Hi all. First I'd like to thank the guy's who answered my question regarding the radio choke. Great advise. I've tested it and placed it back in circuit.

I now have a another request which I hope someone can help me with. Recently I bought a Scuola Elettra Torino valve tester, but unfortunately the valve indicator meter was missing (they come in a set as a tester and voltmeter) so i'm looking for one to replace it.,

To view this set, google; Scuola Radio Elettra, go to Radiopistoia.com - Radiocorriere.it
a window will open showing all the details.
If anyone know where I can buy one of these or a substitute it will be appreciated.
Thanks.
Regareds
Paul.P.

Do you mean what is shown at this link? https://www.radiopistoia.com/infoprovasre_.htm

If so, then the meter concerned looks to be this one, designated Tester mod n 264. : https://www.radiomuseum.org/r/sre_3_tester.html

IMO that would be very difficult -- if not impossible -- to source these days outside of Italy.

I have to ask, why did you choose to buy that obscure Italian tester instead of one of the dozens of commonly recognised brand testers advertised for sale?

Why do you think you need a valve tester at all?

For me, if I have a radio that is fitted with a suspect valve type I will simply insert the suspect valve in the known-working radio and see if it fires up. If not, I get the Paton valve tester out and test the valve.

If there are other ways to test valves for output, I am not familiar with them.

Ian Robertson You asked me "Why do you think you need a valve tester at all?" It because I do, I want to learn about all facets of testing radio parts and valves are one of them. Do you have a suggestion where I can but a valve tester cheaply?
Paul.

Posted in wrong thread: GTC I didn't buy Scuola Radio Elettra the valve tester it was given to me.

OK, in that case you can reconsider the situation.

Many techs never buy or use a valve tester because they don't need to. The best use of a valve tester is to evaluate a batch of valves to determine good from bad -- that is what I use mine for as I sometimes buy boxes of valves at auction.

The wisdom is: the best test for a valve is in the circuit it was designed for.

Valve testers can only approximate any valve's operating conditions and there are generally two types: those that measure transconductance and those that don't; the latter type being the cheaper of the two.

There are numerous considerations when deciding which type and brand of tester to buy and there's a plethora of info about all of that on the web. This recent video is a pretty good summary:

https://www.youtube.com/watch?v=hrXBkpiQ2DI

If you want to learn about radio repair and alignment then I would strongly recommend member Tippy's YouTube channel (and I don't recall him ever using a valve tester):

DavidTipton101">https://www.youtube.com/DavidTipton101

You don't fault find a radio or TV by testing parts. You do so by understanding how it works and then, for starters. measuring voltages.

For radio work, a signal generator is vastly more useful than a valve tester. That and a good multimeter.

Valve testers tell fibs. They can tell you a valve is "bad" when it will work perfectly adequately in the socket in the radio or TV. Or vice versa. And unless damaged by external causes valves are rarely at fault in vintage electronics. I had an example of this yesterday on a TV that exhibited intermittent random black lines and spots in the image, that was actually due to a valve fault. The nature of this fault meant that a valve tester would never have detected it. There were many faults in this 50 year old TV but only one of them was a valve. This is fairly typical.

So you see why a valve tester is a "WOFTAM"!! At least in most cases anyway.

Your learning should start with understanding how circuits work and how to use a multimeter, including being able to recognise when you can and cannot rely on the accuracy of a reading. You need to learn to use your meter.

A signal generator can be used to inject a signal into, say, a radio at each stage, in the process quickly discovering in which stage the fault exists.

I hope the above has not disheartened you.

Hi GTC. Thanks for the information. I also want to use the one I have to test batches of valves. And I will have a look at the youtube videos as suggested. Thanks GTC.

Hi Ian. "WOFTAM"!! That mate made me laugh.. Multi-meters? I used them as an electrical mechanic in fault finding and I always use it when i'm working on a radio. But electronics is new to me and although I understand circuitry, this circuitry 'is' confusing at times.

But I will get it. I don't get disheartened easily it just makes me work a lot harder and more persistent. I assure you all the feed back is read and I appreciated what is said and suggested.

You mentioned ; (A signal generator can be used to inject a signal into, say, a radio at each stage, in the process quickly discovering in which stage the fault exists.) I am aware of this process but I don't really want to blow myself or my equipment up causing "WOFTAM".

I have watched many youtube videos but none that I have seen yet, show where they connect probes when carrying out testing, Oscilloscope readings, doing a signal tests, voltage readings etc.

Using a valve tester is another tool in the arsenal to use until I reach a more satisfactory level.

I would like to ask if you if you would mind helping me with a second opinion please regarding a circuitry problem I have with my 1970 Scuola radio valve tester I mentioned.

Put simply, on the tester site https://www.radiopistoia.com/infoprovasre_.htm the testers builder (Photo-5) has placed a filter in the circuit to avoid auto-oscillations.

But it appears the schematic ( press "HERE" next to photo-5) and the photo showing the position of the filter are not the same.

Photo-1 shows two capacitors, one on the meter outputs, and one between switch positions A & C. (red & white) on the large P 1-9 switches.
All good there.
The inductor and other capacitor are on the function (Funzioni) switch between position I and T1 terminals with capacitor from inductor to a terminal C. P 1-9 switch.

The question I have is, how do you think these are connected? Is the inductor is connected from I to T1 or floating? Is the capacitor is connected to the inductor to a C position on the P 1-9 switch?

The diode is connected from D2 to I as per schematic. But the Schematic shows a different scenario. Or, am I reading it all wrong? I believe the inductor wire is 0.8mm dia, on the schematic it shows a 5mm dia for the inductor and 10 turns. I estimated it to be 2.0uH with Fe. core.
The caps are 120 - 150pF 100V


Thanks for your time Ian.
Regards.
Paul.P.

Hi all,

I test as many parts individually, or in circuit, as practical eg power cord, fuses, Ground, power transformer, output transformer, valves with a valve tester etc etc.. No hard and fast fast rules as it depends on the radio, its condition etc.. .. the point is to eliminate any major faults before applying power to prevent damage to me and/or the radio.

Also, I use a range of test equipment including DMM, Valve tester, Signal/Function generator, oscilloscope, current limiter, Variac etc.. The key point here is to know how to use this equipment, when to use it, understand exactly what it is telling you and what it is not telling you ie its limitations in various situations. ALL test equipment has limitations and ALL test equipment impacts the circuit being worked on.

Do you need it all?? ... obviously not ... but each does have its place in troubleshooting, repair, modification work.

To true Tinkera123

I have watched many youtube videos but none that I have seen yet, show where they connect probes when carrying out testing, Oscilloscope readings, doing a signal tests, voltage readings etc.

The Mr Carlson's Lab series on YouTube probably covers that among the hundreds of videos he has made.

However, the key to all of this testing and measuring is knowing how the circuits are designed to operate. A good understanding of the block diagrams of radios will show how the various stages interconnect, and diagnosing faults correctly is a stage-by-stage process.

I strongly suggest that you get a book or two on the subject of repair and restoration. We have covered that here:

https://vintage-radio.com.au/default.asp?f=2&th=736