Riso RZ370 thin white line on print. is the thermal head on its way out?

**ivorytower** · 11-13-2011

Hi my RZ370 has started putting a really thin white line down all of my prints its located towards the middle of the master.
The master count is 28,000 if that helps, I have cleaned the thermal head with a soft cloth and isopropyl alcohol and it made no
difference. Am i looking at a new thermal head or is there any other cause / solution for the issue?

If someone could help that would be great!

thanks a lot,
Elliott

**RRodgers** · 11-13-2011

Maybe, have you tried cleaning it? If I remember right we would crank up the tph voltage a tad to help fix this back in the day.

**jermyth** · 11-14-2011

Sounds like the Thermal Print Head, but RRodges is right you can try to increase the TPH voltage up A LITTLE to over come the line, but how long that will last is questionable. You have to enter test modes to adjust the voltage by adjusting the resistance value of the TPH. Do you have a manual to look that up?

**20gaugeO/U** · 11-14-2011

Run the internal checkerboard test print to confirm it isn't optics but more than likely it's just time for a new TPH.

**ivorytower** · 11-15-2011

Thanks for the suggestions, i will try turning up the THP voltage a little, i do have the service manual so i will look its up,
is there anything i need to be wary of doing this?

I will try the checker test prints too.
anyone got an idea on the cost of a new thermal head?
is there a better way of cleaning it than just running a soft cloth and isopropyl alcohol over the strip?

thanks!

**ivorytower** · 11-15-2011

Hello,

So i looked through my manual, my machine is currently set to 1705 ohm and the manual says the range is 1200- 2300 ohm.
how much do you think i should increase it by? or is it a case of trial and error.

i am not sure if this can do any irreversible damage or not?

thanks

**RRodgers** · 11-15-2011

Yes if you crank it too much you will kill it. Go in VERY SMALL steps. I would think less ohms means more current so maybe drop it down. On the old boxes I think you actually played with the voltage and it would step up in .5v (it's been a REALLY long time since I've done this) I'm sure someone else can chime in to clarify.

**ivorytower** · 11-15-2011

thanks for that i will wait for clarification, i don't want to damage it.
once the thermal head shows one line does it soon follow with other?

**20gaugeO/U** · 11-15-2011

Soft cloth and alcohol is the only way I have ever cleaned them. Once that segment is burned out, it's gone.
If I remember right increasing the resistance value in TM darkens the image. It's been a while since I did it at a customers request but I think that the direction I had to go to darken it. I don't think you'll see any changes until you adjust at least 25 ohms....I think I left that customers at +100 per their request but I told them it could/would shorten it's life. But if your TPH is already damaged.... you aren't going to hurt the rest of the machine in doing this.

However, the TPH for a RZ 370 is pricey ($$ Like they have always been $$).

**jermyth** · 11-15-2011

You can check what the voltage is in TM 524, displays TPH voltage. Then adjust the resistance in TM 1234 and recheck with TM 524. And record what the orginal Resistance is just in case. It is also on the TPH.