Greetings,

My name is Craig. I live in the Gold Coast Hinterland in Queensland. I have an old Bakelite Bell Radio (sold in NZ/Australia in the 50's and 60's I believe), which has been in my family for many years. It has developed a problem, so I looked on-line for possible tips on repairing it and found this site. I thought perhaps I could describe the problem and a knowledgable member might be able to at least point me in the right direction as to how to rectify it? I would imagine it's a fairly common problem - but I'm no expert!

(I apologise if this thread is in the wrong section...)

The radio used to work reasonably well. However, it was only displayed for many years, without actually being used and therefore built up a fair amount of dust in the back. I recently cleaned it out and turned it on. Initially, it powered up nicely and I was able to tune in ABC 612. However, after about 30-40 seconds, the volume of the transmission reduced until it disappeared completely. At this point, I could also hear a crackling sound and the aroma of something burning! I quickly turned it off.

The radio has five valves - four of which appeared only warm. The fifth (coded as EZ80) was extremely hot and seemed to be glowing more than the others.

I looked underneath the radio (where all the wiring is) and I couldn't see any obvious burning, etc.

Over the past couple of weeks, I have been able to acquire three 'new' valves out of the five and replaced them. I had hopes that maybe one of the valves was faulty. One of the valves I was able to replace was the very hot EZ80.

On testing the unit with the three new valves (and two originals) - I got the same result...it starts up fine, but after 30-40 seconds, the sounds diminishes and then disappears all together. The 'new' EZ80 valve ends up being just as hot as the old one.

I would very much like to get it up and running again. Any assistance would be greatly appreciated! I would be happy to post detailed photographs of the radio if that would be useful.

Kind regards,
Craig.

I would suggest that you do not turn it on again. It is unlikely to be the valves.

As it has been sitting for some time, and this applies to the vast majority of radio;s of its era, both valve as well as some transistor ones now.

The Electrolytic capacitors in them, either dry out or loose polarity after the set has been sitting a number of years. When the radio is powered up they either present as a short circuit, or leak severely and burn something out. Like a very expensive transformer.

Many of these sets also have "metalised paper" capacitors, the bulk of which have passed their use by date. They leak like sieves, and freqently short.

Some sets also have wire insulated with rubber Astor was one of many. This has a habit of tuning to "goo" or becoming brittle & falling off.

A Breville I just refurbished was a classic example. I spotted bare wire on the dial globe wires, which further disintegrated as I removed the reflector; That needs to be done to get its chassis out.

Needless to say that set was checked & refurbished, before power up was even contemplated.

Your radio will now have to be fully inspected to see what damage has been done, over and above what caused it and what I consider needs mandatory replacements on an old set.

Very much the sort of set that should never have been "turned on to see if it works".

The curse of Friday the thirteenth

Like many I get to repair I bet: "The valves still light up", always, even on the bay. Albeit for some bizzare reason they always seem to have the original mains cable?


Marc

Not everyone realises this though whilst it is understandable that curiosity will lead people to switch on an old radio before ensuring it is still safe to use, doing this can often end in disaster. The burning smell and/or any sizzling heard will usually be one of several things:-

1. The power transformer may have been overloaded by a faulty component - perhaps one or more capacitors that have dried out over the years, creating a short circuit when power was applied.

2. A capacitor or capacitors may have dried out and simply started to burn up rather than transferring the pain and suffering to the transformer.

3. A short circuit may have developed in the wiring under the chassis or in a valve.

For someone in your position there is no quick fix and there are three options as far as I can see:-

1. You could take time to learn the ins and outs of circuit restoration and complete this task yourself. Don't expect results in five minutes - they won't be forthcoming because vintage radios have complexity that is not understood until some experience has been gained through research and practice. For a start there are very high voltages inside the circuitry of most valve radios. In a radio made between 1930 and 1960 you can expect to find around 700 volts AC across the outer connections of a secondary transformer winding. After passing through the rectifier valve there is around 350 volts DC. A 'jolt' either side of the rectifier valve will at the least cause pain or injury and at most can kill. This option is the least recommended though it is inevitable that many will want to throw themselves into the job of getting a radio going but extreme care must be taken.

2. Ask someone with experience in vintage radios to either do the repairs for you or supervise you whilst you do them. The latter will afford you some necessary training in how to do the job safely.

3. Simply cut the power cord off (make sure it's unplugged first) and keep the radio as a conversation piece.

Twenty years ago I fell asleep in my bedroom whilst listening to a radio I'd bought a few days earlier. This radio almost claimed my life later that night - a short time after I fell asleep the radio, a Kriesler 11-20, started to billow smoke from the power transformer and if not for the fact that I am a very light sleeper this website simply would have never come to fruition. This event occurred at a time when it was safer to assume an old radio would work well when put back into service. 20 years later, this is no longer the case and every radio should be checked and tested before power is applied by a new owner.

Because of that experience the red text at the bottom of this site, along with the page on basic electrical safety are worthwhile reading.

A suggested way to go about testing is below but it is by no means exhaustive and other tasks may be required to get your Bell going again.

1. Rip out (gently) all valves.
2. Clean the chassis of all dust and debris.
3. Lay your hands on some basic tools - straight edge screwdriver, pliers, snippers, digital multimeter, soldering iron.
4. Carry out a visual inspection of the underside of the chassis, checking and double checking that no short circuits exist. A circuit diagram will help and there's a few sources of these, if you know the model number of your set.
5. If the power cord is in any way worn or damaged or the plug is chipped or cracked replace it, making sure the new cord's connections to the circuit are correct.
6. Use the multimeter (or an insulation tester if you can get hold of one) to check:-
a. Continuity of all windings - there are at least three on most receivers and in many cases four.
b. Insulation resistance between all windings.
c. Insulation resistance between each winding and the iron core of the transformer.
7. Assuming you get low ohms on continuity tests and VERY HIGH ohms on the insulation tests, making sure the chassis is in a stable position (ie: it can't tip over or fall into your lap) apply power for a few minutes and check that the power transformer stays stone cold. If it warms up without the valves plugged in then there are big problems - disconnect power immediately. If the transformer warms up, even slightly, in a no-load situation then the transformer either has a short in one of the windings or there is an unseen short in the radio's circuits somewhere.
8. Assuming the power transformer remains cold, disconnect power and take stock of the large capacitors that are fitted. Typical values are 8μF, 16μF and 24μF at working voltages of between 350VW and 600VW. These capacitors are usually but not always in a red cardboard jacket and of the Ducon brand. Replace these with modern equivalents of the same value and working voltage. Replace only one capacitor at a time. These capacitors are polarised, meaning that they will work well when correctly connected and explode when they aren't. Take note of polarity before removing each old capacitor. Double check all component replacements before going to the next step.
9. Once all the large capacitors are replaced take another look all over the circuit and make sure there are no other components that look charred. If this test is passed then plug in the rectifier valve (usually the closest valve to the transformer but not always - if you quote all the valve types in your set we can tell you which one is the rectifier) then place the chassis in a stable position on the table and apply power and again monitor the temperature of the transformer. It should still remain fairly cold.
10. If there is no overheating, foul smells or sizzling after a few minutes then turn the power to the radio off and plug the rest of the valves into their correct positions. Each valve does a different job so getting their locations right is very important.
11. Reapply power, again monitoring transformer temperature, listening for sparks and buzzing, etc. After thirty seconds the radio should be able to be tuned to a station. If a station can be picked up the clarity of the sound should be fairly clear. If there is any undue crackling, static, or it sounds like a badly-tuned outboard motor then turn it off straight away as there will be further problems to solve.

As mentioned, this list of tasks is not exhaustive and the routine followed will depend on what you are confronted with at each level of restoration. Capacitors are not the only components that fail in radios but in a general sense, replacement of the larger filtering capacitors is sometimes all that is necessary aside from the other checks listed. It is important to remember that each point listed above, plus any other tasks that may be required, not only depend on the age and type of receiver you have but also how well it was looked after and how competently any previous servicing and repairs are done and never assume that another inexperienced person hasn't left you a booby trap. This is an issue in itself and many members here, including me, have horror stories to tell.

The last piece of advice I can give at the moment is be careful where you put your fingers. Manufacturers usually kept live connections and terminals below the chassis but this was not always the case. One example is the field winding on some loudspeakers which doubles as a filtering inductor to smooth out mains ripple in the DC circuit. Connections to these will bite hard if touched.

Update: I just noticed that Marc beat me to the draw and I think his concerns are valid so one thing I would suggest is that before an attempt is made to restore this receiver you would need to ponder on your abilities to attempt restoration and also ponder on your confidence to work around dangerous voltages. If you have the slightest doubts - I would not recommend doing this restoration work unless supervised by an experienced person.

Many thanks for your in-depth replies - they are greatly appreciated!

My skill set with regard to these types of repairs verges on zero - so I won't be touching it further. I'll either hunt down someone in my neck of the woods with the skills or convert the Bell into a nice paperweight!

Thank you once again,
Craig.

Hi Craig
I am in northern NSW if you're ever down this way I can take a look.
ozenginesgmail.com or 0449161753
Peter

Treat this as a sharp learning curve, I and others that either collect or repair, endevour to educate the perveyors of such radio devices locally, as to the the reasons these radio's should not be blindly plugged in.

Along that line:-- Selling mains devices without test tags, either indicating non compliance, compliance, or the unit disabled, is illegal here. As testing electrical devices before sale costs money,many charities like St. Vinnies no longer sell mains electrical goods.

Anything houshold, that falls my way and is a criminal waste to toss. I will test & tag, then move it on to a charity that I know will move it on to someone that needs it. Should it be in good order.

There are adds in the HRSA magazine that may be worth following up (& on their WEB). nfo there too....

I do a bit of outside work, some does come from a fair distance and I do train Club members in the basics of getting them going, or help in bailing them out, if things go pear shaped.

It may be worth posting some "sharp" (tripod) photos of it and the inside of the pan so that we can guage (hopefully) the condition of it and get a vague idea of what needs to be replaced. That may also flush out someone closer that can help.

If someone wants a challenge, take on a Midwest (USA). The three I have refurbished (Mid thirties ) have had 16 or 18 Valves. Parts list of one said 65 caps, that should have been 65 duds.

5 valve ones can be very simple to fix up.

Marc

Suggest we need the equivalent of a "sticky" on the front page giving the dos and don'ts for people coming on here and wanting to know what to do with an old radio they have bought/inherited/found, etc.

Too late in this particular case, perhaps, but I've seen quite a few people ask and we have to repeat the same old everytime. Would be nice to be able to link to a sticky instead.

It's easy enough to make a static page with this information though I wouldn't recommend being too technical with it as different people will have different ideas of what should be done first.

In my post above I did a bit of both - some suggestions I made were fairly succinct and thus probably subject to a more exacting review than I planned and other things I said were just basic to-dos.

There's also something I left out, assuming that every (or even most) new collectors/restorers happen by here before plugging their set in and that is that identification of what type of receiver the collector is looking at should be ascertained first. Is it an AC set, AC/DC set, mains DC or battery DC set? How many of us have acquired a battery set with a mains plug attached only to find that this has been included to run an extension speaker? I know I have on one occasion and if I'd plugged it in without checking it would have blown the bejesus out of the voice coil of the radio's inbuilt speaker. With only about 20 turns of fairly thick copper wire (but still thinner than a 15 amp fuse) it would have made a loud noise.

I'd agree that such a document is worthwhile, though there is more to consider than what has already been discussed. I am going to think about some ways to make this site more discoverable to newer collectors too. People need to read the available information before making their first acquisition.