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I see intensity modulation on both CH1 and CH2 of my 7A26 in its ALT and CHOP modes but in ALT mode, the CH2 has a brighter intensity offset. See this photo. This is consistent with the Z-axis signal in my photo Z-blanking_Left.jpg where, as you say, there are different amounts of leakage on alternate sweeps. I guess in your case, the leakage on one of the sweeps is small enough not to be noticeable. I'm pretty sure the reason for the different leakage levels on alternate sweeps is (in my case) noise from the mainframe on the B7 input. In my Z-blanking_Left.jpg picture, I traced that signal (bottom trace of the three) but at a scale of 1V/div and the noise isn't visible. Here's a magnified trace and you can see a shift of about 40mV on alternate sweeps.

On 2 Apr 2021, at 01:59, Jeff Dutky <jeff.dutky@...> wrote:

Was there another kind of curve tracer made by Tek in the late 80's that used a closer spacing of the binding posts/banana sockets?

They’re for a Tek 571 curve tracer. In fact, they’re precisely the (optional accessory, I think) adapters I don’t have for my 571.

Though my 571 is a repair work in progress that’s on hold whilst I work on other things, and I’m not really in a big hurry to fix it because I have two working 577 curve tracers.

Very nice. I wished I had a 7CT1N. Been looking for one for a while.

For those who did not see, I am offering two boards per person, all you need to is contact me off list, and send an SASE (self addressed, stamped envelope) with enough postage to get the boards back home.? The boards are free.


Photos added in album 7CT1N test fixture

/g/TekScopes/album?id=262570


You will need:

one switch


E-Switch 400UDP1L1BLKM6RE @$3.30

three banana plugs

*Johnson/Cinch 108-0753-001 @$1.35 each*

You may substitute for the banana plugs as desired, as long as they fit.? The E-Switch was picked because of price and size, and that it is a currently available model.? You could just bypass it with two jumpers and not switch between A and B.

Two or four transistor sockets.

Your choice on this, the TO5 case can accept? pin sockets of the right size, or a standard transistor socket, as can the smaller socket.


each board weighs 1/10 oz, or about 3 grams each

Two boards are 2/10 oz, so a stamp, SASE and two boards should weigh well within the limits of US first class mail.

Harvey



**

Only takes a minute to look things up these days...

One paper from '77 indicates their use as a thin film
solar energy conversion array. They are claiming that
an array using Al-SiO2-Si structure, is actually a tunnel
diode. They call it a tunnel MIS solar cell.

In another paper from '79, they describe an AlGaAs tunnel
diode with a band gap of 1.6eV that can withstand very high
solar exposure without degradation.

Another, from 2013, about a solar array "rectenna", that uses
a host of microscopic tunnel diodes in the conversion of solar
energy into power by rectifying the E-M wave of IR light
directly into DC.

So, tunnel diodes are seeing some new applications... Doesn't
seem to help us, though...

-Chuck Harris


On Fri, 02 Apr 2021 09:43:51 -0700 "Bill E" <solartron@...>
wrote:

Chuck, TD for power switching in solar arrays? Why? Sorry, didn't
bother to track down the links, but what's the scenario that isn't
handled by modern stuff? (Just to be clear, not a bash, just
wondering what China thinks).

I have 12 NIB 1N3713 GE TD in original packaging.
Email for photos.
Keith Erickson
Wayzata, MN
Kognw at gte.net

Backward diodes found some use in rf detectors and energy-harvesting circuits, where a low "forward" drop seems to be attractive (it's not quite the advantage that is assumed, for quite fundamental physics reasons). They've never completely gone away for that reason.

I agree with the prevailing sentiment here that restarting (or asking) a fab to make tunnel diodes makes no business sense. A good fraction of the global market for TDs seems to be well served by the Cold War leftovers available on ebay.

Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070

Yes, the negative resistance is what made TDs useful, nothing else, the TD reverse breakdown wasn't anything that made them commercially viable.

Classic tunnel diodes can't be replaced by Schottky didoes. The latter lack the negative resistance region that the former have.

There are so-called "backward diodes", though, which are tunnel diodes that have been doped just heavily enough to eliminate the forward-current peak. That gives you, essentially, a Zener diode with a reverse breakdown voltage that is smaller than the forward drop. Exchanging anode and cathode then produces a diode with a lower "forward" drop than a conventional diode made of the same base semiconductor. That's the only type of tunnel diode for which a Schottky might be suitable. Schottkys will not sub for the classic tunnel diodes whose negative resistance is used for realizing fast, low-voltage flip-flops of trigger circuits.

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070

That's the key. Circuits were designed in the day for the characteristics of the components available. Change parameters without understanding the rest of the circuit, fail.

The issue the D180 in the 284 is its speed. It only had 1.5pf of capacitance to get he 70ps edge speed so in terms of TD it is on the exotic side and the hardest to make. Last time I looked there was a company you could buy from but they were a special run and $280 each diode. However you could buy them in lots of 1 so that is a + I guess

Eric

Hi, "Anorak" Mel-
He's probably sick of answering messages with the same comments over and over again.? Obviously, he needs a hobby to relax and de-stress.? What do non-anoraks do for fun?
-Dave

I understand and agree with all your valid points.
But since you seem to say that there are far better modern alternatives, why can’t they be used to repair let’s say, a Type 284 for example?
PS: I’m not an EE, and know nothing about this. I’m just wondering why people are looking for TD’s at ridiculous prices, if there are better modern alternatives... ??♂?

Chuck, TD for power switching in solar arrays? Why? Sorry, didn't bother to track down the links, but what's the scenario that isn't handled by modern stuff? (Just to be clear, not a bash, just wondering what China thinks).

And, of course, if you want them to fix old stuff (which we all do), realize that's really a non-market. Setting up fab for a few hundred units that only crazy people like us would buy isn't economically viable.

Conservatively, I would estimate 100.

Look at how many of "us" exist, than notice
that we don't all have things that need their
TD's replaced.

Commercially, the requirement would be essentially
zero. They don't exist in TV's radios, or video
games. They really never took off in that sphere.

The Russians were big in TD's, because they were useful,
and something they could do with their foundries in
the 1960's. TD's didn't demand the cleanliness, or
purity of materials that high speed silicon devices
do.

If you want a foundry to start making TD's again, you
are going to have to create some game altering need
for them to exist... in quantity.

Many universities have mini foundries that they use
to teach practical semiconductor manufacturing techniques.

One such application, I think, is power switching in
solar arrays... or so I am led to believe from the papers
on high power TD's coming from China.

I know that my local university was letting grad students
make LED's, and other crude diodes for educational purposes.

To make TD's, you don't need much more than a chemical hood,
some really nasty chemicals, GE wafers, a way to cut them,
a vacuum deposition chamber... AKA: sputterer, and some stereo
microscopes...

They could have also made TD's.

-Chuck Harris


On Fri, 2 Apr 2021 18:08:35 +0200 "cheater cheater"
<cheater00social@...> wrote:

Hi all,

there's a few companies producing clones of modern chips for music
synthesis, including CoolAudio (aka Uli Behringer) in China, ALFA RPAR
in Latvia, and SSI. The first two have their own foundries and SSI
supposedly uses Diodes Corp. Would approaching these people to get a
run of tunnel diodes done be a good idea? ALFA specifically seem to be
a smaller company running a tighter ship, but Uli is into a lot of
vintage electronics so he might be interested as well. Obviously for
every company there's some sort of price cutoff point.

Which means one has to ask, how many tunnel diodes could the world use
within the next 10 years? What do you all think?

Cheers

My opinion, close to zero for the traditional tunnel diode. While they were useful in their time, they just can't do what modern equivalents can do. Not capable of producing much power, and even for tunneling behavior, there is newer tech that is far better, e.g. RTDs (resonant tunneling diodes).
But, while I'm an EE, haven't had any relevant experience with TDs for, hmm, a long time. Which might in itself validate my comment. ::)

I just had a look at the 571 on TekWiki, and the adapter shown plugged into the top left transistor socket in the first, third, and fourth pictures is EXACTLY what I have in hand.

-- Jeff Dutky

In a similar vein, I'm wondering if it is possible to replace the tunnel diodes in a 465/475/475A with something other than a tunnel diode. I thought that there was a recent thread that mentioned replacing tunnel diodes in another instrument (a sampling plug-in?) with Schottky diodes, which got me thinking about this.

-- Jeff Dutky

I think that would be a very good idea.
I read often that many a unit gets trashed or forgotten because a tunnel diode failure. That’s sad IMHO.