The TIV48 Injector/Tracer

[Joe]

Last week Rob T advised me to make one of these which I've just completed.

   

It proved to be one of those rare occasions when such a thing worked first try.

I thought it would make an interesting stylistic contrast to Yorkie's homebrew test gear.

- Joe

[tiv48]

i like it when i was learning my boss a genius called eric lusty used to draw out a circiut and say rob build this birds nest style then find out why it does not work
rob t

[AlanBeckett]

Joe,
I think that you can safely say that you succeeded in adopting a different style to David and his wooden boxes
When I was a lad the objective was usually to cram the works into something like a cigar tube. Do such things still exist? I guess the alternative for old codgers would be a Steradent tube.
Alan

[tiv48]

if you cant afford a signal generator its the next best thing you can start at the af stage then the if stage even the rf stage
and its cheep to make
rob t

[Yorkie]

Joe,
I think that you can safely say that you succeeded in adopting a different style to David and his wooden boxes
When I was a lad the objective was usually to cram the works into something like a cigar tube. Do such things still exist? I guess the alternative for old codgers would be a Steradent tube.
Alan

Not everything I've made has had the 'wooden box' treatment!

I've been making stuff since when I was 12 in 1951, back when it was crystal sets and one valvers. My interest was further stimulated when later, I became a 'paper boy', and on my rounds I used to dawdle along and thumb through such delightful magazines as 'Hobbies Weekly' which often had simple radio articles, and later still, Radio Constructor. Thus, I was able to read the mags free, before the paying customers on my round were able to lay eyes on them!

I've attached a pic of a couple of signal injectors I made many years go - one in an icing syringe bought from Woolworths for a few coppers - the other in a felt tip marker pen. The one in the syringe dates back to 1959, and is still going strong. I could have used two 'Red Spot' surplus transistors (out of spec - ie, low gain) at ten shillings each (50p) but decided to push the boat out and use Mullard OC44s at eleven shillings each (55p). It might not seem to be much of a decision for what seems to be a modest additional outlay of 5p each, but to put it into perspective, 50p in 1959 equates to £8.50 now, and 55p equates to £9.40, so a pair of OC44s in 1959 cost me the equivalent of £18.80 today! Still, it was a sound investment which has paid for itself many times over in fault tracing over the last 51 years since I dug deep into my pocket.

The later injector - about 1985, used a couple of BC108s, which I doubt cost more than 20p each, but even that equates to 64p each in today's money, yet we can buy 20 for a pound nowadays.

The icing syringe injector was built on perf board, the pen case one was built 'ugly style' or 'dead bug style,' with the components wired together on very short leads to make it compact. Neither are pleasing to they eye, but both are functional. I've attached a couple of scope traces to show the waveforms. I haven't bothered to check the frequency, but I imagine that it will be 1kHz to 1.5kHz or thereabouts, rich in harmonics to a much higher frequency so RF/IF stages can be checked as well as AF.

Hope it might amuse and interest someone out there!

Fo anyone who might wish to build a combined signal injector/tracer, there is an excellent Veleman kit - the 'K7000' available from the main stockists of Velleman Kits - ESR Electronics. It's on a neat PCB, with two on-board pots, one for the injector output, the other for the AF volume. It cost about a tenner. Highy recommended. You'll find it at the link below, an a PDF of the comprehensive construction manual:


http://www.esr.co.uk/velleman/products/index_kit.htm

The spec is:

Velleman K7000 Signal Tracer/Injector Kit:

Features:
• Injector:
• 0-2.5Vrms output (adjustable)
• Output impedance: 1.5Kohm
• Frequency: ± 1kHz

• Tracer:
• 3.5mV to 10Vrms sensitivity (adjustable)
• Gain: 40dB
• Input impedance: 50Kohm
• Output power: 0.5W / 8ohm
• Power supply: 7-9VAC or 9-12VDC / 150mA

David

[Joe]

Now that's interesting, David. I've got a couple of icing guns, but as they're metal would need lining with something, and some OC44s - thanks for reminding me as I'll have to test them.

I winced at ten bob for transistors as I'd regard that as pricey even today. Just for comparison's sake, what did valves cost back then?

Cheers
-Joe

[tiv48]

knocked another one up yester day

[Yorkie]

I winced at ten bob for transistors as I'd regard that as pricey even today. Just for comparison's sake, what did valves cost back then?

Cheers
-Joe

At first sight, vales look ridiculously cheap, but not when historical inflation is taken into account. One pound today equates to 5p back in 1958, believe it or not.

You can check prices back and forth from 1751 - 2013 here:

http://safalra.com/other/historical-uk-i...onversion/

I've listed some valve prices from Sept 1958 PW below out of interest.

UCH42 & UL41, ten shillings each = £10.00 each today.
UBC41, UF41 8/6d (45p) each = £9.00 each.

Matched pair of 6V6: 17 shillings (85p) = £17.00

Battery valves such as DK96, DK92, 3S4, 3V4 1T4 etc, as used on valved portables of that era were typically 7/6d, which equates to £7.00 each today.

A 40W soldering iron was on offer at 17 shillings (£17.00).

Surplus (reject) red spot transistors were 7/6 and white spot (RF) 13/6d. Genuine Mullard and Mazda transistors were 21 shillings!

A kit radio - the 'Transistor 8' was £11.10s. I'll leave you to do the sums. late 1950s prices need multiplying by twenty as a rough guide to the equivalent price today.

It's not just the effect of inflation on just how much £1.00 was back then and how little it is now, but the way that the price of consumer electronics has fallen off a cliff. You can new get a decent tablet computer for less than the cost of a kit radio back in the late 1950s. I recall how we 'saddling ourselves' with a 20-year mortgage of £1,500 back in 1961 for our first house - a 'millstone around our necks' for a 3-bed semi. That was the maximum I could then borrow - which we had to match with £700 deposit, so we could only get a 66% mortgage. I recall how we anguished over borrowing such a large amount - 1.5 times my wages, a fairly standard ceiling which then applied.

Our parents wondered why we didn't do what many other young people did back then - put our name on the council house waiting list.

How times change!

[Joe]

Interesting, David. The old valve prices you've index-linked come out at about what NOS ones still sell for. So much for the fantasy of going back in time and stocking up as they'd have proved a very poor investment.

You're right about the price of electronics going off a cliff. I seems plain daft that Sainsbury's sell shirts for more than DVD players.

- Joe

[John M0GLN]

I've got an old receipt here showing that someone paid 9/6 plus 3/1 tax making a total of 12/7 for a PL84 on the 22/4/61

John