards can also be sent to our repair depot in Hayward, CA, and for a fee we will reprogram the settings to become the model needed.