[Misc] E Studio 350 fuser heater question

[cooked]

Hi,

I have a E Studio 350 which has been in service for a number of years and has had few problems until now.

The unit stopped with a C440 error.

I have removed the fuser, checked the two sensors (resistance drops when sensor is heated with heat blow gun) checked the external thermostat (showing close to zero ohms. this is the big one mounted on a white plastic carrier midway down the roller).

It appears that the heater is not being regulated. My question is... does the heater element (This is a heater element not a light) have a internal thermostat built in or is the heater being controlled from external circuit using the edge sensors.?

I either have a heater fault or a board fault somewhere.

Any help appreciated.

I know this is a old machine which we would like to keep going if possible.

The other part to this is that there are scanned documents on the HDD which we would like to get off. The network does not initiate while this fault exists. Help here would be appreciated.

Thanks

Doug.

[Ropariva]

Re: E Studio 350 fuser heater question

Hi Doug, you will need to reset the soft switch through 08-400. Reset this back to 0 and try again. Often power fluctuations can cause this to "trip". It is a safety feature built into many different brands to prevent major meltdowns in the fuser area. Al

[riyadh hossainbd]

Re: E Studio 350 fuser heater question

make sure voltage continuity is ok, then change OEM Thermistor

[cooked]

Re: E Studio 350 fuser heater question

Hi Doug, you will need to reset the soft switch through 08-400. Reset this back to 0 and try again. Often power fluctuations can cause this to "trip". It is a safety feature built into many different brands to prevent major meltdowns in the fuser area. Al

Thanks,

I have done this a number of times after taking the fuser out and checking or rechecking. The result is always the same, machine goes through the motions of starting up then stops with the service spanner and error code C440. 08-400 shows 9.

Doug

[Ropariva]

Re: E Studio 350 fuser heater question

Hi Doug, is the Fuser getting hot at all? If it's heating up after the 08-400 reset then your issue is the thermistors. No heat means the lamp or thermo fuses have failed. Al

[cooked]

Re: E Studio 350 fuser heater question

make sure voltage continuity is ok, then change OEM Thermistor

AC voltage has to be present otherwise the heater would not heat up. I assume the large thermistor in the middle is what you refer to as the OEM thermistor. This is zero ohms. My research shows that this is a one time only device which opens on over temp >250C obviously to cut the power before the unit catches fire.

If this is not what you are referring to, please advise further.

Doug

[Ropariva]

Re: E Studio 350 fuser heater question

Just checked, the 9 indicates the thermistors have detected an over heat situation.

[Ropariva]

Re: E Studio 350 fuser heater question

So....it's getting hot?, or just warm? The thermistors are the flat (usually orange) tabs that sit on the surface of the roller. These are very fragile and even cleaning them can break them. The large round device is the temperature thermostat. It's a bi metallic disc that can be reset by putting in the freezer then banging hard on a desk. If the Fuser was really getting to the high temperature indicated by the error 9, then this should have tripped. Faulty thermistor or thermistors will most likely be the problem. If you have spares change them.

[cooked]

Re: E Studio 350 fuser heater question

Hi Doug, is the Fuser getting hot at all? If it's heating up after the 08-400 reset then your issue is the thermistors. No heat means the lamp or thermo fuses have failed. Al

Yes the fuser is heating up. It is getting too hot. Hence my question as to how the heat element is being controlled. If the thermistor/thermostat is part of the heat element, then my fault is in the heater itself. I have taken it out and cannot see any devices although it is hard to see as the heater element is tightly wound resistance/heater wire.

I have taken the edge sensors off and tested the impedance while applying heat from a blow gun. the impedance drops relative to the heat which is what I expect to see.

If the heater is being controlled from a external pcb, then I need to find that board and check it out further. The manuals don't have circuit diagrams so if it is a pcb fault I will have to put my huntron tracker across it to try to identify the faulty component. I am not sure which pcb is involved or where it is located.

Doug.

[Ropariva]

Re: E Studio 350 fuser heater question

There are two thermistors on the fuser. An edge thermistors and a centre thermistor. The error 9 indicates either of these has detected an over temperature. So it looks as you say to be the control of the IH (induction heating) coil. There is no control itself in the coil. The coil is connected directly to the IH board which is switched by the logic board. I would suspect the IH board is permanently on. It is less likely to be the logic board.

[cooked]

Re: E Studio 350 fuser heater question

There are two thermistors on the fuser. An edge thermistors and a centre thermistor. The error 9 indicates either of these has detected an over temperature. So it looks as you say to be the control of the IH (induction heating) coil. There is no control itself in the coil. The coil is connected directly to the IH board which is switched by the logic board. I would suspect the IH board is permanently on. It is less likely to be the logic board.

Just to add to confusion...

The heater element is not permanently on. It is only turned on when it is required. for example if the side door is open the heater is not on. It just seems that when it is on, it is not being regulated.

So the edge sensors are working. ( The machine is detecting over temp from them ) They must go to a board ( possibly the IH board ?) where they help with the heater regulation. It could be that there is a problem there. Where is the IH board located.?

Doug.

[Ropariva]

Re: E Studio 350 fuser heater question

There are safety mechanisms in the Toshies that cut the 24v rail and therefore all high voltage including feed to the IH coil. Any of the doors opened will cut the power to the IH.
The IH board is directly behind the Fuser unit

If you can check that there is power permanently to the IH coil from turn on to machine fail, then I think your board is faulty.

[blackcat4866]

Re: E Studio 350 fuser heater question

On these old beasts you can have the white sheath worn through, shorting the heater to the roller. If you find the short you need to change the heater and IH board together. =^..^=

[Ropariva]

Re: E Studio 350 fuser heater question

That's absolutely correct. Seems the board and coil are ok in this one, just not switching off. If the coil had shorted there is usually obvious splatter marks and the board will also be dead.

[cooked]

Re: E Studio 350 fuser heater question

Hi all, Update on problem.

I checked the IH board with Huntron and found nothing that would indicate a problem.

This turned my attention back to the sensors. I had previously eliminated them because the impedance dropped with heat which I was expecting. I spliced in some old sensors from a E 351C (and modified the mount to fit), The result was that the heater was being regulated, all be it at a temperature that was too low for proper fusing. This definitely eliminated the IH board and pointed the problem back to the sensors.

I have since ordered and received (took over 2 weeks to arrive in NZ) a set of sensors which has cured the problem.

It appears that the sensors must have gone slightly resistive. The resistance of the original sensors were about 800K when cold. The new sensors where just over 1 M ohms.

Thanks all for the help.