Heathkit Audio Sine-Square Wave Generator
model AO-1U

AUDIO SINE-SQUARE WAVE GENERATOR KIT
This is an inexpensive generator which covers 20 Hz-150 kHz with choice of sine or square waves-the latter to 50kHz.

Output voltages ranges:
Sine-wave 0-100mV, 0-1V, 0-10V. (Distortion less than 1%).
Square 0-800mV 0-8V, 0-80V.
Power requirements 110/200-250V AC 30W.
Size 9X6X5”.
Marketed as an ideal instrument for checking the fidelity and distortion of audio amplifiers and radio receivers. Judging by the date codes on the capacitors this instrument was made in 1964. I understand from Glyn Jones who gave it to me that it had originally been used in a school.

Top and bottom of chassis

Originally the mains lead would have been connected via a 3pin plug and socket. When received the socket had been removed and a permanent connection had been made and the cable held in place with two plastic cable ties threaded through the four holes. I made a blanking plate for the large hole and fixed the mains cable with a proper clamp.


An additional ECC82 valve and associated components had been added to serve as a cathode follower. The  screened lead which would have been connected to the  coax socket on the front panel can be seen connected to the tag strip.

Back in 1964 you could purchase this oscillator as a kit of parts for 14.75 or factory assembled 21.25.

Daystrom was an American company which manufactured electronic equipment under the Heathkit brand name. They set up UK operations in 1959, Daystrom Ltd in a factory employing about 150 people to manufacture and market British versions of their equipment. The factory was in in Quedgley, Gloucester.