These are the further checks I have now made.
With the attenuator set to 100mV, output un-terminated, frequency set to band F at 200KHz, and connected to the scope by a 50 Ohm BNC cable, the output voltage is 1V.
I then connected the generator output to an Advance TP1B pad and the pad output to the scope, using 50 Ohm BNC cables.
With the pad set to 37 Ohm the output is 400mV, when set to 10 Ohm or DA the output is 40mV.
The pad is working correctly. (The TP1B is one I built myself)
The output of the generator is giving an output that is high by a factor of x 4. This is a problem as it makes the attenuator calibration meaningless.
I then continued as follows:
Leaving the generator set to band F at 200KHz (the midpoint) and switching through the bands in order of F to A we get the results that band F is 400mV whilst bands E to A rise to 500mv.
Changing band F to 100KHz (Low end) we get the following:
Band F 400mV
Band E rises to 500mV
Band D falls to 350mV as do bands C & B
Band A falls to 130mV
Diversion:
The Tek 465B scope suddenly had a very bright and large spot dancing on the screen that then vanished, smoke was issued from the L. H. side, I switched off.
I left it off for a while, then chanced turning it back on fully expecting more smoke, but no, it worked quite normally?!! Needs to be investigated.
To continue:
Repeating the same process but with band F at 300KHz (High end) we had the following results:
Band F 400mV
Band E increasing to 500mV
Band D increasing to 540mV
Band C increasing to 500mV
Band B remaining at 400mV
Band A falling to 260mV at 90MHz
The Tek 464B scope is still working fine.
I then stripped out the attenuator and checked the resistor values that all seemed to be OK.
However this switch was nothing like the circuit that I have as it consists of a 2 pole 5 way device.
3 poles on each wafer are bridged out by wire links.
The circuit shows this switch as a single pole 5 position device, why a 2 pole with poles bridged out?
Also resistor values are in some cases different to the circuit I have.
I can’t imagine this came out of the factory as it is now, with the output voltage being 4 x that as indicated.
Regards,
Dave