|
Post by briano on Jun 11, 2022 10:28:19 GMT 12
MY GRANDMOTHER'S RADIOPlease see my backgrounder etc. further below, and photos. I then have these five questions and would really appreciate any help: 1. Was it normal for a cabinet to be chosen and the radio then made to specification? 2. What company is likely to be the manufacture - for cabinet/for assembly? (No manufacturer marks). 3. What year would you place its origin at? (My feeling is circa 1939/40). 4. Do you think it is built to a standard or known circuit? 5. Would the valves still available? BACKGROUNDThis radio is my link to my grandmother whom died five years before I was born. Story goes that the cabinet was chosen in a shop in Wellington. The radio was then made to specification - being it had to receive short-wave without a big outdoor aerial. In the mid-sixties, I used to tune into 4BC Brisbane, and listen to ’The Fabulous Beatles Show'. I have not turned on since. I plan to get the radio back up and running. RADIO DETAILSTwo-bands, MW and SW. Seven-valves, including magic eye Rola K8 2500 ohm loudspeaker VALVESJAN CRC 6SK7, VT-117, KGE, RCA, Made in USA, RH * * 6SA7, Haltron, Made in USA 6K7, RCA 6Q7, RAD, USA 6F6GT, Toshiba 80, Philips JAN-6U5/6G5, VT-98, SC95A, Sylvania, Made in USA (Magic Eye) MY RESEARCH SO FAR1. Escutcheon surrounding the dial - seems to match those of the 'Columbus' Model 36 made from 1938 and the 'Courtenay' Model 36 from the same year. However, the cabinets are different to my radio. 2. From the radio station markings on the radio dial I conclude the radio was made after 8 February 1939. 3. Looking at the valves, most were in common use during the 1930s. However, two of the valves were not produced until the end of 1938 (6SK7 & 6SA7). 4. I did find a similar cabinet in PapersPast (21 October 1939) for an advertisement for Dunedin-based radio brand called "Oxford", Model 71M. Those radios were manufactured by 'Webbs Radios Ltd' in Auckland, and distributed by The New Zealand Express Co. Ltd. However, I could not find any circuit information to see if the circuitry was a match. 5. The loudspeaker is a 'Rola', made in Melbourne, Australia. However, the Columbus, Courtenay, and Oxford brands appear not to use these speakers. A further search found that a Wellington-based manufacturer, 'Collier & Beale Ltd' used Rola speakers in their Gulbransen brand radios. And, appear to have used the same electromagnetic loud-speaker IN CONCLUSIONI would be most appreciative of any light that could be thrown on my questions at the top of my post. Thank you, Brian.
|
|
Steve
Society Members
vintageradio.co.nz
Posts: 734
|
Post by Steve on Jun 11, 2022 23:57:07 GMT 12
Hi Brian, and welcome. Its very rare to have such well-researched questions - you've done a great job of getting yourself started... lets see if I can add a little to it. 1. Yes, for smaller manufacturers / repair shops it would have been normal to choose a cabinet and radio style to go in it. 2. I don't know who made the cabinet, but I have seen it twice (and owned it once). There were a lot of furniture or cabinetmakers in NZ who made cabinets, and I also suspect some were imported. - The Oxford 56M (you found another Oxford model in this cabinet - they used it on a few)... www.vintageradio.co.nz/model/oxford/56m - The Stella S8... www.vintageradio.co.nz/model/stella/s83. I agree with your dating of the set. It could have been as late as 1942, but the desire for SW was possibly to listen to the BBC and other overseas news services to keep up with the goings on of WW2. The speaker MIGHT have a date code - check around the rim, looking in from the back - NZ Rolas had a code that was 1 or 2 digits, then a letter, then another digit. The first 1 or 2 digits are the day, the letter the month (A=Jan, B=Feb etc) and the final digit was the year (9=1939, 0 = 1940 etc). I don't know if Australian Rola's used this code. Rola went to permanent magnet around WW2 so 0 would be 1940, not 1950. As an aside Rola was the single most-commonly used speaker brand in New Zealand. They were made here, but also imported from Australia and the US of A and probably England as well. And its not safe to assume Oxford didn't use Rola speakers - smaller manufacturers would have used what was available (even larger ones were at the whims of what they could get). 4. Its likely a kitset, so I'd be looking at the likely suspects for kitsets in Wellington - Exelrad / Turnbull & Jones would be the first suspect - but it really doesn't look very much like their componentry to me - others may have thoughts on that. The dial is confusing - Columbus and Courtenay were made by Radio Corporation of New Zealand in Wellington (80 Courtenay Place) - but they didn't sell their parts, and nothing about the rest of the set is even remotely Radio Corp. I think that dial has either been fitted to replace a broken one at a later date, or its been re-purposed from a set that was traded in and not worth repairing or reselling. The chassis looks very well made which also suggests it might be a kitset from a larger reseller - a smaller shop likely would make the chassis much more roughly. 5. Yes, absolutely... there is nothing unusual about any of the valves the set has - they are all commonly available. The magic eye will be the most expensive one if you can find a working 6U5. So, in conclusion - probably a kitset chassis - the dial is confusing and does not match any other part of the set, the valves will be available but these might not need replaced - the capacitors almost certainly will though. I would be very surprised if it didn't burst straight back into life with new capacitors in it. You'll probably also want a new power cord with an earth as well. Cheers, Steve
|
|
|
Post by Richard on Jun 12, 2022 9:47:02 GMT 12
unusual that the manufacturer of the radio used 6SK7 and 6SA7 instead of 6K7 and 6A7, but then used a 6K7 as an IF amp. 6SK7 first used in 1938 and 6SA7 in 1939 apparently ?
|
|
Steve
Society Members
vintageradio.co.nz
Posts: 734
|
Post by Steve on Jun 12, 2022 10:22:51 GMT 12
The other thing I am wondering about is the JAN (Joint Army-Navy) numbers on two of the valves - it could be a post-war set made from war surplus stocks? Or they could just be replacements... The round IF cans are possibly new-old-stock since square cans were the order of the day by then - and big coil-cans on top of the chassis were disappearing under the chassis by around 1939 too. Its a conundrum when taking the parts as a whole, but if it was a smaller shop then it might make sense.
The transformer with louvres on top is a C&B kind of thing although I don't recall louvres with different lengths but its not something I've studied in-depth... and they had similar IF cans in Cromwells and Gulbransens in the late 30's and they used square coil-cans in some of their chassis' too.
Questions:
1. is there an ARTS&P label on the set anywhere?
2. Can you add a couple more photos from other angles? Specifically the rear.
3. Is there anything stamped into the chassis - logos, numbers, etc?
4. Are any of the valve sockets riveted in, clipped in, or are they all screwed in (and do all the sockets look the same, and the screws holding them in look the same?)?
Cheers, Steve
|
|
|
Post by briano on Jun 12, 2022 11:08:37 GMT 12
Thank you Richard for your comments on two of the valves. Most interesting. QUESTION: Are the 6SK7 and 6SA7 direct substitutes for the 6K7 and 6A7 valves? Do you think these valves might have been replaced at some time? Thank you Steve for your your kind comments and most detailed and helpful replies. Yes, I too thought it may have been purchased near the start of WWII. My grandmother died in 1945 and was bedridden for some time before her death. So, I think the radio enabled her to keep in touch with the world. I don't think the dial has been replaced but I will look closer. I had packed away the set after taking the photos to keep it safe. I will get it out again. There is no outward evidence of previous holes, cuts. I will upload a closeup of the dial. Thank you for the hint on identifying the Rola loudspeaker age. I will upload a photo - showing a 1P. Thank you for the advise to change the power cord and use an earthed type. I will secure the earth wire to the metal chassis. I need to identify all the capacitors and definitely replace the two big 'can' electrolytics and the other paper/wax types. I am thinking I might sit down and draw the circuit out which will also help me identify what I need to replace. QUESTIONFor the two big electrolytics (8uF and 16uF) I was thinking of the Jaycar 10uF 450V catalogue RE6078. Use three, two of them being in parallel for the 16uF replacement? Alternatively, I could source a 10uF and 22uF 450v ex Aliexpress? Your thoughts appreciated. In regard Steve to your second reply I can answer: 1. I could not see an ARTS&P label on the set 2. I will post more photos 3. I could not see any logos, numbers stamped into the chassis 4. The valve sockets appear to be screwed in. The socket for the 6F6GT Toshiba valve look newer and not rusted though. I will pull the set out again and have another closer look - taking into account your questions. Thank you for your help... Brian.
|
|
|
Post by briano on Jun 12, 2022 11:11:05 GMT 12
|
|
|
Post by Richard on Jun 12, 2022 13:38:26 GMT 12
I maybe wrong, but I think the radio is pretty original, except for the 32uF electro I see under the chassis, I think Steve is correct, in that the valves used were types available at the time. The 6S type valves had their control grid on the actual valve socket pins instead of a "cap" on the top of the valve, but pretty much the same otherwise? its probably just a typical 6 valve set design, similar to a columbus/courtenay design. the Jaycar electrolytics could be used, though I've had failures of these after a short period. I have purchased high voltage electros from ebay and NZVRS(if you are a member?)
|
|
|
Post by Peter Walsham on Jun 12, 2022 18:02:57 GMT 12
My 5cents worth
I would try & source 500 Volt electrolytic filter capacitors, rather than using 450 Volt ones, as the peak voltage on the B+ bus will exceed 450 Volts with a directly heated rectifier valve (as a matter of fact, it will exceed 500 Volts) until the rest of the radio valve heaters warm up, and pulls the peak voltage back down. Some (but not all) 450 Volt rated electrolytic capacitors will happily 'accept' a peak voltage higher than their rated 'working voltage' for a very short period. Like Richard, I have had the Jaycar electrolytic capacitors fail. They literally blow up! Warning: A shorted electrolytic filter capacitor will, more than likely, destroy the rectifier valve, and may also 'kill' the power transformer too. It is vital to use good filter capacitors. As a matter of fact (due to a bad past experience) I always replace the filter capacitors in every radio I work on, and I also wire in a 1 Amp fuse in the phase lead of the power transformer to help protect it from potential catastrophic failure (and potential fire).
Peter
|
|
Steve
Society Members
vintageradio.co.nz
Posts: 734
|
Post by Steve on Jun 13, 2022 0:17:01 GMT 12
So the closer look at the dial reveals no brand markings - which makes me suspect its an Exelrad, or at least Turnbull & Jones sourced part. The magic eye shroud definitely could have come from them - here it is on page 34 of their 1939 catalogue In case you are not aware, Turnbull & Jones sold a line of spares branded Exelrad, many of which (pre-WWII) were made by the same factory (Radio Corp) who made Columbus and Courtenay. They did sell dials and escutcheons that were also used on some Courtenay sets - I can't find evidence of them selling the dial on your grandmothers one - but given it has no branding and the SW frequency bands appear to have been tweaked by hand it could well be that the dial assy came from T&J. This doesn't bring us any closer to the solution of what the rest of the set was - but I am reasonably sure from what I can see that its not an Exelrad kit overall - the trimmers and other componentry just don't look like theirs. I wonder if it could be Australian in origin - Radiokes, RCS or Lekmek? They were popular in the mid-late 30's courtesy of the NZ Radio Times who published circuits all the time, and several retailers sold the kitsets for them. Fears in Willis St was one of them... Cheers, Steve
|
|
|
Post by briano on Jun 13, 2022 12:58:55 GMT 12
Thank you all, for your really helpful replies. Your experience and knowledge is truely valuable. Thank you. Thank you Richard for your comments about the radio being pretty original except for the 32uF electrolytic and also for the fact that the 6S type of valves had their control grid on the valve socket instead of using a 'cap'. In regard to the high voltage electrolytic filter capacitors, yes, I am a member (new) of the NZVRS and have just had a quick look there for components so thank you. Thank you also Peter for your advice on the preference to use 500v electrolytic filter capacitors instead of the 450v types. I have done a search online and they seem to be rather scarce in comparison. I couldn't find any source in NZ other than I see the German F&T brand seem highly respected. Thank you too for your advice on inserting a 1 Amp fuse in the phase lead of the power transformer. QUESTION PETER: Do you solder a glass fuse under the chassis or do you mount externally in a holder? Trying to keep the integrity of the radio, I wonder if I use a panel-mount fuse holder in a separate die-cast aluminium box, outside of the radio, and plug the radio mains plug into that? Thank you Steve for your further feedback along with photo of the magic Eye escutcheon. Yes, looks identical. I appreciate your research into possible sources including the Exelrad branded parts and also possible Australian origin kit-sets. I have just pulled the radio out again and checked the cabinet and chassis over very carefully. Here are updated answers to your questions: 1. There is definitely no ARTS&P label on the set 2. I will post three more photos with this latest post 3. There are no logos stamped into the chassis. However, on one side of the chassis there are hand-scribed markings of "BC SW B S S B". I have taken a photo. Perhaps the first two sets denote the chassis is the dual-wave design. However the other four letters don't make sense to me. They are not the initials of my grandparents so perhaps denote something else to do with the chassis design? 4. All valve sockets are screwed in, except for the 80 rectifier valve and the 6SKY and the 6SA7 valves. These three have a type of cir-clip underneath. Photo included. Now the set is out of its storage carton, I will have a nice initial project of drawing out the circuit and identifying any other capacitors to replace. And, I note the dial cord has come off the drum but does not appear broken.So, I will try to get that back on but feels rather tight. Thank you all for your help. I am immensely grateful... Brian Oliver
|
|
Steve
Society Members
vintageradio.co.nz
Posts: 734
|
Post by Steve on Jun 13, 2022 13:20:28 GMT 12
507 at the bottom of the TCC electro - does anyone know if this is a manufacturing date code for the cap? If so, 50th week of 1937? Or is it something else? That might make the set too early unless they had big stocks of those caps sitting around for a year or so - which seems unlikely for a smaller place due to the cost, and unlikely for a larger place because they would be going through them quickly.
BC and SW will probably refer to the trimmers for those bands (for alignment of the set and dial), while the others are probably trimmers for the oscillator and RF section - the one on the very right will be the broadcast band padder. There are also trimmers on the tuning cap itself so it might take a little reverse engineering to work out what is what. B will be for tuning the broadcast band and S the shortwave.
|
|
|
Post by Peter Walsham on Jun 13, 2022 13:26:28 GMT 12
Hi Brian
I usually solder directly on to the fuse end caps, and use two short pieces of heat shrink sleeving over the metal end parts of the fuse (leaving most of the glass tube visible so the inside of the fuse can be easily seen). The fuse is under the chassis. I don't (and wouldn't) worry too much about changing the integrity of the radio. A burnt out power transformer looks much worse, and renders the radio useless (unless you're lucky enough to source an identical replacement transformer)! You are going to replace the power cord & all of the capacitors anyway, so a small fuse won't look out of place.
A note regarding your comment about the 6F6 valve socket being different to the others. It is a (remote) possibility that the radio originally had a '42' output valve. The '42' is identical to a 6F6, other than having a 6 pin 'UX' base fitted instead of the 8 pin octal as fitted to a 6F6. Replacing a faulty 42 with a 6F6 would have required a socket change. My thoughts on this are based on your photo of the underneath of the chassis, which seems to suggest the soldering around the 6F6 valve socket isn't as tidy as the rest of the radio?
Peter
|
|
|
Post by Peter Walsham on Jun 13, 2022 13:34:45 GMT 12
Hi Brian
I usually solder directly on to the fuse end caps, and use two short pieces of heat shrink sleeving over the metal end parts of the fuse (leaving most of the glass tube visible so the inside of the fuse can be easily seen). The fuse is under the chassis. I don't (and wouldn't) worry too much about changing the integrity of the radio. A burnt out power transformer looks much worse, and renders the radio useless (unless you're lucky enough to source an identical replacement transformer)! You are going to replace the power cord & all of the capacitors anyway, so a small fuse won't look out of place.
A note regarding your comment about the 6F6 valve socket being different to the others. It is a (remote) possibility that the radio originally had a '42' output valve. The '42' is identical to a 6F6, other than having a 6 pin 'UX' base fitted instead of the 8 pin octal as fitted to a 6F6. Replacing a faulty 42 with a 6F6 would have required a socket change. My thoughts on this are based on your photo of the underneath of the chassis, which seems to suggest the soldering around the 6F6 valve socket isn't as tidy as the rest of the radio?
Oh, by the way, please fit a new 3 wire power cord (as previously suggested - it is absolutely imperative (for your safety) that the radio be fed with an earthed power lead), but also fit some sort of a cord clamp to hold it in place (a knot tied in the power cord is now illegal), and carry out an electrical safety test before powering it up.
Peter
|
|
|
Post by briano on Jun 13, 2022 14:58:07 GMT 12
Thank you Steve regarding the marking on the exisiting 8µF electrolytic filter capacitor. For your information, looking at the 16µF capacitor, the code at the bottom reads, "506". And, good thinking on those letters inscribed on the side of the chassis. Yes, you would be right. Thank you.
Thank you Peter for the information on the 1A fuse, and sounds a nice tidy solution using the heat-shrink tubing. I use it a lot for my various electronic projects. Your thoughts around the 6F6 valve being a replacement sounds very logical. I note your comments re replacing the power cord and using new 3 wire one. And, using a proper cord clamp. Thank you.
Cheers, Brian
|
|
|
Post by Peter Walsham on Jun 13, 2022 15:21:21 GMT 12
Further thoughts on the filter capacitors.
The NZVRS have 10uF, 600 Volt capacitors available. These will do as suitable replacements. However, you will probably need to use two of these in parallel to replace the 16uF, 440 Volt one as shown on your chassis diagram. It won't matter if you use even more than 2, but only use one for the first filter capacitor, as if you use anything higher than about 16uF, the peak current flowing through the rectifier valve will be too high, and will likely lead to a shorter rectifier valve life and/or rectifier valve failure, which seriously jeopardises the power transformer.
|
|