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Re: Why you now Paypal

 

I've gotten it occasionally. I usually go there from what Firefox calls a private browsing window. Cookies aren't saved there and the first time going after restarting the browser is when I would get it, if I get it. Like I said, it's occasional.

Vince - K8ZW.

On 11/26/2020 12:09 PM, Frank DuVal via groups.io wrote:
Weird. I NEVER have a Captcha / Not A Robot screen or button when using
PayPal....

I do not save my password. Have to enter it every time, my choice. Works
for me.

I do not understand the "how far along in the buying process you are"
comment. All the screens on PayPal seem logical to me. And there are not
many when sending money, either on their website only or through a
vendor link to send funds.

So far it works well for me! Both as buyer and sending money to friends.
Even for Tek supplies, to keep it on subject.?

Frank DuVal

On 11/26/2020 1:01 AM, Jeff Dutky wrote:
I don't have particular issues, other than complaints about this
particular process (not being offered the options that would have made
this process easy), and about the quality of their buyer interface
(every time I have tried to log into their web interface I have had to
do the "I'm not a robot" dance, and every time the site has responded
with "something went wrong on our end" throwing me back to the "I'm
not a robot" screen, so that I get to do the dance again, and maybe a
third time. That's shoddy UX on PayPal's part, and I haven't got any
patience for that sort of thing. Also there's no indication of how far
along in the buying process you are, so you just have to keep clicking
Continue until suddenly the process is over. That's also shoddy UX).
My only other complaints about PayPal are mere hearsay, but I've heard
too many stories of sellers having their funds frozen over the years
to think that maybe there isn't at least a little bit of fire behind
that smoke.
That said, I understand why people want to use PayPal: they fill a
niche that, even today, has very few players. If you want to accept
payment over the web you just don't have many choices, and the
established choices (credit card merchant accounts) are not well
suited to small players. When PayPal got started they were basically
the only game in town for people who couldn't afford to set up a
merchant account, and that benefit can not be overestimated. Still,
I'm a grumpy sort, and this is one of the things I'm grumpy about.

-- Jeff Dutky


--
K8ZW


Re: Why you now Paypal

 

Weird. I NEVER have a Captcha / Not A Robot screen or button when using PayPal....

I do not save my password. Have to enter it every time, my choice. Works for me.

I do not understand the "how far along in the buying process you are" comment. All the screens on PayPal seem logical to me. And there are not many when sending money, either on their website only or through a vendor link to send funds.

So far it works well for me! Both as buyer and sending money to friends. Even for Tek supplies, to keep it on subject.?

Frank DuVal

On 11/26/2020 1:01 AM, Jeff Dutky wrote:
I don't have particular issues, other than complaints about this particular process (not being offered the options that would have made this process easy), and about the quality of their buyer interface (every time I have tried to log into their web interface I have had to do the "I'm not a robot" dance, and every time the site has responded with "something went wrong on our end" throwing me back to the "I'm not a robot" screen, so that I get to do the dance again, and maybe a third time. That's shoddy UX on PayPal's part, and I haven't got any patience for that sort of thing. Also there's no indication of how far along in the buying process you are, so you just have to keep clicking Continue until suddenly the process is over. That's also shoddy UX). My only other complaints about PayPal are mere hearsay, but I've heard too many stories of sellers having their funds frozen over the years to think that maybe there isn't at least a little bit of fire behind that smoke.
That said, I understand why people want to use PayPal: they fill a niche that, even today, has very few players. If you want to accept payment over the web you just don't have many choices, and the established choices (credit card merchant accounts) are not well suited to small players. When PayPal got started they were basically the only game in town for people who couldn't afford to set up a merchant account, and that benefit can not be overestimated. Still, I'm a grumpy sort, and this is one of the things I'm grumpy about.

-- Jeff Dutky


Tek 2xxx and 3xxx 56x series plugins available

 

Hello to all,

I should have many 3A1/3A6 and other 56x series plugins in my stock.? The problem is they are on the other side of Ohio at my other house.
Let me know what you want and I can look for them in a few weeks. Figure $20-$40 range plus shipping for most.? They will be complete (and most were tested/working years ago), but as-is now.

I also have many letter and 1xx series plugins.

You can email me direct at: jreese7010@...

or phone: 740-947-7103

Regards,

Jim

Jim Reese
Waverly, OH

On Tuesday, November 24, 2020, 12:05:25 PM EST, Brenda via groups.io <brendda75@...> wrote:

Hello Dave, The 3A1 plugins that I have come across ends up not only the 6DJ8 tubes missing, there are 2 8233 tubes that end up missing as well.? There are 4 7586 nuvistor tubes in the front end, but seems like the tube pickers pass over these from my experience. I am in the market for a few 3A1 and 3A6 plugins myself...at a reasonable price, $400 is just way too much!!


Re: 7A26 no signal

 

Thanks for the guidance,

I suppose I have to take the cleaning challenge first as there are couple of suggestions for it.
As I didn't get any signal to R130...

I am also getting another unit to facilitate part swapping.

Regards,

Jouko


Re: A Couple Restorations

 

Bob,

Where are you located? there is a small handheld Tektronix scope in a
surpus store near me and that I can probably get cheaply. As best as I can
remember it is a 2xx model but I don't remember the complete model number.

On Wed, Nov 25, 2020 at 10:09 PM greenboxmaven via groups.io <ka2ivy=
[email protected]> wrote:

My main pleasure with equipment is finding inoperative or basket cases
and restoring them. I just finished a 2230 and an R-631B. This is an
account of the projects, skip now if you aren't interested.

The R361B was obtained from a member of this group, and I was quite
pleased with it when it arrived. I replaced the power cord, and tried it
out. It came alive, had a trace, then a loud snap was heard and it went
dead. I feared the worst, but continued with the work. It needed a bath,
and got it, followed by about ten hours in a hot box to dry it out. I
wanted to see if I could get the power supply working before I put the
jug back in after the cleanup. First tests were aweful. None of the
voltages were correct. The negative 100 volt supply is the reference for
everything else, and it was producing about 115 volts. All of the others
were very low. After a few hours of round and round circuit tracing, I
found the key problem- a partially shorted ceramic condenser. It was one
of the square red Erie brand ones, rated at 200 volts. There were two on
the board, I replaced them with 600 volt ceramic discs. There were two
other old electrolytics, I changed them out as well. The fuse protecting
the high voltage supply was gently blown, not fried and flashed all over
the glass tube. After finding and replacing two fried transistors in the
positive 125 volt supply, everything came alive and right on what they
should have been. I put a fuse in the high voltage supply, it came alive
with an output nearly 4KV, it should have been 3300. I turned the HV
adjustment all the way down, but could not get it below 3500. Both of
the transistors in the HV regulator are "special selected", and tested
good. After studying the manual, and not having exact original
transistors, I added a 12 meg resistor in parallel with the 2.2 meg
resisator coming from the moving contavt on the HV adjust pot. That
allowed me to adjust down to 3300 volts. I cleaned all the switches and
pots in both the mainframe and plug ins, re-installed the jug, and tried
it out. With adjustment of the sweep and position controls, I was
rewarded with a good bright trace. External signals and the built in
calibrator were displayed quite well. The vertical plug in I have is a
single trace differential, not especially useful to me, so I have a 72
dual trace on order. I will let the scope cook on the bench for another
day or so before I put it aside waiting for the dual trace preamp to
arrive. It will probably be used in my RTTY setup, the vertical response
is only about 600 KC.

The 2230 was a genuine basket case, almost entirely dismantled and
filthy with carbon dust. It was a freebee with another purchase at the
Rochester hamfest. I was quite skeptical until I got it home and found
that except for many screws, it was complete. It wasn't stored in the
dirt, it was operated in the filth because the knobs and front panel
were almost unreadable, and the focus pot was completely covered in
fuzz. Getting the front panel and control label plastic sheet off took a
bit of exploration, but WD-40 and a blow dryer softened up the adhesive
on the sheet, and it came off with very little damage. Now I could
remove the front panel to give it the cleaning it needed. Now fully
dismantled, everything got a bath. The cleaner and rinse water were
black as night, but everything cleaned up very well. After re-assembly,
cleaning and lubing switches and pots, it was time to see if it would
come alive. Turning the power on did nothing for a second or so, but the
pilot lamp blinked and the cooling fan moved. I remembered a similar
problem with broadcast waveform monitors and vector scopes, and replaced
all of the smaller low voltage electrolytic condensers in the circuit
that drives the inverter. Now, the same delay but the fan started and
the pilot lamp lit. There were some bright green blobs on the screen,
adjustement of the focus control produced brilliant menu text. After
exploring the controls, I found that one of them had to be pushed in to
display waveforms. I spent an hour or so exploring the locking action of
the pushbuttons, and there was no was to get two of the switches to
latch in, even if I borrowed the latch pins from other switches. The
others that were supposed to latch did. Because the buttons are plastic
stems on the switches, I filed a notch in the bottoms of the two that
would not latch. This allowed them to latch in, a gentle lift released
them. Everything seemed to work fine, the scope has many features I will
probably never use, but it displayed waveforms and would store them.
After several hours of cooking, I put the shield cover over the power
supply section and the brace that supports the top circuit board back
in. I turned it on, and was met with a total disaster. The only thing I
could get on the screen was blobs bouncing around. I shut it off
instantly, and started looking for bad solder joint on the bottom board
where the power supply is located. A solder splat was found and removed,
the scope came on and performed fine. After a few more hours of cooking,
I put the case and back panel on and ran it on test for a few more
hours. It performs very well, it will probably be used mostly in my
shack to troubleshoot RF circuits and monitor transmitter outputs
because it has a 100 MC. vertical bandwidth.

These are examples of the kind of projects I really like. Now, does
anyone have a 224 handheld scope project they would like to find a home
for? 73.

Bruce Gentry, KA2IVY




















Re: Resistor in series

Chuck Harris
 

Hi Tom,

You must have done that calculation before the thread caught my
attention.

I've checked everything I wrote, and I don't see anywhere that I
have said, "but they might still have made a mistake" as you appear
to be attributing to me.

When did I write that, or are you simply making up quotes for effect?

Tektronix had excellent engineers. Way better than most, but in
terms of reliability, they very often compromised the quality of
their designs in production by using poorly specified parts, and
cheese ball fixes for their mistakes. Their "tented" parts are
legion, and some are very embarrassing to see as an engineer.
(See 2465 A1 board for plenty of examples...)

That said, it is a fool who changes the arrangement or parts
selection, of an RF circuit he does not understand.

-Chuck Harris

Tom Lee wrote:

Well, I've presented quantitative calculations explaining why capacitance matters in
this circuit, and thus why series combinations are helpful. In rebuttal, you provide
"but they might still have made a mistake." That's moving the goal posts, Chuck.

I am happy to concede (for the nth time) that Tek's engineers were not flawless. But
the series resistors in the 475A are that way because of capacitance, not incompetence.

--Tom


Re: To pay for Peter Keller's Book ...

 

Thanks

larry


Re: (OT) Where to go for 70s IBM hardware? I'm looking for a terminal.

 

I have a pile of old IBM and Telex terminals from a local school system
when the state moved away from old IBM mainframes. They are stored in my
garage, but I am unable to get to them without help. The IBM terminals are
color, but I don't rember the model number. I believe they are RS232. Most
of the Telex were dead, but I had swapped enough bords to get some of them
to wake up. I am in North Central Florida.

On Tue, Nov 24, 2020 at 2:03 PM cheater cheater <cheater00social@...>
wrote:

Thanks everyone. Not really bothered about the dependency on a control
unit for two reasons. First of all, finding /anything/ of this era will be
difficult, whether it's the rarer RS232 kind, or less rare control unit
based type. Second of all, emulating the bus will likely be part of an
interesting challenge and a good way of figuring out the inner workings of
the display and input device, which is what I want to do, so rather than a
problem it's a positive thing for me. A $10 computer nowadays will be able
to do the job. My current biggest problem is locating those older terminals
in the first place. My assumption is they're mostly in defunct computer
graveyards, warehouses, university store rooms, or bank or utilities store
rooms, dusting and decaying away.






Re: Resistor in series

 

Carbon Composition resistors absorb moisture. Bake them for a while before
tossing them out. Also, high value resistors require voltage across them to
work at their marked value This used to be plainly marked on reels of CC
resistors. I posted a scan once. I caught hell for 'making up that
bullshit'. They also don't realize the first resistor series was 50%
tolerance. yet they were working on pre-war radios. Once again I was told
that I was 'making up that shit'.

On Thu, Nov 26, 2020 at 12:18 AM Jeff Dutky <jeff.dutky@...> wrote:

Tom,

Yes, I had anticipated that these NOS components might not have retained
their specified values. I've been going through my father's effects while
working on his scopes and finding all sorts of now-50-year-old components,
some of which were expensive when purchased new, and thinking that some
fair fraction of them are probably now terribly out of spec, if not
completely destroyed (there are a number of big metal can capacitors that I
know were stored for at least 20 years in a hot attic, and I don't have
much hope that they are still in good condition). I purchased a dozen
resistors in the hope that I could find two that were within spec.

Back in college I worked in receiving QC for a NASA contractor that built
flight-rated systems. We would first receive a lot of 10 or 20 components
of some description, which we would label and ship over to Goddard. They
would eventually ship us back 2 or 3 components with paint marks and
certification sheets, and we were required to use only those marked
components in the parts we built for them. The other components we had
shipped to them had been tested to destruction, and only the surviving 10%
had been returned to us as flight qualified components. Careful selection
of parts is something I have thought about ever since.

But what you're saying is that while my intuition was correct, the actual
math makes a fool of me. I should really just use the metal film resistors
when they arrive because they are lower noise and the inductance is a
non-issue.

I can always gaze lovingly at the old Allen Bradleys. I'm quite sad that
nobody seems to make resistors that have those nice sharp edges anymore
(or, at least, I haven't found them for sale).

-- Jeff Dutky






Re: 7A26 no signal

 

I have just checked input resistances on a working-to-spec 7A26, the results are quite unexpected!. If I use an analogue meter and have the 7A26 powered off then in the 10mV position the DC 'resistance' from each BNC centre pin to its outer is about 350k measured in both polarities. For 20mV and higher the resistance is 1M. If I use a DMM then with either power on or power off the 'resistance' is 1M as it should be. Clearly Q150 needs to be powered in order to have its gate reverse biassed.

Even if Q150 is faulty, its output, together with the output from the 2X balance pot R160 form the two inputs to the differential amplifier U1350, so if U1350 onwards is all OK, the trace should move.

I have just noticed that there is another DC balance pot (R1353) between U1350 and U1450 so that can also be used to narrow down where the fault is. Since the two beams do move in response to the vertical position front panel control it looks like U1550 in each channel is OK so you can swap the good IC from one channel to the suspect position in the other channel and see what changes.

Regards,

Roger


Re: Why you MUST USE the PayPal "FRIENDS and FAMILY" option for Peter's book

 

On Thu, Nov 26, 2020 at 03:01 PM, Jeff Dutky wrote:

....
My only other complaints about PayPal are mere hearsay, but I've heard too
many stories of sellers having their funds frozen over the years to think
that maybe there isn't at least a little bit of fire behind that smoke.
....

-- Jeff Dutky
I thought about this a bit, with the huge volume of paypal transactions every day across the world, the actual number of horror stories would have to be a fraction of a fraction of a percent.


Re: Delay Time Position Vernier

 

I don't recall seeing it in any Service Manual, but our good friend H?kan has produced a document on the topic:



Colin.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Jeff Dutky
Sent: 26 November 2020 00:24
To: [email protected]
Subject: Re: [TekScopes] Delay Time Position Vernier

Colin Herbert wrote:

Your other problem is setting the Vernier where it is supposed to sit when you put it all
together again! They don't all sit at 0.00, There is data about where they are supposed
to read when the pot is at the extreme anticlockwise. If you have problems, just make
them known here and you should get the right advice. Don't just adjust it to 0.00 - it is
likely to be wrong.
Is this covered in the service manual? I would be interested in knowing how this needs to be set, as I am planning to move the guts of one 475 into the frame of another, and that would obviously involve disassembling and reassembling the delay vernier.

-- Jeff Dutky


Re: Tektronix 492A input attenuator repair ????

 

Once I had the same issue with the 492 attenuator. Taking it carefully apart, one of the wafers was burned. I was able to manufacture a wafer myself, using very thin teflon laminate and 0402 SMD resistors. The result was acceptable up to about 8 GHz.

Cheers

Ulf Kylenfall
SM6GXV


Re: Resistor in series

 

OK, yuzz made me look. I found the schematic for the 475A, and my quick assessment is that there's nothing special about low capacitance or inductance or precise value of the R1356/R1544 combo. I also looked at the regular 475 schematic, which appears about the same. Without seeing the actual physical layout, I'd guess that the circuitry is quite crammed in there for space reasons, and two 1/2W resistors "fit" better than a single 1W piece - enough so that it was worth continuing the tradition over modifying the board layout.

Q1344 and Q1352 form a shunt-feedback linear amplifier, and the rest of the circuitry handles all the various conditions the Z-axis must take, which are plentiful. The collector of Q1352 is a low impedance node by virtue of the amplifier power gain, with DC feedback from R1369, while C1352 provides AC feedback and compensation. The output has to drive the DC restorer, a significant capacitive and nonlinear load. R1368 isolates the DC restorer load, and C1352 stabilizes the amplifier - it would likely oscillate otherwise. The presence of all the diode clamps and blocks in the amplifier stages indicate a number of operational conditions are needed, depending on what's going on in the horizontal system.Q1352 provides strong pull in the down direction, while Q1358 and Q1354 form a cascode amp for the up direction, but only during transient conditions - at DC, it's a constant current source. It looks like the two Rs in question supply collector load current for Q1352 whenever Q1358 is in cutoff, to keep the loop closed and ready for fast response to the next event, or from overdrive recovery. Z-axis amplifiers don't need high fidelity, but do need fast response in one direction at least, to properly unblank at the beginning of the trace. The tail end (blank) can be slower since the trace is usually off screen by then.

So anyway, I wouldn't worry too much about these resistors. Yes, there must be a reason they went this way, but whatever it is, I don't think there's anything critical about these parts. The maximum DC in them should be about 7 mA, so about 700 mW, when the output is held near zero. Two 1/2W resistors standing upright should handle it OK - better than a single 1W part laying on the board.

Happy Thanksgiving all. Enjoy.

Ed


Re: 7A26 no signal

 

Colin and Juoko,

If the 7A26 is arranged anything like the 475 then cleaning the AC/GND/DC coupling switches is almost exactly the same as cleaning the rest of the attenuator switches: soak a narrow strip of 100% cotton bond paper in IPA, slide it between the open switch leaves and the contact plate on the PCB, close the switch trapping the strip of paper, gently pull the paper out, and repeat several times for each contact point. I found the process more difficult for the attenuator switches on the 475 because you have to remove each attenuator block to get access to the switch contacts, and because there are contacts on both sides of the PCB, the ones on the bottom side being significantly more difficult to access. That said, with patience and diligence I was able to clean all the switch contacts, so I think you shouldn't have any trouble.

-- Jeff Dutky


Re: (OT) Where to go for 70s IBM hardware? I'm looking for a terminal.

 

Wish I had kept my Commodore PET/CBM systems...
-Dave

On Wednesday, November 25, 2020, 05:59:43 PM PST, - <rrrr6789@...> wrote:

Actually $1200 is completely reasonable IMO. I sold mine for almost that
much 15 years ago and i've seen at least one that sold for almost double
that. Like the prices or not but the really unique and/or first of it's
kind vintage computers are bringing serious money. Even good, clean and
complete Commodore 64s and the Radio Shack computers are bringing hundreds
of dollars and they were sold by the millions.

On Wed, Nov 25, 2020 at 2:00 PM cheater cheater <cheater00social@...>
wrote:

Those prices are not reasonable, and the sellers do not accept offers,
contrary to what's advertised on eBay.

On Wed, Nov 25, 2020 at 4:57 PM Jeff Dutky <jeff.dutky@...> wrote:

A quick look at ePay reveals 3 IBM 5110s, and two 5120s all asking in
excess of $1200 (all but one are OBO, so you might be able to get a
discount). Shipping on these things is going to be bear, however. There
are
lots of watchers on each one.

The 5120 is especially interesting looking, with a larger display, two
vertically mounted 8 inch floppies, and a generally "rounder" look to the
case: the thing just screams 1975. If I had any interest in these
machines
I might be tempted to pick one up.










Re: Why you MUST USE the PayPal "FRIENDS and FAMILY" option for Peter's book

 

John Goller wrote:

I'd like to know what your issues are because I have a
LOT of stuff that I'd like to list here for sale and if there
is some issues that are making things difficult to pay
for things, I'd like to know about it
I don't have particular issues, other than complaints about this particular process (not being offered the options that would have made this process easy), and about the quality of their buyer interface (every time I have tried to log into their web interface I have had to do the "I'm not a robot" dance, and every time the site has responded with "something went wrong on our end" throwing me back to the "I'm not a robot" screen, so that I get to do the dance again, and maybe a third time. That's shoddy UX on PayPal's part, and I haven't got any patience for that sort of thing. Also there's no indication of how far along in the buying process you are, so you just have to keep clicking Continue until suddenly the process is over. That's also shoddy UX). My only other complaints about PayPal are mere hearsay, but I've heard too many stories of sellers having their funds frozen over the years to think that maybe there isn't at least a little bit of fire behind that smoke.

That said, I understand why people want to use PayPal: they fill a niche that, even today, has very few players. If you want to accept payment over the web you just don't have many choices, and the established choices (credit card merchant accounts) are not well suited to small players. When PayPal got started they were basically the only game in town for people who couldn't afford to set up a merchant account, and that benefit can not be overestimated. Still, I'm a grumpy sort, and this is one of the things I'm grumpy about.

-- Jeff Dutky


Re: Resistor in series

 

Hi Jeff,

I've only taken a quick look at the circuit, but it doesn't look overly fussy about the exact resistance value, so the carbon comps you bought are likely to be fine if they are still within tolerance. So don't rule them out just yet.

The noise of a carbon comp is indeed truly wondrous (and it is proportional to dc current; film resistors do not exhibit this effect to any significant degree), but in this particular circuit, the noise isn't of consequence. The signal amplitudes there are so much larger than the noise that you'll never see any effect. So, if you find that the AB resistors you just purchased are within tolerance, I think there's no harm at all in using them. I have to admit to sharing the same nostalgia that you have for these retro resistors. But beyond that, there is also one sound engineering reason to keep some around: Better surge tolerance, owing to the current being distributed over a larger cross section than is the case with film resistors. I'll occasionally specify CCs for circuits that may experience transient overloads, such as some HV circuits which may arc occasionally. Metal film resistors don't tolerate transient overloads as well.

-- Cheers,
Tom

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

On 11/25/2020 21:18, Jeff Dutky wrote:
Tom,

Yes, I had anticipated that these NOS components might not have retained their specified values. I've been going through my father's effects while working on his scopes and finding all sorts of now-50-year-old components, some of which were expensive when purchased new, and thinking that some fair fraction of them are probably now terribly out of spec, if not completely destroyed (there are a number of big metal can capacitors that I know were stored for at least 20 years in a hot attic, and I don't have much hope that they are still in good condition). I purchased a dozen resistors in the hope that I could find two that were within spec.

Back in college I worked in receiving QC for a NASA contractor that built flight-rated systems. We would first receive a lot of 10 or 20 components of some description, which we would label and ship over to Goddard. They would eventually ship us back 2 or 3 components with paint marks and certification sheets, and we were required to use only those marked components in the parts we built for them. The other components we had shipped to them had been tested to destruction, and only the surviving 10% had been returned to us as flight qualified components. Careful selection of parts is something I have thought about ever since.

But what you're saying is that while my intuition was correct, the actual math makes a fool of me. I should really just use the metal film resistors when they arrive because they are lower noise and the inductance is a non-issue.

I can always gaze lovingly at the old Allen Bradleys. I'm quite sad that nobody seems to make resistors that have those nice sharp edges anymore (or, at least, I haven't found them for sale).

-- Jeff Dutky




Re: Choosing the right replacement cap

 

Dave,

Thanks. I saved the URL.

Ananda


Re: Resistor in series

 

Tom,

Yes, I had anticipated that these NOS components might not have retained their specified values. I've been going through my father's effects while working on his scopes and finding all sorts of now-50-year-old components, some of which were expensive when purchased new, and thinking that some fair fraction of them are probably now terribly out of spec, if not completely destroyed (there are a number of big metal can capacitors that I know were stored for at least 20 years in a hot attic, and I don't have much hope that they are still in good condition). I purchased a dozen resistors in the hope that I could find two that were within spec.

Back in college I worked in receiving QC for a NASA contractor that built flight-rated systems. We would first receive a lot of 10 or 20 components of some description, which we would label and ship over to Goddard. They would eventually ship us back 2 or 3 components with paint marks and certification sheets, and we were required to use only those marked components in the parts we built for them. The other components we had shipped to them had been tested to destruction, and only the surviving 10% had been returned to us as flight qualified components. Careful selection of parts is something I have thought about ever since.

But what you're saying is that while my intuition was correct, the actual math makes a fool of me. I should really just use the metal film resistors when they arrive because they are lower noise and the inductance is a non-issue.

I can always gaze lovingly at the old Allen Bradleys. I'm quite sad that nobody seems to make resistors that have those nice sharp edges anymore (or, at least, I haven't found them for sale).

-- Jeff Dutky