The sample, calibration square wave of an old oscilloscope is operational, but shows spikes and reduced amplitude. I suspect that the input resistor is fried. I seem to remember the standard impedance was 1 Meg ohm and that the ersistor is in parallel with a capacitor. Any chance someone will sahke my memory and tell me the the general value? IT has been 20 years and I need more than just a pair of new glasses to go behind the case screw. Trace "A" works fine. I am not too lazy to look, just want to know if the symtoms put me in the ballpark. Thanks! I'm new here so please forgive my lack of 'smarts.'