Platen Heater Overheating

[Colinm]

Hi,

We've developed a problem on our vj1614 where the left side of the platen heater will heat up and not turn off. Eventually the machine will throw up a 077 error which I think is due to the machine overheating. It gets so hot that you can't touch it!

The strange thing is the machine doesn't need to be turned on for the heater to start, only plugged in which I'm guessing is now a fairly major fire risk. Lucky we were around when it started.

I've taken off the platen heater and disconnected the thermistor, plugged the machine back in and again it continues to heat up.

Has anyone any idea what the issue could be?

Thanks

Colin

 

[Bradley Signs]

It's getting so hot you can't touch it? Then there must be a problem.

 

[solock]

Hi,

We've developed a problem on our vj1614 where the left side of the platen heater will heat up and not turn off. Eventually the machine will throw up a 077 error which I think is due to the machine overheating. It gets so hot that you can't touch it!

The strange thing is the machine doesn't need to be turned on for the heater to start, only plugged in which I'm guessing is now a fairly major fire risk. Lucky we were around when it started.

I've taken off the platen heater and disconnected the thermistor, plugged the machine back in and again it continues to heat up.

Has anyone any idea what the issue could be?

Thanks

Colin

the symptom would be a failed solid state relay. Not sure if they are discrete components on that printer or are on a PCB power board, but an SSR can fail full wave on and its like a stuck switch. Usual design of a failed open or shorted thermistor is to power off the heater relay, so SSR sounds like the culprit.

 

[Solventinkjet]

The thermistor could still be bad. Try switching it with one you know is working and see if the problem moves. All the thermistor does is change resistance due to heat. If you unplug it, the resistance doesn't change and the machine thinks it needs to keep on heating up.

If you find out the thermistor is good, you probably are going to need to replace the heater relay board and/or the heater control board.

 

[Colinm]

Thanks for the replies.

I think the heater/thermistor is working as I've turned it 180 and the problem stays on the left hand side. There are 2 heaters in the platen, one on the left, one on the right. Turning the heater 180 meant the problem did not stay with the thermistor but stayed with the power supply, so I think it must be an issue with the heater relay board which would match up with your suggestion of a faulty SSR. Is there any way I can tell if a SSR is faulty? If so is it replaceable? I'm out of my depth when it comes to electrical components.

I've found an ebay posting for the same heater relay board which has a good picture. I've also found a heat relay board transistor but can't see where this would go and can't find any reference to it in the maintenance manual.

I've managed to work around it at the moment by disconnecting the power to the problem heater. The printer's back working but it does mean that I'm having to print without any heat on the platen which may cause problems in the future.

 

[randya]

Check to see if the thermocouple has separated from the heater.

 

[Colinm]

Check to see if the thermocouple has separated from the heater.

I don't think there's an issue with that as it looks to still be connected and spinning the platen heater around causes the problem to stay on the left hand side, ie the problem moves to the other thermistor.

I'm thinking it's likely what Solock suggested however I'm not sure how to fix this without replacing the whole board.
As there are 2 heating elements on either side I'm contemplating taking the power from one element on the working side and routing it to an element on the failed side. This would mean I could get an even heat right across the width of the machine. I think this cable should be work. Does anyone see any problems with this?

Thanks

 

[devahoch]

I think, you have a bad heater Relay for thermocouple, This Relay is electric (not electronic) and conntact is still continue, not work when is turn on or off. You need replacing only this, nonecessary to replacing hole board.
This is usualy small black plastic box on the board, if you turn on heater, this make sound "CVAK", you can feel this if you have finger on this. If you don't feel this sound when heater turn on, this bad.
You can take this down, with values on this buy a new Relay and raplace this. I think is cost is cc 2,00eur

 

[Aalekki]

I had a similar problem with VJ1304. The strangest thing was that in my case the relays didn´t click at all. I felt that there weren´t any kind of life on those. But still without the platen heater 1 every other heater worked fine. I would place my bet on the transistor, if your printers show the temps normally. In the heating board what I had, there was a 2 transistors(S202S02) and 2 solid state relays. Platen heaters where “controlled” by transistors. SSR.s were for the pre and after heaters. In my case the problem was exactly the same as you described and when I changed the transistor the problem disappeared. The transistors I am talking about are attached to those heat spreaders. I don´t actually know when those normal relays should click, but in my case they don´t seem to click at all. That is feels to me quite strange, but everything is working as they should be.