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2236 Sudden Tick Mode


Dave Ahrendt
 

Hi all,

I’ve got a 2236 that’s been working for years other than a broken VFD display. I just found a replacement VFD and installed it and now have just a tick at startup.
The scope does about 5-6 ticks and then trails off and becomes silent.

The only thing I did to replace the VFD is to remove the outer case and swing the CTM board out of the way on its hinge. Removed the dead display, installed
the new display and connected its two ribbon cables. Put the CTM back down, installed power cable and hit the power switch.

I know no one can tell exactly what happened but guesses are welcome. Where do you start to troubleshoot tick mode? I’ve been looking it over and don’t see that
anything has come loose or shorted. Think it’s a good idea to remove the CTM board (about 15 connectors) and try without it? I’ve already disconnected the new VFD board.

Dave


Sam Reaves
 

Sound like the power supply is in hiccup start mode where it thinks or has
a short on a power supply. I would first start by checking all of the
supply lines with a ohmmeter to ground.

Sam Reaves
ARS W3OHM
Owner and Moderator of:
LeCroy Owners Group on Groups.io (Current and Future Group)
Electronics and Mechanical Hardware Design Engineering Manager
Andritz Rolls Global Research Center (RETIRED)


tekscopegroup@...
 

Power supply is in self protect mode due probably to some external overload condition.
If no other clear indication of the cause if found, I think the logical step would be to go backtrack and remove the new VFD module and see if that makes any difference.
If it does than you know what is wrong. Otherwise it might be something else you inadvertently caused during the replacement process, and that is hopefully reversible.


Dave Ahrendt
 

Thanks for the tips so far. As of now I’ve narrowed the problem to the 30 volt line to the CTM. It’s used only for two 6118 driver chips to the VFD and a set of three transistors that drive the A segment of the VFD since they ran out of pins on the two driver chips. With the 30 volts isolated from the CTM the scope powers up and behaves like it should. Still baffled as to what I might have done.

It’s too cold in the shop to do anything else today so if I have any power after the ice tonight I’ll continue on tomorrow.