Testing tunnel diodes

[woodchips]

After the very generous offer of three Tek scopes, prodded me into trying to test some tunnel diodes I have. Had a 547 many decades ago, and didn't trigger, so made a TD tester that ran from the calibration output, sorted the problem, even could still get TD then.

The cal output is a positive going pulse from millivolts to 100V, this fed through a resistor and pot gave an adjustable TD current range from 1mA to 22mA. Using a function generator isn't so easy, the output is + and - 0V. Did find one with an offset so could generate 0 to about 70V peak.

The cal waveform was a pulse, and looking at the result from the TD gave the same pulse. Using triangular was much better, can see the peak point switching high and the valley point switching low, so demonstrated the TD is good. Varying the output voltage shows the switching points moving along the triangle wave.

But how to the curve tracers give the whole waveform? The switching speed is a nanosecond or so, ao how does this appear on a scope? I have the GE TD manual and they use an old, 1961, scope with 10MHz bandwidth or so. Yet the tester gives the whole Y shaped trace. Just interested, the GE tester is far more than I need to just prove functionality.

[Oldmadham]

Originally Posted by woodchips

After the very generous offer of three Tek scopes, prodded me into trying to test some tunnel diodes I have. Had a 547 many decades ago, and didn't trigger, so made a TD tester that ran from the calibration output, sorted the problem, even could still get TD then.

The cal output is a positive going pulse from millivolts to 100V, this fed through a resistor and pot gave an adjustable TD current range from 1mA to 22mA. Using a function generator isn't so easy, the output is + and - 0V. Did find one with an offset so could generate 0 to about 70V peak.

The cal waveform was a pulse, and looking at the result from the TD gave the same pulse. Using triangular was much better, can see the peak point switching high and the valley point switching low, so demonstrated the TD is good. Varying the output voltage shows the switching points moving along the triangle wave.

But how to the curve tracers give the whole waveform? The switching speed is a nanosecond or so, ao how does this appear on a scope? I have the GE TD manual and they use an old, 1961, scope with 10MHz bandwidth or so. Yet the tester gives the whole Y shaped trace. Just interested, the GE tester is far more than I need to just prove functionality.

We had a "TU-5 Pulser" which we used for TDR applications.
It contained a tunnel diode & was also supplied from the calibration output---this time on a 545B.

You could see a bit of the slow rise of the calibration waveform before the "vertical cliff face-like" leading edge of the tunnel diode!

Many years later, I found a TU-5 in some junk I had received from various sources, & often thought of making up a valve multivibrator to substitute for the 545B calibrator, but never had the bits to hand.
I ended up giving it to a bloke who had a 545B.

[RogerEvans]

I am not at all sure about this but if you have a resistor in parallel with the TD whose value is less than the (absolute) value of the negative resistance region of the TD then the parallel combination is stable subject to some caveats about stray L and C. You then need to correct the display by subtracting off the current through the resistor, ie subtracting some fraction of the voltage trace from the current trace.

Regards,

Roger

[John_BS]

I would say exactly the same as Roger, but not based on experience, just theory!

John

[Audiophile_AU]

Hi all,
I had the oscilloscope triggering problem back in the 60s with tunnel diodes. As I recall, the usual curve tracer showed a blank as the switching time was so fast. Fortunately one of the research labs had a Tek sampling oscilloscope (1GHz?) and I rigged up a test jig and observed a sub nanosecond rise time on a repetitive signal. Quite impressive for the time, I thought.
regards from Down Under
David

[factory]

I've got a Heathkit curve tracer IT-1121, the HP 140A with opt. H20 1405A X/Y plug-in is used for the display. I had to test some tunnel diodes for a HP 5248M counter, which still doesn't work with good replacements of a different type (originals were blown).



A HP 186A switching time tester, with HP sampling scope would be nice to find, but I doubt any are left in the UK.

David

[WME_bill]

Testing Tunnel Diodes.
Like David Audiophile AU, I have found that the negative sweep is too fast to show. And I am very happy with that, as it shows that the tunnel diode is working. If you shunt a resistor across the diode, that will slow it down to show something, but I doubt the benefit.
Many years ago, I built a tunnel diode tester, based upon WirelessWorld March 1965 using an old bell transformer, 2-0-2v AC mains and a couple of rheostats (show how rough and ready it was). But with a normal oscilloscope, it served very well. If it was blank during the negative switch, fine, it worked.
I attach a sheet of data for the usual tunnel diodes which also shows the circuit and scope X & Y amplifier settings. Start with the current lowest, no more than say twice the peak current to avoid over-heating the diode.
Quicker than getting out my curve tracer Telequipment CT71 and setting it up.
wme_bill

[loulou31]

Dear all,

Please find on ct71 curve tracer
Vertical 10mA / div
Horizontal 0.1V / div


Jean-Louis

[woodchips]

Upgraded (?) to fibre broadband, and been offline for nearly two weeks, and it took two lady engineers to get it working!

I had lots of non-search time and tested some tunnel diodes using the triangle wave from a function generator. The switching is very obvious with a two channel scope, input and diode. Don't really see that anything more sophisticated is needed.

[Alan Bain]

This may be well known but someone has drawn out the circuit of the HP tunnel diode tester ET2294A

https://hpwiki.mcguirescientificserv...e_curve_tracer

It doesn't look very hard to build one of these although it does use a UJT. I've tended to test them on the Tek 575.

[Chris55000]

. . .Perfect!

. . .That circuit will go in Part 11, Chapter 116, "Tunnel Diodęs" of my T & M Theory and Repair Book, with a suitable acknowledgement as to its source, of course!

Chris Williams

[loulou31]

Hi Chris,

Please could you provide référence of your book " T &M theory and repair Book" .
Thanks

Jean-Louis

[Chris55000]

My T & M Theory and Repair book is still being written and is a very large project involving many, many hours of research and writing–up, and preparing diagrams for it!

It is not something that you can buy or download, the chapters will be posted on here as I complete them – I have written (most!) of about 90 chapters so far and the whole work, as envisaged, is 275 Chapters in 22 Volumes!

There will be no charge for this work, but I'm afraid it'll be a few years before I can complete it in full, as quite a few chapters need equipment building or buying!

This will be a very high quality work written in the style of the very best British Servicing Authors, such as Gordon J. King, Vivian Capel, Eugene Trundle, H.W. Hellyer, Good Old Uncle Les, and Donald Bullock, and I don't want to publish anything until it meets my very strict quality, correctness and clarity standards!

Chris Williams

[Craig Sawyers]

This later in the book has a series of test circuits for complete characterisation of every aspect of tunnel diodes

https://www.worldradiohistory.com/BO...ition-1961.pdf

What is also interesting is that Leo Esaki (the inventor of the tunnel diode), along with Ivar Giaever and Brian Josephson won the joint Nobel Prize for Physics in 1973 for electron tunnelling in semiconductor materials. In fact the tunnel diode was originally called the Esaki diode.

Craig

[loulou31]

Thank you Craig, and congratulations for Chris,

Very interesting Book. I discovered that we can use tunnel diode with a lot of circuits. Now transistors and IC Can Do thé same for lower price....
Chris you project is very impressive. Good luck ans congratulations.

Jean-Louis

[factory]

Well I have the pictured HP 130A oscilloscope (needs full restoration), a decade resistor box (not Genrad) for the curve tracer test setup. They have most drawings for the three low inductance jig parts, except the mounting base. Test box seems quite large for what is in it, mostly switches & the power supply.



David

[Craig Sawyers]

The other standard manufacturer's data was in the RCA tunnel diodes book

https://www.worldradiohistory.com/BO...ition-1961.pdf

That also has quite a bit on measurement methods too.

It is amazing how much out of love the industry became sometime through the mid 70s. Tektronix for one used them mainly in trigger generators and fast pulse generators. For high speed you need a combination of high Ip and low capacitance (rise time is about Cp/2Ip). As an example, the TD in the 284 pulse generator is 21mA Ip and 1.5pF to give about 35ps rise time (instrument spec <70ps). High Ip and low C is not a reliability recipe. When Tek sold the last of this tunnel diode the price was $800 each.

But alternative technologies soon took over. Non-linear transmission lines can take a mere 70ps pulse as an input and produce a 2ps output.

Now you can do sub 30ps rise time with this https://www.leobodnar.com/shop/index...roducts_id=375 for a hundred quid. Powered from a USB port.

Craig

[WME_bill]

testing Tunnel diodes.
I seem to have missed the attachment to my posting of 24 Aug, #7 below.
My apologies. Attached herewith.
While of interest, the main need now-a-days seems to be for testing and to find possible substitutes for replacement in scopes or pulse generators.
As you cannot now purchase a tunnel diode with special features, I don't bother to check all parameters. The only parameter of importance is the Peak Point Current for germanium. Matching that will at least get the instrument working.

Testing. Never use the ohms test on your Avo or DTM. It will destroy the tunnel diode.
Use the Tek 575 or Telequipment CT71 curve tracer if you must, but a simple tester using your oscilloscope as I have sketched out above is quite adequate. Taken from Wireless World March 1966.

The RCA Manual of 1963 and the GE Manual of 1961 referred to above by others are on the web with much design information. With TO18, Pill or Stud packaging.
For specifications of tunnel diodes, my attachment is taken from a GE list of 1971, by which time GE were the only maker, having absorbed RCA. Using top-hat DO17 or bead packaging. All other makers seem to have ceased for these applications.

I attach the GE 1971 list and Philips 1969. American-Semi has a good list, using GE type numbers. Russian Pill style have been available on the web from Eastern Europe; details on Tek-Wiki tunnel diodes.
Others turning up from time to time are:Thomson SFD4163 =1N3716 5ma but inverted connections, Siemens TU410 =10ma, STC JK20 = 5ma. I have data on some other strays, as well as all those referred to above.
I have a small stock of GE diodes, so have not yet tried the Russian ones.
wme_bill

[veedub565]

Originally Posted by Chris55000

My T & M Theory and Repair book is still being written and is a very large project involving many, many hours of research and writing–up, and preparing diagrams for it!

It is not something that you can buy or download, the chapters will be posted on here as I complete them – I have written (most!) of about 90 chapters so far and the whole work, as envisaged, is 275 Chapters in 22 Volumes!

There will be no charge for this work, but I'm afraid it'll be a few years before I can complete it in full, as quite a few chapters need equipment building or buying!

This will be a very high quality work written in the style of the very best British Servicing Authors, such as Gordon J. King, Vivian Capel, Eugene Trundle, H.W. Hellyer, Good Old Uncle Les, and Donald Bullock, and I don't want to publish anything until it meets my very strict quality, correctness and clarity standards!

Chris Williams

Looking forward to seeing some of this work Christopher, let me know if I can help with any scans from the technical library.

Ben

[Kentode]

I found this in my Practical Oscilloscope Handbook (Rufus P. Turner, 1964).

Figure 4-14 certainly seems to agree with the picture in post no. 8.

Hope this helps.