Grid-bias from Single Cells

Radio Record, Volume III, Issue 32, 21 February 1930, Page 28

Grid-bias from Single Cells

Soldering to . Zine A SINGLD cell ig often used nowadays to provide the grid biasing potential for radio-frequency valves. Unless some special form of mounting with spring contacts is used, this necessitates, as a rule, the soldering of leads to the cell itself, a job which requires rather careful handling. It is very important that in the process of soldering the cell should not be unduly heated up or it may suffer internal damage. There is not, as a rule, much -¢iffieulty about attaching a wie to ‘the little brass cap which forms the positive contact, for in most cases this will be found ready tinned. With a clean, hot iron the job can be done so quickly . that no serious amount of heating up occurs. The important point is that the iron should be hot. If it is not, it has to be applied for far too long before the solder will flow, and the cell is warmed up to an undesirable degree. Soldering to the zinc pot in order to make the negative contact is not so easy, and unless one is careful, a dry joint may be made which, though it may look all right, will come adrift sooner or later-probably sooner. ‘ First of all the zine should be thoroughly cleaned at the point at which the lead: is to be affixed by scraping well with an old knife. A small amount of flux ean be applied. After this, a. little solder is run on, and the legd, well tinned, is fixed in place. It is quite useless to employ a small, light iron, for owing to the comparatively large area of metal to be dealt with, heat is absorbed from it so rapidly when it is applied to the zine pot that almost instantly it becomes too cool to do the work properly. A medium-sized or a large iron does not lose its heat so quickly, and with such a tool, a good, sound joint can be made. After soldering leads to cells always be careful to give each a:good pull in order to test its strength. One is not infrequently surprised at finding that a good-looking joint is really no joint at all.