432: Difference between revisions

{{Oscilloscope Sidebar

|series=400-series scopes

|model=432

|summary=25 MHz dual trace portable scope

|image=Tek 432 trace.jpg

|caption=Tektronix 432

|introduced=1971

|discontinued=(?)

|manuals=

* [[Media:070-1103-00.pdf|Tektronix 432 Manual]]

* [[Media:070-1104-00.pdf|Tektronix 432 Operators Handbook]]

* [[Media:Tek 432 and 434 fcp april 1972.pdf|Tektronix 432 and 434 Factory Calibration Procedure, April 1972]]

Each 432 vertical signal path starts with the coupling switch, then a [[rotary cam attenuator]], then a dual-JFET source-follower  

buffer amp, then a [[155-0050-00]] differential amplifier (switched to [[155-0050-01]] after serial number B239999).

Triggering is done by a 4.7 mA [[tunnel diode]] that is fed by a discrete trigger amplifier.

 

==Links==

* [[050-0674-00|Handle Replacement Modification Kit]]

 

 

Tek 432 1.jpg

Tek 432 2.jpg

Tek 432 3.jpg

Tek_432_internal_1.jpg|This shows the area around the BNC input connectors for channels 1 and 2.  This photo was taken when the owner was cleaning the vertical gain rotary switches which had become flaky after 45 years.

Tek_432_internal_2.jpg|View from the rear.  The vertical gain attenuator switches are under the metal covers.

Tek_432_internal_3.jpg|When the metal covers are removed, one can see the shaping/compensation capacitors.  These can be unplugged, each one has 6 legs.

Tek_432_internal_4.jpg|Another view of the shaping capacitors.  Work on one channel at a time to avoid mixing these up. Carefully clean the legs with isopropal alcohol and paper towels. 

Tek_432_internal_5.jpg|In order to access the rotary gain switch fingers, one must first remove these BNC connectors, which means unsoldering the central wire (connects to a resistor/inductor feed-through) plus a debouce capacitor and lead going to the x1 x10 indicator lights.

Tek_432_internal_6.jpg|Close up view of BNCs

Tek_432_internal_7.jpg|Close up view of BNCs

Tek_432_internal_8.jpg|Close up view of BNCs.  These need to be unsoldered for removal, but nothing else must be unsoldered to access/clean the vertical gain rotary switch.

Tek_432_internal_9.jpg|View of the input preamp.  This board needs to be unplugged only, but not removed or unsoldered.  It has four 2-pin connectors.  Then it can be removed, still attached to the compensation capacitor carriers.

Tek_432_internal_10.jpg|Lifting off the assembly consisting of the 2 compensation capacitor carrier  plus the vertical preamp board  plus the  push-button switch board for CH1/CHOP/ALTERNATE/CH2.  The switch board has two plug connectors below that must be removed.  It helps to have long fingers or a good pair of needle nose pliers.

Tek_432_internal_11.jpg|Second view under the assembly being removed.

Tek_432_internal_12.jpg|The rotary switches exposed. Each one has four contact fingers underneath.  They are cleaned using small (5mm) wide strips of paper soaked in isopropanol alcohol (2-propanol).

Tek_432_internal_13.jpg|One can just see the four contact fingers peeking out.  You can get paper under them using small tweezers.  Patience and calm are required.

Tek_432_internal_14.jpg|A view of the variable-gain potentiometers. Note that the bodies are both cracked in the same place.  Both had been noisy, but the noise was largely eliminated by sweeping them back and forth a dozen times.  That may have scrubbed off the oxide.

Tek_432_internal_15.jpg|A view of the contact fingers underneath the capacitor shaping blocks.  Each channel has 8 NC and 8 NO fingers (the other half are on the bottom).  These are easy to reach and clean as described.  So each channel has a total of 20 contact fingers to clean.