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Chat => Tech Chat => Topic started by: burakkucat on March 19, 2012, 02:24:40 AM
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A while ago, I saw an item offered for sale which was described as an ex-GPO tester. As I have a liking for old test equipment, I splashed out £1-04 and purchased it.
Upon arrival, I gave it a good clean and checked it over. Very impressed with the discrete components and the quality of its construction. Needless to say, it is in excellent working condition. I estimate that it dates from the 1960s and was built to a standard that far surpasses current manufacturing standards.
For whom was it manufactured? I'm not too sure whether it was the GPO, Post Office Telecommunications or the BBC. I envisage that it would have been used by a member of the engineering staff of one of those bodies when configuring a land-line for an outside broadcast.
Does anyone recognise it or have an opinion, please? (I'm on the look-out for a copy of its Handbook, No. TP64.)
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Not sure if this is any help, but one thing that might narrow down its vintage would be to determine if the transistors are germanium or silicon. Germanium transistors were of course gradually spuerceded by silicon. I'm not sure of timescales and may stand corrected but if it contains germanium transistors I'd say it's likely to be of 60s origin. If silicon, then early to mid 70s onwards would be more likely.
There's probably many wikipedia pages describing transistor names, but as I recall Mullard and other major European manufactures of 60's/70s devices, had a convention whereby germanium transistors began with an 'A', silicon with a 'B'. Japanese transistors tended to use a different scheme, commencing with a number and a letter, such as 2N....., but I'm betting your tester will contain devices with the european markings, thus making germanium/silicon easy to distinguish.
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Thank you for that advice, 7LM. I have now made a note, on my ToDo list, to examine and document the semiconductor devices within that Level Measuring Set.
Regarding semiconductor devices, the only one that I recall by part number is an OC71. I have vague memories of BCxxx and 2Nxxx devices but valves were really the devices of my earliest electronic experiences. :)
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Ah, I also remember OC71's. Some specimens were glass with a rubber sleeve and, if you peeled off the rubber sleeve, you could experiment with them as photo transistors.
But I feel bad now, as I said they all began with either 'A' or 'B'. Ooops :blush:
The document in front of me when I composed that was a rather fragile, small orange pocket book that was once once on my Christmas list as a child, entitled "MULLARD DATA BOOK 1970" (priced at a reasonable 4/- (20p )). If I'd turned over the page, and if the pages hadn't cracked, from page 9 'SEMICONDUCTOR DEVICE TYPE NOMENCLATURE SYSTEM' to page 10 'OLD SYSTEM', I'd have remembered...
O = semiconductor, followed by..
A = diode or rectifier
C = transistor
:)
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You might find the handbook at http://www.telford-electronics.co.uk/manual.php?alpha=H ... scroll down and it is listed as a Hatfield Instruments product. Telford sell the manuals/handbooks.
Colin
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Thank you for the link, Colin. I shall give that site a good examination, later today. (After I have been asleep . . . )
I'm not too sure where "Hatfield Instruments" fit into the "picture", for the device is marked "WAYNE KERR WKC/1". :-\
Looking again at the image I have posted, I see that the manufacturer / model line (above the battery check buttons) has been lost in the shadow cast by the rubberised casing.
Anyone like to guess how I obtained that image? No, not a camera nor a WebCam but by placing the device on a flat-bed scanner! :D
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On the Wayne Kerr info, the WKC/1 is described as "WKC 1: 20Hz-120kHz Measuring Set". The Post Office (yes, that old) reference is possibly the original Hatfield reference. I believe Hatfield Instruments were subsumed into the Wayne Kerr empire at some time.
I know it is a long shot, but you might be able to get a pdf of the manual from Wayne Kerr themselves by using their manual request form at http://www.waynekerrtest.com/asp/manualyourdetails.asp
Colin
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Done a bit more digging in my old files - Hatfield Instruments Limited, based in Devon is now owned by JDSU! Full circle!
Colin
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Thank you for that updated information, Colin. You have provided me with sufficient details for some more detective work.
Now where did I put that "round tuit"? ::)
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Now where did I put that "round tuit"? ::)
I've got one on my desk here - I rest my coffee cup on it!
Colin
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It's time that I made an update to this thread.
Following on from Colin's suggestion, I contacted Wayne Kerr (the manufacturer) to see if they could help with the relevant documentation. A prompt reply, of the negative kind, was received. So on to Plan B. I made enquiries of Telford Electronics for the supply of the Product Manual, for the Hatfield Instruments device.
At the beginning of this month I realised that I had never had a reply from Telford Electronics. :( So I sent a repeat of the e-mail and received, by return, a positive response. In exchange for a small "pocket money" sum, I possessed a copy of that manual before the week was out.
I attach scanned images of the front & back covers and of the first two printed pages. From the first page I obtain some more information:
"Post Office Specification RC 5816 (and addendum and corrigendum dated Jan. 1977)"
The second page, the History Sheet, gives the Post Office Approval Reference for the Manual which was first issued in July 1978.
The Wayne Kerr device (WKC/1) that I own is certainly from 10 - 15 years earlier. There are physical differences between the Wayne Kerr and Hatfield Instruments devices but the logic of operation is identical.
There is no urgency but I shall still continue to seek a copy of the Wayne Kerr Handbook No. TP64.
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I continue in another post so that I can attach the two scanned images of the Hatfield Instruments device's circuit diagram, below.
There is (at least) one difference between my Wayne Kerr LMS 35A and the newer Hatfield Instruments LMS 35A. That is centred around the batteries test circuitry. I have two buttons to press, one for each battery, to check that they are able to deliver the requisite voltage, whereas with the Hatfield Instruments device that functionality has been built into the Input Level control.
Perhaps the circuit diagram will allow 7LM to reminisce on the subject of discrete semiconductor devices? ;)
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I contacted Wayne Kerr (the manufacturer) to see if they could help with the relevant documentation. A prompt reply, of the negative kind, was received
'Tis obvious why you got a useless reply: the clue is in the name. :bye:
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'Tis obvious why you got a useless reply: the clue is in the name. :bye:
Ive no idea what you mean (https://forum.kitz.co.uk/proxy.php?request=http%3A%2F%2Fwww.emotionless.co.uk%2Femotes%2Fchar%2Fangel10.gif&hash=909e5c61ab11bb960b0cb293612f61ad9508b7e0)
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Me neither. Would you be kind enough to go into a detailed explanation, renluop ??? ;)
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Perhaps the circuit diagram will allow 7LM to reminisce on the subject of discrete semiconductor devices? ;)
Does that carry some insinuation about my vintage? ;D
Seriously, I enjoyed the days when you could tell, from looking at the schematic, what a circuit was meant to do.
Mind you, that's also my main criticism of OO software... a single line of code, that looks so innocent, can do so much. Bring back TTL and machine code, then I'll stand a chance. ;)
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Transistor-Transistor Logic ........ I remembered that from my ONC in electrical engineering. Get in there !!! :P
Seriously, that's about all I can remember, apart from the Capacitor and Resistor in series (variable ??) being a kind of timer before the 666 chips came into being ?? Long time ago and way, way, way out of my comfort zone.
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Transistor-Transistor Logic ........ I remembered that from my ONC in electrical engineering. Get in there !!! :P
Seriously, that's about all I can remember, apart from the Capacitor and Resistor in series (variable ??) being a kind of timer before the 666 chips came into being ?? Long time ago and way, way, way out of my comfort zone.
Are you perhaps referring there to the NE555 BS ? ::)
You can build a simple band pass filter with a resistor and a capacitor in series. If you take the output from across the cap you would get a low-pass filter, if taken across the resistor, a high-pass filter.
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Transistor-Transistor Logic ........ I remembered that from my ONC in electrical engineering. Get in there !!! :P
Seriously, that's about all I can remember, apart from the Capacitor and Resistor in series (variable ??) being a kind of timer before the 666 chips came into being ?? Long time ago and way, way, way out of my comfort zone.
Are you perhaps referring there to the NE555 BS ? ::)
You can build a simple band pass filter with a resistor and a capacitor in series. If you take the output from across the cap you would get a low-pass filter, if taken across the resistor, a high-pass filter.
Ha ha, that's the one Black Eagle. I didn't know that about the 'Band-pass' filter though. I can only assume that's how the ADSL dongle filters are assembled ??
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Are you perhaps referring there to the NE555 BS ? ::)
Ah yes, the appearanceof 555 timers does bring back memories, especially of a very elaborate windscreen wiper controller I designed for a 1970 Ford Escort. It featured variable intermittent wipe as well as a variable 'on' time after you used the washers.
Come to think of it... , I probably should have patented that, they all do it now :o
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Perhaps the circuit diagram will allow 7LM to reminisce on the subject of discrete semiconductor devices? ;)
Does that carry some insinuation about my vintage? ;D
Well as I am a "valve cat", these new-fangled semiconducting devices are a mystery to me! With valves you knew when they were powered on (they glowed). In the winter, they provided a source of warmth to "cold paws". All the other discrete components were of similar size (at least I could see the resistors, capacitors, inductors, bulbs, transformers . . . ) :-\
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Perhaps the circuit diagram will allow 7LM to reminisce on the subject of discrete semiconductor devices? ;)
Does that carry some insinuation about my vintage? ;D
Well as I am a "valve cat", these new-fangled semiconducting devices are a mystery to me! With valves you knew when they were powered on (they glowed). In the winter, they provided a source of warmth to "cold paws". All the other discrete components were of similar size (at least I could see the resistors, capacitors, inductors, bulbs, transformers . . . ) :-\
:lol:
Couldn't agree more. And not only were the components big enough to see, the capacitors usually had values in plain english, while the resistors had only three big, bold, colour stripes (ignoring the fourth, gold or silver). These days, many low value cap's also seem to be marked in codes known only to the secret services. As for the resistors, they not only seem to have made them unnecessarily tiny, they've crammed in more colour bands.
Any chance of a peek inside the LMS35A device? Even just a soft-focus pass on the scanner might be interesting?
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Is this turning into a wrinklies' nostalgia session? :oldman:
My first radio didn't have valves. It used a small crystal and a fine wire with a sharp point, which I had to move around over the crystal to find a sensitive point. We didn't just build the equipment, we had to make the components too. ;D
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Any chance of a peek inside the LMS35A device? Even just a soft-focus pass on the scanner might be interesting?
Certainly. I've scratched made a note to remind myself to remove the back and see what is scan-able.
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We didn't just build the equipment, we had to make the components too. ;D
And what fun it was! When the "main station" was the BBC's Light Programme, broadcasting via the Droitwich transmitter (http://en.wikipedia.org/wiki/Droitwich_transmitting_station) on 200 kHz (1500 metres Long Wave), winding the coil, setting up a long wire aerial to the end of the garden and establishing a good earth connection was an afternoon's occupation. :)
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Any chance of a peek inside the LMS35A device? Even just a soft-focus pass on the scanner might be interesting?
It must be a day for miracles, for b*cat has remembered 7LM's request and so is happy to offer the best image that his flat-bed scanner could obtain. ::)
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Any chance of a peek inside the LMS35A device? Even just a soft-focus pass on the scanner might be interesting?
It must be a day for miracles, for b*cat has remembered 7LM's request and so is happy to offer the best image that his flat-bed scanner could obtain. ::)
Thanks for that.
It reminds me to add 'single layer pcbs' to my wish list, for a return to the old days, and the ability to make a very good guess about a device's function just by looking at it (and holding it up to the light) :)
I also like the amount of pcb real-estate given over to the big push button. But I also recall some of these big chunky switches with their large slider contacts did tend to corrode readily. Same may go for the rotary switches. A squirt of switch cleaner may be called for?
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Ah, yes. Rotary switches with multiple wafers of the Yaxley disposition. A quick squirt of Electrolube switch cleaner worked wonders. :)
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It's late, and so apologies in advance if I'm overlooking the obvious and asking a stupid question, but what does the large push button actually correspond to on the schematics?
The schematics show two apparently independent single pole 'on' buttons, S3 and S4, either one of which would seem adequate, and annotated LH and RH. Any clues?
7LM
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Well as I am a "valve cat", these new-fangled semiconducting devices are a mystery to me! With valves you knew when they were powered on (they glowed). In the winter, they provided a source of warmth to "cold paws". All the other discrete components were of similar size (at least I could see the resistors, capacitors, inductors, bulbs, transformers . . . ) :-\
Ah, so your favourite voltage is 6.3v ??
Valves were a little before my time although I did build an amp based around EL84's !!
My dad was a TV & Video engineer who did his appreticeship in the 50's. I well remember him stripping our 28" decca console on a regular basis with its bradford chassis. Mullard PL508 anyone ??
Electrolube !! Good stuff, and there is a can of it in my toolbox, along with freezer and Servisol screen cleaner !! Meters are AVO 7 & AVO 8 & a digital (early) fluke although I cannot tell from the fluke if a transistor is good or bad. Can from the AVO's though !!
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It's late, and so apologies in advance if I'm overlooking the obvious and asking a stupid question, but what does the large push button actually correspond to on the schematics?
The schematics show two apparently independent single pole 'on' buttons, S3 and S4, either one of which would seem adequate, and annotated LH and RH. Any clues?
Clues? Let's see . . . :hmm: Hmm, the schematic diagram that you have consulted is for the newer Hatfield Instruments device. I did mention that there was a subtle difference (or two) between it and the original Wayne Kerr device. The two single pole push buttons, S3 and S4, are on either side of the Hatfield Instruments device. Something to do with equal opportunities for left- and right-handed people! The Wayne Kerr device just has the "on" push button on the left-hand side . . . that is the large push button of your query. :)
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Ah, so your favourite voltage is 6.3v ??
Why, yes, it is. To date, I have absolutely no idea why that particular voltage was chosen. I am referring to the peculiar "extra" 0.3 of a Volt. Why not just 6V ? Ideas, anyone? ???
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Something to do with the typical voltage of lead-acid cells perhaps?
Edit: Yes, that's it - http://www.r-type.org/addtext/add014.htm
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Well I never knew that! Thank you, Eric.
However I suspect there is a minor logic error in the page whose link you have provided. A freshly charged Lead Acid Cell will provide 2V. Three LAC's in series (as in an American car battery of that era) would be 6V. However to ensure that the car battery remained charged, greater than 6V would need to be provided by the car's charging circuit. Hence I assume that is where the "extra" 0.3V comes from.
I seem to have a memory that modern day vehicles, with 12V electrics, can have up to 14V supplied to the SLA battery and so any in-vehicle electrics are designed to be input voltage tolerant -- 10 to 15 volts, I believe.
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However I suspect there is a minor logic error in the page whose link you have provided. A freshly charged Lead Acid Cell will provide 2V. Three LAC's in series (as in an American car battery of that era) would be 6V.
No, that's not quite right. The fully charged voltage of a lead-acid cell is a bit over 2.1V, so a nominal 6V car battery would actually have a voltage of just over 6.3V when fully charged.
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:hmm: Hmm . . . b*cat pads off to check his electro-chemistry. :-\
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I must admit, whilst I was probably curious as a youth (among other youthful interests ;) ) about the 6.3V filaments convention, there was no easy way (pre www) of researching such things and so I suppose I just came to unquestioningly accept it.
Good to see it being discussed again, I'll read with interest :)