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Test equipment for valve radio repair
I need some advice from you experts out there. I have a small collection of valve radios most of which work although a few are a little 'sick'. My cornucopia of repair equipment is very basic (soldering iron, keen eyes, simple meter for volts,amps, continuity etc.). I need to move on and be more scientific to check caps, resistors, valve voltages and the like. What equipment should I obtain; where can I get it and will it cost me an arm and a leg? And don't worry folks I know of all the dangers of working with steam radios!
Richard |
Re: Test equipment for valve radio repair
You've probably got enough there to make a start. Resistors and coils can normally be checked with a simple meter, capacitors are best checked by replacement, valves can be evaluated by measuring the voltages around them or by substitution.
A decent RF/IF signal generator would be the next thing to consider, then you can start with alignment (though this is not always necessary if the sets have not been "got at"). A mains isolation transformer would be advisable to go with this. A 'scope or a valve tester are a luxuries for domestic radio repair and you don't really need them to begin with. |
Re: Test equipment for valve radio repair
Just about any fault on a radio can be diagnosed using a multimeter, either analogue or digital as preferred. DMMs can be bought exceedingly cheaply these days.
As for testing capacitors just forget it. Replace waxies and Hunts on sight. If you don't want to do that remember that the failure mode of these is to leak electrically and behave like resistors. This will result in incorrect voltage readings. For example low screen grid voltage or positive voltage on a control grid. If you want more test gear invest in a signal generator. As for valve testers, scopes etc. forget them. They rarely need to be used. |
Re: Test equipment for valve radio repair
Studio263 and I posted at the same time and came up with the same answers!
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Re: Test equipment for valve radio repair
A cheap DMM is really all you need. This will measure voltage, current and resistance. You can't test valve radio capacitors easily even with sophisticated capacitance meters because of their typical failure modes, so the best method of finding bad ones is to look for voltages where there shouldn't be any with the DMM.
An RF signal generator is useful for AM alignment, but you can do just as good a job with care using off-air signals. A wobbulator and scope is really needed for accurate FM alignment but it's possible to check the ratio discriminator alignment with just the DMM - many professionals wouldn't have owned a wobbulator back in the 50s, and that's how they would have done it. Paul |
Re: Test equipment for valve radio repair
If you get to aligning sets, then invest in an analogue multimeter (a second-hand 'AVO' 8 is ideal). Observing peaks, dips, and rate-of-change is far more easily undertaken with a pointer than a digital display.
Some circuits specify the voltages with regard to a particular meter loading (eg: the cct diagram may say: 'all voltages maesured using 20,000 Ohms/Volt meter'). Using a DMM is perfectly acceptable providing you accept that a reading may be higher than specified. |
Re: Test equipment for valve radio repair
Hi Richard,
Whilst I agree with the other contributors about 'scopes and valve testers being luxuries, you will find that a 'scope will give you much greater insight into what is going on, and unlike valve testers, 'scopes are dirt cheap, especially as you don't need anything esoteric by way of bandwidth for most radio use. Any mains driven test gear will of course demand greater respect in regard to connections made to radios that don't have isolating mains transformers. Good luck, Peter |
Re: Test equipment for valve radio repair
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Re: Test equipment for valve radio repair
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Re: Test equipment for valve radio repair
I forked out on a valve tester fairly early on, its been quitr fun using it but I wouldn't bother. I'd agree most work can be done well with just a meter (DMM or analogue) but if you're feeling your way there's nothing like seeing a trace on the 'scope. Mines a 90quid crappy one from Maplins. Dual trace isn't hugely useful except for telly work.
Isolating transformer and variac have proved very useful as has a decent soldering iron I've been poking away with a 15W antex for years and not really understood just how much nicer a proper heft voltage controlled one is - they're not that expensive either. I picked up a nice sig gen for a tenner at Harpenden and that's been useful, both in diagnosing and aligning but also in aiding my understanding of various things. Also its got nixie tube read out of the frequency which is cool!... |
Re: Test equipment for valve radio repair
My three ha'porth,
1) An AVO is more use than a DVM as the voltages in the service data that we are generally working to will have been determined using analogue meters, often a mk7 or 8 avo and so will be more meaningful on similar kit. 2) It is actually useful to have a couple of AVOs as you can check conditions simultaneously around a complicated circuit - as they are dirt cheap, there is no problem with having several. 3) A reasonably accurate RF signal generator. It doesn't have to be an all singing all dancing one but something that will give you the common IF frequencies and the MW/LW bands with AM modulation will do all of the older sets. The above will do nearly all AM domestic sets. If you are going to set up more sophisticated sets, especially communication sets (AR88 etc) then a good wobbulator and a scope is pretty essential (anything where you want to accurately set up filters where the skirt shape is important). Much as scopes are nice toys and I have to admit that I have far more than I should, unless you are going to be doing this sort of stuff then they are not really necessary. Once you go beyond this then it just depends how many toys your budget can extend to. I have a valve tester and it is immensely helpful. I also have a very good Marconi comms set analyser which is way way beyond the sort of gear that is really necessary but it does make some things very easy. Other useful items are valve volt meters when you can find them. I also have a megger which gets used for testing the mains side for insulation. The thing to remember is that test gear comes under the heading of nice to haves and I can just do X better if I have a thingy and it only costs xxxx I'm sure I can find a home for it. All of us can do most of what we do with 1, 2 and 3 above. It is rare that I actually break out the full tool set and only when I want to do something insane like setting up a complete RA17. Robin |
Re: Test equipment for valve radio repair
If I'm ever forced to get rid of test gear the last four items I'd get rid of would be Valve tester, 'scope, Signal Generator and Multimeter in that order. I probably got them in the reverse order.
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Re: Test equipment for valve radio repair
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A 100W incandescent lamp is a useful tool, connected - initially - in series with your device under test, and will limit current nicely if you haven't got a variac. A 'Megger' (available on the surplus market) is also useful for testing transformers and insulation resistance, and will give an indication of leakage when applied to a capacitor of appropriately rated voltage. |
Re: Test equipment for valve radio repair
It all depends what you want to do and how far you want to go!
If Richard has been bitten by the electronics bug I'd recommend a good multimeter, I'd go for the AVO 8 but that is my bias. The majority of valve receiver manuals will have the voltages measured on a sample set using an AVO so you can expect to get reasonably close using one. They are also excellent for the beginner as they are fairly robust and have the trip button for the times when you forget to change range. I would advise building your own test gear too. A simple signal injector (valve or transistor) is a simple project and building test gear is a good way to learn how circuits work. There are lots of constructional articles in the old magazines like Radio Constructor or Practical Wireless. PM me and I'll send you some suitable articles. You can certainly have a great deal of fun and learn a lot with simple equipment. Regards, |
Re: Test equipment for valve radio repair
Looking back to when I just had a DMM, I would say go for an analogue meter for sure. AVO's can be had at resonable prices.
As for other items which I now wonder how I did without : SIG GEN - GET ONE ! I really wonder how I managed before, especially when a nice FM set arrives and you need to align. PEAK ATLAS LCR meter - Not expensive and VERY useful when you have dodgy mica caps to contend with ( thanks Ferranti ! ) Hi voltage PSU - Dead useful for reforming caps, powering up AC sets without the rectifier in, and other valve experiments. Bit of 'nice to have' but if it saves a few hours, it goes in the workshop ! Not strictly TEST GEAR , but... Extra Hand Tools : These make any job easier and are worth their weight in gold ! One handed automatic strippers. Bench magnifier/light Nut holder BA sockets/nutspinners Screw starter set of needle files If you have to pick just one ( sounding like desert island discs !) Go for the SIG GEN. You'll really wonder how you managed without .... Andy |
Re: Test equipment for valve radio repair
As others have said, you need very little to carry out most fault diagnosis and repair. However my experience has been that in setting myself up for this type of work I have developed an interest in collecting the test equipment itself. Professional laboratory instruments, by makers such as Marconi, HP, Avo and Tektronix, that cost many hundreds of pounds thirty or more years ago can now be picked up for a song. There is also much cheaper but good equipment around such as that by Heathkit which will still provide good service. In the case of Heathkit, because it was designed for home assembly, it is particularly easy to maintain. Such equipment turns up on auction sites or at the BVWS events such as Harpenden. It may even be offered on this site from time to time.
I admit that the equipment is usually far more highly specified than is required for our purposes but there is satisfaction in using such beautifully made equipment and keeping it working long after the end of its intended life. Edward |
Re: Test equipment for valve radio repair
Here's my brief suggestions: Build yourself a safety series lamp for testing sets, if you haven't already done so. IMHO the test lamp is superior to the much vaunted variac and it is certainly much cheaper. Ideally, both a good analogue meter - say, a model 8 Avo - and a DMM both have their uses. The former is good for watching changes in voltage or current, such as when aligning for signal strength (the reading on the DMM tends to jump about) but the DMM is quick and accurate and some can test capacitors - I use a capacitor test on new components before I fit them and use the Avo on high ohms to check old caps for leakage. A reasonable sig gen is very handy, too, but I use my scope only occasionally for radio work, though it was used a lot on colour TV servicing (years back!)
-Tony |
Re: Test equipment for valve radio repair
Having come from a digital electronics background - way back fixing and modding ttl circuits, latterly switch mode supplies, monitors and laptops, I started driven by the need to search for a measurable fault on radios I worked on. In my naive fashion I assumed there would be "a fault" which when fixed would make the set burst into life. Poor fool!
The reality is that many components will have become leaky, changed in value or indeed in antiquity have been replaced with something unsuitable! With this in mind, and as others have suggested, a blunderbuss approach is often more successful, and a simple dmm is the most useful tool in this, but NOT with caps! Firstly, mistrust all of these, especially Hunts and waxed paper, also most electrolytics, though you may be lucky with these. Then resistors, in many sets you will measure these and find the values all over the place, usually high. In spite of this they may not materially alter the operation of the set due to the tolerant operating parameters of hot bottles. If in doubt don't try to intellectualise the problem, change the component! I've got all the kit apart from an FM sig genny. Mostly by a huge margin I use my £13 Dmm and AVO 8 I've had 37 years, but most useful is the Soldering Iron! |
Re: Test equipment for valve radio repair
What a response! Many thanks to all you electronic geniuses out there; and so much other useful info as well. I think I shall treat myself to an AVO 8 meter to go with my ancient bakelite megger in it's beautiful metal box. But where to obtain such a gorgeous thing? Any ideas?
Richard |
Re: Test equipment for valve radio repair
Richard, you are not a million miles away from Wooton Bassett. The next WB event (for BVWS members) is on Sunday 2nd of December. If you are not a member, you could probably join on the day. I am sure that there will be many stallholders selling AVOs on the day.
Neil |
Re: Test equipment for valve radio repair
How about making this thread sticky?
A lot of new visitors must have similar questions going through their minds. William |
Re: Test equipment for valve radio repair
Good thought - thread duly "Stuck"
Regards, |
Re: Test equipment for valve radio repair
As an amateur enthusiast who will probably never graduate further may I add my less professional take on this. I sometimes find it hard to replace electrolytic capacitors, the inevitable main culprits. The usual values, 47 + 47 uF, or 100 + 100 uF are often difficult to obtain in the necessary working voltage, 350 - 450 DC. Single Plessey capacitors often fetch a small fortune on eBay. Paper capacitors must also, as a rule, be replaced, but plastic foil caps that do the trick are much easier to come by. Maplin does the whole range. Carbon resistors are replaced with similar ease. As for the electrolyitics, I do not find capacitance meters useless. Sometimes a choice has to be made between a cap from a dodgy source but dated let's say 1989, and a cap made by Plessey in 1965. I always test these, and choose the one which produces the reading closest to the nominal value and which shows the better retention of a DC charge. The latter is a simple test.
Gerry Wells keeps telling me that valves never go wrong. While that is an exaggeration, problems posed by valves are straight issues. I always replace valves which appear not to perform according to specifications. Sometimes this is a costly policy. Maplin has a 48W digitally controlled heat soldering iron for 30 quid, great value I think. This is what comes to mind in brief. And best of luck. |
Re: Test equipment for valve radio repair
IMHO it's not what you have for testing, it's being flexible and realising what you can do and what you can't do with what you've got! A simple diode detector can be added to an analogue multimeter for comparative RF measurements on an oscillator. You can make a simple 'Equivalent Series Resistance' checker for electrolytic C's. (http://ludens.cl/Electron/esr/esr.html) You can use a PLL HF receiver instead of a frequency counter. Make a signal tracer in a small box with an LM386, a PP9 and a small speaker, add the diode detector and you can follow the signal back up the IF strip. Add a couple of sockets across the speaker for your analogue voltmeter and you have a high impedance VTVM. You're only limited by your own ingenuity.
Good luck and best regards - Martin |
Re: Test equipment for valve radio repair
I have a useful home made gadget which is very simple but could save a nasty moment. It's a simple neon lamp in a holder on the wall by my workbench. One pole is connected to earth, the other via a resistor to a lead with a test prod. Just poke anything you are proposing to touch with the test prod first...
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Re: Test equipment for valve radio repair
One of the less common pieces of test gear is the Grid Dip Oscillator.
Widely used in Ham radio circles, it can also be useful for some types of general repair work. When coils need rebuilding / rewinding, they are a simple way of getting the inductace right, and can also be used to find the capacitance of low value C's. |
Re: Test equipment for valve radio repair
Excuse my ignorance, but is a function generator the same as a signal generator?
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Re: Test equipment for valve radio repair
A simple function generator usually generates a choice of sine, square or triangular waves. The sine waves are often a bit distorted at the peaks. Sophisticated function generators (often called arbitrary function generators) can be programmed to generate any waveform. Most FGs only go up to 1MHz or so. They often go down to fractions of a Hz. Frequency can often be swept over a wide range so they can work as a wobbulator if they go to high enough frequencies.
Signal generators produce sine waves. Sometime also squre waves at lower frequencies. They usually have facilities for amplitude modulation, sometimes FM too. |
Re: Test equipment for valve radio repair
I started in electronics as an apprentice 44 years ago and have serviced all kinds of appliances from the usual toasters, heaters & shavers etc, TRF valve radios (from elderly customers) valve TVs, radios and radio telephones of the slightly more modern era, through to all solid-state colour TV, radios, radiotelephones etc. Next to a good multimeter the most useful instrument I ever had was a small battery operated high voltage insulation tester.
In my opinion their value and usefulness is highly under-rated. I still use one regularly and with a choice of 250, 500 and 1000 volt outputs it is surprising how much it can tell you about a lot of components that a multimeter can't. I am not overly fussy about the maximum rated operating voltages for various components either, if they can't stand a test voltage 100 volts or so in excess of their rated working voltage then they are not going to be reliable in service. I recently bought some NOS oil-filled .1uF 1000 volt caps which checked out perfectly with a multimeter but they all leaked a little at 250 volts and a lot at 1kV. I too prefer an analog multimeter for most servicing and although I own several AVOs of various marks, my meter of choice for general servicing is a Hioki AS100D 100,000 ohms per volt sensitivity and 22 volts at the probes for high-ohms testing. It is a good compromise between the higher loading of a 20k-ohms/V AVO on low voltage ranges and the very high input impedance of digital meters and has a large and very clear scale. For my business I have a wide range of test equipment including several scopes, signal generators and some other fairly exotic goodies but when it comes to fixing radios, nothing much beats a comfortable seat and a good meter. Incidentally, I am rather envious of the range of service sheets you have available, because although we did have circuits for most radiotelephones and TVs, and books of circuits that covered most Japanese transistor radios, almost all valve radio servicing was done without the benefit of a circuit, enforced experience that stands me in good stead today. Cheers Billy |
Re: Test equipment for valve radio repair
HI. Whilst I would agree with almost all the previous comments I would like to add a couple. NEVER switch on an mains wireless that you have no knowledge of or has not been in use recently without first disconnecting the electrolytic smoothing capacitors. You can easily get a BANG and a nasty mess and a requirement for a new rectifier.
Having said that I always try to reform electrolytic capacitors that have not been in use for some time, even new old stock. This is easy to do and I reckon I have had 95 per cent success even managing some wet electrolytics from the 1930s. You need a DC supply of 250-300V. It should be at the same voltage as the caps are going to be used at but I find if you can only get 250V then they will almost certainly be OK for a bit more. Connect the cap in series with a 15k resistor and a multimeter, on suitable current range, with corerct polarity across the DC supply. Initial current will be several ma but will quickly drop and in time will eventually settle down at, hopefully a low value. Leakage current is always present in electrolytics but should not exceed (for plain foil types - these are likely to be the earlier ones) 0.15 X cap (in mfd) X voltage, microamps. For Etched foil types it should be 0.5 X cap (mfd) X voltage, microamps This equates to about 1 ma for a 450 V 16 mfd. If the cap is noticeably warm at the end it is probably doubtful. Good luck Pat |
Re: Test equipment for valve radio repair
A while back I happened across a brochure for what I suppose was the industry standard scope of the 50s. The Cossor Double-beam. It cost 550 pounds sterling - about a year's wages.
That wonderful thick steel-tube trolley was extra. |
Re: Test equipment for valve radio repair
In the case you'll like to test capasitors (excluding Hunts!) have a look to the link:
http://www.radio-ghe.com/isotest6.plan.htm IsoTest tester ( by Mr. Heigel) is a suprior tool if you like to repace just leaking capasitors and save as many "original" as possible. Unfortynately this tester is not commeriaclly available but it is not so difficult to make it. regards Ake |
Re: Test equipment for valve radio repair
I would say the 'must-haves' for Radio (Electrical) restoration's are a High resistance multimeter, RF sig. gen. (optional), and a selection of tools e.g. Pliers, Cutters, Screwdrivers, trimmer tools as well as Soldering Iron & Solder).
On my work bench I have numerous bits of test equipment which spends most of its life just 'dust gathering'. Though it does look 'the business' I suppose !!!! As mentioned by other restorers.... Basic tools and a multimeter is usually all that is needed. |
Re: Test equipment for valve radio repair
Indeed, a simple meter is enough for simple tube radio. The story changes, when you try to do something with high tube count device, like old TV set. I got one - made in 1952 - a combination of radio receiver and TV set. 32 tubes. Instead of buying a replacement set, I ordered a tube tester. I also consider it to be a nice vintage device by itself - why not to have it in collection?
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Re: Test equipment for valve radio repair
Gents - have posted this elsewhere ( and I'll keep on posting it ,till message gets through) --voltages into a mains set =230/250 v AC ( SO POSSIBLY AS HIGH AS 350V).
Output of DC rectifier - possibly as high as 300v DC . With a CHEAP meter - do you get leads that are tested up to this sort of voltage , or higher .For most jobs ,I'll make do with a set of leads made from a bit of mains flex ( possibly ok at these sorts of voltages) - I've never had a problem on mains .BUT -do you really want to put your life on the line for a cheap set of leads ? For as little as £5 you'll get a set of CAT111 leads from someone like Maplin (1000v 10A). |
Re: Test equipment for valve radio repair
Hi,
I'll add what's arguably a 'nice to have' to the list. I was going to design/build a capacitor leakage tester with several selectable voltages, basically a high-voltage meg-ohm meter, until I discovered a device already existed which does exactly that. I'd always assumed that insulation testers (usually 'Megger' though there are others) used a fixed voltage, often too high (500V) for capacitor leakage testing. Then I encountered the Megger BM8/2 - a multi-voltage insulation tester. It's analogue, battery-operated, the internal circuitry is fairly simple (so should be repairable); measures resistance at selectable voltages with ranges as follows:
This looks much more useful than a fixed-voltage tester; one of those "why didn't anyone tell me these things existed sooner?" bits of test gear! They're not particularly expensive as they've been superceded by a digital version, seem to be fairly common and turn up second-hand often enough. I've just bought one (though I wouldn't class it as 'essential'; in-circuit measurements, substitution and 'on-sight' replacement of certain types have served adequately well so far.) But, given the amount of faulty vintage electronic hardware I've accumulated, anything which helps identify faulty components more readily means I might get more of it working! Regards, Kat |
Re: Test equipment for valve radio repair
Just a passing thought......A valve signal generator might be a better bet than a solid state one when working with valves, as a slip of the probe could result in damage to a transistor type, whereas a valve sig genny would just "hold its nose" if a couple of hundred volts was momentarily applied to the output socket. A D.C. blocking capacitor does not necessarily get round this problem, as a cap. has to charge up. causing at least a momentary voltage surge . Usually enough!.
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Re: Test equipment for valve radio repair
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Re: Test equipment for valve radio repair
Everybody above is correct, however the most often used item is a soldering iron and the king is a Weller. It is isolated(for those times you are working with power on) and the tip lasts. A good high impedance multimeter is essentual. The AVO 8 is tough and robust but I don't know if it has such a high impedance. Detuning when measuring is a pain and AGC circuits are easily affected. A good signal tracer is easy to build and will trace from the front end to the last AF stage easily. It will test the filaments(hum), oscillator(hiss) and if you can hear the signal in the IF stage then the fault could be the detector, ect.
Billy, I am so envious of you, the AS100d is a beatiful meter. Mine got stolen and I have never got over it. Peter. |
Re: Test equipment for valve radio repair
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However, this is now getting OT: we're talking tools; the Thread is "Test Equipment". Al. / Skywave. |
Re: Test equipment for valve radio repair
The most useful bit of kit I've got is a home made continuity tester based on an NE555 IC. Granted I've now got twenty-five years experience with it (crickey, that makes me feel old) but I know what things should sound like on it.
It's handy for far more than testing fuses, lamps and the like; it's even a good guide for capacitors. I tested a couple of high voltage electrolytics earlier today by a method similar to that detailed above and the results matched what I'd expected. I'll try to find the circuit and post it. - Joe |
Re: Test equipment for valve radio repair
Just to add my 2p worth, if you're newish to valve electronics and radio in particular, is the now classic Scroggie's Foundations of Wireless, like having your own lecturer to teach you. That aside, as others have mentioned here, a decent analog multimeter, and somewhere well lit and comfortable to work, it can make all the difference no matter what test equipment you end up with. Don't forget possibly the most important bit of gear is between your ears....
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Re: Test equipment for valve radio repair
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Here's the Continuity Tester circuit as promised. I hope it's clear enough as I haven't had to draw one neatly for two-and-a-half decades! Mind you, I couldn't tickle them up on a computer then.
There's no need to get hung up on the speaker impedance as over the years I've used everything from 8Ω to piezo transducers. Mine has got an 80Ω one along with a socket so I can use this a high (ish) impedance test speaker. I keep meaning to add another one so I can use the tester's output as a crude signal generator but on the rare occasions I've wanted such a thing have just put jump-leads on it. Basically the higher the tone it makes the lower the resistance it's testing. Very high resistances will produce a series of pips and it's surprising how it can be pipping every couple of seconds on things that other meters have read as infinity. I hope other people find it as useful as I have. - Joe |
Re: Test equipment for valve radio repair
Hi Joe,
I found your continuity tester to be just the ticket, knocked one up from stuff in my junk box, works a treat. Thanks! |
Re: Test equipment for valve radio repair
Glad to be of service.
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Re: Test equipment for valve radio repair
Once one has obtained service sheets (or as a minimum cct diagrams) for "radios to be worked on" the most useful test equipment (in order of importance) must be a pair of DVM's (or a pair of 20,000 Ohms per volt Avo 8's if you want to stay period); both DVM's must have full complement of resistance, DC/AC current and voltage ranges (not all do).
An assortment of Insulated tips and probes for the above may seem a luxury, but aren't. Measuring HT current and voltages (at the same time) is often key to fault finding on ill radios. A 250VA variac fed from a quality 500VA isolation transformer is a sensible safety precaution (for a small table top radio) for live working on a set that has not seen power for aeons. A 20Meg dual beam Oscilloscope (plus a pair of x1/x10 probes) is a very flexible tool and a good one can be picked up for less than £100. If your radio for repair has been tweaked or fiddled with then a LF/HF signal generator may be required..... Spot wobulators are for the advanced or experienced engineer who knows all there is know about critical RF coupling and double humping. |
Re: Test equipment for valve radio repair
The 20k ohm per volt avo is a must for old service sheets with voltage reading assuming 20k ohm per volt loading (correct scale is important).
many DVMs are not Ohm per volt but simply 1M ohm absolute for cheap meters and 10M ohm absolute for expensive meters on all low voltages. Some may be higher resistance at higher volts. |
Re: Test equipment for valve radio repair
It depends whether you want to just repair radio,or restore the set.
For basic repair, soldering iron and testmeter, analogue of course. Next some sort of signal generator. To restore a set you need a good signal generator properly calibrated with uv output, an output power meter. Additional equipment,sweep generator scope and valve tester. The valve tester is one of the more usefull bits of test equipment, it can save a lot of time and exspense. Forgot to mention,an LCR meter is very usefull for checking capacitors especially, I would rate this essential even for basic repair. |
Re: Test equipment for valve radio repair
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As you all know now, I am in my infancy concerning vintage radio repairs I think I should start by purchasing a soldering iron. A recommendation would be most helpful https://www.vintage-radio.net/images/smilies2/dunce.gif |
Re: Test equipment for valve radio repair
You become an expert by using one. You can do many tests before you even power up a radio, like checking the resistors, continuity of transformer and coil windings, continuity of valve heaters, continuity of inductors, continuity of loudspeakers. continuity of mains leads and switches etc. etc.
Once the equipment is powered up you can check voltages against those given in the service sheet. Significantly high or low readings indicate a fault. Experience will teach you the likely cause. |
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