QUESTIONS AND ANSWERS

Radio Record, Volume X, Issue 5, 14 August 1936, Page 46

QUESTIONS AND ANSWERS

"TVYyX14N" (Christchurch) ; First, the re- . placement of the 227 valves py ‘the 56 types is probably all right, as they are very similar. The cathode — resistance should be from 2300 to 2700 ohms,, depending on the actual plate voltage ap plied. The 45 type wil] often give that blue glow on the glass in the best of valves; the writer having at the present a pair which ave operating in this manner. The other trouble is probably due to the local-distance switch or aeria]’ coupling coil, but is mogt certainly an intermittent contact, mY 8.7." (Nelson) : The capacity of the * condenser which you inquire about, Wwe are able to estimate, from the templates sent in, as being very close to 0.0001 mfd, "Cov" (Thornbury): From the symptoms you give concerning your set it looks as though there is no fault in the set itself; that is, no consistent fault. Between 1000 k.ec. and 1400 k.ec, there are very many stations whose channels are so close together that it is impossible for the average set to discriminate between them; some actually interfere with each other, so that no set could ever separate them. The variations you notice in the mixing and whistling is caused by variations and times of starting up and stopping broadcasting of N.Z. and Australian stations concerned. Not having particnlars of your set, we cannot suggest whether apy improvement can be made at all, but in any case the improvement would only be slight. "Zee (Opotiki) : As your questivn will require diagrams and more space than can be spared in these columpy we suggest that you write in for a_postul reply for which the fee is one shilling "PUZZLED" (Dunedin): There are many possibilities as to the source of the noise that you get, bnt with the other trouble taken into account also. there seems to be trouble in the align ment of the set; and before worrying about anything else we would sugges! that the set be checked by a serviceman for its correct alignment. The noise you refer to-as "aeroplane" eould come from power main interference, but this should disappear when you remove your aeria! Wire from the aeria] terminal. "PUZZLED" (Waikino) : The addition * Of phones to your set and algo for use of a microphone are beat carried ont by a servicemun, ae without previous experience the jab is likely to' be troubleeone, The headphones have to be inStalled so' that there is no danger of 4 shock ta the user, for there ié 3 source of danger bere. a _ The lack of other stations in daylight je most likely due to the locality giving poor reception to distant stations, dnd YA being the closest comes in best, If you are having the additions niade to the set, then get it checked over for any weak valves or misalignment. *

"K I," (Palmerston North): The use * of a pick-up with a transformer to feed into the set is better than without, as the signal is usually greater... If a proper matching traucformer for the pick-up ie not available, then a good audio transformer of ahout 8 to 1 ratio will do. .Try several ratios and makes and yse that which gives the best response. "TT R.F." (Roxburgh); If the difficulty ° yoy are experiencing with your T.R.E, is lack of selectivity, then the "Pre-Selector" would help a lot, We lave a letter from a user of ane of these which will be published in next week’s issue, as his experieiges haye been ryery good indeed. so The addition of A.V.C. to the set: wonld of course be useful for the fading trouble, but the expense of so doing might be more than you wish to incur. Get a quotation for the job from a good man and see whether it seems too high or not.