HP 54601B Channels 2 & 4 "No Active Signal"

[bradyhylla]

Good morning folks, I have an HP 54601B 100MHz 4 Channel scope that wont display a trace on channels 2 and 4.  Both channels will turn on but any function pertaining to the channels such as " Autoscale" yield a dialog "Scope cant find active Signal, Please check connections." 

I've tried different probes but get the same results.  At first I thought it was an operator error but after reading the user/service manual sveral times and trying every setting i can find im still getting the same results.  Google and youtube searches have all lead to dead ends.  The troubleshooting section of the user/service manual suggested checking voltages at a few spots on the board and they were all fairly close to spec.  none of the components on any of the boards looked damaged.  I removed the front pannel and the BNC jacks are all firmly secured. No burnt plastic smells anywhere.  i hear relays clicking when I hit auto scale for those channels but there no different from when i autoscale the working channels. 

Im still not 100% convinced its not and operator error.  Could there be a setting that I overlooked? I'm still quite a newb with scopes and troubleshooting.  Any suggestions are greatly appreciated.  I've been scanning the forum for a while now and looking for answers all over the web but i keep coming to dead ends and beggining to pull hair.

The picture Ive included is with all 4 Channels turned on.  Channels 1 & 2 are both connected to the squarewave gen on the scope, 3 & 4 dont even have probes connected but you can still see that channel 3 will show still shows a trace but chanels 2 & 4 wont, despite being turned on.