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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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#61 |
Nonode
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
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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. |
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#62 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
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Hear hear!
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
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#63 |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
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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. |
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#64 |
No Longer a Member
Join Date: Dec 2007
Location: Bristol, Avon, UK.
Posts: 184
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Of course, but for beginner I was thinking of digital readout which many more modern scopes have.
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#65 |
Nonode
Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
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I thought my 1970's Gould OS3000 'scope was modern!
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#66 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
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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
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
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#67 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,528
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I'm a firm believer in the idea that digital equipment is always precisely wrong whereas analogue kit is approximately right
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#68 |
Nonode
Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
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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).
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Richard Index: recursive loop: see recursive loop |
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#69 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
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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
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
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#70 | |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
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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. |
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#71 |
Nonode
Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
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Absolutely.
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Richard Index: recursive loop: see recursive loop |
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#72 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
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Several posts move to a new closed thread here:-
https://www.vintage-radio.net/forum/...d.php?t=120085
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
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#73 | |
No Longer a Member
Join Date: Dec 2007
Location: Bristol, Avon, UK.
Posts: 184
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#74 | |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,273
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#75 |
Octode
Join Date: Sep 2004
Location: St. Albans, Hertfordshire, UK.
Posts: 1,477
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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?
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Regards, Richard, BVWS member |
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#76 | |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
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![]() Al. |
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#77 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
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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/ |
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#78 |
Retired Dormant Member
Join Date: Sep 2003
Location: Bristol, UK.
Posts: 808
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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 |
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#79 | |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
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![]() 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. ![]() ![]() Al. |
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#80 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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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!
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If I have seen further than others, it is because I was standing on a pile of failed experiments. |
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