Golborne Vintage Radio

At long last I've got round to making one - see attached. This is particularly incompetent as David very kindly sent me one of his splendid boxes and front panels and a PCB including the critical components. I'm afraid it was largely lethargy on my part Anyway, this latest bout of bad weather plus the need to measure the capacitors on the MM galvanised me. Actually it was very straightforward, I just followed David's instructions. I built it incrementally starting with the Regulator, then the Oscillator and finally the rest, testing as I went along.

I made some simple additions and modifications along the way:-
I gave it four stick-on rubber feet.
I increased the LED series resistor to 1k as mine is very small.
I hadn't got any suitable spacers, and anyway I didn't want to marr the front panel, so I glued (Araldite) four long M3s to the back of the panel.
I made a new scale having calibrated it with an R-Box. I suspect that the meter may have changed slightly since the original.
I only made one cockup on the way, I left it on all night - about 10 hours. The Duracell PP3 was down to about 8 volts in the morning but it was still working fine, so I suspect provided I remember to switch it off one battery will last a long time.

And that was it. Brand new Electrolytics measure less than one Ohm. A couple of old bangers, which I'd more or less written off, came out quite well at around two Ohms, so a bit of reforming plus verifying the actual capacitance should mean they're usable. C18 from the MM measures at about six Ohms which potentially is dodgy, but in practice works fine.

So, thanks again David for a splendid box, PCB and design.

Alan

[attachment=4012]

Glad you got around to finishing it Alan and are finiding it useful!

As to the length of time to get round to finishing it off, some of my projects have very long gestation periods! I've been rummaging about in the loft among my half-started stalled projects and to my horror, came across a box marked 'Curve Tracer' in which was a PCB I'd etched and built, and all the other bits needed to complete the project, together with the magazine article from 'Electronic Digest' dated Autumn 1980 (Why did I think I needed a curve tracer? But maybe I'll finish it off now that I've unearthed it!).

l also built all the PCBs to make a multi-band QRP 'G3TSO' SSB transceiver which featured in Radcom in the late 1980s using the excellent Plessey SL600 series of communcations ICs, and built and tested the VFO and digital readout, but then I lost interest in amateur radio. Realistically, I doubt that I'll ever re-kindle that interest, and I'm never going to finish that project, so, I think it's going to have to go when I can get round to advertising it in perhaps the G-QRP SPRAT magazine for someone else to finish.

David

Nice-looking finished job Alan ~ well done.

Al.

I forgot that I'd had a bash at this some months ago. I built it on stripboard so I had to base it on the diagram that Mr.Topcap showed on VRRR. I recall he used a SIL array which I didn't have and neither did I know what one was at the time, so had to fudge around hence the mess of resistors, tacked together to see if it worked. It didn't.

So back in the project box it went along with the other parts. I appreciate this is an easy project for some of you with a lifetimes experience in electronic design but possibly a project too far for me! I may have another bash one day though I have a Peak ESR meter.

Andrew

I forgot to add thanks to David for sharing the project in the first place, it kept me thinking for a weekend.

I reckon that you'd be well advised to have a close look at the underside of that strip-board and check the component interconnections. It is very easy to misplace a jumper wire or wire in a transistor the wrong way round. I've built many projects on strip-board and know just how easy it is to make mistakes like that. Look at it from this angle: it is a proven design, so provided the components were 'good' to start with and still are (bearing in mind what I've written above), I would expect that patience, persistence and perseverance will get it working.

Al.

Hi David, I am interested in building your revised ESR Meter, I would be grateful if you could give me a link to the full build and operating instructions, and any other material you may have regarding this project.

many thank
phil

Thanks for your interest Phil.

Based of feedback and suggestions from others, I’ve extensively modified and updated the original design over time, and as a result, there have been so many posts to this thread that it’s all become rather confusing for anyone who wishes to build one! Also, as this is a relaxed forum with a ‘light touch’ moderation policy, (a big plus point IMHO), we do tend to drift off topic somewhat, so not all the posts are relevant or helpful to new readers.

If you wish to have a go at building the project, Posts # 1, 2 & 3 in this thread are relevant. Post 4 describes building and troubleshooting, and Post #40 shows pics of the latest PCB artwork and component layout. However, a number of builders have found the circuit a bit confusing as it didn't show how to wire the meter and off-board zero adjustment pot. Neither did it incorporate the additions that I’ve made over time, albeit I did update the PCB artwork and overlay. To help you or any other potential builders, your post has prompted me to update the circuit layout, incorporating all the additions that I’ve made, so I’ve done that today and have attached it to this post.

The original designer's article is here:

http://www.members.shaw.ca/swstuff/esrmeter.html

The Schematic is here:

http://www.members.shaw.ca/swstuff/esrschematic.png

The Original Parts Layout is here:

http://www.members.shaw.ca/swstuff/esrbuildit.png

Original x-ray of parts placement is here:

http://www.members.shaw.ca/swstuff/esrxray.png

Those should be viewed alongside my updated layout and parts placement, showing the changes to the layout. Most parts placements are the same, but where I’ve added components and altered the layout, I’ve highlighted those on the PCB overlay.

I hope that’s helpful to you or anyone else wishing to build the project. Many have successfully been built, and if anyone gets stuck, I’m happy to help as best I can. It isn't a temperamental circuit, the parasts are widely avaiable and cheap - even the meter movement isn't too expensive, and once built, it's a very useful item of test gear.

A quick explanation once more as to how it works and what the various bits of the circuit do:

IC1 is a hex Schmidt trigger. One of the six gates, along with C1 and R1, form an oscillator circuit, which is as simple as an oscillator gets. The values of C and R determine the oscillator frequency, which the designer states as 150 or 156kHz, but is in fact nearer to 100KHZ, though this isn’t critical and has no bearing on the accuracy of the meter. Most ESR meters work on a similar principle - the application of a low amplitude AC signal, usually of a frequency between 100kHz - 200kHz, to the capacitor under test. I’ve tried various 74HC14N ICs in this design and they’ve ranged from 100 – 105 kHz. More about that in the footnote. . (The ‘N’ suffix simply denotes a 14 pin DIL package. Any prefix denotes the ID of the maker)
Pin 2 of IC is the output of the oscillator, which goes to the input of the other gates at pins 3,5,9,11 & 13. The outputs of those five gates appear at pins 4,6,8,10 & 12 and go to the five 680 Ohm resistors R2,3,4,5 & 6, to form a buffer and Low Pass filter. At the junction of those resistors - which are all coupled together on their outputs - there should be a waveform of approximately 250mv peak to peak at about 100KHz. The next stage is the input protection stage (D5, D6, C5 etc) which protects the meter from damage should it get zapped with an un-discharged capacitor attached to the test leads.

From the junction of R8, D5, D6 and C5, there should be a waveform of about 180mV peak to peak, but it’s important to note that this is only when the test leads are shorted, or a good cap with a low ESR is connected to them. This AC waveform then passes via C2 to the base of the 2N2222A which is an AC amplifier with a gain of approx 10.5. Its role in life is to raise the 180mV p-p input to nearer 2 Volts p-p. This then passes to the meter rectifier D1,2,3 &4, for the meter movement. But without the test leads shorted, or a known good electrolytic cap with a low ESR attached to the test leads, there will be zero Volts at the input (base) of the 2N2222A and nothing at its output, (collector) so no deflection on the meter. The meter rectifier enables the meter to function as an expanded scale AC voltmeter. Full scale is zero Ohms, mid-scale is approx 10 Ohms. There is no DC output until approx 75 Ohms of ESR is seen at the test terminals, (ie, a bad cap), at which point the meter will barely deflect.

The meter reads like an analogue Ohmmeter, that is when you short the test leads, the needle deflects across tot the right hand end of the scale. But whereas on an Ohmmeter you have to set the zero each time you use it, because this project incorporates a 5V regulator and is powered from a 9V battery, once you’ve set the on-board pre-set pot to enable the meter to read full scale deflection, it shouldn’t be necessary to adjust it again. If the needle doesn’t go to FSD with the test leads shorted, it is a sign that the battery Voltage has fallen below 5 Volts and needs replacing

As I explained in an earlier post, while I originally used a 50 uA meter from the aptly named ESR Electronics, I later found that Rapid Electronics supply a larger 50uA meter (70mm x 60mm):

http://www.rapidonline.com/Electrical-Po...70-48-0300

Hope that helps.

To David, many thanks!

phil

(08-02-2013, 07:57 PM)phil333 Wrote: [ -> ]To David, many thanks!

phil

No probs Phil. If you do decide to build it and run into any problems, do let me know - I'll be pleased to help in any way possible.

Really, the whole thread has become rather like a large helping of alphabet spaghetti, and is in need of a good spring clean, which I think will be attended to. As it stands, it would probably take longer to read the thread than to build the project! I'd had it in mind for some time to update the original circuit to incorporate the mods I'd made, and I'm pleased that your post gave me the nudge that I needed to get on with it. I'm afraid that CAD is not on of my strengths, so I hope the end result, which I just used MS Paint to do, is at least passable, and when read in conjunction with the PCB layout, makes sense.

Welcome to the forum by the way Phil.

It's very friendly and informal, with just five sensible rules which you can see at the top.

One of the benefits is that there's scope to discuss other interests such as woodwork and metalwork, which are often ancillary to the hobby of vintage radio and electronics.

(08-02-2013, 09:10 PM)Yorkie Wrote: [ -> ]Really, the whole thread has become rather like a large helping of alphabet spaghetti, and is in need of a good spring clean, which I think will be attended to. As it stands, it would probably take longer to read the thread than to build the project!

A condensed version is now available here.

- Joe