HP-65 and HP-67 card reader how to test the amplifier ?

[albertofenini]

Hi everyone,

this was my setup :

the head was disconnected from the card reader except for the ground cable which was connected

the head cables red and yellow connected to the scope : positive of the scope to the red cable
and ground (negative of the probe) to the yellow

the scope settings are as follow :200micro Seconds and 500milliVolts

However, when a card goes thru nothing come on the screen,

What I'm doing wrong ?

The idea is to check what comes out from the magnetic head when a card is read

Updated photos here : HP-65 and HP.67 card reader photo album updated