Date   

Re: Your generosity is STUNNING!

Brian Cockburn
 

Dennis,

Just as a frivolous matter, what contribution value would have resulted in enough to pay this year's bill given the number of contributers?

My vote is also to put the money aside for the future of the group please.

Regards, Brian (with a 2245A in the UK).


Re: 7L5 dot frequency reset bug - any clues or a fix?

Dave Casey
 

Cliff -

Did you see my response from December 8? I have a late 7L5 (> B090000) that
doesn't sound like it works any better than yours with respect to the reset
behavior.

Dave Casey

On Mon, Jan 20, 2020 at 12:19 AM Cliff Carrie <cliffcarrie@hotmail.com>
wrote:

UPDATE:
The change of U830 (dot frequency counter) from PN 155-0117-00 to
155-0198-00 at 7L5 SN B060000 changes this part from a leadless ceramic
carrier to a leaded (DIP) ceramic carrier. I don't know yet if the reset
bug was fixed in the newer chip, Having recently acquired one of the later
155-0198-00 leaded chips, I wonder if it could be installed, temporarily
for a test or permanently in the leadless carrier socket without damaging
it. Pinout seems unchanged. I visualize a plastic backup block under the
chip between the two rows of pins to hold them against the leadless socket
contacts. I can easily create a pressure pad between the chip and the
adjacent circuit board to ensure it doesn't pop out of the socket.

Has anyone ever tried this (installing a DIP leaded chip) in any leadless
socket (not necessarily in a 7L5)?

I certainly don't want to replace the 40 pin socket for a test that may
show no change and/or some new incompatibility.

One more note: the serial number on a 7L5 does not tell the whole story
about the circuit level. Tek released at least 3 versions of a major update
kit 040-0872-xx. If your 7L5 has an added front panel "B - save A" lighted
pushbutton it is B070000 or higher or has this kit installed. Mine with
serial B03xxxx and the 040-0872-01 kit is equivalent to at least SN
B081400. Two boards (Storage and Digital Averaging) were also replaced with
a single board. Note that there are other serial numbers where boards
changed part numbers, but auditing my 7L5 against the manual, there don't
seem to be any circuit changes or improvements not covered in the update
kit.

Cliff Carrie




Re: 7L5 dot frequency reset bug - any clues or a fix?

Cliff Carrie
 

UPDATE:
The change of U830 (dot frequency counter) from PN 155-0117-00 to 155-0198-00 at 7L5 SN B060000 changes this part from a leadless ceramic carrier to a leaded (DIP) ceramic carrier. I don't know yet if the reset bug was fixed in the newer chip, Having recently acquired one of the later 155-0198-00 leaded chips, I wonder if it could be installed, temporarily for a test or permanently in the leadless carrier socket without damaging it. Pinout seems unchanged. I visualize a plastic backup block under the chip between the two rows of pins to hold them against the leadless socket contacts. I can easily create a pressure pad between the chip and the adjacent circuit board to ensure it doesn't pop out of the socket.

Has anyone ever tried this (installing a DIP leaded chip) in any leadless socket (not necessarily in a 7L5)?

I certainly don't want to replace the 40 pin socket for a test that may show no change and/or some new incompatibility.

One more note: the serial number on a 7L5 does not tell the whole story about the circuit level. Tek released at least 3 versions of a major update kit 040-0872-xx. If your 7L5 has an added front panel "B - save A" lighted pushbutton it is B070000 or higher or has this kit installed. Mine with serial B03xxxx and the 040-0872-01 kit is equivalent to at least SN B081400. Two boards (Storage and Digital Averaging) were also replaced with a single board. Note that there are other serial numbers where boards changed part numbers, but auditing my 7L5 against the manual, there don't seem to be any circuit changes or improvements not covered in the update kit.

Cliff Carrie


Re: What Tektronix means to me

Dave Seiter
 

Grin!  Things were different back then.  In high school we had dial up line to a HP2000 at the Stanford business school using DECWriters, and one could wander through the directories, browsing students projects. It was usually very responsive, but sometimes it would really bog down, and we'd have to use one of the in-class micros (PET/APPLEII/TRS80) to work on our projects.  But they were all more reliable than our PDP8/E; we had to use that for Fortran, and it was always breaking down.  I think I was one of the last people to learn how to use a keypunch machine!
-Dave

On Saturday, January 18, 2020, 09:43:04 AM PST, Dennis Tillman W7PF <dennis@ridesoft.com> wrote:

Hi David,
Something similar happened to me when I tried counting clock cycles on a mainframe:
I learned assembly language programming by myself on the S-100 microcomputer I built. When you need a delay in a microcomputer program you use a software loop. You look up how many clock cycles are in each loop instruction and then you divide the time delay you want by the total clock cycles in the loop. That gives you your loop count.

I learned the hard way this doesn't always work. I was working on some simple software that ran on an IBM 370 mainframe when I needed my program to wait a few seconds when a particular situation arose. I had no way to know how long the 370 clock cycle was or how many cycles each instruction used. So I just guessed. I started out with a small number at first and kept raising the loop count until I got a long enough delay. It was not that straightforward however. For one thing I couldn't figure out why the delay was not consistent. Sometimes it seemed shorter than I wanted and other times it seemed longer. It was good enough so I forgot about it.

A few days later my manager called me into his office. He asked me to explain the latest computer bill he had received which showed I used over $7,000 worth of computer time that week. I was stunned and had no explanation. When he took a look at my program he broke out laughing. I was on a timesharing system and each time my program put the IBM 370 in a loop the entire mainframe was dedicated to me for those few seconds. During normal business hours that mainframe was handling anywhere from 200 to 300 other users and I was sharing it with everyone else. But I was developing and testing my software in the evening when I almost always had the entire 370 to myself. Each time the 370 encountered my delay loop it ran full out doing nothing at all. What I did not know was when you are using a time shared computer you pay for how much of the mainframe's CPU cycle time you consume. Fortunately the billing department also had a sense of humor and forgave me for making a novice mistake.

When you want a delay on a mainframe you insert a "pause" instruction in your code and specify how many seconds you want to wait. The mainframe sets a timer and takes care of everyone else until the timer goes off and then it resumes running your program.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave Seiter
Sent: Friday, January 17, 2020 11:20 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] What Tektronix means to me

I took an assembly language class once where we had to build a working traffic light simulator for a normal intersection using a very simple assembler.  One of the primary objectives was understanding the cycle counts of commands and how they related to the micro's timing.  We discovered that published data is not always correct...
-Dave




--
Dennis Tillman W7PF
TekScopes Moderator


Re: Risetime calculator (in tekwiki)

Roy Thistle
 

On Sun, Jan 19, 2020 at 12:03 PM, Chuck Harris wrote:


And, the schematic is just fine. The negative terminal is
implied.
Hi Chuck:
Ok. That's a roger.
I removed the comment.
As long as the connection(s) are implied there won't be any confusion.
Best regards and wishes.
Roy.


Re: Risetime calculator (in tekwiki)

Roy Thistle
 

On Sun, Jan 19, 2020 at 12:03 PM, Chuck Harris wrote:


Roy, your last two comments make no sense.

Albert has already determined that the taper of the pots is
*linear* and the scales of the two pots are *linear*, and
proved it out mathematically.
Hi Chuck:
Yes! Thanks. I need to be reminded to make sense!
Sometimes I get confused.
I deleted my last three comments.

I saw all the the 5000 ohm pots are paralleled with a ( 4.95K resistor in series with a trimpot)... but I read the following.

#163442 On Fri, Jan 17, 2020 at 08:14 AM, Chuck Harris wrote:


Of course it is an analog computer!

It is using the sum of three log pots to balance with a fourth
to get a result that is read on the fourth dial.
Thus... no matter what the math told me, I thought Chuck knows they are log pots... that's what he wrote... so what gives... I've got to figure out how it works using log pots.
Best regards and wishes.
Roy


TDS3000B polarizer film

Tom B
 

Hello All,

I picked up a TDS3012B oscilloscope with a bad polarizer on the LCD.  It looked like it was melted or something but there was no other damage to the 'scope.  I have no idea how it got that way.

From what I can see see, the display is working but without the polarizer there isn't much you can see.

The display is an NEC6448C20-08.  Polarizer film comes in 0, 45, 90, and 135 degrees.  How can I determine the correct polarizer to use?

Tom Bryan
N3AJA


Re: Your generosity is STUNNING!

Petru Ulici
 

Hello, Dennis and Michael
Just try to reconsider your decision to return the amount.
Arguments:I think that the fees for the transaction (transfer + return) is not returnable, it will only be Paypal profit.You will spend a lot of time to return the amountThe group tax will definitely increase in the next years.In the future, probably the group will exceed the reserved space and there will be additional costs.All participants do this from hearts and consider this to be one of the best investments.The transfer of  $50 may be less financial effort than $5 from the other member.Everyone trusts you and Michael Dunn.I personally suggest that you and your wife (and Michael, too) spend something for a romantic dinner. This way, we can partially compensate the time spent for this group, not with your family. I think everyone agrees, your contribution to this group is wonderful.
Petru

On Monday, January 20, 2020, 01:59:47 AM GMT+2, Phillip Potter <p.potter@sbcglobal.net> wrote:

Soooo, do what others suggest, nice dinner for you, Michael, and your
wives!!!

Phil

On 1/19/2020 1:43 PM, Siggi wrote:
Hey Denis,

looks like many people have reported they don't see their PayPal
transaction IDs in your log. I'm going to guess that PayPal assigns
different transaction IDs for each end of the transaction, at least in the
case where there are fees to pay and/or a currency exchange to be made.

Siggi


Re: Your generosity is STUNNING!

Dave Brown
 

Dennis
Would prefer you just hang onto the money- you'll need it next time anyway.
International xfers thru paypal always cost something nowadays-best to keep it for next time.
DaveB, NZ


Re: Your generosity is STUNNING!

Phillip Potter
 

Soooo, do what others suggest, nice dinner for you, Michael, and your wives!!!

Phil

On 1/19/2020 1:43 PM, Siggi wrote:
Hey Denis,

looks like many people have reported they don't see their PayPal
transaction IDs in your log. I'm going to guess that PayPal assigns
different transaction IDs for each end of the transaction, at least in the
case where there are fees to pay and/or a currency exchange to be made.

Siggi


Re: Risetime calculator (in tekwiki)

Tony Fleming
 

Where is the calculator?
I do not want the virus one - someone said that one downloadable calculator
was a virus or bad calculator....
Thank you very much.
Tony

On Sun, Jan 19, 2020 at 9:15 AM Roger Evans via Groups.Io <very_fuzzy_logic=
yahoo.com@groups.io> wrote:

Albert,

Thanks for pointing that out, the calculator is quite different to what I
had imagined. I thought the resistance would increase in the clockwise
direction and each pot would just be connected as a two terminal variable
resistor. That does rely on having a good approximation to a square law
for the taper of the pot. As you pointed out the resistance increases ccw
and I can't see immediately why the maths works for the combination of
fixed resistor in parallel with the three terminal connected pot. It might
be a rather clever piece of algebra or an approximation that is good enough
for the intended application.

Roger




Re: Your generosity is STUNNING!

Siggi
 

Hey Denis,

looks like many people have reported they don't see their PayPal
transaction IDs in your log. I'm going to guess that PayPal assigns
different transaction IDs for each end of the transaction, at least in the
case where there are fees to pay and/or a currency exchange to be made.

Siggi

On Sat, Jan 18, 2020 at 11:57 AM Dennis Tillman W7PF <dennis@ridesoft.com>
wrote:

Wrapping up the TekScopes pledge drive, Michael Dunn and I are STUNNED by
your generosity and all the positive comments we received. Your
contributions have exceeded the $340 paid to Groups.io by almost 1,000%.
You
sent us 203 contributions totaling $3,341.77!

We agree this is a problem that I will have to fix since it was my bright
idea. I did not realize when I sent my request for help that people would
be
so generous. I wrote, "So I am asking for small contributions". What
happened was anything but "small".

Leo Bodnar, a friend, stunned me when he contributed the entire required
amount two days later. This was the first sign I should have chosen a
synonym such as "tiny" or "teeny" instead of small. It was too late at that
point. I could see there was a tsunami headed my way and I had no way to
stop it. I think the contributions have finally stopped. The last one (I
hope) arrived three days ago.

Michael and I have decided that this is far too much money for us to keep
on
behalf of TekScopes. The simplest solution is for us to tear up the checks
and return all the PayPal contributions above $10.00 (actually all those
above $10.05) over the next few days, with our sincerest thanks. This will
result in exactly half of the contributions being kept and half being
returned. PayPal allows me to do a total refund very quickly; we considered
partial refunds, but the process would take much longer. If, after you
receive your refund, you would still like to make a contribution to
TekScopes, please don't send more than $10.00. If you do, we'll be forced
to
spend it on wine and DMMs.

Thank You,
Dennis Tillman W7PF
Michael Dunn VA1XY

As I promised, here is every contribution I received. The four checking
account contributions are listed in numerical order by their bank account
number. Following those, the 199 PayPal contributions are listed in
numerical order by their transaction number. I double and triple checked
the
PayPal notices that came to me or to my wife, Marian, to be sure I didn't
miss any. If I missed your PayPal contribution please let me know so I can
find out what happened to it. The most common contribution was $10.00 and
the average contribution was $15.94.

CHECKING ACCOUNT
0000*255 $50.00 TO BE REFUNDED
0035*054 $20.00 TO BE REFUNDED
4650*2065 $50.00 TO BE REFUNDED
9179*1067 $50.00 TO BE REFUNDED

PAYPAL TRANSACTION
02079*******9581B $10.00
03E74*******9033E $100.00 TO BE REFUNDED
05P54*******33704 $20.00 TO BE REFUNDED
0DV52*******9640N $20.00 TO BE REFUNDED
0FX24*******0225D $12.61 TO BE REFUNDED
0GH61*******5321H $10.00
0H164*******7324J $5.00
0HP31*******79205 $10.00
0TB16*******6233S $10.00
0V228*******9483Y $15.00 TO BE REFUNDED
0WE54*******4492F $20.00 TO BE REFUNDED
0XD49*******99831 $10.00
0XX33*******5571C $20.00 TO BE REFUNDED
10F89*******59157 $20.00 TO BE REFUNDED
11D81*******1581M $25.00 TO BE REFUNDED
13W62*******8082B $5.00
16621*******82104 $20.00 TO BE REFUNDED
16T81*******89037 $21.00 TO BE REFUNDED
16U30*******4884J $10.00
17T42*******7831E $10.00
1C179*******04615 $10.00
1C830*******8112P $10.00
1KB10*******35308 $10.00
1KC35*******1823E $10.00
1KK41*******81702 $40.00 TO BE REFUNDED
1MJ87*******7921S $20.00 TO BE REFUNDED
1PL71*******8194S $20.00 TO BE REFUNDED
1SF61*******75325 $6.28
1U469*******7321A $10.00
1UN19*******71331 $21.50 TO BE REFUNDED
1XL88*******0010V $10.00
21K47*******0942J $5.00
26M35*******2652B $20.00 TO BE REFUNDED
26W48*******18439 $10.00
27955*******6435G $2.00
28784*******31459 $10.00
2AJ63*******9742M $20.00 TO BE REFUNDED
2BB60*******7284T $10.05
2C041*******7435F $15.00 TO BE REFUNDED
2CF51*******55300 $10.00
2GN07*******6691P $21.36 TO BE REFUNDED
2HA37*******2763N $20.00 TO BE REFUNDED
2JP56*******9614M $6.00
2L669*******5001S $20.03 TO BE REFUNDED
2LL81*******2181A $10.00
2NX73*******6334E $25.00 TO BE REFUNDED
2PE83*******8434J $20.00 TO BE REFUNDED
2R866*******6484Y $25.00 TO BE REFUNDED
2S663*******60054 $10.00
2UD84*******92512 $20.00 TO BE REFUNDED
2WG55*******8174X $10.00
30988*******3613G $10.00
31532*******3440H $25.00 TO BE REFUNDED
32S52*******3263Y $25.00 TO BE REFUNDED
33N46*******8874F $20.00 TO BE REFUNDED
35J04*******2071X $5.00
37611*******3481X $30.28 TO BE REFUNDED
38D56*******6900H $40.00 TO BE REFUNDED
38H00*******74637 $10.00
39503*******91844 $10.00
3C222*******60057 $5.00
3DL81*******49307 $10.00
3DN03*******6580W $10.00
3HN95*******74316 $20.00 TO BE REFUNDED
3JY75*******0415H $10.00
3MK47*******8000V $20.00 TO BE REFUNDED
3ML12*******7670M $30.00 TO BE REFUNDED
3RW61*******7583B $110.00 TO BE REFUNDED
3SV52*******0093K $10.00
3U066*******6064R $10.00
3W759*******4273V $10.00
3WN84*******32644 $20.00 TO BE REFUNDED
3X630*******09454 $10.00
43V15*******1315P $30.00 TO BE REFUNDED
43W14*******2963X $10.00
4C132*******25402 $20.78 TO BE REFUNDED
4CP43*******1271K $15.00 TO BE REFUNDED
4E489*******92025 $20.00 TO BE REFUNDED
4GU02*******14949 $10.00
4H892*******5443S $10.00
4NK97*******39943 $30.00 TO BE REFUNDED
4NS27*******8414L $20.00 TO BE REFUNDED
4PM01*******5380X $10.00
4RA41*******16029 $20.00 TO BE REFUNDED
4V179*******50029 $25.00 TO BE REFUNDED
4VU25*******5244C $10.00
4WE10*******2420U $12.00 TO BE REFUNDED
4WG41*******2952L $20.00 TO BE REFUNDED
4XH55*******98246 $10.00
4XM94*******9951L $20.00 TO BE REFUNDED
4XU29*******2203A $5.00
52Y94*******9314H $10.00
53E69*******9450U $15.00 TO BE REFUNDED
53M48*******1162D $10.04
54264*******83607 $20.00 TO BE REFUNDED
54350*******3123J $10.00
56419*******9740B $10.68 TO BE REFUNDED
57958*******19248 $10.00
57M28*******3463Y $15.00 TO BE REFUNDED
58J72*******8751M $5.05
59K74*******6614F $10.00
59M25*******3721R $10.72 TO BE REFUNDED
5FC22*******9632C $10.00
5GA43*******4223M $5.00
5K650*******2512S $10.00
5L001*******9890K $30.00 TO BE REFUNDED
5L631*******0780F $5.00
5P795*******19647 $20.00 TO BE REFUNDED
5SE25*******18324 $20.00 TO BE REFUNDED
5UP40*******89642 $20.00 TO BE REFUNDED
5UU92*******40032 $10.20
61H86*******4671Y $15.00 TO BE REFUNDED
61W04*******0651P $5.00
62172*******4981K $10.03
62762*******2074B REFUNDED
64M95*******0450J $20.20 TO BE REFUNDED
69567*******7993L $10.00
69G97*******6681W $5.00
6AX91*******2221W $10.00
6DC49*******7192J $2.20
6DY20*******43532 $10.00
6FR77*******2981V $20.00 TO BE REFUNDED
6GH42*******5101K $25.00 TO BE REFUNDED
6JF13*******51538 $13.42 TO BE REFUNDED
6M239*******2634X $20.00 TO BE REFUNDED
6M818*******3010R $10.75 TO BE REFUNDED
6MW55*******8294T $4.00
6NN32*******4542V $10.00
6PN72*******3184X $20.00 TO BE REFUNDED
6SJ24*******7280W $10.00
6TX54*******6691J $10.00
6UC87*******60625 $5.00
6W050*******3122G $25.00 TO BE REFUNDED
6YC11*******1694V $10.00
6YR09*******24211 $10.00
70R50*******48816 $40.00 TO BE REFUNDED
71A57*******04246 $20.00 TO BE REFUNDED
71B15*******9210H $5.00
77749*******2345C $5.00
7AA50*******6582S $5.00
7BH77*******10502 $10.00
7C686*******0453C $20.00 TO BE REFUNDED
7C834*******0923E $10.00
7CK01*******1245K $5.00
7D080*******7730E $10.00
7HC88*******8542G $50.00 TO BE REFUNDED
7JC48*******6100G $50.00 TO BE REFUNDED
7LV25*******2193G $30.00 TO BE REFUNDED
7M285*******92740 $25.00 TO BE REFUNDED
7MK85*******1842C $10.00
7MS44*******5362B $15.00 TO BE REFUNDED
7NK34*******5412S $31.44 TO BE REFUNDED
7PE90*******5070C $15.00 TO BE REFUNDED
7PW51*******11256 $5.00
7SB72*******7192F $20.00 TO BE REFUNDED
7UJ45*******9004U $5.00
7V986*******7741K $10.00
7WL39*******4140E $10.00
80874*******3273N $20.00 TO BE REFUNDED
82A24*******71901 $20.00 TO BE REFUNDED
85T72*******59347 $10.00
86464*******0522V $25.00 TO BE REFUNDED
89L93*******2080C $20.00 TO BE REFUNDED
8AB06*******94251 $20.00 TO BE REFUNDED
8BM27*******0873M $20.00 TO BE REFUNDED
8BP86*******45402 $20.00 TO BE REFUNDED
8DF32*******6052V $10.00
8EJ68*******08541 $12.00 TO BE REFUNDED
8FJ75*******8872W $20.00 TO BE REFUNDED
8GC22*******34141 $25.00 TO BE REFUNDED
8GT73*******09326 $12.61 TO BE REFUNDED
8MC99*******59946 $11.00 TO BE REFUNDED
8N867*******6281R $20.00 TO BE REFUNDED
8P783*******6711A $23.00 TO BE REFUNDED
8PJ76*******6821F $10.00
8TL81*******09540 $20.00 TO BE REFUNDED
8X573*******06030 $10.00
8XN50*******4422L $20.00 TO BE REFUNDED
90T91*******35713 $10.00
91410*******3142B $10.00
91U38*******2105T $11.00 TO BE REFUNDED
92261*******0350X $10.00
94C22*******3914J $50.00 TO BE REFUNDED
97618*******3223U $20.00 TO BE REFUNDED
98Y68*******70508 $1.24
99954*******8720E $5.00
9A088*******0853S $20.00 TO BE REFUNDED
9AP46*******63352 $10.00
9B390*******8403F $10.00
9DH47*******6461J $10.00
9GJ81*******0164P $10.00
9HK96*******73147 $25.00 TO BE REFUNDED
9HS74*******5364F $20.00 TO BE REFUNDED
9HY36*******94500 $10.00
9KN17*******5330K $5.00
9N383*******7605L $5.36
9SK43*******0851N $22.57 TO BE REFUNDED
9SN87*******3420T $10.00
9UB93*******8990M $20.00 TO BE REFUNDED
9V074*******7422K $5.37





--
Dennis Tillman W7PF
TekScopes Moderator




Re: Your generosity is STUNNING!

Paul Amaranth
 

I concur. Consider it an appreciation award from the members of Tekscopes :-)

Paul

On Sun, Jan 19, 2020 at 01:17:54PM -0800, Errick wrote:
A nice dinner for two $250
A couple of bottles of wine $100
Taking care of TekScopes, Priceless!
Dennis and Michael should: Put some of the money in your wallets.
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix & Windows


Re: Your generosity is STUNNING!

Errick
 

A nice dinner for two $250
A couple of bottles of wine $100
Taking care of TekScopes, Priceless!
Dennis and Michael should: Put some of the money in your wallets.


Re: Your generosity is STUNNING!

Richard in Edenton NC
 

Dennis, I did not see mine in the list.

January 1st for $20.00

3SH79206CC5260117 via PayPal

I don't need it back. Please put it in a savings account aside for the future of the group. Or donate to a local ham club. Glad the group is here and I learn lots and enjoy it much.

73 Richard W4MCD


Re: 465 (Late S/N) Timing Board (A7) 670-3467-00?

DaveH52
 


Re: Your generosity is STUNNING!

DaveH52
 

Maybe ask for just one dollar next time.
Enjoy your new DMM!


Re: Risetime calculator (in tekwiki)

Albert Otten
 

On Sun, Jan 19, 2020 at 09:07 PM, Leo Bodnar wrote:


It's not intuitive but if you do the math it is, indeed works out perfectly
linear - assuming the trim pots are set to the value of 50R.
Whoever designed it, deserves to be an employee of the month.
These days such a gadget would have at least some duino inside it.
Leo
On Sun, Jan 19, 2020 at 05:28 PM, Albert Otten wrote:
Actually the math appears to be surprisingly simple and in theory the
instrument shows EXACT results with LINEAR pots..
This originates I think from the idea that around a maximum or minimum a function is quadratic plus higher order terms.
If you short together both ends of a linear pot then the resistance to the wiper is maximum midway and decreases quadratically (in this case exact, without higher order terms) when moving away from midway. In our instrument consider a wiper as a wiper of a 10 k pot, blocked midway in one direction.
I must confess that I only recognized the trick after further investigation.

Albert


Re: Your generosity is STUNNING!

Phillip Potter
 

Hi Dennis,

As a list owner, I can attest to the amount of work that it can be.

PLEASE keep my donation for the future, and even (as someone else said) take your wife and Michael and his wife out to a nice dinner on us.

Best wishes for 2020,

Phil


Re: Risetime calculator (in tekwiki)

Leo Bodnar
 

It's not intuitive but if you do the math it is, indeed works out perfectly linear - assuming the trim pots are set to the value of 50R.
Whoever designed it, deserves to be an employee of the month.
These days such a gadget would have at least some duino inside it.
Leo

On Sun, Jan 19, 2020 at 05:28 PM, Albert Otten wrote:
Actually the math appears to be surprisingly simple and in theory the instrument shows EXACT results with LINEAR pots..

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