QUESTIONS AND ANSWERS

Radio Record, Volume VII, Issue 15, 20 October 1933, Page 27

QUESTIONS AND ANSWERS

"W\ARG" (Dargaville): 1: 7.5 ma. is about correct for the De Luxe 5. R.F. 3.5 ma, Det. .5 to 1 ma. Ist AF. 3 ma. according to bias used, which should be about 9 vy. for 185 y. on the plate. 12 v. bias is required for the class B stage. 2. The apparent broadness of tuning on the higher frequencies may be due to the large number of stations there. The narticular type of band-pass used atso has the failing that it tunes less sharyply at the lower wavelength end of the dea A special type of band-pass coupling could be used, but would be ioo complicated for the home-builder to a4-. just. H V. BAKER (Waiuku): Detaiis ef * the coils for the 1982 Outspan 4 wil: be found in the "Times" for Neovember, 1982. We would suggest, however, that you build the 1983 version, and stick to 2-volt valves, as the set was designed for them. A clip on your 6-volt battery will take care of your 2-vo’r fila ments, Further, using §6-volt valves will upset the bias arrangements ' iD W. DEVERY (H.B.): We regret * that the published circuit and iay- out diagrams of the Outspan 2 are incerrect. The G.B. terminal of the transformer should be connected directly to the B negative end of the 600 onm resistor, and nowhere else. 2. What type of speaker should be used, and what may be received on it? A.: Any light cone type. Probably 1YA, 2YA, 3YA, and the local stations. 3. The tuning condenser is of .000385 mfd. capacity. 4. The reaction condenser is of .00025 or .00085 mfd. capacity. 5, Any good quality 3-1 or 5-1 audio transformer is suitable, Ww MULLINS (Lower Hutt): Your * copy of the "Radio Record" forwarded. The aerial described will be satisfactory if you are in a noisy location.

"Py X141MC": The dial simply requires to be moved on the condenser shaft in the proper direction to correct your readings. "NTHW CHUM" (Christchurch): No harm whatever will be done to an A.C. set by storing it indefinitely. However, dust it thoroughly before using again. " M.P." (Nelson): Insufficient de- * tails to hand for pick-up connections. What type of set is it, how many valves, battery, A.C., ete.? Your log is excellent. H L. WARD (Auckland): 1A. The * combination band-pass coil requires to be earthed in the same way, in the De Luxe Band-Pass 7. 2, Can I use electrolytics in place of the high-test block type? Shall I use 2 o: 3? I am using a Jensen D8 2500 ohm field as the second choke. A.: Yes. Use 3. ° 8. The by-pass for the 56 cathode is shown as 2 mfd in one place and 4 mfd in another, A.: Hither will do. The 4 mfd will give slightly better reproduction. "HYDRA" (Auckland) : Motor-boat-ing and howling in a 5-valve re-sistance-coupled Browning-Drake, using a B eliminator, may be cured by decoupling each of the B plus tappines with a 1 mfd. condenser or larger, The condenser should be connected from the tap to earth. The insertion of a 50.000 or 100.000 ohm-resistor in one or each of the B plus leads may also help. Try replacing the detector plate resistor. [I)*484 ( ): The specifications for a 160-metre coil for the Night-Ow] + are: Valve-base former, 8 turns aerial, 50 turns secondary, and 12 turns tickler; 24 S.W.G. D.U.C. or D.S.C. for pri. and see.; and 380 for the tickler. "FRATTERY" (Westland): Q1. wishes to replace his valves with Mullard 2-volt series in an all-wave set. — A.: Replace A409 detector with PM2DX or 280; replace A415 1st audio with PM1ILF or 230; replace B406 2nd fudio with PM2,. 230’s are mentioned because of their economical characteristics. 2A.: No bias changes will be necessary. . W.H.’ ’(Auckland): Q. Can any of * the types 280, 224, 227, 245 be replaced with modern valyes without alterations? A.: 224’s can be replaced with 224A’s and 227 with 56. 2A.: A.V.C. is not worth while in your set and the cost would be prohibitive. 8A.: See above. . W. KING (Ohbakune. Junction) : We strongly advise you to wait for the November "Times," when an up-to-date set wil] be described. ' §. (Christchurch): Why is a green * stain left by the positive one of two wires placed on a fresh slice of potato? A.: The stain is due to the attack of an acid in the potato, on the copper. This acid is set free by electrolytic action, and

collects about the positive wire. The same effect may be observed in the appearance of a brown stain on a slice of onion. "PENTODE" (Devil’s Elbow): 1A. We are afraid you have burned out your 4volt valyes by using a 6-volt "A" battery. Haye them tested. 2A.: A 5 mfd. by-pass condenser will do in place of 1 mfd. 8A.: By all means rebuild to a modern circuit. Valve-base coils, however, are quite O.K, for S.W. work. D. LEIGHTON (Trentham): For * information on power amplifiers, see the "Radio Times" for February, March, April and July, 1933. 1A.: Use a 56 rather than a 245 between the 55 and 2A8’s. Your ideas are quite on the right track. 2A.: Using resistance coupled pushpull is hardly feasible with an audio stage between the 55 and 2A3’s, as this would be virtually a two channel amplifier, with a 55, two 56’s and two 2A3’s, The 55 will not drive the 2A3’s properly, so use transformer coupling and a 56. Communicate with any of our kit advertisers for prices, etc., of. your requirements. UZZLED" (Christchurch): My 5valve ac. T.R.F. set develops a tinny sound after operating for an hour or so. A.: Try replacing your valves. If this has no effect, we are afraid it is a job for a serviceman.

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