Lexmark T64X -- False 927.02 Errors

927.02 is a 'cartridge fan stalled' error. Its likeliest cause is an open 10 ohm resistor, R30.^[1] Lexmark published a bulletin about this saying to replace the System PCA to solve the problem. Doing that certainly does solve the problem, but there's a cheaper way -- solder in a replacement resistor.

Here's a view of R30. It's near the upper front corner of the PCA.

R30 is at the centre of the photo. In the event of a 927.02 error, check R30 with an ohmmeter. It should read 10 ohms or very close to it. A very high reading is a certain indication that R30 is open.

There's no need to remove the defective surface-mount resistor, just solder a replacement conventional resistor in place across R30.

We didn't have any 10 ohm resistors on hand when I went to try this repair, so I had to use two 4.7 ohm resistors in series -- close enough. Here's a view of the completed repair after flux removal with flux solvent.

That board went back into a T644 with two add-on 500-sheet trays, and I ran quite a lot of paper through it with no recurrence of the error. All indications are that this is a sound, legitimate fix.

Soldering Technique

No special equipment is needed for this. I used an old Weller WTCPT soldering station with a TC201T iron and an 800° Fahrenheit tip, like so.

60/40 tin/lead solder works fine. There is one catch -- you have to have suitable liquid or paste flux^[2] so you can apply flux prior to applying heat/solder. Here's how it's done:

a) Cut and shape a resistor's leads A/R to fit in place at the ends of the existing surface- mount resistor.

b) Apply flux to the area of the solder joints.

c) Hold the prepared resistor in place.

d) Load a bit of solder onto the soldering iron's clean tip and apply the solder-bearing tip to one connection point. The flux acts as a very effective heat-transfer medium. It takes only about one, maybe two seconds for the solder to flow and produce the effect seen in the second photo above. Repeat for the remaining connection point and you're done.

It's nice, but not essential, to clean away the flux residue with flux solvent. The residue from proper electronic solder flux is quite benign and will do no harm.

- - -

Notes:

[1] On the resistor it says "100". What that means is "10, with zero zeroes before the decimal point". By that notation, a 100 ohm resistor would be marked "101", 1,000 ohms "102" and so forth.

[2] I still have liquid flux left from my circuit board repair days. The stuff is still available, but it's sold by the gallon. It's Kester No. 1544, Kester P/N 63-0000-1544.

An alternative is Kester's 186 RMA Flux Pen, Kester P/N 83-1000-0186.

Don't use the common paste flux meant for soldering copper pipe. That stuff leaves a corrosive residue.

# # #

FEEDBACK

# # #