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Hi Albert,
redone the measurement using 10 ohm in series to the winding.
Photo here : /g/TekScopes/photo/281947/3539966

Max

Thanks guys

The final (for now) version here

There are more details of the Sony/Tektronix joint venture on the vintageTEK website at:

--
Bob Haas

Sony made this deal with Tektronix to sell their products to the US
government. By law they couldn't sell their industrial video equipment to
government agencies, unless it was fully supported by a US based company. I
was in the US army when this happened. They were converting from 2" Ampex
machines to Sony Umatic playback machines for on base Educational TV. This
was 1972/1973 when I had to install an Emergency Alert system that would
override the normal TV and take control of the civilian cable TV that fed
to the bae in an emergency. This involved a bank of relays to switch to a
single video source at the ETV building, and a high isolation RF relay
where the Cable TV system entered the base. Possibly the first system of
its kind, since that relay had to be custom built. It was connected to the
ETV building by a dedicated dry telco pair.
A decade later, this function was done at the IF stage of the HSP or
modulators in Cable TV headends. I modified our alert system to display a,
"This station is off the air' message because stations weren't on around
the clock. This was in the early '80s It also gave a constat , daily test
of the emergency system without disrupting regular service. The HSP had a
Carrier Detected Output so it only required a 1N4001 diode on each unit to
provide isolation between the two functions.

HSP = Heterodyne Signal Processor

On Mon, Dec 12, 2022 at 12:50 PM Michael W. Lynch via groups.io <mlynch003=
[email protected]> wrote:

Would you be able to share the Serial number? It would be interesting to
see if this was assembled in Japan or just a "rebadged" product. This
looks like a standard 468. It does have a slightly different color
filter.

It is my understanding that the Sony/Tektronix partnership was partially
intended to allow TEKTRONIX to make inroads into the Japanese market and
bypass import restrictions on "non-Japanese" products. I could be wrong.

--
Michael Lynch
Dardanelle, AR

Hi max,
This is when you connect 1k and winding in series. The result is nevertheless comparable to what you found earlier (but you have to know how to deduct R (if unknown) and L from the ellipse).
This is why I mentioned 10R or perhaps 100R as series resistor. Then you can ignore the resistor effect on the ellipse shape.
Albert

I redid the measurements using the Tek 564 with 2 3A6 plugins.
The result is visible here:/g/TekScopes/photo/281947/3539929
I'm getting more and more confused.

Max

a high SN 7B92A is fine (when working), but even a defective low SN one normally has many good parts.
It's a good idea to have parts mules. (Some like to repair, some don't. It takes time, of course.)
High SN 7B92A circuits are improved, the componets are fine tuned to work better.

Stefan

Would you be able to share the Serial number? It would be interesting to see if this was assembled in Japan or just a "rebadged" product. This looks like a standard 468. It does have a slightly different color filter.

It is my understanding that the Sony/Tektronix partnership was partially intended to allow TEKTRONIX to make inroads into the Japanese market and bypass import restrictions on "non-Japanese" products. I could be wrong.

--
Michael Lynch
Dardanelle, AR

What is the serial number? If it starts with "3" than it was built in Japan. I'm not aware of any 468's being built in Japan. Most of them were built in Beaverton or Heerenveen in the Netherlands. It probably just had the handle label replaced for sale in Japan.

--
Bob Haas

Yeah, I would think it would at least be useful as a parts mule.

I'm in the process of collecting parts mules myself. Can't just have one of anything when your stuff is vintage...

Jim Ford
Laguna Hills, California, USA

You threw into a dumpster a beautiful 7B92A? Sacrilege!

Hi Gianni;

Excellent work, thank you so much!

Best Regards,
Ken

Great contribution Gianni and definitly a good source to solve the problems in my 7904, thanx!
搁别苍é

I am looking for a working, complete 7B92A S/N >80000. I had bought one off 'that site' that supposed to be a high S/N. It was a low number that was total rubbish now in a dumpster. Thanks.

I Albert,

I did the measurement again with another pair of probes. Checked compensation and gain.
Virtually identical result.
Please note that all other windings are open, since I disconnected Q1195 and lifted up one leg of CR1219, C1235 and C1253. And obviously I've detached U200 multiplier and CR1213 to be sure.

Max

Hi Max,
Ah yes, 50R, I was thinking of my SG502 (600R) which I used recently because of the cleaner sine wave output.
Now your reported voltages would lead to an open FG502 voltage of almost exactly 10 V pp, the output setting you stated earlier.
So it's starting to look as if 30 mH is real. But nevertheless check your setup please (too high frequency especially). I would not have an explanation for that high inductance. Rather large probe input capacitance could increase the observed inductance value but our normal probes (even 1X probes) have small input capacitance.
Albert

On 11 Dec 2022, at 08:08, gimew73444@... wrote:

I acquired a tek 468, but it is the sony/tek model, the CRT is not the common type as shown. Is it rare or special model ?

I have uploaded the photos

Looks to me like the same as the TekWiki photo, differing only in a broken Cursor / Sweeps knob and yours has a darker CRT filter.

Hi Albert.
The FG502 has 50 ohm nominal output impedance, I can clearly see it from the schematic of its output stage.
Maybe you are confusing with my other generator, the HP? The HP actually has 600 ohm output impedance.
I'll check the probes' calibration for safety.

To state more precisely the formula (to avoid misunderstanding)
Let VR = voltage across 1k resistor
Let VL = voltage across winding

ωL = VL/(VR/R) = (VL R) / VR

L = (VL R)/(VR 2 π f)

Using VL = 8.8Vpp and VR = 4.6 Vpp finally I obtain L = 30 mH

I will check my setup tomorrow with more attention.

Max

Hi Max,

I read 9 V pp (winding, vertically) and 4,5 V pp (across 1k, horizontally). That gives 32 mH. Maybe you are mislead by Miguel's equation with a "y" in it.
The deep inside source of the FG502 would see a series load of 600R (internal) + 1k + winding inductance (2j k) and voltage sqrt( (1.6 *4.5)^2 + 9^2) = 11.5 V pp. Does the FG502 deliver that unloaded?
What's wrong? Plugin calibration? Probe calibration (also in horizontal compartment)? Frequency? Effect of floating scope?
I hate to work with floating instruments grounds. Just for sure do it the robust way with scope and generator grounded. Put 10R and winding in series between ground and FG output. Measure across 10R and measure total. The 10k has almost zero influence on the total, so total can be read as across winding. End so on. (100R would also be OK.)

Albert

The scope is selected for A vertical (left vertical plugin). The trigger mode it's ininfluent since I'm using another vertical plugin in the horizontal compartment.
When I disconnect the signal in left plugin I see a perfect horizontal line coming from the other 7A16 in horizontal compartment.

Max