Tenma 72-5016 Function Generator Help

[Tom]

I bought a used Tenma 72-5016 5-MHz sweep function generator, and I
can't get it to output positive voltages. All waveforms that it
generates clip at zero volts with the positive part missing. No
matter how I adjust the aplitude or DC offset, it still does this.
For example if I generate a sine wave with no DC offset, only the
negative half is present.

Does anyone have any idea what the problem is?

Thanks for any responses!

 

[Matt J. McCullar]

I'm only guessing, but it could be one of a couple of things.

Let's assume that the oscillator circuitry is working fine. Something tells
me that if it was fouling up, you wouldn't get any output, period, as it
depends on both positive and negative cycles to run.

It's likely that there's something in the final output buffer circuitry
that's acting up. It could be a shorted protection diode, or a faulty
op-amp.

I've seen faulty op-amps in arcade game X/Y video-output motherboards do
things like this: clip off half of the playfield.