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Old 1st Apr 2011, 9:20 pm   #41
ThePillenwerfer
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Default 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
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Old 1st Apr 2011, 10:55 pm   #42
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Default 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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Old 2nd Apr 2011, 11:52 am   #43
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Default Re: Test equipment for valve radio repair

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.

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Old 4th Apr 2011, 9:33 pm   #44
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Default 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!
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Old 4th Apr 2011, 11:03 pm   #45
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Default Re: Test equipment for valve radio repair

Glad to be of service.
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Old 6th Jun 2011, 7:46 am   #46
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Default 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.
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Old 7th Jun 2011, 12:03 pm   #47
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Default 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.
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Old 3rd Oct 2011, 5:59 pm   #48
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Default 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.
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Old 10th Dec 2011, 8:31 pm   #49
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Default Re: Test equipment for valve radio repair

Quote:
Originally Posted by Station X View Post
Just about any fault on a radio can be diagnosed using a multi-meter, either analogue or digital as preferred. DMMs can be bought exceedingly cheaply these days.
Gosh this post jumped out at me ']Just about any fault on a radio can be diagnosed using a multimeter' Please how can I become such an expert using one of these. I was looking at this equipment at Wootton Bassett but put it back on the table knowing nothing about how to use it?

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
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Old 10th Dec 2011, 9:15 pm   #50
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Default 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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Old 14th Dec 2011, 2:07 am   #51
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Default Re: Test equipment for valve radio repair

I would whole heartedly agree with Station X that "Just about any fault on a radio can be diagnosed using a multi-meter", and for most checks such as continuity tests etc, it does not even need to be a particularly good meter.

However, don't forget that the radio under test will need power.

For a mains powered valve radio, you need a way of applying power at first switch-on more gently than just applying full mains. I prefer ramping up the voltage slowly with a variac while monitoring supply current, but the much cheaper lamp limiter will do the task of limiting the current in case of a fault, and also gives clue about the supply current will do the job almost as well.

For transistor radios, not strictly on-topic here, you need a variable low voltage supply for sets where the batteries will not stay in place with the case open (the Philips Popmaster was my earliest memory of this problem - it used 4 AA cells in a "holder" consisting of the 2 halves of the case)
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Old 25th Jun 2012, 2:07 pm   #52
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Default Re: Test equipment for valve radio repair

Glad I don't require much more than a multimeter for my Blaupunkt Stuttgart.
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Old 9th Sep 2015, 12:46 pm   #53
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Default Re: Test equipment for valve radio repair

This Thread seems to have been dormant for some time ...?

Has anyone investigated the Raspberry Pi Wobbulator - I like the idea of using some of the latest technology to test vintage valve radios!

http://asliceofraspberrypi.blogspot....roduction.html

I've already built a couple of RPi Projects, most recently using the IQAudio Pi-DAC+ to provide a second digital streaming service in my attic.

Gives me something to listen to while doing my radio restoration work!

P.S. Some recommendations please for a decent temperature controlled soldering iron to upgrade and replace my trusty 25W model.

Last edited by DonaldStott; 9th Sep 2015 at 12:48 pm. Reason: Missed a sentence
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Old 9th Sep 2015, 1:36 pm   #54
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Default Re: Test equipment for valve radio repair

The wobbulator is excellent. I bought one of the first kits and although I haven't used mine very far up the frequency scale, it is a very capable tool from low audio up into RF. Now that the software is on it's 'n'th iteration, it has some useful features.
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Old 9th Sep 2015, 2:56 pm   #55
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Default Re: Test equipment for valve radio repair

Thanks for the response mole42uk - good to hear that someone else shares my views.

I'm new to this Forum and currently restoring a 1956 Philips set - I've got most of the basic tools/equipment but got a bit put off by the talk of RF/IF signal generators, oscilloscopes, mains isolation transformers, valve testers etc. etc. I've even got a second-hand AVO 8 on my Christmas List although my existing DMM seems adequate!

Once I get my basic restoration work complete and start looking at alignment I may be back in touch about the RPi wobbulator?
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Old 9th Sep 2015, 3:12 pm   #56
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Default Re: Test equipment for valve radio repair

Quote:
Some recommendations please for a decent temperature controlled soldering iron
Take a look at the EEVBLOG for cheap (and good) irons, from China of course.
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Old 9th Sep 2015, 4:10 pm   #57
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Default Re: Test equipment for valve radio repair

Or type soldering iron in the search box above to find a host of threads on the subject.
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Old 2nd Oct 2015, 7:02 am   #58
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Default Re: Test equipment for valve radio repair

Quote:
Originally Posted by astral highway View Post
Quote:
Originally Posted by Station X View Post
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.
Hmmm... but the OP was about 'getting more scientific.' Arguably, a 'scope is an inevitable essential if you want to do this.
If you are going serious about any restoration, you have to have the correct equipment. You may be able to find faults with just a multimeter,but you wont be able to do a full test.
You need a power output meter,and a calibrated signal generator,(to do accurate alignment and sensitivity checks)
You also need a RC bridge, to check capacitors,and also a insulation tester,to check capacitors and other checks.
A valve tester would come next, an oscilloscope may be usefull if it had a frequency meter.
With this equipment, a set can be restored to proper working condition.
All capacitors need to be checked for capacity and leakage at the working voltage,(you cant check leakage with a multimeter) valves should be checked for emission etc,if the overall sensitivity check shows low, if sensitivity check should be better than 39uv for 50mw output) for 1 if stage,but see service sheet.

Last edited by Station X; 5th Oct 2015 at 9:47 pm. Reason: Thread split.
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Old 2nd Oct 2015, 8:44 am   #59
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Default Re: Test equipment for valve radio repair

Quote:
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an oscilloscope may be usefull if it had a frequency meter.
All oscilloscopes have a frequency meter. That's what the graticule and the time/cm control is for.
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Old 2nd Oct 2015, 9:29 am   #60
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Default Re: Test equipment for valve radio repair

As many others have mentioned earlier. Four items required to repair 99% of domestic broadcast receivers.

1 A cheap digital meter. These can be obtained for as little as 2.50 delivered including post and VAT. Incredibly they are accurate [I have a couple] and have a decent ohms and voltage range. If you blow it up accidently just buy another! If you want to keep it vintage, a working AVO 8 can be bought for not much more but can be difficult to use if your under 40....

2 A good range of screwdrivers, pliers, box spanners, cutters all of which can be purchased from time to time in stores such as Lidl for silly money.

3 The knowledge of HOW TO USE THEM with a basic knowledge of radio and valve technology. It's often the case of 'All the gear but no idea.' Technical radio books are virtually given away at table top sales.

4 A calibrated signal generator such as the Advance E2, AVO alignment oscillator and many others. Virtually given away at WB and Harpenden. You can add bits as you go along such as jump leads [short lengths of wire terminated with crocodile clips for those all important links outs when fault finding.

A good second hand scope is cheap,usefull, and a great assett to television servicing but tends to collect dust most of the time on the radio service bench.
Just my own thoughts. John.
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