Welcome to
Azur Electronics

September 2019

The HP 180A Oscilloscope on initial testing indicated a fault with the triggering not operational and Channel B Attenuator is intermittant.

Cleaning all the switches with switch cleaner solved the intermittancy.

The HP 1821A is located at the bottom right hand side of the case. The side cover is easy to remove as it is just held on with 2 latches. Access to the pcb is a bit restricted. There is a HP 10407A Plug-In Extender, but I don't have it, probably very rare.

Testing the Triggering PCB
Checked the +100V, -100V, +15V and -12.6V power supplies first and all ok.

Checking through the circuit with an external trigger source connected showed that the trigger comparator Q104 & Q105 was not switching the tunnel diode CR106. Fortunately Q105 was faulty (a 2N3904 NPN) rather than the tunnel diode and was replaced. The 2 Plug-In units are easy to extract from the 180A Mainframe, although soldering has to be done from the component side.

Tested the triggering and now working correctly.

Calibrate signal, normal sweep, internal triggered, +ve slope, dc coupled,
main (left) and mixed (right) displays 
External signal, normal sweep, external triggered,
+ve slope (left), -ve slope (right), dc coupled, displays 
External signal, normal sweep, external triggered,
+ve slope, dc coupled, mixed timebase (left) display
and 100MHz, magnifier x10, main timebase (right) display
Completed performance tests and adjustments.