Test equipment for valve radio repair

[Restoration73]

I would always pair an analogue readout signal generator for RF with a digital frequency
meter, so you don't have to guess what frequency you're on.

[Station X]

Originally Posted by Heatercathodeshort

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

John.

Hear hear!

[Skywave]

Mechanical tools aside, for me, the importance of my test equipment is in the following order:

1. Fluke DMM
2. Tektronix 'scope
3. HP signal generator
4. All the other items of test kit that I own.

That order reflects that my time at the bench is approximately equally divided between equipment repairs and equipment custom designs.

Al.

[happytiger]

Originally Posted by mole42uk

All oscilloscopes have a frequency meter. That's what the graticule and the time/cm control is for.

Of course, but for beginner I was thinking of digital readout which many more modern scopes have.

[mole42uk]

I thought my 1970's Gould OS3000 'scope was modern!

[Radio Wrangler]

It was, back in the 70's

I've come across people using digital storage scopes with automated marker measurements expecting frequency readouts to be accurate like a counter. It takes some explaining to get them to see that it's just the calculated reciprocal of the positions of two markers, and to do an estimate of the range of error possible.

If it's written in digits, someone will always believe it.

It's DIGITAL, innit?

David

[Herald1360]

I'm a firm believer in the idea that digital equipment is always precisely wrong whereas analogue kit is approximately right

[mole42uk]

The most serious mistakes I've made in recent years have been when using an autoranging DMM and failing to read the decimal point position when measuring around transistors. It's virtually impossible to make that mistake when using an analogue scale. However, I do have one of those cheap ebay transistor testers that works very well and gives me a digital readout of Hfe, pinout and polarity. At least it tells me if the transistor works under test conditions or not!

I think that using a 'scope to check frequency measurements is good because it encourages me to think about what I'm doing. Check the timebase setting, measure the length of the wave on the screen, then calculate the frequency, or do a quick bit of mental arithmatic to see if it's in the expected range (or as the Americans would say, in the ballpark).

[Radio Wrangler]

I've come to see autoranging asmore of a detriment than an advantage. Before probing something, you should have a good idea of what should appear and of what faults could give, so you can set the right range manually before poking a probe in anywhere. THeadvantage then is that you get quick readings without waiting for the autorange to chug its way thrpugh several settings. If I'm working on a radio with 12v highest supply, a 20v DC range will be fine for just about everything.

For general looking around, my primary test instrument is a scope, not a meter. Scopes show voltage well enough for most work. They do it fast and they let you see all sorts of other clues.

David

[Heatercathodeshort]

Originally Posted by Restoration73

I would always pair an analogue readout signal generator for RF with a digital frequency
meter, so you don't have to guess what frequency you're on.

Absolutely! This would not have been possible 30 years ago due to the incredible cost of frequency counters. Everything is given away today with a packet of cornflakes.
RF generators, even basic designs can be set up to give a satisfactory result.

Don't forget the humble neon test screwdriver and a 15W pygmy bulb on a length of 'test wire'.
As a very young kid that bulb got many jumble sale receivers working.
Bright = high AC
Dull and maybe pulsing slightly = DC.

You learn by the reaction of the bulb filament to the character of the voltage rather like the speed of the AVO 8 needle when presented with a S/C. Happy Days!The lessons learned by these very simple bits of 'high tech' test gear proved of great value in later life when called in to carry out an emergency repair without warning, tools or any test equipment.

Tip: Don't tell anyone what you do for a living. If you do you will discover a pile of ancient radios, television receivers, record players, Baby Belling cookers and gas fires awaiting your attention when attending a 'friends' invite to dinner or a house party.

Tell everyone you are an UNDERTAKER! You will probably not be bothered..

Many elderley customers [mosly ladies] always had a household tool kit in the kitchen drawer containing screwdrivers and a pair of pliars. A test lamp could soon be cobbled together.
I doubt if that would be the case with the younger generation or am I being a sad old man?

Of course at that time I was dealing with tough valve monochrome receivers and of course these temporary methods would not be good practise today!
Few would have produced a scope from the wardrobe but it did happen once but luckily I did not need to use it!

Happy memories but such a long journey. Regards, John.

[mole42uk]

Originally Posted by Radio Wrangler

For general looking around, my primary test instrument is a scope, not a meter. Scopes show voltage well enough for most work. They do it fast and they let you see all sorts of other clues.

Absolutely.

[Station X]

Several posts move to a new closed thread here:-

https://www.vintage-radio.net/forum/...d.php?t=120085

[happytiger]

Originally Posted by Heatercathodeshort

Don't forget the humble neon test screwdriver and a 15W pygmy bulb on a length of 'test wire'.
As a very young kid that bulb got many jumble sale receivers working.
Bright = high AC
Dull and maybe pulsing slightly = DC.

You learn by the reaction of the bulb filament to the character of the voltage rather like the speed of the AVO 8 needle when presented with a S/C. Happy Days!The lessons learned by these very simple bits of 'high tech' test gear proved of great value in later life when called in to carry out an emergency repair without warning, tools or any test equipment.

Its surprising what can be used. The 15W pygmy lamp,connect one wire to mains live,and you have an AF sig gen, other to grid of OP valve,will also check frame timebase,but dont do this with transistor equipment.

[peter_scott]

Originally Posted by Heatercathodeshort

A good second hand scope is cheap,usefull, and a great assett to television servicing

... and maybe an isolating transformer to avoid problems with "neutral" chassis.

Peter

[Dickie]

Originally Posted by happytiger

Its surprising what can be used. The 15W pygmy lamp,connect one wire to mains live,and you have an AF sig gen, other to grid of OP valve......

I don't understand that. The grid of an o/p valve is going to be at high impedance so you are going to apply nearly 240V ac to it. I would have thought that's likely to have unpleasant results, or am I missing something?

[Skywave]

Originally Posted by happytiger

Its surprising what can be used. The 15W pygmy lamp,connect one wire to mains live,and you have an AF sig gen, other to grid of OP valve,will also check frame timebase, but don't do this with transistor equipment.

That sounds like a dangerous technique to me.

Al.

[paulsherwin]

Indeed. Quick and dirty old school shortcuts like these should only be used by experienced people who understand exactly what they're doing. Even then they're bad practice.

To inject tone into RF and AF stages you can use a basic two transistor signal injector. These make excellent constructional projects for beginners. None of the components are critical so they can be built with bits from scrap equipment. http://www.eleccircuit.com/simple-si...by-transistor/

[wireful3]

The basic test gear needed depends on aspirations. My own interest is collecting interesting radios from boot sales and auctions. I then aim to make them work acceptably. With such simple aims I find I need very few items of test equipment. A multimeter is the prime one and I have both digital and analogue. I use either with really no preference. The digital meter is auto ranging and so needs less thought. A signal generator is the next in importance though I find a second portable set to check that the LO is working very handy. It also gives me a signal for injecting into the AF stages.

The slightly controversial item is a scope. It is an old not very sophisticated model but I find I rarely use it. Mainly to check what is happening in IF stages. It is also useful when the sound is very distorted to see where the problem starts.

This I find avery basic kit but even then if the scope stopped working I could probably manage quite well. No doubt my very simple needs help. Obviously a boot sale radio costing very little, with intractable faults, can always donate parts if my test gear is not up to finding the problem

[Skywave]

Originally Posted by wireful3

The slightly controversial item is a 'scope: it's an old not very sophisticated model but I find I rarely use it.
. . . if the 'scope stopped working, I could probably manage quite well.

For the type of kit you are accustomed to working with, I can readily believe that. However, in my case, I've always regarded a 'scope as an essential piece of test gear. Perhaps that's because after many years of employment in the electronics & radio industries, I've been spoilt . In my case, I spend as much time repairing and renovation communications receivers as I do repairing test equipment, plus designing my own items of test gear. For those activities, a 'scope is an essential: at least, it removes a great deal of guesswork; at most, some repairs & design projects would be impossible without one.

In the final analysis, it all boils down to what one does in this hobby - and what can be afforded. Seems to me that the main objective - like any hobby - is to have fun. Yes, I'd love an all-bells-and-whistles RF network analyzer, but have you seen the prices of that type of kit? Ouch!

Al.

[julie_m]

I have a hand-held digital storage oscilloscope. The plastic case and battery power supply make it suitable for use, with care, on live-chassis equipment. It hasn't the world's best bandwidth, but is good enough for MW and LW radios. It also uses standard probes and when switched to 10:1 attenuation, doesn't unduly influence the circuit under test.

An analogue 'scope can be just as useful, though; so don't chuck it if you have one!