|We don't aim this at complete beginners. Until you have enough knowledge of basic modern electronics, working on safe voltages, you won't be safe to tackle a valve set. When you know the basics of the modern things, and you know how to read the values of resistors and work out what to measure and how with your multimeter, you are ready to have a go at some real electronics. We have a rough guide to how valves work, and another on how Superhet radios work. Once you know all that, read this and fix your set!
Pick Your Victim!
The world is not short of old valve radios. It may seem that it is, when you've only got the one, but another will turn up. And one of the most important factors in your first few radio restorations will be the raw material. If the set looks horrible, with a lot of rust on the chassis, rot in the wiring, and bits missing or broken, it will be trouble. Don't do that one until you are confident. The best raw material for your first try will be simple (no FM) and well built, and also in reasonably good condition. It would also help if it was quite common. This will help in the event of any slightly difficult parts being required.
You will need equipment. The first thing to get is the service data for the set. Leave the heroics until later. You won't guess what's meant to be happening on your first set. Get the data and make sure you know.
And then read the data and relate the various bits in the diagrams and layout sketches to the various bits on the chassis. Is the chassis in the set exactly the same as the one in the diagrams? If not, trouble may well be just around the corner. You need to know where the major parts of the set are, and which adjustments do what, so that you know what you're doing while working on the set.
Once you are familiar with the set, you will need some tools. The most important thing will be a set of various screwdrivers. Get some with nice insulated handles, and get plenty of different sizes. You'll need them. Then you need a pair of pointy-nose pliers, not too big and not too small. The "Electrician's" variety will be fine. And a pair of wire cutters. A smallish pair will allow neat trimming of odd bits sticking out after your soldering, but a pair which is too small will not cut very thick wires. Then into the vaguely technical stuff. A soldering iron and a stand for it. You need about 25 watts for a valve set, as a smaller one will have trouble melting the solder on the chassis points. You want a fairly small bit, say 3mm. No good trying to solder with a pin or a pig's trotter. And some solder. Proper electronics solder, please, with resin core, but nothing fancy required. Given a choice of thin or thick, personal preference is the guide. Thin stuff if you always tend to put too much solder on a joint. Thick stuff is usually cheaper.
As for test gear proper, you would be unlucky not to be able to get by with just a multimeter. Here again, don't buy cheap rubbish. It will load the circuit so much that its readings will be meaningless. But then, if you have an accident, the multimeter will probably be the victim, so don't go mad. A middle-of-the-range digital job will do nicely. If you can't stand digital meters, get a half-decent analogue type. Either will do, but you may be able to drop a digital meter once and get away with it.
First we have to cover the basics, and the most basic basic is safety. Old radios were made in the times when electrical safety was taken a lot less seriously than it is today. Most of the old sets have some characteristic of their design which would fail to meet modern standards. Having said that, though, there is no reason why, with a little bit of know-how, and a bit of common sense, the average radio cannot be sorted out in such a way that it is perfectly safe to use.
But we're never going to make an old valve radio safe to work on, are we? These things have 250V DC, if not more, running through their veins. The golden rule is never to come into contact with this yourself. Unless you are taking voltage readings or adjusting the alignment, you ought to switch the set off and pull the plug before you get too involved with its innards. And if you have to do something to a set which is running, do it very carefully, with insulated tools. An accident with this sort of voltage could be fatal. At the least it will be very unpleasant. So you will need the tools and the working environment to make sure that accidents do not happen. If you don't fancy it, there is always a professional who can do it for you. It's better to be safe than dead.
Another thing to check on is that the main capacitors in the set are not storing charge after the set is switched off. There are faults which can (and often do) pop up, which produce the symptom that the main electrolytic capacitor in the set charges right up, but the power has nowhere to go. If your finger strays there, that will catch the full blast, even after switch-off, if the capacitor is still charged, and you won't like it at all.
The solution to this is to fit a pair of well insulated wires into a bulb holder, and fit plastic test prods to the ends of the wires. Fit a 60W 240V bulb in the holder, and get into the habit of touching one prod to chassis and the other to the terminals of the main capacitors after switch-off, before you work on the set. If the bulb flashes, it has just taken away energy that could have given you a nasty belt.
Now we have some idea how to tackle the thing safely, it would be a good idea to have a look around the chassis for obvious snags. Once the chassis is free of the box, any problems should be a lot more simple to spot. Components which are obviously burnt are signs of trouble, and waxy tubular capacitors which have dribbled out a lot of hot wax have obviously had enough as well. Reference to the circuit diagram will tell you the values of the burnt resistors and melting capacitors. You might as well order up replacements now. They will have to be changed.
Before the chassis is introduced to the mains, it is essential to get it equipped with a proper, modern, safe and well fitted mains lead. If the set has a mains transformer and the "Earth" terminal is connected to chassis, use a piece of modern PVC 3-core flex of modern regulation colour code, and solder the earth lead to chassis, even if it only had a 2-core lead in the first place. If there is no mains transformer or the "Earth" terminal goes to chassis via a high voltage capacitor, a 2 core lead should be fitted, and no earth used. The mains lead needs to be anchored firmly to the chassis in some safe way. The originals often went in through a grommet in the back of the chassis and had a knot tied in them, just inside the set, to stop it being pulled out by accident. While modern safety regulations don't like this at all, we maintain that if this is the only secure way to do it, then better a secure installation with a knot than a wonky one with a plastic clip or a plastic cable clamp. Common sense will be required.
On a set with no mains transformer, the chassis will be connected to one of the mains wires. It would obviously be silly to have a live chassis, so make very sure that when you solder the wires to the back of the switch, the neutral one goes to chassis. Even then, you have to be very careful when working on a set with a non-isolated non-earthed chassis, and when you put it back in its cabinet, make sure no metalwork is accessible. It's OK when everything goes well, but what about the day when you inadvertently discover that socket which some dumb-head sparky has wired up with the live and neutral crossed over?
While fitting the mains plug, remember the 3A (or 2A) fuse. It saves the lead catching fire in the event of a fault.
When the chassis is first introduced to the mains, the main electrolytic capacitors and the rectifier valve are likely to feel the strain, especially if the set has been laid up for years. This is because the electrolytic capacitors re-absorb the gas layer that is the dielectric of the capacitor, and hence take a significant current as the rectifier first starts to work. One of four things can happen. The nice outcome is that the rectifier and the capacitors simply shut up and get on with it, with no further problem. However, the capacitors might not re-form that layer of gas properly. They may over-gas and blow up. Or they may under-gas, pass too much current for too long, and kill the rectifier. And then there's the chance that even the short-duration current surge through the rectifier as two reasonably healthy electrolytics re-form will see it off for good.
The proper course of action is to re-form the electrolytics. This is done by appling their working voltage through a high value resistor (say 100K ohms) until the current through the resistor settles down (a few minutes). Alternatively, you can power up the set on a variable voltage transformer, so that it starts up very slowly and the capacitors re-form in the set. But the beginner doesn't have a source of high voltage, and he doesn't have a variac transformer. So he has two options. One is the tin-hat and stand well back for a minute tactic, and the other is to fit new electrolytics anyway, and they won't need re-forming. If the old capacitor has signs of having leaked goo at some time, or the end is bulging fit to bust, you might as well change it. Otherwise, the choice is yours.
Once you've got the mains lead right, done whatever with the electrolytic capacitors, and replaced any barbecued components, it's time for the mains.
You will need a speaker connected to the chassis, and an aerial plugged into the right socket. Any long bit of wire will do at this stage.
The warm-up time seems like an hour when you first try a set. After twenty to forty seconds, depending on the set, you should hear some hum and noise in the speaker. Try turning the volume full up, and setting the tone control half-way. If you can't hear anything, you've got a problem.
You might be lucky and get a station. Have a go, you never know!
Nothing in the Speaker
Problems with the output stage are simple to find. Check for HT volts on the main electrolytic capacitors. If there aren't any, switch your meter to AC volts and see what's going into the rectifier. If there's no input, switch off and check the connections and any resistors in the AC circuit feeding the rectifier. If there is input but no output, or very little output (the service data will tell you roughly what voltage to expect) and the valve heater seems nice and hot, switch off and use your ohmmeter to find out if the HT line is shorted to chassis. If it is, just follow it around until you find the problem. If it's all clear, it's time for a new rectifier.
If there is HT on the capacitors, and especially if there are more than the sheet tells you to expect, it's a good bet that the power is not getting to the output valve, which should be driving the loudspeaker. Measuring the voltage at the anode and second grid of the output valve will show what's going on. If there's no voltage at the anode but second grid is healthy, turn off at once (output valves don't like this way of working) and check the output transformer winding which is in the anode circuit of the output valve. Odds on it's open-circuit. New transformer required.
If the second grid of the output valve has no voltage, this will lead you to some problem with a resistor or a smoothing choke.
If it all seems OK but there's nothing going on in the speaker, check the output valve's cathode voltage. If it is not a few volts positive, the valve is not passing any current and can be replaced with confidence.
If the output valve has cathode voltage and everything else is in order, check for dodgy wiring or switches leading to the speaker, or a duff speaker (their coils or terminations sometimes rot away).
Once you have the output valve working, you should hear something, even if only a quiet hum, in the speaker. If the volume control being advanced makes a noise, it's a good bet that the audio amplifier valve is working too. If not, turn off and check for open circuit or high value resistors.
If the output valve seems to be overheating or the cathode voltage is high, the valve could well be drawing too much current because the capacitor which couples the signal from the anode of the valve before is leaky. Even a high resistance leak here will cause trouble and this capacitor is a frequent source of trouble. Replacement will eliminate it from the enquiries.
Once you have the thing working as far as the volume control, you will probably find that the volume control makes scratching noises when it is turned. You can get switch-cleaner spray for just this sort of job. Switch off, squirt some cleaner in through any handy hole in the volume control, and turn backwards and forwards a few times. Wait while the cleaner dries off, and then try it out again. If that doesn't cure it, check the capacitor which feeds the signal to the volume control. A leaky capacitor will cause crackles. A replacement may well be worth a try. If that doesn't do it, it's time for a new volume control.
IF Amplifier Stage
If you're lucky, you might find that by now, you're picking up stations. If not, it's time to see what is going on with the IF amplifier valve. Change the wavechange switch while the volume is well up. Lots of loud crackles as the switch goes around mean that the IF and frequency changer stages may well be alive and well. Quiet crackles or no crackles mean trouble.
Checking the voltages around the IF amplifier may reveal a problem. Quite often the second grid is not getting sufficient voltage because the capacitor which bypasses this grid to chassis is leaking away merrily. If the anode is not getting any voltage, it's time to switch off and test the resistance of the anode coil in the IF transformer. If this is open circuit, you'll need a new IF transformer and some more work besides. See later!
If everything in the IF amplifier stage seems in order, try touching one of your meter probes to the control (first) grid of the IF amplifier valve. A click or pop from the loudspeaker gives you a rough-and-ready indication that something is going on. No reaction means that there is something amiss with the IF amplifier and it's time to check it again.
On to the frequency changer. If everything else is working, you should find that there is quite a pronounced background hiss in the speaker by now, on full volume. If there is plenty of hiss, try getting hold of a good bunch of the wire used for an aerial, and tuning up and down MW. If you have a TV or striplights handy, switch them on. If you pick up interference but no stations, the frequency changer is amplifying but the oscillator is stopped. If this is the case, try LW and SW too, and see if the oscillator has stopped on all bands or just some. If it goes on SW but not MW or LW, try a new valve, but if it works on LW, it's unlikely to be a valve problem. Test the voltages around the oscillator part of the valve. If nothing obvious is amiss it's down to the circuit diagram. Time to switch off and test coils and switches.
If the frequency changer is not giving any background and interference pick-up, then it's quite likely that you will find the fault by testing the electrode voltages.
If there's nothing amiss with the voltages, you can try another dodge, which consists of touching your test aerial to the first (control) grid of the hexode section of the frequency changer. If this brings in stations, probably several at once, then there is a problem in the aerial coils or the wavechange switch and the aerial signal is not getting to the input of the frequency changer.
If there is not even a click in the speaker when the control grid of the frequency changer is touched with the aerial, the changer is not working and it is time to go back to the voltage checks and maybe try another valve.
It Goes, But It's Too Quiet!
Nasty. We don't like this one. First step is to work out where all your signal has gone. Are there lots of stations received, all of which are quiet to whispering? If so, the frequency changer and IF are working fine, but the audio stage is poor. Or is there only one station even with a big aerial? That would mean a problem with the frequency changer or IF amplifier.
You can poke around with a voltmeter, but odds on if there was anything wrong, you'd have found it already. However, never neglect the possibility of a duff valve. Can you get or borrow some which are known to work? Do you know a mug with a valve tester? Can you take your valves and plug them in someone else's set? One tell-tale sign is that the cathode voltage for the valve is low when measured. The other tell-tale is that the anode and second grid voltages are rather higher than the service sheet suggests.
The next job is to switch off, discharge the capacitors, and have a go at checking resistor values with the ohmmeter part of your multimeter. Remember that they were probably only within 20% of the marked value when new, and to make a lot of difference they will need to be quite well off value. A lot of multimeters only test to 2 Megohms. This might mean that you can't prove anything about the 2.2 Meg resistors in the AGC line, which are involved with grid bias for the IF and FC stages. If this is the case, and you are really clutching at straws, you could replace all the resistors you can't test. You never know, you might be lucky! We have been, several times.
If the problem is an audio one, don't overlook the output transformer. Occasionally some odd faults pop up here, and a few shorted turns will cut the power to the speaker quite badly, but not really show up on DC voltage tests, or even on resistance tests with the set switched off. You can always get a spare transformer and try its effect. You'll need one before too long for something, anyway. Alternatively, if you have a mains to 6V transformer, you could try that for comparison. (Mains winding in anode of valve.) It's not the right thing for the job, but it's close enough for an indication, especially when you're clutching at straws.
Checking everything in the audio stages usually does not take too long, and if the fault was here, you stand a good change of finding it.
If the fault is in the FC or IF stages, however, you may have more fun. Try all of the different wavebands. If it's useless only on one band, check the wavechange switch, the coils involved, and cast a suspicious eye over the trimmers and iron dust cores in the inductors. Any sign of someone messing around here could mean re-alignment. Try touching the aerial onto the grid of the frequency changer on the affected band. Lots of volume with lots of interference confirms the diagnosis that the alignment is out on that band.
If the alignment is out on SW, you need to get hold of a signal generator. If it's out on MW or LW and you can get a station through the set at both ends of the band, you can do the re-alignment using stations off-air. It's not good, but you can do it if you have to. The service sheet will tell you what to adjust at which frequency. Just use the nearest known and trustworthy on-air station and do what it says.
If you can't get a station through on that band at all because it's too far out of alignment, you're basically stuck until you can get your hands on a signal generator.
If all of the bands are useless to the same extent, then it's a fair bet that there is a problem with the IF alignment to some extent. You can do IF alignment by ear, with an off-air station. It's not the best way to do it, but if you don't own a signal generator, it's the only way to do it. Tune in a station and use just enough aerial so it's audible, but nothing like loud, with the volume full up. Touch up the trimmers or cores in the IF transformers one by one and peak them up for maximum response. They should not need a huge adjustment. Any which do need large adjustment should raise suspicion, and those which make very little or no difference as they are adjusted should raise suspicion as well. As you go along, and things hopefully improve, just use less and less aerial to keep the signal input low enough that the radio has to use full gain to get anywhere with it. If the re-alignment of the IF is successful, then something must have wiggled out of adjustment over the years, and with any luck you now have a good set.
If the IF alignment showed up an adjustment which was miles out or didn't do much, it's time to investigate. If the one which was miles out has been "got at" by the phantom wrecker who had the set before you, that's hopefully all that's wrong. However, if not, either the coil has shorted turns or the capacitor has decomposed and gone off value. Capacitors off value can be replaced. Shorted turns on coils mean it's going to need a repacement IF transformer.
If one of the adjustments didn't do much, check the DC resistance of the IF transformer coils with the set switched off. You're looking for a resistance of less than 15 ohms, usually. If one is low and the other higher, it's a good bet that the coil with high resistance has partly rotted wire and again, a replacement IF transformer will be needed. If it's not the coil, it must be the thing which makes the adjustment. If that is an iron dust core, it may have disintegrated. If it's a trimmer capacitor it may have done a similar trick. Either could be fixed if you have the pieces.
If you have to fit another IF transformer, with any luck you can get an identical one off a chassis very similar to yours. Ask around! In this case, you just fit the transformer, wire it in, and turn on and set up the alignment just as outlined above. It's quite likely that the new IF transformer will be nearly right for your chassis when you fit it. Most chassis of one type are very similar, so the tuning should be very similar from one chassis to another.
Tried Everything, but the Stage Won't Work!
Tried everything? Can't get the stage in question to work? Must have a nasty obscure fault. Check for clues. Assuming that the voltages are as close to the service sheet values as you can reasonably expect, and that you have checked up the coils, transformers, switches and other troublesome things, it's time to go looking for something nastier.
Have a look at the valve sockets. You will see a contact for each pin. Do any of them look bent or slack or broken? Try switching on and wiggling the valve around in its holder. Do you get a lot of popping and crackling and occasional indications that it might be trying to work? Time for a replacement valve holder. It's not a nice or easy job, but if you label the connections as you take them off, you know where to put them on the new holder.
Check the connections to chassis points and solder tags. Are the chassis points firmly connected to the chassis? A loose screw could cause disaster here.
Is the wiring rotten? Old rubber wiring perishes and wires can touch. But wires insulated with a brown woven sleeving which is varnished are signs of trouble. The varnish decomposes into glue and then partially conducts electricity. If this is the case and leakage between wires seems possible, try temporarily seperating the wires. If this improves matters, time to re-wire.
It Goes for Ten Minutes, and then....
If you get audio distortion after a few minutes, try measuring the cathode voltage of the output valve when cold and again when hot. If the voltage increases fairly markedly, there's a leak somewhere. If the coupling capacitor coupling the signal into the first grid from the anode of the audio stage valve hasn't been replaced, now would be a good time. If that doesn't cure it, and it's a UL41 or a UL84, you'll want a new valve. Otherwise, have a look at the valveholder. If it is looking burnt and blackened, replace it. It wouldn't be the first one to have died this way. If it's still happening with a new socket, it must be the valve after all.
If the volume drops away, see if there are still as many stations, even though at reduced volume. No shortage of stations means an audio fault, which is rare and often comes down to the audio or output valve. A shortage of stations means an FC or IF fault, and isn't that rare.
If the fault is with FC or IF stages, try turning the lights on and off a few times, and making interference on the radio. If this changes things you have an AGC fault, and it's time to investigate the high-value resistors which make up the AGC system. You'll find they're usually between 470K and 2.2M ohms, and can be found connected to the bottom end of the grid winding on the first IF transformer and the grid of the FC valve. Other faults will usually show up quite readily if the voltages are checked when cold and again when hot.
It Hums for England!
That's not uncommon. Try turning the volume right down. Does that change it? If so, it's got some bad wiring with faulty earthing taking the signal to the volume control.
A bad hum usually means that the main electrolytic capacitors have come to the end of the road. However, that's not the only cause. The output valve can cause the hum by having poor insulation between its heater and its cathode. While this can happen with any valve, you'll find it happens most often with a UL41. The same can happen with the audio valve, but it doesn't very often. If you suspect it has, temporarily disconnect the coupling capacitor taking the signal to the grid of the output valve. That will stop any hum coming through from there.
Then there are the rare occasions when the output transformer suffers an insulation breakdown between the primary (output valve anode) winding and the core. This causes an overload on the HT power supply rail, and will lead to hum because the smoothing is not sufficient for the increased current. Replacement is the only cure for this.
Lovely. If the set has a mains transformer, and will run with a valve removed, try removing the valves one by one, starting with the frequency changer, and ending up with the audio valve. If it still crackles with the audio valve out, the output stage is crackling. Otherwise, the valve you'd just removed when the crackle cleared up was the stage causing the trouble.
If the set doesn't have a mains transformer, the valve heaters are all in series and the set won't run with a valve out unless you solder a temporary wire link across the heater pins of the valveholder of the valve you want to remove. The rest of the valves will be over-run a bit if you do this, but as long as you don't do it for long, and don't do it to the output valve, you'll get away with it and learn something into the bargain.
Once you know which stage is causing the crackle, it shouldn't take long to find. Look for resistors and capacitors playing dirty tricks, dodgy valveholder connections, bad solder joints, rotten wire, etc.
One particular oddity to look out for is the crackle which is after the IF stage, but goes down in level as the volume control is decreased. So it's after the IF and before the AF. This narrows it down very much, and it usually ends up being broken down resistance in the wavechange switch. The problem is usually caused because the HT to the oscillator is interrupted on Gram, so HT is taken to the switch, but on Gram the audio is switched away from the radio detector and onto the gram sockets in stead. And the HT leaks to the audio. The solution is normally to remove the HT feed and the wire to the oscillator from the switch, join them together and insulate them, and cure the problem at source.
It Howls, Screeches, Whistles, or Bangs
Let's take the motor-boating first. It sits there going pop - pop - pop - pop continuously and loudly. This is a sure sign of an unhealthy power supply. Normally this is caused by the main electrolytic capacitors losing some of the moist goo which makes up a good proportion of their innards, and losing their capacitance. This means that the amount of energy stored in the power supply is seriously reduced, and when the output valve draws current, the HT voltage drops, which alters the current taken by the audio valve, which in turn is coupled back to the output valve, and causes its current to change. A vicious circle is thus formed and the end result is that the output valve swings violently between hard off and hard on, doing the outboard motor trick as it does so. To repair, fit some new electrolytics.
Then there's shreiking and howling which gets worse as the volume increases and depends on what is coming out of the loudspeaker. There is audio present, but it sounds very excitable. This is positive audio feedback, and the audio stage and output stage are trying to oscillate. Sometimes they manage it. Have you replaced the output transformer? Does the set make any connection to the secondary (speaker) side apart from grounding one wire to chassis? If so, you've had a 50-50 chance and blown it. You've connected up the secondary so that the negative feedback of which your set's designer was so proud, is now positive and causing problems. Reverse the connections to the secondary.
Then there's the problem if instability in the IF stage. This will show up as a lot of whistles being received, which can be tuned in like stations, and often when a station is tuned in, there is an accompanying shreik which drops in pitch as the station is tuned closer and closer, falling to a howl and then to a low frequency rumble as the tuning is about spot on, and the rising in pitch as you tune off the other side of the signal.
This IF instability can be a real nightmare. First check the grounding. Is the valve of a type which is metallised? If so, is the metallic coating flaking away, especially where the wire comes up out of the base and is supposed to make contact with it? If so, it's time for a new valve or some aluminium foil wrapped around the valve and making contact with the wire.
Is all the gubbins under the valveholder nice and firmly rivetted or screwed down? Pay special attention to the earth tags etc.
Are the decoupling capacitors in good condition? Not just the ones in this stage. Check around. Try temporarily connecting a new capacitor across each old one in turn.
Did the instability start when you tweaked the IF alignment? You might have it too sharp. Try de-tuning each adjustment just a little. If you can get adequate volume without instability, you've just learnt why you want a signal generator to do IF alignment properly.
If the IF amplifier valve has a cathode bias resistor, check it's on value.
Checked all that?
Try adding a small capacitor (say 0.047uF) across the main HT line for the set, preferably where it comes nearest to the IF stage. If this cures it, your main electrolytic capacitors have more impedance at high frequencies than the rest of the radio could stand. A new set may be the full cure.
Check the grounding of obscure things like the tuning capacitor frame and the cans of the IF transformers. You never know.
If it's a Pye with an EF39 valve, try a brand new EF39. No idea why, but it often works!
If all else fails, try a grid stopper. This is a small resistor connected in the wire between the grid terminal of the first IF amplifier and the grid of the valve itself. Try small values such as 220 ohms. Work up until stability returns. With any luck you haven't got such a large resistance of grid stopper that there's no gain left either.
Am I Having Fun Yet?
How do you know when you've finished? How good is good enough?
Ask some simple questions.
If I was buying this set new, years ago, would I be chuffed with this? Bear in mind that a long time ago, less was expected, but by the mid 30s, radios weren't bad at all. Distortion was expected to some extent, as was a warm mellow sound.
Was this set ever meant to be brilliant? If it was expensive and complex, it should get lots of stations. If it was cheap and simple it probably never managed anything more fancy than more-or-less local stations.
Are there any special circumstances? If it is a set with heavy negative feedback used for improvement of audio performance, especially if the tone control is involved in the feedback, then it probably never was capable of going too loud. Loud enough would have been deemed loud enough. If it is an ex-rental set, it will not go too loud, even on maximum volume, but it will be built like a tank for reliability. If it was a portable, low battery consumption was more important than loads of stations and window-rattling volume.
Cleaning Up and Polishing
We don't want to teach grandmother how to suck eggs, but here are a few hints on cleaning and polishing your freshly-revived pride and joy before you put it back together.
1) Never clean the writing-side of the dial with anything damp, and don't scrub too hard. The writing will come off, and you'll wreck it.
2) Waxy goo stuck all over things in a thin layer will wipe away easily if dissolved in a squirt of WD40 first.
3) Sticky labels come off fine if soaked with WD40 first. It breaks down most self-adhesive glues.
4) Brasso is great for Bakelite.
5) To get the knobs clean, use warm water, old-fashioned Jif-style cream cleaner, and a nail-brush. This will clean out all the grooves and niches.
6) Wood which looks old and tired can often be transformed with an application of boiled linseed oil. If you repeat the procedure when it looks like it needs it, you'll keep it in top condition.
7) Small gouges and deep scratches in stained and polished wooden cabinets can be disguised by rubbing in the right colour brown wax (available from DIY shops) and cleaning off any excess with white spirit. Clean off white spirit with aerosol multi-surface polish straight away. It'll damage the finish otherwise. Same treatment to hide woodworm holes.
8) Rexine covered cabinets can be cleaned with a damp cloth, Jif-style cream cleaner, and a nail brush, and another damp cloth. If there's not too much colour left when you have scrubbed the dirt off, an application of the nearest colour Meltonian Shoe Cream will bring it back to its former glory. If Meltonian isn't available in the colour, you can mix it like paint, and make up the colour you want.