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? I plan to replace the MUX (U2530) this weekend and wonder if I can put solder mask on the guard traces between signal pins?? I would use Circuit Works CW2500 epoxy which is good to 350 C.? I cant think of any downside and it would help avoid solder shorts.? The guard traces are very close to the signal pins and shorts mean rework with solder braid.? 14 pins at this pitch are sure to get one that needs touch up.?
I haven't decided yet whether I will do hand soldering or hot air.? I purchased a griddle at Walmart for $18.00 to act as a preheater and calibrated it with my IR temperature meter.? Its easy to hold the temperature around 170 C.? I will use a hand held fan to cool the board after soldering and before lifting it off the griddle so I don't temperature shock the board.? But I may loose my nerve and just hand solder the new part.? Either way, I think solder mask over the guard traces would help keep the solder from overflowing.?

On Fri, Apr 27, 2018 at 08:24 am, Fabio Trevisan wrote:

The 3K9 resistors at the emitter of the top transistors should have about

25V across them. Lift one of their leads and measure their resistance, to be
sure they're still at 3k9. If the resistors are within tolerance, and the
voltage is about 25V, then you know the collector current of the output
transistor pair is correct.

My measurements of the 3k9 resistors:
R1152 -- 3k95 Ohms & 26.83 Volts
R1132 -- 3k97 Ohms & 27.19 Volts

Measure the voltage at the collector of Q1136 and Q1156... they both should

measure about 4V (relative to ground)...

My measurement were:
Q1136 -- 5.75 Volts
Q1156 -- 5.58 Volts

Finally, measure the voltage across the 120ohm resistors at the output... It

will give you an idea of how much current is being drawn by the load circuitry
downstream. By no means this current can be more than the quiescent bias
current going through the output transistors, which is about 6mA. My wild
guess is that it shouldn't be any greater than half of it, or about 3mA,
because otherwise this would seriously upset the quiescent point of a Class A
amplifier.

My measurements were:
R1157: measured 122.3 Ohms, Voltage Drop: 6.2mV
R1137, measured 123.3 Ohms, Voltage Drop: 1.5mV

All told, I'd say the section is operating normally; the voltage drops across
the 120 Ohm resistors varies a lot from your hunch, but maybe that's a good
thing. For now I'll do a bit more cleaning up with larger 20k resistors and a
top-hat heatsink for Q1156 and try some more checks of the entire instrument.

Thanks again!

--Al

From: Brad Thompson <brad.thompson@...>

Hello--

The late (and not often lamented) surplus-component business
known as "Poly Paks" offered tunnel diodes in "bargain pak [sic]" format.

Pick a catalog and count the number of different products that are in it. Then go through all 70 years of catalogs and do the same thing. Don't forget the things that didn't appear in the catalogs like cal fixtures or things that never went into production (I have several of those). There were separate catalogs for Television products and military products and lots and lots of Mods. Then eliminate the duplicates. That will give you all the unique products Tek made or make now. My order of magnitude estimate is Tek made / makes between 5 x 10^6 to 1 x 10^7 unique products. That is 5,000,000 to 10,000,000 unique products.

-----Original Message-----

Maybe we should have a group for each Tektronix instrument of interest
where users from the main TekScopes group can post their albums. This would
give some organization to the images allowing for a browsing capability
based on the instrument. Right now, you can't find anything.

Best,
John

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Chuck Harris
Sent: 30 April 2018 20:15
To: [email protected]
Subject: Re: [TekScopes] Nuvistors/TD

I read that manual from cover to cover, over and over again, as an information starved boy will. I
was
all ready to conquer the world with tunnel diodes, and went off to Radio Shack to buy some, and....

RATS!

They had no idea what the heck I was talking about. Neither did Capitol Radio...

Radio Shack of the late 1960's was vastly more interesting then it was in later years... but still
no tunnel
diodes.

Then the Motorola Semiconductor Reference Manual, the TI TTL manual, and MECL manuals came to
me, and I forgot all about tunnel diodes.... Until tektronix scopes brought them back into my life
(585A).

-Chuck Harris

Kevin Oconnor wrote:

"See this 1961 GE TD manual:"

I remember that manual from long long ago. I did high school at the end of the 60's and was the
first

class in college in EE to not study "tubes", EEs were going all solid state! The Esaki TD was only
invented
in '57, that manual published in '61, and essentially un-mentioned until my grad school studying
from
Simon Sze Physics of Semiconductor Devices.

My point is that the TD is a good historical example of industrial exuberance in addition to a

fascinating device. At the time that manual was published the TD was going to revolutionize logic
switching design it was so fast. Tubes were out, now there was something better than the transistor!
Ah, but that was a "discrete" world view. As it quickly became evident, you couldn't really
integrate
with them, the on/off states had poor noise margin compared to other logic and in less than a decade
they were relegated to discrete applications in oscillator, tuner and gating apps. Three terminal
devices are just better at noise margin and I/O isolation.

It is interesting to note that the TD effect is a majority carrier action, unlike a conventional
PN

junction. There is another majority carrier diode that, while older than the transistor, was rapidly
assimilated into power devices and integration and is still in use today. That would be the Schottky
barrier diode! Two very interesting junction barrier effects with quite different commercial
outcomes.

Still, it is a bit cool to hold a TD knowing the amazing physical phenomenon that the simple
little

device demonstrates.

Kjo

"See this 1961 GE TD manual:"

I remember that manual from long long ago. I did high school at the end of the 60's and was the first class in college in EE to not study "tubes", EEs were going all solid state! The Esaki TD was only invented in '57, that manual published in '61, and essentially un-mentioned until my grad school studying from Simon Sze Physics of Semiconductor Devices.
My point is that the TD is a good historical example of industrial exuberance in addition to a fascinating device. At the time that manual was published the TD was going to revolutionize logic switching design it was so fast. Tubes were out, now there was something better than the transistor! Ah, but that was a "discrete" world view. As it quickly became evident, you couldn't really integrate with them, the on/off states had poor noise margin compared to other logic and in less than a decade they were relegated to discrete applications in oscillator, tuner and gating apps. Three terminal devices are just better at noise margin and I/O isolation.
It is interesting to note that the TD effect is a majority carrier action, unlike a conventional PN junction. There is another majority carrier diode that, while older than the transistor, was rapidly assimilated into power devices and integration and is still in use today. That would be the Schottky barrier diode! Two very interesting junction barrier effects with quite different commercial outcomes.

Still, it is a bit cool to hold a TD knowing the amazing physical phenomenon that the simple little device demonstrates.

Kjo

Thanx folks.

Nope - never found any documentation on the TM504A but I do see them out on Ebay - it looks more modern then the other main frames in the series.
Apparently is is quite rare indeed but also maybe newer than most main frames in the series?