Shenhui Twin Tube Laser- One Tube On Constant

Hi Guys;
I am having a problem with the Shenhui laser- twin 80 watt tubes.
Tube 1 laser power is on continuously, when the Laser switch is on -even when the control swutch is off.
I thought the laser power supply needed an input from the control card in order to fire.
A bit of history
I replaced one of the tubes with a new EFR ZS tube and a new EFR power supply. Input wires to new supply
needed to be changed a bit as plug assignments slightly different.
New tube and power supply work fine
Old tube now fires contantly when Laser power switch is turned- even with control switch off. I'm thinking that
problem may be with control card as signal to turn laser on comes from control card.
A side note: CAUTION: On Shenhui machines, 220VAC is live at HV power supplies even with all switches off
Anyone have an idea what's going on??
Thanks
Best regards
GM Perzel
Laserarts

I would look at the old power supply for the old tube. A constantly firing tube is often a sign of a malfunctioning power supply.

Thanks Doug- good idea
Best regards
GM Perzel
Laserarts

Changed the power supply- still have same problem
Best regards
GM Perzel
Laserarts

I pulled the laser control connector (CN6) from the RDLC320A control card and the problem went away. It appears that the laser trigger signal is stuck on the "on" level.
Will change the control card and advise.
Best regards
GM Perzel
Laserarts

Indeed a bad control card- laser power supply trigger from control card locked in "ON" position.
Best regards
GM Perzel
Laserarts

Good find! http://www.engraver1.com/gifs/thumbsup.gif