开云体育

And here's one covering the installation tool.



Vince.

--
Michigan VHF Corp.

Just wanted to contribute to this compilation of long-gone electronics
surplus dealers.



From the late 1960s through the early '80s, I knew of three such stores in
the northern Virginia suburbs of Washington, DC. For a "paper" town, DC
generated quite a bit of electronic surplus, due to government R&D
facilities like NBS and NASA Goddard, military installations, and numerous
contractors and manufacturers serving the national-security market.



Sasco Electronics was an old storefront on King Street in Alexandria, across
the Potomac from DC. Thanks to the construction of a Metro station, the
area is now very upscale, with lots of trendy restaurants, boutiques and
antique shops, but back then it was mostly utilitarian businesses like auto
parts and office supplies. Sasco's display windows and deep, narrow sales
floor were crammed with all kinds of equipment and parts, all at very low
prices. There was also a dungeon-like basement, with bare light bulbs on
the ceiling and rows of crude wooden shelves piled high with every
imaginable type of part, especially big transformers, inductors and
capacitors, most of it top-quality stuff salvaged from military and
commercial gear. The owner was usually seated behind the counter puffing on
a pipe, while a kid at a bench in the back disassembled some piece of
equipment for parts.



Ritco Electronics was a similar operation, housed (as best I can recall) in
one or more large sheds or garage-like buildings in Annandale. Perhaps due
to their larger space, they seemed to have more big/heavy, complete pieces
of equipment than Sasco did.



Electronic Equipment Bank in Vienna was the biggest of the three, and the
one I'm most familiar with since I worked there, for owner Dick Robinson,
occasionally and part-time for a couple of years. Dick was an EE who had
previously been in test equipment sales (for HP, I think). Unlike the other
stores, whose customers were pretty much all hams and other hobbyists, EEB
also did a substantial commercial business. This was in an era when a lot
of vacuum-tube "boatanchor" test gear like Tek 500-series scopes and those
big HP signal generators (606/608?) were still considered viable lab
instruments and could bring real money.



EEB was housed in a large space in a warehouse building with a loading dock,
with neighbors like an HVAC contractor and building supply distributors.
There was an office for Dick and a bookkeeper/admin lady, a showroom, a lab
with two benches, a library/lunchroom with at least six four-drawer file
cabinets stuffed with manuals, a calibration standards lab equipped with
various salvaged items, and a vast storage area on two levels, divided into
several rooms, with heavy steel shelving and equipment piled high
everywhere.



A lot of our stock came from the federal government (GSA) surplus auctions
at the Washington Navy Yard, held in the cavernous former Naval Gun Factory.
The equipment was usually sold in lots which seemed to be randomly assembled
by someone unfamiliar with the merchandise; rumor had it that the security
guard at the exit was there not to prevent theft, but to make sure that no
winning bidder got away without taking *everything* he'd ended up buying!



To get his often huge hauls back to the store, Dick would sometimes hire a
young man of the hippie persuasion, who drove a Step-Van (former Postal
Service truck. I believe) painted in a Star Trek motif, complete with the
Enterprise's "NCC-1701" number, and with a bed for his German Shepherd on
the passenger side.



At some point Dick had acquired two enormous balun transformers, probably
from some high-powered military HF station. They were two long brass
cylinders, maybe 10-12 inches in diameter and 8-10 feet long. They'd been
sitting in our warehouse forever, with no interested customers. But when
our trucker saw them, he immediately knew what to do with them - they became
the "engines" on the roof of his four-wheeled "starship"!



Anyway, one of EEB's specialties was 500-series Tek scopes. They were piled
everywhere in the showroom and warehouse, along with every kind of plug-in.
I worked on a lot of them, and was able to fix quite a few despite my
minimal knowledge of electronics, thanks to the excellent manuals and
assistance from some of Dick's friends who had worked in field service for
Tek or for the various instrument rental and calibration companies in the DC
area.



Albert



From: TekScopes@... <mailto:TekScopes@...>
[mailto:TekScopes@...]
Sent: Sunday, July 31, 2016 9:40 PM
To: TekScopes@... <mailto:TekScopes@...>
Subject: [TekScopes] Re: Eli Heffron's electronic junkyard





I believe that the place in Amesbury was Delta Electronics, I think I still
have one of their old catalogs. Used to run up there a lot in the late 70s.
He would let you wander the place and I do remember the pigeons on the 3rd
floor. Not much good stuff up there on the 3rd floor anyway. Meshna was also
a popular spot, got the 68705P3 for my first Morse Code keyboard from
Meshna. Came out of a gas pump control.

Coming from the Hartford area, we would hit Active Electronics in
Framingham, then up 495 to Verrada in Lowell continuing on to Delta which
was near where 495 and 95 merged. From there, down 95 to the Lynn/Lynnfield
area for Poly Paks and Meshna and then on to Boston to Solid State Sales and
a few computer stores in that area. Made for a long day...

ed WA1TWX

[Non-text portions of this message have been removed]

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I just stumbled across this about BNC repair:



Ed

Tek had a very strong "do it ourselves" attitude. Since they had to make
many jigs and tools they made many of the tools even one could buy them I
use to have a small collection of parts used to make tools, for example
unused "raw" Execlite handles and shaft material. When ready one would heat
the shaft push it into the handle and twist finally letting it cool.

Think about it, you have one of the best model shops around and the
machinist, when idle a perfect time filler.

-pete

On Wed, Apr 25, 2018, 2:34 PM Ed Breya via Groups.Io <edbreya=
yahoo.com@groups.io> wrote:

A quick search found this in a few seconds:



:

Note there are a lot of tools, including a number of offset, slotted hex
drivers for the BNC back-nuts, etc - kind of equivalent to a crow-foot
socket, but nicer, low profile for getting in close-quarters behind the
panel. Didn't see any of these nut driver style ones for holding the front
though. I'm still convinced these were commercial products. Tek could have
made them in-house, but I doubt they needed to. Even way back, there must
have been plenty of demand for various BNC tools, and someone to fill it.
Every connector type has special tools to go with it.

Ed

Lorn...
Ah, in time... about your writing:

On Wed, Apr 25, 2018 at 12:28 pm, blackholenulled wrote:

I'm still suspicious about the readings on pins 1 and 16. It will be
interesting to see if they change when biasing 2 and 3 with the resistor.

Since between pins 2,3 and pin 1 there's only the base-emitter junction of the IC's input transistor... if the input is at 0,7V or so, it's expected that pin 1 will rise to about 0V, instead of staying at the nominal -0.8V or so... This even testimony in favor of the IC, that its input transistor isn't defective.
As for pin 16, since this is a differential input pair, the upper side being heavily (postively) biased, it's natural that it will bring the emitter of the complementary xsistor up... In fact, this is exactly what the differential input pair is meant to do.
One may be fooled by the fact (so often found on Oscilloscope's Vertical and Trigger amplifier circuits, ICs or discrete) that the transistors don't have their emitters tied together to a single "long tail" resistor and thus, not spotting right away a differential amp., but Y connected emitter resistors and Delta connected are mutually convertible and the set is indeed a differential input pair.
If one is heavily driven into conduction, the other will be driven into cutoff from its emitter.
R
FT

A quick search found this in a few seconds:



Note there are a lot of tools, including a number of offset, slotted hex drivers for the BNC back-nuts, etc - kind of equivalent to a crow-foot socket, but nicer, low profile for getting in close-quarters behind the panel. Didn't see any of these nut driver style ones for holding the front though. I'm still convinced these were commercial products. Tek could have made them in-house, but I doubt they needed to. Even way back, there must have been plenty of demand for various BNC tools, and someone to fill it. Every connector type has special tools to go with it.

Ed

Dennis guesswith the pictures is correct.

It was made by Tek. Tek had (when I was there) part of it's model shop a
tool modification and manufacturing department. There was at one time a
catalog of sorts.

-pete

On Wed, Apr 25, 2018, 1:38 PM Dennis Tillman W7PF <dennis@...>
wrote:

Hi Larry,
I just uploaded some pictures of the tool. They are at
/g/TekScopes/album?id=45980
Dennis Tillman W7PF

-----Original Message-----
From: Of Larry McDavid Sent: Wednesday, April 25, 2018 12:18 PM

Someone here mentioned a BNC installation tool. I took that in context to
mean a tool that holds a chassis-mount female BNC jack while tightening

the

backside nut but I don't find any such tool when searching, only tools to
disconnect mated BNC connectors.

Did I misunderstand what was suggested for straightening bent BNC
connectors or can someone point me to such a tool?

Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)

--
Dennis Tillman W7PF
TekScopes Moderator

hi Lorn,
On your previous writing:

The transistors are socketed but the chip is not. So it's not practical to

Look carefully... it's more likely it's socketed than not.
Tek used a lot a kind of socket that is made of individual socket pins that go directly on the board... (on really wide PCB holes),
To bare eyes, it's very easy to overlook it.
When I was still new to my 464 I also thought they were soldered.
Rgrds,
FT

Hi Larry,
I just uploaded some pictures of the tool. They are at
/g/TekScopes/album?id=45980
Dennis Tillman W7PF

If I'm not mistaken, 1/2" 6061-T6 aluminum tubing with two slots cut in it 180-degrees apart would do just about as nicely as anything for that.

Thanks,
Barry - N4BUQ

Yes, that BNC T-wrench on ebay is yet another form of installer. I have two different kinds from long ago, both commercial tools, but I have no ID or source info. One is made just like a nut driver, but the business end is a hollow cylinder with slots, that fits the outside. The other is a strange looking socket that has the same type features, but is made to go on a 1/4" square driver. I also built one way back, before I acquired the "real" ones. I took a male cable-end type BNC, and soldered it into a stubby-handled nut driver, in such a way that the outer ring was locked to the core. The original driver tip was whatever hex size that the BNC end fit closely enough to solder in. In use, it just goes on the female BNC as if it was a cable, but allows holding the position or slight torquing for installation, then unplugs just like a cable.

Be aware when using these things, that the BNC bayonet pins are not very strong, and will easily deform or even shear off if over-torqued. The real compression force and torque for installation should be applied to the nut in the back, while the tool just keeps it from rotating out of the desired pin position in the early tightening phase.

Ed

Hi Peter,

Besides the check to the power supply's capacitors, as Chuck noted and, as you will notice follwoing up the threads, is a kind of "standard" advice for all equipment of this vintage...
It may be helpful (for further troubleshooting by the group or yourself) if we can differentiate if the wide trace is due to problem with focus, or if it's wideband noise related..

Since you mentioned that readout is fine, there's less likelihood of being focus related, but still, not being familiar to the 2445's focus circuitry, there can still be an explanation for a focus problem while drawing the actual signal trace on screen, as many scopes have "auto-focus", circuitry that dynamically adjusts the focus for the often different intensity of the readout.

To rule-out focus from noise, it usually suffices to display a good square wave on the screen (e.g. calibrator).
At moderate sweep speeds, such as enough to display a single cycle on screen, the rising and or falling edge should look cleaner and sharper (while the tops and bottoms still look fat) if the issue is noise related. At slower sweep speeds it won't be much conclusive as you would barely see the rising and falling edges.
However, if the "fat" is due to focus, the rising or falling edges are likely to show just as fat.

Other resource to help rule-out noise as a source, is turn on the Bandwidth limit (usually to 20MHz)... this usually makes a "fat" noisy baseline to look sharper (if the issue is noise).
If, however, engaging BW limit doesn't improve matters, than it may tend more to be focus related.

Rgrds,

Fabio

On Wed, 25 Apr 2018, Larry McDavid wrote:

Here you go, works like a charm:



I bought this exact wrench couple of years ago and very happy with it.

Someone here mentioned a BNC installation tool. I took that in context to mean a tool that holds a chassis-mount female BNC jack while tightening the backside nut but I don't find any such tool when searching, only tools to disconnect mated BNC connectors.

Did I misunderstand what was suggested for straightening bent BNC connectors or can someone point me to such a tool?

---
*
* KSI@home KOI8 Net < > The impossible we do immediately. *
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
*

Ok, cool. So I need to isolate whether the input transistors are leaky or whether there's a problem with the chip.

The transistors are socketed but the chip is not. So it's not practical to casually take the chip out. So I'll try removing the transistors and put in the 51 ohm on 2 and 3 as you suggest. Even if I can't take the chip out, this should tell me something. If the voltages are all nominal then, that would point upstream to the transistors.

While I have the transistors out I can ohm them out to check for a leak. The B side transistors should be identical and for the most part the B side works, so I could also swap those transistors and/or use them for comparison when ohming.

I'm still suspicious about the readings on pins 1 and 16. It will be interesting to see if they change when biasing 2 and 3 with the resistor.

Thanks!
Lorn
KK4KRI

snippet of the previous measurements:

U7331

Pin, expected Vdc, actual
1. -0.8, -1.1mV
2. 0, .761 V
3. 0, .761 V
4. 4.9 actual (tied to +5 through 1k resistor)
5. -8, -7.95
6. -1.0, -.959 (close enough)
7. ground, -.5mV (effectively zero)
8. 10.6, 10.72
9, 10.6, 9.73
10. 0, -39.7 mV
11. 10.5, 10.68
12. -0.9, -.852
13. 7.1, 7.18
14, 0, .7 mV
15. 0, .7 mV
16. -0.8, -204.6 mV
<< end snippet


On Wed, Apr 25, 2018 at 11:46 am, Fabio Trevisan wrote:

Hello Lorn,
I also own a 464 and mine also had a problem triggering... And while looking
at your description I looks like deja vu to me.
On mine one of the FET transistors of the input circuitry were leaky...(it had
about 200kOhms impedance between source and gate, while reverese biased. The
good ones measure Infinite, or very high Megohms.
The leak developed a voltage drop on the 1M resistor at their gates and make
the output voltage to have a huge offset of... wow! 70mV...(that's 1/10th of
what you're getting).
70mV offset was enough to take the preamplifier IC so off that trigger would
only work by adjusting the level potentiometer near its end of range and,
still, after warming up, the offset would grow just a bit more and then even
taking the Level potentiometer to the end was not enough to make it trigger.
On yours it seems the offset is some 0.7V, so no wonder why it doesn't
trigger.
Your course of action is exact and removing the FET transistors will allow you
to rule-out if the positive offset is coming from the IC, or if it's coming
from the buffer stage into the IC.
It's likely, however, that if you just leave pins 2 and 3 opened, as they will
get when FETs are removed, you will be fooled by false voltage readings at
pins 2 and 3, due to the input pins need some biasing.
So, after you remove the FET ICs, connect a resistor of - say - 51R between
pins 2.3 of the preamp IC to ground.
The impedance at the other side of this balanced input differential amplifier
is roughly 50Ohm, so biasing pins 2,3 with 50Ohms will make the input
perfectly balanced.
In this condition, pins 2 and 3 must read a low voltage, close to 0V. By no
means it can be more than 50mV... as I told, my 464 had 70mV and that was
enough to screw up the triggering.
Alternatively, you can check the FET input buffer's offset, by taking the IC
out and measuring voltage directly at pins 2.3 of the IC socket...
Don't worry, taking the IC out is safe... nothing that's past of the IC will
burn because the IC isn't present. (I had this same doubt back then).
Set the Trigger input to EXT, coupling to DC, and ground the Ext. input, so
that you're sure that you're not feeding DC into the input buffer, and its
output should be very close to 0V.
If the transistors are perfectly matched and thermally even, in theory, the DC
offset of this input buffer is exactly ZERO.
Good luck,
Rgrds,
Fabio

Someone here mentioned a BNC installation tool. I took that in context to mean a tool that holds a chassis-mount female BNC jack while tightening the backside nut but I don't find any such tool when searching, only tools to disconnect mated BNC connectors.

Did I misunderstand what was suggested for straightening bent BNC connectors or can someone point me to such a tool?

--
Best wishes,

Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)

Hello Lorn,
I also own a 464 and mine also had a problem triggering... And while looking at your description I looks like deja vu to me.
On mine one of the FET transistors of the input circuitry were leaky...(it had about 200kOhms impedance between source and gate, while reverese biased. The good ones measure Infinite, or very high Megohms.
The leak developed a voltage drop on the 1M resistor at their gates and make the output voltage to have a huge offset of... wow! 70mV...(that's 1/10th of what you're getting).
70mV offset was enough to take the preamplifier IC so off that trigger would only work by adjusting the level potentiometer near its end of range and, still, after warming up, the offset would grow just a bit more and then even taking the Level potentiometer to the end was not enough to make it trigger.
On yours it seems the offset is some 0.7V, so no wonder why it doesn't trigger.
Your course of action is exact and removing the FET transistors will allow you to rule-out if the positive offset is coming from the IC, or if it's coming from the buffer stage into the IC.
It's likely, however, that if you just leave pins 2 and 3 opened, as they will get when FETs are removed, you will be fooled by false voltage readings at pins 2 and 3, due to the input pins need some biasing.
So, after you remove the FET ICs, connect a resistor of - say - 51R between pins 2.3 of the preamp IC to ground.
The impedance at the other side of this balanced input differential amplifier is roughly 50Ohm, so biasing pins 2,3 with 50Ohms will make the input perfectly balanced.
In this condition, pins 2 and 3 must read a low voltage, close to 0V. By no means it can be more than 50mV... as I told, my 464 had 70mV and that was enough to screw up the triggering.
Alternatively, you can check the FET input buffer's offset, by taking the IC out and measuring voltage directly at pins 2.3 of the IC socket...
Don't worry, taking the IC out is safe... nothing that's past of the IC will burn because the IC isn't present. (I had this same doubt back then).
Set the Trigger input to EXT, coupling to DC, and ground the Ext. input, so that you're sure that you're not feeding DC into the input buffer, and its output should be very close to 0V.
If the transistors are perfectly matched and thermally even, in theory, the DC offset of this input buffer is exactly ZERO.
Good luck,
Rgrds,
Fabio

Hello Vaclav.
This forum doesn't take attachments...It's sort of controversial, but bottom line is that it doesn't.
You need to post the pictures to the photos section and... since there's no way to "search" on the photos section, you better copy the link to the album and post it on the message thread, so that anyone can quickly jump to the photo.
Rgrds,
Fabio

I would appreciate some assistance to find out why my 464 has this problem.
I do have a shop manual.

PS this is? my first post here so please no flames if I did it wrong.
Vaclav in Houston TX

I have two 465s. I have repaired one. They way it is constructed does not lend itself to be easily repaired. One must be patient with repairs on a 465. Also be very careful about moving boards around. I love these scopes when they work. I use at least one daily to repair electronic equipment. It was a great functional design, not the best design to allow access to parts.

It's not the 190A either, it is much too small and has a big vertical dial that would be easy to see (I have one); I'd assume the 190B would be similar.
-Dave From: Jerome D Leach <jeromeleach17@...>
To: TekScopes@groups.io
Sent: Wednesday, April 25, 2018 12:40 AM
Subject: Re: [TekScopes] Another Tek in media sighting

Type 130 L,C possibly? Wasn't a lot of Tek stuff with meters. 105 square
wave gen., and the 190 A and B constant amplitude signal gen.