Re: Tutor needed for college student

[Fred Cisin via cctalk]

Jim,
THANK YOU

You are taking it further than most of the high schools were 20 years ago.
It was incredibly rewarding when I could assist an epiphany, such as that 
arithmetic could be done IN binary/hex/octal, WITHOUT conversion to 
decimal/arithmetic/conversion back!



California mandated "Computer Literacy" in the Community College system. 
But, they didn't DEFINE it! It was left to college administators to make 
THAT decision.  Not even the curriculum committee could have input.  The 
administator would typically define computer literacy as being about half 
of what they knew.  And we had a guy who would write a memo about room 
change for a meeting in WordPervert, print it out, scan it, and attach the 
JPG to an email with subject of FYI and content of "See Attached".  Half 
of wht he knew wasn't even enough for the remedial job training for the 
digital sweatshop.


Then, ten years ago, California also added a mandate for "Information 
Competency".  Again undefined.  The state even permitted the schools to 
declare that they already had suitable courses or even that "Information 
Competency is adequately covered, diffused throughout the curriculum". I 
created a course outline for a single semester lower division 
undergraduate (community college) course introducing Information Science. 
I never got a chance to teach it :-( Our administration declared that 
topics such as Precision, Recall, Relevance, Bandwidth, File structures, 
information representations, Search Engine Optimization, computer/internet 
ethics, internet economics, internet history, etc. were inappropriate 
below grad school level.  (If THEY didn't know it, then there was no 
reason to permit teaching it, even though they permitted Chemistry and 
Calculus)


--
Grumpy Ol' Fred ci...@xenosoft.com

On Mon, 12 Oct 2020, Jim Manley via cctalk wrote:


Cindy - if he can't find any other alternative, please feel free to forward
his contact info to me, or send my e-mail address to him (a Reply To will
expose it), cc: me.

The rest of this is background for those who may be curious about the state
of our educational system from someone on the inside - those with lives may
return to them now.

In the olden days, before CS was offered Pretty Much Everywhere, discrete
math courses were often disguised by titles such as Finite Automata and
State Machines and offered in Science or Engineering departments, while
courses on Predicate Calculus, and Number Theory (e.g., Groups, Fields, and
Rings) were typically required to be taken in Math departments.

Some requirements have been gradually sliding down into earlier grades, to
the point where Number Theory is now taught in small bites (pun fully
intended) starting in middle schools as early as 5th grade (beginning the
hierarchy with Whole numbers).  Eventually, a number type or two,
properties, identities, etc., are added, potentially up through Real
numbers in high school, depending on whether Physics and/or Advanced
Electronics is going to be taken.

Some states are mandating CS fundamentals in every grade, from K through 12
(Virginia has come up with one of the best I've seen, as it includes
sample lesson and unit plans in addition to the curriculum requirements).
CS in K - 12 may sound ridiculous, but the sooner you can expose kids to
the most basic concepts, it's much more likely they'll be able to continue
the progression.  I've taught binary math to kindergartners using pennies.
They don't know that a penny is 1/100th of a dollar, because they can't
understand what either of those concepts are, but they do know that pennies
are shiny (I go to the bank to get rolls of new ones) and they see that
others who are older use them to buy things.

I just use pennies to represent ones, and absence of pennies as zeroes in
binary, usually in egg cartons to immediately show the organization of
bits, and making more obvious where the absences are.  Kids learn how to
read and say binary numbers (e.g., 10 isn't "ten", it's "one-zero", and
they haven't learned decimal ten yet anyway, which is a good thing).  It's
much easier to teach binary math first, and higher-order number
representations later, than the other way around.

Then, we go through the four rules for binary addition - zero plus zero
equals zero, zero plus one equals one, one plus zero equals one, and one
plus one equals zero and carry a one to the left.  It's easy for the kids
to learn this by handling the pennies and moving them between egg carton
depressions in accordance with those rules.  In later grades,
multiplication by two by moving each penny one space to the left is
likewise a piece of cake, as well as division by two by moving each penny
to the right.

When kids learn a concept, they get to keep the pennies used in that day's
lesson, and kids will do lots of things to become shiny penny hoarders.
That includes stealing other kids' pennies, whereupon, when, not if caught,
we make a detour into computing ethics, 

Re: Firing up the pdt11

[Chris Zach via cctalk]

Well, the drive is working. Better.

Summary: The PDT11/150 needs to have resistors on the harness to the 
floppy drives to limit the current for the sector LED. Without it the 
LED will be "off" and you will get a quick 8 stepper motor clicks 
without any click to load the heads. Looks like the PDT uses the sector 
count signal to determine if a disk is in the drive, and if it doesn't 
see that it just fails with a quick braaap!


And after trying a 47 ohm resistor (marginal) and a 22 ohm resistor (no 
luck at all) it turns out you want to use around 67 ohms of resistance 
for best results on the sector led. I didn't have any 67 ohm resistors, 
but I did have two 140 ohm resistors, so putting those in parallel gave 
me 70.


Drive PD1: now boots, reads disks, and seems kind of happy. I still need 
to clean up the whole board and put this harness in the drive, but at 
least it's running with two floppies again.


On the bad side (and something to think about): My memory must be in 
error: I can't format RX01 floppies with the PDT11. I recall that the 
PDT would literally rewrite the sector information along with the actual 
data track on each write (why) but this is not enough to format or init 
a blank disk apparently.


Which is odd, because I have a few Elephant Memory systems floppies that 
still work and obviously *are* formatted for RX01/PDT. But I never owned 
an RX02 so how did I get these formatted in the first place?


On to the RX02 again I guess. I'm going to put this pdt11/150 back 
together and start thinking about how to format floppies. I've heard 
that the RX02 can format an RX01, but can it? Certainly not with an 
RXV11 controller, I'll need to either find an RXV21 or get a Unibus 
pdp11 working so I can use this RX21 controller someone graciously lent 
me (or find my Quniverter and try that, but that would be 
stupid-complicated).


Which could be interesting: I have two Unibus pdp11's: My 11/05 (which I 
think only has 24kw of core memory anymore) and my 11/24 (which I have 
never gotten to work right and doesn't have any memory boards). Quick 
question to end this thread: Can an 11/24 come up to ODT without any 
memory? I've never seen anything on the serial ports.

Re: Tutor needed for college student

[Jim Manley via cctalk]

Cindy - if he can't find any other alternative, please feel free to forward
his contact info to me, or send my e-mail address to him (a Reply To will
expose it), cc: me.

The rest of this is background for those who may be curious about the state
of our educational system from someone on the inside - those with lives may
return to them now.

In the olden days, before CS was offered Pretty Much Everywhere, discrete
math courses were often disguised by titles such as Finite Automata and
State Machines and offered in Science or Engineering departments, while
courses on Predicate Calculus, and Number Theory (e.g., Groups, Fields, and
Rings) were typically required to be taken in Math departments.

Some requirements have been gradually sliding down into earlier grades, to
the point where Number Theory is now taught in small bites (pun fully
intended) starting in middle schools as early as 5th grade (beginning the
hierarchy with Whole numbers).  Eventually, a number type or two,
properties, identities, etc., are added, potentially up through Real
numbers in high school, depending on whether Physics and/or Advanced
Electronics is going to be taken.

Some states are mandating CS fundamentals in every grade, from K through 12
(Virginia has come up with one of the best I've seen, as it includes
sample lesson and unit plans in addition to the curriculum requirements).
CS in K - 12 may sound ridiculous, but the sooner you can expose kids to
the most basic concepts, it's much more likely they'll be able to continue
the progression.  I've taught binary math to kindergartners using pennies.
They don't know that a penny is 1/100th of a dollar, because they can't
understand what either of those concepts are, but they do know that pennies
are shiny (I go to the bank to get rolls of new ones) and they see that
others who are older use them to buy things.

I just use pennies to represent ones, and absence of pennies as zeroes in
binary, usually in egg cartons to immediately show the organization of
bits, and making more obvious where the absences are.  Kids learn how to
read and say binary numbers (e.g., 10 isn't "ten", it's "one-zero", and
they haven't learned decimal ten yet anyway, which is a good thing).  It's
much easier to teach binary math first, and higher-order number
representations later, than the other way around.

Then, we go through the four rules for binary addition - zero plus zero
equals zero, zero plus one equals one, one plus zero equals one, and one
plus one equals zero and carry a one to the left.  It's easy for the kids
to learn this by handling the pennies and moving them between egg carton
depressions in accordance with those rules.  In later grades,
multiplication by two by moving each penny one space to the left is
likewise a piece of cake, as well as division by two by moving each penny
to the right.

When kids learn a concept, they get to keep the pennies used in that day's
lesson, and kids will do lots of things to become shiny penny hoarders.
That includes stealing other kids' pennies, whereupon, when, not if caught,
we make a detour into computing ethics, which is one of the sets of
concepts required to be covered in every CS course!

BTW, one of the reasons that we have to get girls exposed to STEM in a
friendly way as early as possible is because peer pressure against them
excelling in STEM starts around the fourth grade.  I've actually overheard
conversations among girls that young that go something like this: "Oh, you
don't want to be too good at math and science because then you'll make the
boys not like you because you're smarter.  Then, they won't ask you out on
dates, you won't get married, and you'll never have kids and grandkids."  I
am not making this up, and there are geographic/ethnic groups that
reinforce this in spades - girls are supposed to get married after high
school, have kids, and raise a family ... period.

Based on what I've observed going on in K - 12 STEM in most states, I'm
seriously wondering who will be keeping the lights on, let alone the rest
of our infrastructure running, when I'm at the age where getting my
favorite flavor of pudding will be the high point of my day.  People with
humanities degrees (almost no universities offer true liberal arts programs
any more, where science and math are given equal emphasis to literature,
history, etc.) are now preferable to become STEM teachers than people with
STEM degrees.

Part of it is because there are now ten people with humanities degrees for
each job opening requiring them, but there are upwards of two STEM jobs for
each person with such a degree, so people with humanities degrees are
simply cheaper to hire.  It's even worse in education, where recruiting
people with STEM degrees is very difficult due to competition from
commercial organizations, especially high-cost-of-living metro areas.
Educational administrators almost all have humanities degrees now, as the
old-timers who have STEM degrees and come up through 

Re: Tutor needed for college student

[Kirk Davis via cctalk]

Hey Cindy

Just to add to the good suggestions already given here I’d suggest looking on 
Craigs List. Typically there are some good (starving) grad students that do 
tutoring on the side.

Kirk

Sent from my iPad

> On Oct 12, 2020, at 8:14 AM, Cindy Croxton via cctalk  
> wrote:
> 
> If anyone has spare time, and is familiar with discrete mathematics, I have 
> a friend who is a young college kid and desperately needs a tutor. His prof 
> just says to read the book, and take online quizzes. He is failing. If you 
> can help, please email me. He is in Delaware.
> 
> -- 
> Cindy Croxton
> Electronics Plus
> 1613 Water Street
> Kerrville, TX 78028
> 830-370-3239 direct
> 

Re: Tutor needed for college student

[dwight via cctalk]

Remakable. It was not the descrete math I know, then. It would vary heavy on 
logic and set theory stuff. Not the kind of stuff I deal with at work. It was a 
long time ago though. Things have changed. The closest we go to a real computer 
was a Monrow calculator.
Dwight

From: cctalk  on behalf of Bill Gunshannon via 
cctalk 
Sent: Monday, October 12, 2020 1:54 PM
To: cctalk@classiccmp.org 
Subject: Re: Tutor needed for college student

On 10/12/20 4:29 PM, dwight via cctalk wrote:
> I'm not too sure Hackers will have someone that is into Discrete Math. It is 
> way beyond what a typical engineer will go through to get a degree. It is not 
> a course someone would take without expecting to get into theoretical 
> mathematics.

Seriously?  Every CS and CIS student at the University where I
worked for 25 years had to take Discrete Math.  I am sure most
other engineering disciplines required it, too but I would have
to  look it up to be sure.

bill

Re: Tutor needed for college student

[Guy Sotomayor via cctalk]

I agree with the others: go look for other textbooks.  There are also
surprisingly good "webinar's" on various math related topics on YouTube
(free), so it might be worthwhile to have him do a bit of searching.

Oddly, I never had any discrete math courses in school...it was "old
school EE" so everything was differential equations and stochastic
processes.

I did end up teaching myself about finite fields (Galios Fields to be
specific) when I needed to do some work with error correcting codes.  I
ended up with 3 or 4 different textbooks on the topic.  I have since
gone back to refresh myself about them and found several good video
courses on YouTube.

TTFN - Guy

Re: Tutor needed for college student

[Fred Cisin via cctalk]

If the textbook isn't working for him, . . .

1) Look at OTHER textbooks on the subject.
There is even a Schaum's "made easy , "Outline Of Discrete Math" by 
Lipschutz.
The title promises more than it can deliver, but it might help get through 
some of the more troublesome sections.


2) Seek out other students who had taken that specific course, from that 
specific prof.



We used to have a "Computer Math" course.  Some of the instructors used a 
Discrete Math textbook for it.  Instead, I concentrated on things such as 
binary representations of negative and floating point numbers, because the 
majority of the computer students who showed up for it had been UNAWARE 
that anything but positive integers could be expressed in binary!

FOR REAL.

For your amusement: The calculator included in Windoze purports to have a 
"Programmer" mode.  But within that calculator non-integers do not exist 
in the "programmer" mode.  Although it does have some 2's complement 
negatives.


Even had a few students who had been told in school that "PI is about 
3.1416 or 22/7" by teachers who interpreted that to mean (about 3.1416) 
or ([EXACTLY] 22/7).  and similar, comparable misinformation.  That is 
apparently STILL being taught!
(60 years ago, I got sent to the principal's office for discipline in 5th 
grade for disagreeing with my teacher, and pointing out that since 22/7 
was NOT "about 3.1416" (3.142857), why would they say that it was about 
3.1416 if it is 3.142857, and that PI was NOT a "rational number" )


So, I'm not the right person for Discrete math.
For a course entitles "computer math", I considered getting competence 
with hex, octal, binary, including negatives and floats, to be a higher 
priority than the math theory.

I made the students manually calculate the (first 32) bit pattern for PI.

--
Grumpy Ol' Fred ci...@xenosoft.com

Re: Tutor needed for college student

[Bill Degnan via cctalk]

On Mon, Oct 12, 2020 at 4:58 PM Will Cooke via cctalk 
wrote:

>
> > On 10/12/2020 3:29 PM dwight via cctalk  wrote:
> >
> >
> > I'm not too sure Hackers will have someone that is into Discrete Math.
> It is way beyond what a typical engineer will go through to get a degree.
> It is not a course someone would take without expecting to get into
> theoretical mathematics.
> > Dwight
> >
> Hacker Spaces are filled with lots of different people.  Not all are
> engineers.  It might even be safe to say they are in the minority.
>
> Will
>

I might be weird, but I thought discrete math was easier than most other
maths I took, but I took it in grad school and by then I was more serious
about studying.  It's more of a programmer's math not as much of an
"engineering math".  I wish I had time to help, but I live near the U of
Del and I'd suggest contacting the U of Del math department,there are a lot
of students there looking for part time jobs.

Bill

Re: Tutor needed for college student

[Bill Gunshannon via cctalk]

On 10/12/20 4:29 PM, dwight via cctalk wrote:

I'm not too sure Hackers will have someone that is into Discrete Math. It is 
way beyond what a typical engineer will go through to get a degree. It is not a 
course someone would take without expecting to get into theoretical mathematics.


Seriously?  Every CS and CIS student at the University where I
worked for 25 years had to take Discrete Math.  I am sure most
other engineering disciplines required it, too but I would have
to  look it up to be sure.

bill

Re: Tutor needed for college student

[Will Cooke via cctalk]

> On 10/12/2020 3:29 PM dwight via cctalk  wrote:
> 
> 
> I'm not too sure Hackers will have someone that is into Discrete Math. It is 
> way beyond what a typical engineer will go through to get a degree. It is not 
> a course someone would take without expecting to get into theoretical 
> mathematics.
> Dwight
> 
Hacker Spaces are filled with lots of different people.  Not all are engineers. 
 It might even be safe to say they are in the minority.

Will

Re: Tutor needed for college student

[dwight via cctalk]

I'm not too sure Hackers will have someone that is into Discrete Math. It is 
way beyond what a typical engineer will go through to get a degree. It is not a 
course someone would take without expecting to get into theoretical mathematics.
Dwight


From: cctalk  on behalf of Adrian Stoness via 
cctalk 
Sent: Monday, October 12, 2020 9:24 AM
To: Cindy Croxton ; General Discussion: On-Topic and 
Off-Topic Posts 
Subject: Re: Tutor needed for college student

have you looked into your local hackerspaces at all?
https://hackerspaces.org/ list of them all over the world.



>

Re: Mystery QBUS memory card

[Ethan Dicks via cctalk]

On Sun, Oct 11, 2020 at 5:38 PM Noel Chiappa via cctalk
 wrote:
> Hi, I'm trying to ID this:
>
>   http://ana-3.lcs.mit.edu/~jnc/tech/pdp11/jpg/QBUSMystMem.jpg
>
> mystery QBUS memory card. I think it's a 64KB card

It is.  4 banks of 4116 16Kx1 DRAMs.

I don't recognize the logo, but I _might_ have one of those in a
Dataram Qbus box.  I know that box has 3rd party memory but I don't
remember what brand.

Even if I do have one, I've never had a manual for it.

-ethan

Re: Tutor needed for college student

[Adrian Stoness via cctalk]

have you looked into your local hackerspaces at all?
https://hackerspaces.org/ list of them all over the world.



>

Re: Firing up the pdt11

[Chris Zach via cctalk]

Curiouser and curiouser

On a lark I got a 47 ohm (actual reading 50.1 ohms) resistor from the 
box, put it on the anode supply line of the sector pulse LED on the 
drive that is in the PDT11 (not the one with the blown LED) and hooked 
it up to the power supply.


With the resistor in I fired up the supply, set the voltage to 3v, and 
checked the current. Now the LED only draws about 30ma measured at the 
supply instead of over 120ma without the resistor. So, different.


Then I put this assembly into the actual PDT11 circuit: Now when I check 
voltage at the resistor point I see 1.9v across the diode instead of 5v. 
And when I put a disk in the PDT11 does drop the solenoid down and tries 
to "read" the disk (but fails, but it is 8 slow failures, and not 8 fast 
ones). So I think the LED is now "lit".


Then I looked closely at the wires on the actual floppy drive to board 
interface. I see on the *other* plug (the one that runs the track zero 
detection) that there *is* a small resistor in line on the harness 
itself. Haven't checked the value but I'm guessing it's 68 ohms or so. 
But there is no similar resistor on the line to the sector pulse LED. I 
just checked the broken drive, same deal.


Maybe they "forgot" the resistor on the sector pulse LED? They didn't 
put it on the board or I wouldn't see +5 with the LED lit. More 
interestingly maybe the actual disk assembly for a PDT11 is 
*deliberately different* from an RX01 so you would have to order the 
"right" specific part. I don't know; I haven't taken apart my RX02 to 
see if that resistor is in line on the disk drive itself for either of 
these.


It could also have been an oversight, I'll check the top disk to see if 
the resistor is visible. Maybe the LED works at full +5v brightness for 
awhile, then opens at +5 but is still closed at lower voltages and lights.


This brings up another issue: As these are soft-sectored, does the 
amount of light the LED produces matter? Maybe my LED+resistor is bright 
enough to trigger sector pulses, but they are now not where the data is 
anymore? How critical is sector pulse alignment for an 8 inch floppy drive.


This is progress, and this is interesting. I wonder how deep this rabbit 
hole goes...


CZ



On 10/12/2020 11:11 AM, Tony Duell wrote:

On Mon, Oct 12, 2020 at 4:04 PM Chris Zach  wrote:



In a 'real' RX01, each sensor LED (track 0 and index) has the cathode
grounded and the anode connected to +5V via a 68ohm series resistor.
If you measure the voltage across the pins with the LED disconnected
(or if the LED is open-circuit) with any reasonable meter, it'll read
5V. The meter will not draw enough current for the resistor to drop a
noticeable voltage.


Ok, that makes sense. Is the resistor on the board or on the drive wire
harness somewhere?


I'm pretty sure it's on the PCB.



I'll jumper the disk 0 sensor into my test board here (actually just the
extender board from another PDT11) and see what the voltage looks like,
then compare it to the same spot on the second drive.


I'd look at the voltage on each pin of the LED in the 3 other sensors
(index and track 0 for both drives)

-tony

Tutor needed for college student

[Cindy Croxton via cctalk]

If anyone has spare time, and is familiar with discrete mathematics, I 
have a friend who is a young college kid and desperately needs a tutor. 
His prof just says to read the book, and take online quizzes. He is 
failing. If you can help, please email me. He is in Delaware.


--
Cindy Croxton
Electronics Plus
1613 Water Street
Kerrville, TX 78028
830-370-3239 direct

Re: Firing up the pdt11

[Tony Duell via cctalk]

On Mon, Oct 12, 2020 at 4:04 PM Chris Zach  wrote:
>
> > In a 'real' RX01, each sensor LED (track 0 and index) has the cathode
> > grounded and the anode connected to +5V via a 68ohm series resistor.
> > If you measure the voltage across the pins with the LED disconnected
> > (or if the LED is open-circuit) with any reasonable meter, it'll read
> > 5V. The meter will not draw enough current for the resistor to drop a
> > noticeable voltage.
>
> Ok, that makes sense. Is the resistor on the board or on the drive wire
> harness somewhere?

I'm pretty sure it's on the PCB.

>
> I'll jumper the disk 0 sensor into my test board here (actually just the
> extender board from another PDT11) and see what the voltage looks like,
> then compare it to the same spot on the second drive.

I'd look at the voltage on each pin of the LED in the 3 other sensors
(index and track 0 for both drives)

-tony

Re: Firing up the pdt11

[Chris Zach via cctalk]

In a 'real' RX01, each sensor LED (track 0 and index) has the cathode
grounded and the anode connected to +5V via a 68ohm series resistor.
If you measure the voltage across the pins with the LED disconnected
(or if the LED is open-circuit) with any reasonable meter, it'll read
5V. The meter will not draw enough current for the resistor to drop a
noticeable voltage.


Ok, that makes sense. Is the resistor on the board or on the drive wire 
harness somewhere?


I'll jumper the disk 0 sensor into my test board here (actually just the 
extender board from another PDT11) and see what the voltage looks like, 
then compare it to the same spot on the second drive.



The thing that puzzles me is why you read 5V across an LED that seems
to work on the bench. I wonder if a connection is open somewhere.


Not many places for the connection to be open: The LED most certainly 
did work and did provide IR light on the bench and in-circuit. Weird.


C

Re: Firing up the pdt11

[Tony Duell via cctalk]

> One is for the solenoid that lowers the pad onto the disk to allow
> reads/writes.
>
> One is for the sensor to detect track 1 (LED and detector)
>
> One is for the sensor to detect sector pulse
>
> One is for the servo motor that moves the head in and out
>
> One is for the read/write head
>
> One is for the 110v power to the drive motor itself that spins the belt
> and the disk via the center spindle.
>
> I did not move the 110v power wire because that is from a common harness
> between the drives and it's pretty obvious the disk is spinning. :-) The
> other five were switched between controller channel 0 and 1 (PD0: and PD1:)
>
> At this point I think I'm onto the sector pulse LED not working due to
> 5v being applied to it. Will be working on that more this morning with a
> better/more precise power supply.

Jumping in at this point...

In a 'real' RX01, each sensor LED (track 0 and index) has the cathode
grounded and the anode connected to +5V via a 68ohm series resistor.
If you measure the voltage across the pins with the LED disconnected
(or if the LED is open-circuit) with any reasonable meter, it'll read
5V. The meter will not draw enough current for the resistor to drop a
noticeable voltage.

Of course there is no reason why the resistor couldn't be between the
cathode and ground (with the anode connected to +5V). It's a simple
series circuit, the current is the same everywhere.

The thing that puzzles me is why you read 5V across an LED that seems
to work on the bench. I wonder if a connection is open somewhere.

-tony

Re: Firing up the pdt11

[Chris Zach via cctalk]

When you swap the cables (and keep the drives in place), do you mean
that you swapped the data connection **and** the power supply cable(s)?


There are six wire bundles and connectors that hook an RX01 floppy drive 
sub-module to the RX01 read/write controller board (or the PDT11 
controller board)


One is for the solenoid that lowers the pad onto the disk to allow 
reads/writes.


One is for the sensor to detect track 1 (LED and detector)

One is for the sensor to detect sector pulse

One is for the servo motor that moves the head in and out

One is for the read/write head

One is for the 110v power to the drive motor itself that spins the belt 
and the disk via the center spindle.


I did not move the 110v power wire because that is from a common harness 
between the drives and it's pretty obvious the disk is spinning. :-) The 
other five were switched between controller channel 0 and 1 (PD0: and PD1:)


At this point I think I'm onto the sector pulse LED not working due to 
5v being applied to it. Will be working on that more this morning with a 
better/more precise power supply.


CZ

Re: FIRE SALE!

[rice43 via cctalk]

-- Original Message --
From: "Al Kossow via cctalk" 
To: "General Discussion: On-Topic and Off-Topic Posts" 


Sent: Monday, 12 Oct, 2020 At 00:54
Subject: FIRE SALE!
http://www.vcfed.org/forum/showthread.php?77118-Fire-sale-PDP-11-stuff 

Seems my account isn't activated (still), could these pics be posted 
somewhere there isn't a login-wall?

RE: Firing up the pdt11

[Henk Gooijen via cctalk]

See below.

Van: Chris Zach via cctalk
Verzonden: maandag 12 oktober 2020 03:14
Aan: Richard Pope; On-Topic and Off-Topic 
Posts
Onderwerp: Re: Firing up the pdt11

Well, by "location" I mean there are plugs on the controller board for
PD0 (typically called the "top" drive) and PD1 (typically the "bottom"
drive). My test swapped the cables so the top drive was using the PD1:
logic on the board and the "bottom" was using the PD0 logic. In that
situation the PD1: channel with the top drive worked so the problem is
not in the logic board.


Chris,
When you swap the cables (and keep the drives in place), do you mean
that you swapped the data connection *and* the power supply cable(s)?

Henk