TRIO SG-402

[oli44]

Hi, just acquired a TRIO SG-402 up to 30MHz Sig generator but my question is what kind of mod do I need to apply to it to transform it into a sweep generator??? Any detailed answer is highly appreciated tnx.

PS. I could do with the service manual PDF but as I.m new here is out of reach @ the moment.

[ppppenguin]

Welcome to GVR.

I've looked at the scheamtic in the GVR archive and I don't think there's any plausible way to make this generator do sweeping.

What are you doing that needs a sweep generator?

[pamphonica]

Welcome also.
If you really need sweeping, I would experiment by adding a variable capacitance diode across the main frequency-setting capacitor VC1, fed with a ramp waveform via an RF choke . Maybe add a cap in series withe the varicap so the DC cannot upset the FET oscillator bias.
You probably only need a few 10s of pF swing on the varicap diode if you are for instance sweeping a 465KHz IF by 10KHz or so. You would obviously need to make a ramp generator to produce the necessary voltage sweep across the diode.
Be prepared for modern varicaps to be absolutely tiny, surface mount devices. Best soldered carefully to something like a tiny scrap of veroboard with wire tails as they won't take repeated soldering and desoldering .
Have fun!
Jeremy