Multimeters and test equipment.

[Brissieboy]

The Uni-T 2000 series Benchtop oscilloscope is a bloody marvellous piece of kit. The sig gen I created to run speedos was having interference problems when plugged into 12v. Yet I could only see a nice looking square wave at the 555 timer chip, on the Allosun handheld. I found that having a power lead more than a few centimeters causes the rise on the wave to become fuzzy so I will purchase a small rechargeable 12v battery to install on a new sig gen I am making. I really do recommend the Uni-T as a reasonably priced unit.

Before you bother with the battery idea, try puting a 0.1uF ceramic or vitramon or similar capacitor across the supply rails right at the 555 (pins 1 & 8). And make sure your ground rail is solid and short as possible. Digital circuits need power supply decoupling.