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Guy,

Thanks for your insights Where I have been focused the last day is to
try and understand why the CLKOUT stays at 25mhz both in the hung and
running fine state. Actually its probably 24mhz due to the 48mhz
oscillator, I think its supposed to be doubled to the log stated 50mhz
(48??) as one of the ending steps of the boot sequence. There may be a
PLL lock problem or the clock setup fails for some reason, I really do not
know for sure at this point that the 50mhz applies to the MPC860 core and
the external CLKOUT remains at 25 as I am reaching out for conformation.
Personally I think the external clock need to be 50mhz as 25 is really slow
for what they have here, all that said it seems to run fine at 25mhz and I
have not seen any issues after a successful boot.

Temperature testing is a bit of a challenge and I have spent a bit of
time on it since the failure mode really mimics a sensitivity to being
warm or cold but nothing I have tried will force it to ether the fail or
pass state. I have been heating or cooling primarily in sections of the
board from larger areas down to the device level. I have done the whole
board and supplies but intentionally limited it in the acquisition section.
I use a large and small heat gun and have used most of a large can of
freeze spray, I track the temperature with a handheld FLlR IR camera that
has resolution down to the SMD passives sizes and shows the temp very
accurately.. Temp wise my upper limit has been ~160f to -40f or so for
some spot areas like the DRAM. I will work up a plan to try to temp cycle
the whole thing as you suggested, definitely worth a try.

When the unit is in the hung state I did see the refresh but did not
measure the period and will put that on the list. After all time spent
with this if I could offer some off the wall perception of the problem that
may or may not make any sense: Its seems like its a 'charge' or maybe a
given 'impedance' somewhere and their value shifts in one direction while
its on and the other direction while it is off -very- slowly. This 'charge'
or 'impedance' change over time is not affected by temperature very much
but when the value crosses some point it will cause it to fail.

Best Regards,
Mike

If I'm not mistaken, there's an "odd" resistor with something like 90.9 labeled
on it. I'll have to get that back out and see exactly what value it is. I got
these resistors from an estate sale and it looks like they've never been used
for anything.

Yes, it's just to get the HV set on the cathode of the CRT. Technically, it's
supposed to be within 1%. I have a Triplett 630-NA that has a 6000VDC range
that I've used as a rough check but I want to get this much closer than that.

Thanks for the good info.
Barry - N4BUQ

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

From: "edbreya=yahoo com" <edbreya@...>
To: "tekscopes" <[email protected]>
Sent: Thursday, February 8, 2024 1:52:17 PM
Subject: Re: [TekScopes] Method to measure HV

Barry wrote "I presume that because the probe uses a 75M and a 75k in series and
the 10M voltmeter is across the 75k, the 10M has minimal effect on the
divider's ratio. Is that correct?"

It depends on what you mean by "minimal effect." In reality, for a commercial
1,000X probe at 75 megs input, the "75 k" termination resistor is likely 75.643
k, which is about right to attain nearly the ideal value of 75.075...k when the
10 megs DMM input R is paralleled. That's why Jean-Paul mentioned being sure of
that 10 meg value.

Your 10X probe deal should work just fine, but be aware of the dependence on the
DMM's input R, and whether it's connected. If you get into a situation where
the 90 megs of R are left dangling out there, it's a current source backed by 3
kV, so can run up to 33 uA into whatever it could contact. It can't hurt you,
but could damage certain parts if contacted. If the DMM is always securely
connected, it's still a current source, but limited to 300 V. The main thing is
to keep it wrapped up to avoid any mishaps. The exact same thing can happen
with any HV probe if it's ground connection is forgotten or inadvertently lost,
so always be sure it's secure.

You can also opt for a higher divide ratio like 100 or 1,000X, which is what
most HV probes do, to get more comfortable measuring voltage, It's quite easy
to adapt any high-meg resistance into a nice HV divider. The higher the divide
ratio, the more flexibility you have in hitting the values right and handling
multiple load values. For instance, you could go with 100X instead of 10X, and
be able to drive a 10 meg or 1 meg input. With the same 90 megs of inlet R,
you'd want the bottom R to be 90 M/99, so 909.09... k. This can be conveniently
made with a 1 M termination paralleled with the DMM's 10 M input R, or, a 10 M
termination with a DMM (or scope) input R of 1 meg. These are all idealized
values, of course. The actual ones have to be worked out. It's most important
to know the tempco, voltco and actual value of the inlet R - everything else
can be worked out to accommodate it.

Anyway, since your application seems simple enough here - just checking a scope
one time (right?), and not needing extreme precision, your 10X thing is already
the way to go. It's good to consider options too, if more of such needs are
expected.

Ed

From John with permission, personal friend of Dennis...

Just got a call from Dennis. He sounds very good.

On Saturday, Feb 10, they put in only one stent, the second being unnecessary.
The one stent went in high up in the aorta rather than one in each in branch.
I remind you that I still am 4 years away from my MD, so please excuse me from
any medical errors.

Dennis was very impressed with not only the size of the room used in the
procedure, but the number of machines there. Especially impressive was the
computer controlled (of course) X-ray machine that took pictures from different
angles and, of course, gave immediate results.

The doctors told him he was the ideal patient, totally immobile while under
total sedation during the actual stent installation. (Not everyone is immobile
during anesthesia.) This is important because the stent is inserted in an
artery in the groin and any motion there could result in major bleeding. They
told him to call 911 if that happened. Medical humor.

He will remain in Massachusetts for a while so the doctors can monitor his
recovery. He expects to be on a plane back to Bellevue on about February 25.

It was a long Thanksgiving vacation.

The movie “Apollo 13” famously showed the astronauts
doing a calculation on a slide rule. It was the “pocket” model and was
identical to the consumer one

I too thought the article was quite wonderful....and re slide rules.
Walter and I talked about them a bit. great guy and sorely missed..i
still use my 6 in slide rules ....my 18 in is bamboo and belonged to my
dad. Dad gave me a 6 in pickett aluminum while in high school....I used
it in College along with my 6 in circular ( it was tossed by friend
after getting "the NEW hp35") for my engineering classes...most of my
colleagues had the HP calculators (( out of my budget!)...so on the top
on exams I had to write "slide rule" since my numbers were not
"EXACT"...but good enough....I Still use them all....but I do like my
HP35, 25 and 11C all of which I use...but the slide rule is always
around if the batteries die..especially in the 25 and 35...battery packs
need rebuilding....a 6 inch is always in arms reach even in the car!
oh well fond memories, Walter will not be forgotten.
搁别苍é别

On 2/10/24 7:50 PM, Jim Ford wrote:

Yes, I had only bought once or twice from Sphere, but Walt and Susan did

include some useful goodies. Say, that NYT article mentioned slide rules
made out of bamboo, and I'd never thought about it until today, but my
dad's old slipstick from the 1960s had the open grain at the ends and was
almost certainly made of bamboo! I'm too young (born in 1965, engineering
school 1983-1991 including grad school) to have used one, but I'm starting
to think I missed out. Say, what make and model would you folks recommend
for an EE with a bent toward RF, microwaves, and fiber optics? Steve,
interestingly enough, my dad is a chemist turned software engineer who used
to teach p-chem! Definitely not my thing, and I jumped to EE after starting
freshman year as a biochemistry major; those chem labs blew it for me.
Rest In Peace, Walter. Jim Ford Sent from my T-Mobile 4G LTE Device

-------- Original message --------From: stevenhorii <

sonodocsch@...> Date: 2/10/24 6:08 PM (GMT-08:00) To:
[email protected] Subject: Re: [TekScopes] Walter Shawlee obituary in
the NY Times I miss Walt. I first got acquainted with Sphere Research
through sliderules. I had saved mine from my university days. I still have
the DietzgenN1725 Vector Log Log. My father was an architect and bought it
for me at adiscount since the firm he worked for had a contract with
Dietzgen fordrafting instruments. That slide rule got me through p-chem. I
only usedthe hyperbolic scales to see how they worked. I did use most of
the othersfor homework problems.A lot of my collection came from Sphere
Research - new-in-the-box Pickettrules including their famous N4, also a
vector log log. I have one of thosenuclear bomb effects circular slide
rules and got it in the book “TheEffects of Nuclear Weapons” but on eBay,
not from Walt. Since then, I alsofound a Soviet version. Being a
radiologist, I thought that understandingthe dangers of the radiation from
these weapons was something I should knowabout.It was only later that I
started buying electronics from Walt. He wasalways generous and would
include a bonus bag of parts. Most were farbetter than the usual “floor
sweeping” sorts of stuff; a lot of usableparts in those bags.I’m sad that
he’s gone but glad Susan carries on. The effects of his yearsof catering to
many of those in this group are probably well known sinceI’m sure many of
you would turn your browser to his site the minute his“Stuff Day”
announcements appeared.Steve H.On Sat, Feb 10, 2024 at 16:37 John Griessen
via groups.io <john@...> wrote:> That was a nicely
done bio.>>> >>>