Early Tektronix products are great examples of hand crafted electronics made in USA. Their versatility and superior abilities over their competition makes them complex instruments to service and restore. Marketed in 1960, the Tektronix 321 was the first transistorized and truly portable oscilloscope since it can operate on batteries also. The operating bandwidth of the scope was 6 MHz, which was average in those days. The vertical front end amplifier had one tube, a Nuvistor by RCA so it really was a hybrid. The 321 would be replaced by the 321A . The 321A had improved circuitry and eliminated the Nuvistor tube with a new transistor called the Field Effect Transistor or FET in 1964.
Article is on The Tektronix 321 Serial Number 2149. Later productions made changes to the cabinet and went to a round CRT bezel over the rectangular one shown. Some panel changes were made to the charging switch and knobs for vertical input and time base selector. Incremental circuit changes were done thoughout the model run including newer and improved transistors.
REPAIR date May 2015
I own two Tektronix 321's and a 321A. The 321A is totally transistorized. Most of the transistors used are germanium type as silicon transistors were not widely available. Two of these oscilloscopes had no sweep and displayed a dot on the CRT face. This failure could lead to a CRT face burn if the intensity is too high. Repairing Tektronix products can be difficult because of the complex circuitry that provides the high performance offered. This scope has been in storage for many years and when things really settled down it was time to take it on.Here are some interior views of the Tektronix 321:
1. The CRT- Tektronix designed and built their own cathode ray tubes for consistency and highest performance.
3. Tektronix 321 S/N 2149 Calibrated and Functioning Again 4. Two versions of the 321. The left is the earliest model
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