Tektronix 2235 oscilloscope

The Tektronix 2235 is a 100 MHz dual-trace, dual-timebase portable scope.
Tektronix 2235 has two channels and delayed sweep.

This is still a pretty decent analogue oscilloscope (if you are looking for an analogue oscilloscope) with Large, Bright CRT screen. This oscilloscope has the U shaped handle that has detents which allow it to double as a stand.

Tektronix 2235 100 mhz Oscilloscope- When Only Analog will do….

The manufacturing of this scope model started around 1983 by Tektronix, Inc. In 1984 the price was $1,650 ($4,300 in 2021 dollars). It was also sold to the military under the model name AN/USM-488.

It was then advertised with features like: Tektronix 2235 ensures measurement quality and reliability while reducing instrument cost. Tek started with the innovative architecture of the 2200 Series: fewer boards, fewer mechanical parts, less cabling and electrical connectors. This approach, plus advanced circuit design and a focus on essential features, has led to a scope that is more accurate, more reliable, lighter and more serviceable-and simpler to use-than any other 100 MHz scope. Features like rugged design, light weight and easily learned front panel make the 2235 an ideal service scope.

The 2235 delivers 2% vertical and horizontal accuracy in normal operation. Accuracy of 3% or better is maintained across a wide range of environmental extremes.

This oscilloscope has 100 MHz bandwidth, which is a quite good bandwidth and also the vertical voltage goes down to 2m volt. With oscilloscopes like these, Tektronix specifies the bandwidth at the probe tip when the proper probe is used. The quoted bandwidth is given at -3dB (http://www.ens-lyon.fr/DSM/AGREG-Physique/oral/Notices/N036-003.pdf) to be (at least) 100 Mhz from 5mV to 5V/div and 90 Mhz at 2 mV/div… And it also deacreses by 10 Mhz when the ambient temperature rises above 35 degrees celsius. If you can accept some measurements errors, you can do some measurements event at higher frequencies. The 2235′s 100 MHz will cover enough above and beyond 108 MHz if you have probes that will go well above 100 MHz.

The input capacitance of this oscilloscope is around 20 pF.

You also get delayed sweep with the 2235. Delayed sweep is a technique that adds a precise amount of time between the trigger point and the beginning of the scope sweep. When the scope is being used in the sweep mode, the start of the horizontal sweep can be delayed. In some applications it can be useful, but you probably won’t end up using much.

The calibration adjustment are done with pots, that can change their position slightly due to mechanical vibrations for example. Service manual is still available on-line.

Manuals:

2235 Oscilloscope Operators Instruction Manual
https://www.tek.com/en/oscilloscope/2235-manual/2235

2235 Service Manual
This manual contains information to check performance, adjust, and service the 2235 oscilloscope.
https://www.tek.com/en/oscilloscope/manual/2235-service-manual

Tek Wiki 2235
https://w140.com/tekwiki/wiki/2235

Videos:
Tektronix 2235 – 100Mhz Dual Trace, Dual Time Base Oscilloscope
Affordable Portables Tektronix 2200 Series Oscilloscopes 1986
Tektronix AN/USM-488 2235 Oscilloscope repair and calibration 1 of 7
Tektronix AN/USM-488 2235 Oscilloscope repair and calibration 4 of 7

Links to sources and more material:
https://www.computerhistory.org/collections/catalog/102733015
https://www.eevblog.com/forum/testgear/tektronix-2235/
http://www.linear.com/docs/4138
http://circuitslab.case.edu/manuals/Probe_Fundamentals-_Tektronix.pdf
https://www.antiqueradios.com/forums/viewtopic.php?t=147362
https://www.testequipmentdepot.com/usedequipment/tektronix/oscilloscopes/tek2235&2236.htm
https://accusrc.com/product-Tektronix-2235-3929