All Keeler instruments use genuine Halogen and Xenon technology, yielding a brighter, whiter illumination and a longer life.
Look at the bottom of your bulb to identify if your instrument is 2.8v (blue - dry cell battery) or 3.6v (red - rechargeable)
Accurate diagnosis depends upon a number of factors. Of these, top quality illumination ranks as one of the most important.
Only excellent visualisation allows you to use your diagnostic skills to the full.