Odd Goodwill Function Generator Find

Stillhouse

Stillhouse

Well-Known Member
Made a buzz through my nearest GW today and saw a BK Precision 3011B Function Generator on a rack. My curiosity got the better of me and I took a look. Came with a brown cloth carry bag in which were the test probes, with some odd moddifications: Two metal plates were wired to them. Curiosity going bonkers, I pulled the unit itself out and noticed some paperwork, old printed pages from 1990 describing "electro-magnetic therapy" and a list of ailments and their prescribed frequencies for treatment, among other instructions. For $5.99 I couldn't resist taking such an odd piece home and I could have a use for it in the future. I gave it a good disinfecting with rubbing alcohol before fiddling around with it. No telling what it's been subjected to. :eek
 
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Be careful! A friend gave me a B&K 4011. After I restored it, I used it with a direct-coupled power amp. The 4011 had DC offset and would not lower the signal voltage to zero. Because of the DC offset, I melted the speaker protection relay since the restored amp worked like a power Op amp and output enough DC through the relay contacts to cause overheating. After I discovered the 4011 DC offset issue, I used another sig gen to complete testing with no damage or issues with the amp, but I had to replace the relay.

If you have the same issue with DC offset and cannot lower the output signal to zero, consider building an add-on box with BNC cables. The box would simply have a 2.2uF film cap in series with the output to block DC and a 50K control so the output can be dialed to zero.
 
So.... very..... weird. The previous owner did some other mods to the unit itself, consisting of removing one of the BNCs from the front, replacing it with a toggle switch(labeled HI/ LO) which is wired to a second transformer at the back of the unit. Apparently to raise the output to a level that could be felt by the unfortunate "patient" through the metal plates on the probes. The instructions sound like pure snakeoil and have settings prescribed for everything from cancer to "puffy gums."
 
Indeed, restoring it will be no problem. As it was modified, the output connector was only delivering a low voltage via the "HI/LO" switch from the added transformer. Nothing from the actual unit itself was going through the output AT ALL! Essentially someone took this and turned it into a glorified joy buzzer. The "patient" gets a slight buzz in their feet through the metal plates, with the rest of the unit serving as nothing more than some dials, buttons and a frequency readout to add to the supposed efficacy of the treatment. Damn thing could've done more harm than good.
 
Sounds like somebody (maybe Tim Allen - more power) modified it for TENS treatment. Foot plates suggest it might have been used for diabetic nerve pain. A very interesting GW find indeed.
 
Yeah, it does function similarly to a TENS device, except that the instructions that were with it called for the plates to be placed in a small tub or basin of water and then the person's feet went on top of the plates. Again, it's a wonder no one was harmed by this modded device.

Undoing the changes were as simple as unsoldering two wires going off the switch onto the output connector and resoldering the original ones that had been taped off to the side. And what soldering WAS done by the previous owner was the poorest job, took just the shortest touch from my iron and the conncetions came free with no effort.
 
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