Occasionally, I get a loud spark when connecting the ground of the sig gen probe to a radio chassis. What causes this? will the sig gen perform adequately otherwise?

:Occasionally, I get a loud spark when connecting the ground of the sig gen probe to a radio chassis. What causes this? will the sig gen perform adequately otherwise?

Sam,

Is this with all sets - or just some sets? Perhaps it is with AC/DC sets - where the chassis is "live" or "hot" and you are shunting that voltage to ground through the generator> Next time it happens, try measuring the voltage between the radio and the generator (or ground) and see if it's near line voltage. For safety's sake, perhaps you should consider powering up the radio through an isolation transformer when aligning AC/DC sets - this will reduce shock hazzard and will probably eliminate your problem.

Isolation transformers will reduce the shock hazard and your spark problem significantly. However, if you currently don't own one, there is no need for your signal generator to be grounded. If it uses a 3 wire cord, disconnect the ground from the chassis. If it has a capacitor going from the line cord (either one of the regular current carrying wires) to the chassis, make sure that it is not leaky. Make sure that any similar capacitors in radios you are working on are not leaky, either. However, even if they are not leaky, if your signal generator is plugged in one way and the radio is plugged in the other, you may see a spark when you connect the generator to the radio's chassis.

If your generator is grounded, and you connect it to an AC/DC radio where the line cord is connected directly to the chassis, not only will you see a spark (a BIG one), but all of your lights will probably go out, too, or the wire going from the generator to the radio may melt.

T.

If the signal generator has a 3 pronged plug you can isolate the signal generator by using a 3 prong to 2 prong adapter plug.

Peter,

Or use something as simple as a .1MFD cap between the generator ground lead and the radio chassis.

Radiodoc
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:If the signal generator has a 3 pronged plug you can isolate the signal generator by using a 3 prong to 2 prong adapter plug.

Be sure not to touch the generator and the radio at the same time, though, if you decide to leave the generator grounded (I don't see the necessity...I disconnected the ground wire someone added on mine...but some people like to ground them).

Also, in case you were wondering, since I was kind of vague, I was referring to a ground wire being connected from the generator's 3 wire cord to the generator's chassis (since I didn't specify what chassis). Such a wire isn't necessary, though if you leave it connected, Peter's or Radiodoc's suggestions will work.

T.