Useful Hints

Radio Record, Volume III, Issue 24, 27 December 1929, Page 27

Useful Hints

} A Test for Overloading. HEN testing with a milliammeter for overloading, it should be noted which way the needle kicks. If it goes ' to the left it is a definite sign that the overloading in that particular ‘ valve is caused by the incoming sig- : nals making the grid too much posi- ’ tive, and that grid current is occurring. So, sometimes, by altering the ' grid bias to a larger negative oltage, . this particular kick can be eliminated, the overloading stopped. If, howaver, the‘kick of the milliammeter is to the right, it shows we have too much ti bias and partial rectification is occurring, and we either have to increase the B battery supply or decrease the grid bias. It is to be assumed, of course, that the overloading is not so ' great as would cause an _ overload which ever way the grid bias was altered, making the milliammeter kick in both directions.

Discarded Hand-drills. F you happen to have an old handdrill, which has been discarded either because it has seen its best days or because its chuck will not take 8-8in. drills; the tool; or rather a part of it, may be given a fresh lease of" useful life. In most patterns, the shank of the chuck is held in place. by a.pin running through the boss of the lower small bevel gear wheel, File off the riv-eted-over end of this. pin and punch it out, The chuck and its shank can then be withdrawn. If you have to deal with any small round piece of work, which requires to be firmly held, place the shank of the chuck in the jaws of the bench vice and use the chuck itself to grip the work. WHEN overhauling your earth con- ~ nection remember that just as the strength of a chain is that of ‘its weakest link, so is the efficiency of an earth connection largely determined by the ‘soldered joint with the-earth: wire.