View source for 432

{{Oscilloscope Sidebar |manufacturer=Tektronix |designers= |
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=
* [http://bama.edebris.com/download/tek/432/Tek432.pdf Tektronix 432 Manual (PDF)]
* [[Media:Tek 432 and 434 fcp april 1972.pdf|Tektronix 432 and 434 Factory Calibration Procedure, April 1972 (PDF, needs OCR)]]
}}
The '''Tektronix 432''' is a 25 MHz dual-trace portable solid-state oscilloscope.  

There is also a rack-mount version, the R432.  

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).

The vertical and horizontal output amplifiers are fully discrete, using silicon bipolar transistors.

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

The 432 consumes 55 watts maximum and weighs 20 pounds.

P31 [[phosphor]] was standard.  P7 was also available.

==Specifications==
[[Category:Specifications needed]]''please add''

==Links==
* Ken Matheson, ''Servicing the 432/434 Oscilloscopes''. In [[Media:Tekscope 1972 V4 N5 Sep 1972.pdf|Tekscope Vol. 4 No. 5, 1972]]
* [[050-0674-00|Handle Replacement Modification Kit]]

==Pictures==
<gallery>
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. 
</gallery>

[[Category:400 series scopes]]
[[Category:Specifications needed]]