Valve Sets. No Signals

First examine all connections for broken joints, see that all switches, dials, knobs, etc., are really in their proper positions for correct operation.

Note whether the valves do light up when switched on. Check over the voltage of the H.T. supply, as if a battery, it may have a broken circuit concealed therein.

Examine the set thoroughly to make certain that nothing has been altered in any way since the last time it operated properly. If the valve or valves light up apparently correctly, ascertain that the valve leg contacts on the plate and grid terminals make proper contact in the valve holder, the split valve legs or pins may require opening out slightly. If still there are no signals, try the effect of changing the valve for a spare one, since the fact that a valve filament lights up is not evidence that it is in working order; there may be something wrong with the plate or grid circuits inside the valve. If soldered joints be used in the set, make certain that one has not come adrift, and is just not making contact. Make certain that the transmitting station you wish to receive, is really working, also check over the points mentioned at the start of this article, re aerial, earth connection, headphones or loud speaker, etc., these being in order, the receiving set must be at fault, and close examination, with as an extreme measure the substitution of one part at a time by a known " to be in order " item will certainly find the defect. It should be noted that it is here assumed that the set has already worked correctly, and has not been altered in design since that correct working.

Weak Signals

Firstly check over the aerial, earth connection, headphones or loud speaker as previously mentioned, also tuning adjustments ; if these be in order check the voltage of the accumulator and battery. If a filament resistance be used, and signals are better when more of this is cut out, also that the signals even then decrease more or less quickly, then this is a certain sign that the accumulator requires recharging, and is run down, in addition the signals will probably be distorted, due to the accumulator voltage altering with the current demands upon it, and so being unable to keep the correct charge upon the valve. The accumulator being found to be not at fault, then try the voltage of the H.T. battery, just before switching on and immediately after having run, say 10 minutes, if it is run down, then a distinct difference will be found between the two readings ; if, however, a correct reading voltmeter is not available, then test the batterv with a low reading ammeter, it should show at least a discharge of one-half ampere, a new battery should show at least five amperes. To test between each 4 1/2 volt terminals with a small electric lamp may show some fault, but this is a tedious method, and it is not always easy for an unskilled operator to tell which may be a defective group of cells.

In any case of doubt re the H.T. battery, the simplest method (failing the use of a meter) is to borrow a known good battery and test the results of using it on the set. If the set has until recently been giving good strength signals, then any decrease will generally be found to be due to one or more of the following : the transmitting station has decreased its strength, the valve or valves are nearing the end of their useful life, the accumulator or H.T. battery is running down, or due to some joint or connection in the set circuit not making good contact.

General Remarks

1. It should by no means be assumed that any transmitting station is sending out pure undistorted transmissions, or that it has not altered its strength, or that it is working exactly on its advertised wave length or even working at all ; failure to recognise these possible faults with the transmission leads to a lot of unnecessary worry to those operating receiving sets.

2. ;Due to the above reasons, it may be necessary during reception to alter the tuning of a receiving set slightly to get louder signals, or to increase the filament current, and it may be quite impossible to get pure reception.

3. ;If the reception comes through in rushes of extra loudness, followed by short quieter periods, this is probably due to the accumulator being run down.

4. ;An intermittent crackling noise may be due to either atmospherics, or to the H.T. battery being run down.

5. ;If headphones are being used, and frequent short breaks are heard in the reception, this is most probably due to a break in the flexible cord of the headphones.

6. ;Any receiving set that requires any adjustment to be " hard over " in any direction, in order to get the best out of the receiver, probably requires altering so that more adjustment could be given in that direction, it would be very curious if the maximum adjustment already possible happened to give the best that ever could be got out of the set under any improved arrangement.

7. ;Some valve sets have no adjustment for regulating the filament current, i.e., a filament resistance ; such sets cannot give out their best possible results under all conditions.

8. ;An earth connection to a gas pipe may work well, but it may not do so, and a connection to a water pipe, direct on the main is far preferable, positively direct to earth is better still.

9. ;A receiving set with " flat tuning." i.e., one in which it is difficult to find the best position over a large range of the tuning device, may often be considerably improved by placing a small fixed condenser between the aerial and the receiving set : these are cheap, and two of, say 001, capacity can be tried, using first one, then the two in series, and then in parallel, keeping to the arrangement that suits best.

10. ;An outdoor aerial should give louder and longer range signals than can be got from an indoor aerial, but it has the disadvantage that it cannot be used with perfect safety, either during a thunderstorm, or without some device to quickly disconnect the aerial from the receiving set and connect it to earth. An indoor aerial properly arranged is very much more effective than generally considered, especially for a local transmitting station, and is perfectly safe to use, or otherwise, during a thunderstorm.

11. ;When going over a strange set for any alleged fault, take no statement for granted ; check and test everything.

12. ;When replacing any valves into position, it is a very safe precaution to disconnect the H.T. supply first, and in the case of rewiring or rearranging a set, it is a sound proceeding to try it out with a spare old valve or valves first, in case of a fault which might burn out a good valve.

13. ;Keep the top of the accumulators free from any moisture by the use of a dry cloth : this will decrease leakage between the terminals.

14. ;If the accumulators have transparent cases, note the difference of the colour of the positive plates, when freshly charged and when discharged, i.e., very dark when charged fully, and much lighter when discharged. This gives a ready means of judging whether a recharge is necessary.

15. ;Serious notice and warning should be taken of the danger that may be run by anyone (without expert electrical knowledge or advice) arranging their set to run off the electrical supply-mains. If this be done without proper precautions then various bare metal parts of the set, some of the terminals, and possibly the flexible leads to headphones or loudspeaker will be charged from the supply mains, and sooner or later an accident will occur, and given certain conditions this accident might result in a death. The precautions to be taken may involve the use of insulating material, condensers and transformers, each case must be treated according to its requirements in order that no shock can possible be received, and expert electrical knowledge is absolutely necessary. A high voltage shock from a H.T. dry cell battery is as nothing compared to that from the supply mains, owing to the great difference of power available.