October 15, 2008
There are two versions of the 281 Quad Function Generator. I have one of each in my system. The older version has blue PCBs and circuitry for remote control. The newer, yellow PCBs and the "remote" switch does nothing more than turn on the LED. I received this older one as part of a trade, in dysfunctional condition. Just one of the 4 envelopes was working. The panel is beat up, some of the silk screen has come off, presumably from stickers being stuck to it for 30 years. The knobs were discolored and the arrows had worn off. One switch was broken and one was missing.
I replaced the switches and all the knobs. Then, I attacked the circuitry. After some song and dance, I found that the CA3080s on all three and the LF356s on two were not working. The odd part is that 4 out of 5 of these were already in sockets (not all the chips were) and all 5 were metal cans. It seems so much less cool to put in plastic DIP chips, but whatever works. Aren't these bad boys supposed to be MORE robust?
This design has resistor values on the schematic for 15volt systems or 10volt systems. i came to find out that mine is set up for 10volt systems, which makes it match my yellow board version. Anyway, it's nice to have it working.