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VINTAGE RADIO By JOHN HILL How to date old valve radios This month, we 're going to take a general look at the subject of dating old valve radios. In particular, the following information should help newcomers to vintage radio in determining how old their sets are. If I were about 80 years of age, I would probably have a better idea of how old some of my radios are for I would remember seeing them at some time in the past. But as radio had been established in Australia some 15 years before I was born, I remember very few of the really early receivers. For this reason, dating some of my old radios initially presented some real problems. A few years further down the track, I have now reached a stage where I can date most sets to within a year or so of their manufacture. It is an important aspect of collecting to be able to accurately estimate the age of one's treasures, whether they be old radios or anything else. Come in sucker One of my early "come in sucker" purchases was a radio that was supposed to be a 1925 model. Although I was fairly green about such things at the time, I knew it was no 1925 model but it did look fairly old. Imagine my disappointment when I saw 1948 on some of the components inside. The outline of a barretta tube, which could be seen through the back cover, gave the impression that the set had very old valves in it. But I was wrong - the other valves were octal types and they certainly weren't around in 1925. Being able to date a set, even approximately, can be a distinct advantage when buying, for anyone selling an old radio usually exaggerates its age to get a better price. You'd be surprised at how many 1930s sets become 1920 models when buying from antique shops. Most antique dealers have no idea of how old a radio set is so they just make a guess - usually a very inaccurate one. There are some fairly clear-cut ways to date some receivers so let's start with the easy ones first. Dating by the label ,ei,. , Large components and a 59 output valve date this old Airzone receiver to the early 1930s - probably 1932-33. A good knowledge of the valve types used can often date a receiver quite accurately. 12 SILICON CHIP In 1934, Australian radio manufacturers fixed a label to the chassis of all locally made receivers. The label made mention of patents and reminded listeners that the set required a licence. It also carried a serial number which was preceded by a letter prefix. In 1934, the prefix was "A"; in 1935 it was "B" and so on. This letter prefix system was abandoned when production stopped during the early war years. The latest prefix I have seen is "G", although I suspect there may be a few "H's" around even though I haven't seen one. The earliest labels consisted of a plastic plate which was rivetted to the chassis. After a couple of years, this was replaced with a blue The AW A Radiolette receivers used this characteristic "cathedral" shape from 1936-38. Note also the styling of the dial which used both numbers and station call-signs. Several factors combine to suggest that this Stromberg Carlson receiver is an early post-war model. These include the cabinet style, the use of octal GT valves and an ARTS&P sticker without a letter prefix. 4 This in strument was mant,factured under a lieense granted by AUSTRALIAN RAD!O TECHNICA L. SERVICES AND PA TENTS COMP ANY LIMITED in r espect of patents controlled by it for the reception in the Commonwealth of Aus t ralfo, and such territoriell as may from time t.o tim e be ,1dministered under mandate by the said Commo n wealth of sound broad• cas t by wireless hut only fo r privat.- use and not for operation for any public or comm~. ial or revenu.- No. earning purposes. N ..8.-A Poist Office Lic: em~e is necessary. B 43482 Australian-made receivers of 1934-35 vintage carry a plastic label which is rivetted to the chassis. The B prefix on the serial number of this label indicates that the set was made in 1935. Note that listeners required a Post Office licence to operate the set legally. ARTS&P [Australian Radio Technical Services and Patents) transfer. Unfortunately, these transfers are inclined to flake off and the all important letter prefix is frequently missing or unreadable. Post war receivers used unprefixed blue or olive green labels but if there is any accurate dating system related to these transfers, I have yet to discover the details. While the previously mentioned lettering system conveniently dates those domestic receivers made between 1934 and the early war years, there are problems if the transfer is not intact. If this has happened, other information must be used to date the radio. Australian radio service manuals are of great assistance in this regard and checking out the model number [if it's known) can soon date a particular set. I have only one such manual - a 1938 edition but it has helped me quite a lot. Using the valves The valve types used in a radio can also indicate when the set might have been made although this method of dating can be a bit vague. At best, it is usually a "not earlier than" guide only. To give an example, I have a 1937 radio which was originally fitted with octal based metal valves which came into use in Australia from 1936 onwards. However, it would be wrong to assume that any radio with octal valves is a 1936 model or later. I have also seen a 1939 radio of the same make that was fitted with the old pre-octal 6 and 7-pin valve bases. Therefore, it must be realised that valve dating can have discrepancies. Then again, in some cases, valve dating is not all that bad. During the late 1920s and early 1930s, an incredible number of new valves appeared in a relatively short period of time. In fact, new valve types were so numerous during this era, few remained current before being superseded by a better valve. So in some cases, valves can date a receiver quite accurately. For example, the 2.5V era was roughly between 1928 and 1933, after which valves with 6.3V heaters were rapidly introduced. In many instances, these later valves were identical to their 2.5V counterparts, the heater voltage being the MAY 1989 13 Service manuals and advertising material from old magazines and newspapers can also be used to date valve radio receivers. In some cases, it may be necessary to consider a number of different factors to accurately determine a set's age. only difference. The 58 and 6D6 are just one such example. The old 2.5V valves can even be subdivided to get a more accurate indication of age. For example, a receiver with a 47 output valve is likely to be a year or two older than a set with a 59 output valve. I would date a radio with a 47 as around 1931 whereas a radio with a 59 is more likely to be of 1932-33 vintage. A set with a 2A5 in it may well be another year further on. I have an old Airzone that has a valve complement of 80, 5 7, 58 and 59. I believe these valves date that set to about 1933. As there is no label attached to the chassis, it must be pre-1934. It is perhaps interesting to note ..::~-:;·•· :}, \: .- ;~ ;:; r;!~~i~~:H: ,~;i1::d:;:;~~l:~~1;::~~~:: S~: -<ti:<.:1 & isicn!'!, (<r P1•1. i!r.i.i>~ r(fs.p<:: <: 1 !:If .p~h~.nh <a,iroi!1~d by it for the fP.~(}pt:cn ir, trm (~rnm(t'(!¥ we\'Slt'h d Aoit;a!i..,. <'!~d $Ut:ht,omf',ei,nft.S l!t~ <rutY frt,;ro tin);,;, •Q lor,(l ~ itdrt\imtmtod Hf\d.cr roand.ato bythse 1itJ {Q-rtil'l'<UflW<l&.hh tif s~~nd_b~oad~$1 bv Wt-rek"\l> ~t-1-1 tudy,, {9'.f ;:s,riv:♦1~ ~< .clom,$fit tir~ .. tnd ~®I' for vv~~1~!10:-. bt ,·my pul,!it or ('ommc((.ial o r ,~venue¥ .o,.;rmng ~,rpQ-~e. N!l.-A PeM Offi(.6-lic~ru:e 11 nec(l'$$i3t\'. .. '$fl(X TRANSf!R.S" G.W.GRHN&SONS»:'T"' ll'D. 1<1trnOURNi· -J..J...-_ _ _ ___,J Receivers made in Australia after 1936 carried a blue or olive-green transfer instead of a plastic label. Unfortunately, post-war receivers did not carry a letter prefix so the label cannot be used for dating. 14 SILICON CHIP that no Australian radio manufacturer was using 2.5V valves in 1936. This statement also probably holds good for most 1935 models. Octal valves Octal based valves were in common use from 1937 to the early 1950s when they were superseded by baseless miniature valves. GT octals are most likely to be found in post-war receivers although they were in service during the war years. Radios with mixed valve complements (octal and miniature) were fairly common around 1951-54. The European "P" base valves were never as popular in Australia as the American types but there were quite a few sets (mainly Philips and Mullard) which had Phased valves in them. These side contact valves were in use from 1936 onwards and were phased out with the advent of the baseless miniatures. Unless you are very well informed, dating radios by their valves is a guessing game with a fair margin for error. Even so, many types of valves give an accurate indication of a receiver's age and can, in some cases, place a set into quite a narrow time slot. Dial markings Station call signs are another way of dating old radios. There are a number of stations that either changed their frequency or their call-sign, or started transmission, at certain times. By knowing when these events took place, one can often pinpoint the age of a particular receiver. One of the more significant stations in this regard is my own local station: 3CV Central Victoria. 3CV has undergone both frequency and call-sign changes in the past with the call-sign change being the most significant of the two as far as dating is concerned. 3CV commenced transmission from Maryborough, Victoria in 1938. Prior to this, the station transmitted from Birchip under the call-sign 3MB, on a frequency of 1470kHz. This simply means that if a radio dial has 3CV marked on it, then it must be more recent than 1938. If it has 3MB on it, then the set must be pre-1938. Unfortunately, 3MB was such an insignificant station that many pre-1938 dials don't even give it a mention. 3SR Shepparton is another station that has changed call-signs. From 1933-1937, this station transmitted on 1260kHz using the call-sign 3WR. Another Victorian station, 3MA Mildura, had a frequency change in 1937 when it moved from 900kHz to somewhere around 3MB's old frequency of 1470kHz. Sill another station of interest is 4GY in Queensland which commenced transmission in 1942. Thus, any set with this station marked on the dial is likely to be a post-war receiver. Bringing it together Now let's put some of this dating information to work. One of my many Airzones is a pre-war model but has lost its blue ARTS&P transfer. It has octal valves (could be 1936 or later), it has 3MA marked on the dial at its old frequency (changed in 1937), and also lists 3WR (also changed in 193 7). In addition, the model number is just one short of my 1938 service manual, so it looks like an early 1937 model to me. Anyway, who 's going to argue? Post war receivers usually have YOU NEED THIS TV TEST EQUIPMENT SHORTED TURNS TESTER Including meter for checking EHT trans, yoke windings, drive trans. $78.00 + $3.00 P&P HI-VOLTAGE PROBE Including meter Reads positive or negative 0-50kV For TVs, microwave ovens and high voltage equipment $84.00 & $5.00 P&P TV TUNERS (PHILIPS) This receiver is from the early 1930s as indicated by the huge chassis, the numbered dial and the use of valves with 2.5V heaters. Valves with 6.3V heaters took over from about 1933. ECL 2060 Repair or exchange UV461 Repair only $17 .00 ea + $2.00 P&P CHEQUE, MONEY ORDER, BANKCARD OR MASTERCARD TO ':Y.V.TuNERs) 216 Canterbury Road Revesby 2212, Sydney, Australia Phone: (02) 77 4 1154 sole cabinet with turned legs would also be around 1928-33 vintage, while legless consoles were in vogue from the mid 1930s onwards. Sets from the 1920s This old 1927 model Astor is typical of the style used in the mid-1920s. Any receiver that is of pre-1930 vintage is truly an antique radio. a date or two stamped in ink dn some of the components. If one cares to look, Rola loudspeakers, speaker transformers and high tension chokes will have the manufacturer's date stamp on them somewhere. While this date only indicates when the component was made. one assumes that such bits and pieces went into service in a reasonably short time. Of course, it should be remembered that components such as HT chokes and speaker transformers are inclined to burn out and there is always the possibility that these components may not be the originals - so look closely. Another good method of dating is to compare a particular set with old advertising material. In recent years,- there have been a number of publications relating to the subject of vintage radio and these books have repoduced many of the old sales brochures that were used to advertise the sets. Matching a set to an advertisement gives fairly reliable dating in most cases . Only if a particular model ran for a number of years would this method be unreliable. A less accurate method of dating is by the style of the cabinet. Gothic or cathedral style cabinets were popular in the early 1930s. A con- Although I'm no real authority on sets from the 1920s, they too can be divided into certain categories. If a set has variometer tuning (ie, swinging coils), it is most likely of pre-1925 vintage. Sets with multiple dials (two or three) are usually around 1926-28 vintage. In fact, it can be said with reasonable certainty that if a radio has a separate loudspeaker, a solid timber cabinet and 4-pin battery operated triode valves, it is a valuable relic from the 1920s. Any set that is of pre-1930 vintage is truly an antique radio. Yes, there are many ways of estimating the age of an old radio, with some methods being more accurate than others. Experience is also a great help for it can give a "gut feeling" as to the age of a particular set. In short, everything helps. it MAY 1989 15