2nd Oct 2015, 9:33 am | #61 |
Nonode
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Re: Test equipment for valve radio repair
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. |
2nd Oct 2015, 9:50 am | #62 |
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Re: Test equipment for valve radio repair
Hear hear!
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2nd Oct 2015, 10:12 am | #63 |
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Re: Test equipment for valve radio repair
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. |
3rd Oct 2015, 3:26 am | #64 |
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Re: Test equipment for valve radio repair
Of course, but for beginner I was thinking of digital readout which many more modern scopes have.
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3rd Oct 2015, 9:59 am | #65 |
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Re: Test equipment for valve radio repair
I thought my 1970's Gould OS3000 'scope was modern!
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3rd Oct 2015, 11:14 am | #66 |
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Re: Test equipment for valve radio repair
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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3rd Oct 2015, 11:41 am | #67 |
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Re: Test equipment for valve radio repair
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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5th Oct 2015, 7:03 am | #68 |
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Re: Test equipment for valve radio repair
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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5th Oct 2015, 7:48 am | #69 |
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Re: Test equipment for valve radio repair
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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5th Oct 2015, 8:40 am | #70 | |
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Re: Test equipment for valve radio repair
Quote:
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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5th Oct 2015, 10:46 am | #71 |
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Re: Test equipment for valve radio repair
Absolutely.
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5th Oct 2015, 9:53 pm | #72 |
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Re: Test equipment for valve radio repair
Several posts move to a new closed thread here:-
https://www.vintage-radio.net/forum/...d.php?t=120085
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27th Nov 2015, 10:33 am | #73 | |
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Re: Test equipment for valve radio repair
Quote:
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27th Nov 2015, 11:18 am | #74 | |
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Re: Test equipment for valve radio repair
Quote:
Peter |
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27th Nov 2015, 11:37 am | #75 |
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Re: Test equipment for valve radio repair
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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27th Nov 2015, 11:52 am | #76 | |
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Re: Test equipment for valve radio repair
Quote:
Al. |
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27th Nov 2015, 12:18 pm | #77 |
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Re: Test equipment for valve radio repair
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/ |
27th Nov 2015, 1:35 pm | #78 |
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Re: Test equipment for valve radio repair
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 |
27th Nov 2015, 9:55 pm | #79 | |
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Re: Test equipment for valve radio repair
Quote:
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. |
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29th Nov 2015, 3:56 pm | #80 |
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Re: Test equipment for valve radio repair
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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