QUESTIONS AND ANSWERS

Radio Record, Volume V, Issue 36, 18 March 1932, Unnumbered Page

QUESTIONS AND ANSWERS

FRANK

KEE

The Technicai Editor will, through these columns, be pleased to help readers experiencing trouble their sets. Queries are limited to three-for more than this a shilling fee is charged, and-a similar fee is payable for queries answered by post. Supplying layouts, circuits and solutions of intricate theoretical problems is beyond the seope of this service. — A coupon must accompany all requests for information. Nonappearance of the coupon in any issue eannot be regarded as a: reason for its not being used. Address all queries, The Technical Editor,’ Box 1032, Wellington.

od M.A. (Waikanae): The capacities of * the condensers are: .0005 and 00025, We are sending you a circular concerning the, DX Club. The "Radio Times" will eéyitain all news of interest to both dxerpand short-wavers, and will be published monthly at a cost of 9d. a copy. Music LOVER (Waiuku): Probably there is a defective resistance in your set, and this can be located only by instruments. If you do not possess these you must get in contact with someone who has them. The fact of the set humming hasa direct bearing on its irregular functioning, 2. 5d1 is a multi-mu valve, 224 a screen-grid, 247 a pentode, and 280 a rectifier. You will find their characteristies set out in the 1982 "Guide."’ which will be on sale shortly. Fp*14 (Hamilton) : There is a scratching noise as I rotate the dial. The set seems dead at certain points. : There is dust between the vanes of ‘your or one of the moving ‘vanes is touching one of the fixed in certain places. 2. When I bring up the yolume on certain stations, I have to re-tune. wt by volume you mean the reaction, it is quite understandable, for that

is a well-known phenomenon of reaction using sets. It is not uncommon to have ‘o adjust the tuning with volume. You should improve your reception, if you had three "B" batteries and 9 volts "©." BoNG (Waikato) : We cannot give you the number of turns as you do not state what the coil is to match. 2. The top of the primary connects with the ‘plate of the valve, the bottom to B+, 3. I could not get ‘the "Outspan Five" to oscillate. I tried different voltages with the same result. A.: Did you try reversing the connections to the differential condenser? ‘This is probably the cause of your trouble, GAPP (Auckland): The coils for the Hammarlund-Roberts are: RF coil, 2Qhin. former; secondary, 24 d.s.e., 84 turns; primary, 24 d.s.c., 18 turns, wound in an orderly fashion, and placed inside the secondary. The regeneraformer has a similar secondary to the aerial coik; the primary consists of 26 or 28 d.s.c. wound in an ordinary fashion and tapped in the centre. The tickler has a diameter of 1 5-8in., and the winding length is #in., the wire used being 24 d.s.c. Further particulars of the construction of these coils appeared in the 1930 "Radio Guide." 270381 (WELLINGTON): Will it not contravene any regulations to operate an a.c. set without the earth connected to its correct terminal? .: The chassis must be earthed through the three-pin wiring system, otherwise an earth is necessary. 2. When the set is switched on -after being idle for a number of hours, it emits a bad howl, something like a siren, for about 20 seconds. ; A.: This is due probably to one of the valves or a defective resistance. Try changing the valves round, only make certain that you keep the types correct in interchanging, You could easily find out which valve is causing the trouble’ hy starting at the radio end while the sét is howling and pull out the valves as quickly as you can and note which one causes it to stop. Then try exchanging that valve with one of the others of the same type. Failing that, examine the circuit associated with it. X22MC (Rangiora): What steps should be taken to put an s.g. valve in the place of a 227 in the r.f. stage of my Browning Drake? A.: A suitable circuit of the electric "Radiogram" appeared in last year’s "Radio Guide." This will give you the necessary connections,

KNOBS (Lower Waikato) : The wire 1s 26 ds.c. At 90 volts PM3 consumes 2mamps. A415, approximately 1.75, and A409. 2 mamops. 8. You could obtain instructions for the "Night Hawk Two" and "Differential Two" from our Office.HL L.M. (Milton): We advise you to * get in touch with Mack’s Radio, at his new address. Probably the installation ‘of a fuse wovld save your valves. ~ NOVICE (Christchurch): Yes, your scheme about changing over your accumulator would be quite feasible, but unless your generator is provided with a commutator, it will be a.c., and need rectification, and under these cireumstances would not be very suitable for a charger. For further information concerning the radio serviceman’s examination, apply to the Registrar. Box T96. Wellington. Wikk (Waiuku): We cannot say if the valves you mention will suit vour set. Tf those you at present use are

of the same type. then most certainly you eould use them. It is unlikely, by the wry, that you can use P625A, as that is a | six-volt valve. and it is most unlikely that your set will be wired for that. We do not know enough about it to say whether it would be suitable for dx work or not, but it would probably be. We will not make any promises about giving details concerning the Beverage aerial in the "Radio -Guide." but if space permits it will be there. PENTODE (Auckland): My tuning dial is divided into equal divisions. Is there any way in which TI could find ont the corresponding kilocycles? A.: The only way you could do so is by making a graph, or if you do not want to go to that trouble. keeping a list of stations and their dial readings, together with their kilocycles. so that you can get a rough idea of the dial readings in connection with.any kilocycles. The making of a graph was described in the "Radio Record" some time ago. Your best plan would be to replace your valves with exactly the same type.

RAStTUS | (Christchurch) : "The voltage ' On the mains is generally 230 volts a.ec., and is sufficient to kill a person, al» though such is unlikely unless yery firm contact is made with mains in a damp situation. ; 2. Short-wave crystal sets _are not practical propositions. 3. Wind -100 turns on a 24in. former, shunt the condenser across the coil, bring ing. the aerial to the middle tap and taking the bottom of the coil to the set.: "THANKFUL (Oamaru) : "Yes, your valves would be suitable. for the | "Super Six." If I remove the grid leak from my cet it goes just as well. : That has been fairly fully explain« ed in the 1932 "Guide." A leakage is taking place either in your valve, in the valve sockets, or your baseboard. If your set is working quite satisfactorily, there is no. need to worry about: the phenome non,

Information Coupon (To be used with all requests for information.) Name ot set Number of valves ..eccccssccscccccs Name ‘Address SPORT HO SHEED OHSOELOSESEE PoC eee OeeTeseseeeeFesseess FFP PHOS SA EHEHTHSTESHESESSESEOHEOEOEEOEES TREO TE HEE HE SEEESEEESESESEOSOEOS "Nom @e@ plume ....cecccccecccsees To be kept in subsequent inquiries . Date Please ‘Note :- (1) Re specific and brief, tabulating, if possible. (2) Write legibly. and on one side of the paper. (3) We do not’ design circuits, but accept suggestions for feature articles