MPC2800 SC542 Error

**Masterx81** · 03-28-2019

Hi, i have an MP C2800 that give me the SC542 error. I've reset it but it came back every time.
I've checked the thermistors and are ok (3 sensors at around 200kohm at ambient temp, lowering when heated - ntc). I've checked resistance of the lamps and is correct for both the double one and for the single one. I've checked on the psu unit connector cn902 (the one that goes to the fuser unit) and at power-on i see 220v only on 2 lamps out of 3 (the single one is not turned on). The triac is good, is the logic board that not turn on the lamp.
It's normal that only 2 lamps (of one roller) are heated at power on?

Tomorrow i measure the current absorbed by both lamps to check if both are healty, and maybe temperture of the fusing unit...

Someone have some idea? Thanks!

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**slimslob** · 03-28-2019

I noticed that you did not mention the thermostats/thermo fuses. They cause most recurring problems because the SC table does not mention them therefore most inexperienced techs don't think of them. You can check them with an ohm/continuity meter. If on reads open you can bypass it while you wait for a new one.

**Masterx81** · 03-28-2019

Originally Posted by slimslob

I noticed that you did not mention the thermostats/thermo fuses. They cause most recurring problems because the SC table does not mention them therefore most inexperienced techs don't think of them. You can check them with an ohm/continuity meter. If on reads open you can bypass it while you wait for a new one.

Forgot to say, already checked them (3 in the fuser unit) and are all at 0 ohms when cold. They are in series at the lamps.
Tomorrow measuring the absorbed current i can see if one of them open too early. Thanks for the suggestion!

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**GIUBOSS** · 03-28-2019

hi, if the belt is deformed or shows signs of damage, it may not constantly and uniformly contact the thermistors. Thermostats usually do not give problems if they give continuity. I would do a firmware update and in any case the 3 thermistors if old replace them. A look also at the electric line.

**Masterx81** · 03-28-2019

Originally Posted by GIUBOSS

hi, if the belt is deformed or shows signs of damage, it may not constantly and uniformly contact the thermistors. Thermostats usually do not give problems if they give continuity. I would do a firmware update and in any case the 3 thermistors if old replace them. A look also at the electric line.

Fuser belt and pressure roller are new. Copier has near 300k pages printed.
The 3 ntc sensors give the same readings, also the one more distant (less stressed), i suspect that is an ambient temp sensor, so i suppose that are ok.
I've measured with a typek sensor the temperature on the surface between the 2 rollers (where the paper exit) and at first power on not reach 80°c, after few tries it go at around 140°c and not go any higher.
I've measured the current flowing to the lamps, and the voltage across them. The current is 2.23a on one lamp (at 220v are 512w), and the other one is 3.09a (at 230v are 710w). The 2 lamps are rated 460w and 640w at 220v. My measurements are a bit higher as here i have near 230v vs the 220v rated.
The tension at the lamps is ok, 230v as the line.
The strange thing is that out of 3 lamps in 2 rollers, only the 2 lamps on the same roller are lit at power on/warm up. I've checked the opto before the scr, and the npn transistor that drive it, all ok, so it's really the logic board to not lit the third lamp (0v at the base of the transistor). I will check if maybe the wire isn't interrupted between boards.
I want also try to update the firmware... but i not know where find them

Thanks all for the support!

**mikadonovan** · 03-28-2019

The machine can give you the actual temps in SP mode, no need take manual temperature readings. You probably need new thermistors.

**MIGUELMARCHENA** · 03-28-2019

Hi good dayAs you have already indicated, I would change the thermistor

**Masterx81** · 03-28-2019

Wow, missed the menu 1-106! The reading from the 1-106-1 (fusing:center) is erratic and not stable, jump a lot (but the resistance measurement of the thermistors was rock solid). The other 2 readings are stable. What sensor refer that reading?
---EDIT---
Found something that seem an ir temperature sensor (mounted under the paper out mechanism) pointing on the center of fuser belt... I suppose that it's the faulty one?
It's called a "thermopile" on service manuals...
---EDIT2---
Disconnecting the sensor from the wiring stop the reading to -20 fixed, so i think that i need to order this sensor. Tried to clean the lens without effect, so it's gone...

**slimslob** · 03-28-2019

Originally Posted by Masterx81

Wow, missed the menu 1-106! The reading from the 1-106-1 (fusing:center) is erratic and not stable, jump a lot (but the resistance measurement of the thermistors was rock solid). The other 2 readings are stable. What sensor refer that reading?
---EDIT---
Found something that seem an ir temperature sensor (mounted under the paper out mechanism) pointing on the center of fuser belt... I suppose that it's the faulty one?
It's called a "thermopile" on service manuals...
---EDIT2---
Disconnecting the sensor from the wiring stop the reading to -20 fixed, so i think that i need to order this sensor. Tried to clean the lens without effect, so it's gone...

That is the main temperature sensor. All thermistors are secondary.