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VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG The Astor RQ – the Lady’s Handbag Radio Back in the days of valve radios, portable sets were a luxury item. They were expensive to buy in the first place and they were even more expensive to run. The Astor RQ set we look at this month was even more of a rarity in that it did not look like a radio. When visiting a friend of mine recently, he brought out a lady’s handbag which he said he was going to give to me. I thought, “He’s having me on, giving me a lady’s handbag. What’s he up to?” As you can see from one of the photographs it does indeed look rather like a lady’s handbag. When the bag was opened, an attractive compact Astor portable radio was revealed. Then I knew I wasn’t being conned. When you think about it, the set was probably meant to look like a lady’s handbag, with a stout brown leather case and a shoulder strap. As with all advertising there is an aim to entice various groups to purchase their wares, and so it is in the radio retailing business. This set, an Astor RQ, was produced in 1955 and probably up until that time the main emphasis had been on selling to the man of the house. The “Little Lady” got scant attention, particularly in the portable radio market, and probably for two reasons. Sets had been much too heavy for women to comfortably carry and the sales people hadn’t yet thought of women as having a mind of their own let alone an income of their own. Astor obviously woke up to that fact and produced this set that would have been quite attractive to the more independent young women of the day. It opened up a whole new market. How well Astor did with this model and similar sets I don’t know. They probably sold many thousands of sets that they wouldn’t have sold if Below: running the set from a battery eliminator is more practical than using batteries which don’t last long at all. 84  Silicon Chip Fig.1: the circuit of the Astor RQ is typical of many 4-valve sets of the era. Note the unusual method of obtaining grid bias for the 3S4 output valve, taken from the oscillator stage. they had stuck to the “tried and true” methods of sales pre­sentation. What’s in the handbag? Compromises have to be taken in some way or another when equipment is miniaturised. By today’s standards the set is large but in 1955 it was quite small, around about the same bulk as the Astor KQ which was produced back in 1947. Several compromises were made to ensure that a small set of reasonable performance could be achieved. Small sets of this calibre rarely had an RF stage which limited their performance in country areas. However, there was a saving of LT and HT current. Because these “personal” portables were small, rather inadequate inbuilt loop aerials had to be used. However, in this set, an 8" x 3/8" ferrite rod aerial/antenna was installed, which was virtually an industry standard for broadcast band loopstick aerials from the mid 50s onwards, and hence the signal pick up is quite reasonable. Batteries were a real problem. They were heavy if they were to have reasonable life in the set, expensive and bulky. However, in this set and in much later sets, the smallest batteries available were used, with limited operational life. In this set, they opted to use two D cells to supply the 250mA of filament current and a 467 67.5V battery to supply the 10mA of HT current. A battery life of 50 hours would probably be all that could have been expected. Much later an Australian-made Kriesler transistor portable set used a 286 battery which gave a claimed operational life of 1000 hours. That is some difference. Back bias Most of the later battery-powered radios used back bias to obtain the grid bias for the 3S4 or 3V4 output valve. This was done by putting a resistor between the negative terminal of the HT battery and the set chassis. The battery negative was taken via a resistor to the grid of the 3S4/3V4 and hence it had a bias of around -7V for a 3S4. The negative voltage was devel- oped due to the current drain across the battery negative to chassis resistor. This did away with the separate bias battery commonly used by sets that used the 2V series valves. There is one significant disadvantage of doing this, as the -7V bias is taken away from the 67.5V total HT voltage, which means in this case that only around +60V is available for opera­tion of the set. How could the circuit be arranged so that the full HT voltage was available and still not have to use a sepa­rate bias battery? Astor got around this nicely. They attached the 3S4 grid resistor to pin 4 of the 1R5 which is several volts negative due to the operation of the local oscillator; simple but effective. With only 67.5V HT available the maximum audio without noticeable distortion is around 180 milliwatts, and as the bat­ teries discharge this will decrease to below 100 milliwatts. Taking into account the state of the batteries and that the output transformer is around 66% efficient, an output varying between 60 and 120 milliwatts is available to the speaker. August 2000  85 will do the trick. So they can but they will end up costing quite a few dollars too. If you really want to use the set as a portable this is probably the only practical solution. A l t e r n a t i v e l y, y o u n e e d a mains-powered battery eliminator. Battery sets using 1.4V and 2V valves require up to 300mA at 1.4V or up to 1A at 2V and high tension voltages of 67.5V, 90V or 135V at less than 25mA. I built a suitable supply several years ago that will power dry battery radios and some that use wet cells too. I used this to power the set. (Editor’s note: If there is sufficient reader interest, SILICON CHIP could present a suitable circuit). Restoring the handbag radio No, it’s not a lady’s handbag but a nice little 4-valve portable radio. The speaker, a Rola 3C, is certainly not very efficient so overall there is not much chance of entertaining all the neighbours with the set going full bore. There is no disputing that sets of this nature are “personal” portables. What is the RQ like? An initial look at the back of the set indicated that it would be quite reasonable to dismantle and restore. Regrettably, on closer inspection a few problems become apparent. If valve re­placement is the only requirement for service, the 1R5 can be easily replaced. If the other valves require replacement a small screwdriver will be needed to lever the valves out as it isn’t possible to get fingers around the valve envelopes. More serious service work requires the set to come out of the cabinet. This is achieved by removing the hand-span tuning knob and the off/ on-volume knob, then the speed nuts on plastic spigots in the cabinet. My experience of undoing these is that the plastic spigots often break and compounding this, long needle nosed 86  Silicon Chip pliers are needed to turn the speed nuts. Even taken with great care the job can result in broken mounting spigots. Powering the set – how? The difficulty of powering a battery set has probably caused many collectors and restorers to bypass battery-powered sets. Assuming a suitable power supply is available, caution is needed to ensure that high voltage is not applied to the fila­ments by mistake or through a measuring probe slipping off a point being measured and shorting HT to the filament line. Should this happen all these low voltage and current filaments will be burnt out. Indirectly heated valves will stand a short term short circuit without damage. It isn’t hard to put a couple of D cells in to provide the LT supply but the HT supply is a different story. 467 type bat­teries are generally unobtainable and when they are, they are extremely expensive and their quality is often suspect. Some decide that a string of eight 216 9V batteries As mentioned earlier I had expected the set to be easily overhauled but it didn’t prove to be quite that easy. The back came off easily; too easily like many Astor sets with plastic cabinets. With time and heat, the plastic warps and the retaining clips no longer make good contact. In fact, the previous owner had used sticky tape to hold the cabinet together. The valves could be removed with a little bit of persist­ ence and each was tested with an ohmmeter to make sure that the filaments were still OK – they all were. Check what voltage and current your multimeter uses to do its measurements before checking battery valves. With the probes short­ ed, the current must be under 50mA or the valves filaments may be blown while being tested. To make the wiring and components more accessible for in­spection (and replacement if need be) the chassis had to come out. First of all the two knobs were pulled off. Then the speaker wires and an earth wire were removed from the speaker frame as I couldn’t remove the speed nuts from the speaker mounts without breaking the mounts. Next, an attempt was made to remove the three speed nuts securing the chassis to the cabinet. Two responded and could be twisted 90° with needle-nosed pliers and re­ moved. The third was a different kettle of fish. When the speed nut was put on it was just pressed on and locked in place but there was no room to twist it 90° as the tuning gang fouled it. So it was a matter of undoing the three ELECTRONIC VALVE & TUBE COMPANY It looks like this inside the case with the batteries installed. screws holding the tuning gang to the chassis and lifting it clear so that the speed nut could be turned and removed. The gang was then put back in place and the mounting screws reattach­ed, after which the chassis was withdrawn for inspection. I like to work with a circuit diagram as it makes things just that much easier. Alas, this time I didn’t have one. (As it happens, I did obtain one after I had finished restoring the set). What I did was to look and see if I had any other portable 4-valve Astor circuits. I fortunately came across the circuit of the KQ which mechanically is quite different and the design is nine years older – but would you believe it is virtually identi­cal? So the moral of the story is if you don’t have the circuit of the set you’re working on, look for a circuit by the same manufacturer with a similar valve lineup and doing a similar job. Even other manufacturers’ circuits for similar sets are better than nothing. This neat little set uses a 1R5 converter, 1T4 IF stage, 1S5 detector and first audio stage, and a 3S4 for the audio output. The paper capacitors weren’t particularly leaky but battery radios are not very tolerant of any leakage. The replacement polyester capacitors were roughly the same colour and size which means they didn’t look out of place. The resistors were all checked and a few were found to have gone high and out of toler­ance, so they were replaced too. The rubber wiring insulation had gone hard and cracked. I made sure I didn’t shift it otherwise I would have had to replace it all, not that there was a lot in such a simple set. Next to be checked was the speaker transformer. These are often a source of problems as they can go open-circuit in the primary. And sure enough, it was open-circuit. One problem: the replacement had to be smaller than usual as the one in the set was quite small. If it was too big the cabinet back would not fit on. Fortunately I had a suitable one. It is interesting to note that the speaker transformer frame is connected to the +67.5V HT rail. This was done in an attempt to overcome the problem of electrolysis caused by small currents between the primary and frame. Astor often did this with their battery sets. Didn’t work this time! Having done all these things and made sure everything visu­ally looked OK it was time to connect the dry battery power supply. First, I double-checked that the power supply was providing the correct voltages (1.4V and 67.5V) and all was well. It was a case of connecting the battery clips to the supply via small jumper clip leads. As the set was still out of the case at this stage, clip leads were also used The Electronic Valve & Tube Company (EVATCO) stocks a large range of valves for vintage radio, amateur radio, industrial and small transmitting use. Major current brands such as SOV-TEK and SVETLANA are always stocked and we can supply some rare NOS (New - Old stock) brands such as Mullard, Telefunken, RCA and Philips. Hard to get high-voltage electrolytic capacitors and valve sockets are also available together with a wide range of books covering valve specifications, design and/or modification of valve audio amplifiers. PO Box 487 Drysdale, Victoria 3222. Tel: (03) 5257 2297; Fax: (03) 5257 1773 Mob: 0417 143 167; email: evatco<at>mira.net New premises at: 76 Bluff Road, St Leonards, Vic 3223 P.C.B. Makers ! • • • • • • • • • If you need: P.C.B. High Speed Drill P.C.B. Guillotine P.C.B. Material – Negative or Positive acting Light Box – Single or Double Sided – Large or Small Etch Tank – Bubble or Circulating – Large or Small U.V. Sensitive film for Negatives Electronic Components and Equipment for TAFEs, Colleges and Schools FREE ADVICE ON ANY OF OUR PRODUCTS FROM DEDICATED PEOPLE WITH HANDS-ON EXPERIENCE Prompt and Economical Delivery KALEX 40 Wallis Ave E. Ivanhoe 3079 Ph (03) 9497 3422 FAX (03) 9499 2381 • ALL MAJOR CREDIT CARDS ACCEPTED August 2000  87 This photo shows the set with the batteries removed from the case. to connect the speaker to the receiver. Now for the moment of truth: the power was turned on – and I was greet­ed with silence. I put the multimeter probe on the grid of the 3S4 and was greeted with a click and a little bit of hum. So far so good, now try the 1S5 grid – nothing. I’d tested the filaments and found them all OK but that doesn’t mean the valve will work and this one didn’t. I have a small supply of battery valves so I rummaged around and found one. After replacing the valve (after turning the power off), I then touched the grid with the probe and got a healthy blurt out of the speaker – still no stations though. I put the signal generator output lead near the input to the first IF transformer and wound up the output while sweeping the gen­ erator around 455kHz. In a moment, the beautiful tone of the generator came through. So the IF was OK. I then tried forcing broadcast signals through the set by connecting the generator lead over the insulated lead coming from the loopstick aerial but no go. Perhaps the 1R5 converter was faulty. I put a fresh one in and the noise level out of the receiver came up and I could hear stations as I tuned 88  Silicon Chip across the band. It looked like I had overcome most of the set’s problems. The next thing was to go over the alignment. Some folk are reluctant to touch the alignment and if the set sounds reasonable it is left alone. I knew that the oscillator and aerial circuits were a bit out of alignment so the IF would probably be too. I fed a tone modulated signal on 455kHz from the generator into the aerial tuned circuit, at a level that produced a noisy signal through the speaker. I tweaked the four slugs in the IF trans­ formers for peak performance – they were only a little out of tune. It isn’t possible to do this unless the chassis is out of the cabinet. From there it was necessary to determine how far the align­ ment was out. The set is intended to tune from 535kHz to 1610kHz. The slug in the oscillator coil was adjusted so that 535kHz was received with the gang fully in mesh and the oscillator trimmer was adjusted so that 1610kHz was received with the gang fully open. This was done as the oscillator slug is difficult to access with the chassis in the cabinet. Having got the oscillator fre­quency range approximately correct, the chassis was then put back into the cabinet. Now the control knobs and the radio station scale were fitted. With the station scale in place it was possi­ble to get the stations on the correct places on the dial. Ad­justing the oscillator coil slug wasn’t easy but it required very little to get it correctly adjusted, and likewise the trimmer. The aerial/antenna circuit was easy to adjust. First, the small adjustable coil on the loopstick was slid along it for best performance at around 675kHz (2CO) and the aerial trimmer adjust­ed at around 1400kHz for best performance. As these do interact, you need to go over the adjustments until no improvement is observed. Always try to do this with relatively weak signals if you are doing it all by ear. Finally, seal the trimmers, oscillator core and the sliding antenna coil with a little beeswax or hobby glue to make sure the adjustments don’t shift with time. The IF adjustments were rea­sonably firm and shouldn’t shift. That was about it, other than giving the cabinet a cut and polish. Due to the warping, deep scratches and so forth that happen to plastic cabinets, they don’t come up to the high stan­dards of finish that we’ve come to expect with wooden or Bakelite cabinets. Summary The Astor RQ was a nice little set, not a tremendous per­former but typical of most 4-valve portables of the era. It filled a niche particularly for women who wished to listen to what they wanted, not dictated to by their husband or boyfriend. Battery life would not have been particularly good and the cost of batteries would have been high. As a simple set it was not as well thought out for service as it could have been. Battery radios form a small but important part of our radio history, so even if they are not your cup of tea some other collectors like them. As batteries are either expensive or unob­tainable, running the sets as true portables is not practical. Mains-operated battery eliminators are really the only practical way to power sets such as this. Many people have thrown out their battery valves as use­ less. They are much rarer than mains valves and due to their relative fragility don’t last as long, so don’t throw them out - give them to someone who restores battery SC radios.