Author Topic: Wavetek 116 VCG function generator teardown photos  (Read 3790 times)

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Offline radioFlash

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Wavetek 116 VCG function generator teardown photos
« on: December 23, 2014, 03:26:28 pm »
I picked up a Wavetek 116 that was sold as not working. I replaced the output ground binding post, which had broken off, and the BNC jacks which had corroded. It generates signals, although there is a noticeable ringing in the signal. I'm not sure if this is because I haven't properly terminated the output--I've just connected the output to the scope probes.

The schematics in the manual are dated around 1966. Some components seem to have date codes around 1968, although some other components seem to have date codes around 1987/88. It could be that it was refurbished or repaired sometime in the 80's.

The inside top of the case had a strip of foam to cushion the boards in place, but the foam disintegrated which is what the black dust on the boards is.

The mechanical construction is interesting. There are four hexagonal bars with grooves cutout that run from front to back which hold the boards in position.

Frequency Range: .005 Hz to 1 MHz (mine actually tops out at around 800 kHz)
Signals: Sine, Square, triangle, ramp

Manual: http://bitsavers.informatik.uni-stuttgart.de/pdf/wavetek/112_115_116_Oct69.pdf
« Last Edit: December 23, 2014, 03:43:24 pm by radioFlash »
 

Offline radioFlash

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Re: Wavetek 116 VCG function generator teardown photos
« Reply #1 on: December 23, 2014, 03:36:10 pm »
Photos of the front panel, sub panel, main, trigger, and VCG boards.
 

Offline radioFlash

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Re: Wavetek 116 VCG function generator teardown photos
« Reply #2 on: December 23, 2014, 03:38:32 pm »
Photos of the power supply, output panel, and motherboard.
 

Offline radioFlash

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Re: Wavetek 116 VCG function generator teardown photos
« Reply #3 on: December 23, 2014, 03:39:46 pm »
And some sample output signals.
 

Offline c4757p

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Re: Wavetek 116 VCG function generator teardown photos
« Reply #4 on: December 23, 2014, 03:42:32 pm »
Wow, look at the ringing in the sine and triangle!!

No, that's not because you've not terminated it. Something's funny in the generator, probably around the current steering network (assuming it works like most analog function generators; I haven't looked at the schematics).
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Offline krivx

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Re: Wavetek 116 VCG function generator teardown photos
« Reply #5 on: December 23, 2014, 04:22:50 pm »
It almost looks like clock noise - could the square output be pulling hard on the power supply during transitions?
 

Online SeanB

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Re: Wavetek 116 VCG function generator teardown photos
« Reply #6 on: December 23, 2014, 04:35:21 pm »
Probably the decoupling capacitors on the 6V rail have died, and seeing as there are only 2 100uF capacitors that have to do this work a replacement will solve the noise issue. Replacing all the electrolytic capacitors in this will be a good idea as well.
 

Offline radioFlash

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Re: Wavetek 116 VCG function generator teardown photos
« Reply #7 on: December 28, 2014, 02:57:24 am »
I've now replaced the electrolytics on the power supply rails. The noise/ringing is smaller in amplitude but still quite obvious. The pulled caps all measured fine. Here are the before and after traces for a 500 kHz sin and square wave.
« Last Edit: December 28, 2014, 03:01:38 am by radioFlash »
 


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