Hp3314a function generator front panel display not working

Hp3314a function generator front panel display not working. So i checked the rail voltages. I hv when all other boards are unplugged +15 -15 +5 volts rails showing correct voltages across the cap on +24 v rail i hv +31 volts and across the cap on -24v rail -32 volts and the led comes on on the board. However when plugging in the other boards the voltages drop and the led does not light also no readout on the front panel the voltages show +15v = 11 v -15v = -1 v +5v = 0.5 v across cap on -24v rail = 0 v and across cap on +25v rail = +30 volts… could you help where i need to check whats causing this please
 
It sounds like supply rail short. I would start with replacing all Tantalum capacitors, they have a tendency to fail short, if that doesn’t fix it then I would check the temperature of the parts to see which ones are getting warm.