Date   

Re: Tek 4041 GPIB Controller

Gary Robert Bosworth
 

Monty: My 4041 has a full complement of functionality. It has the full
512KB ram memory. The system looks basically like it is brand new. I would
be interested in purchasing one of your 5-1/4" 360KByte floppies with all
of the files on it. My floppy drive is in excellent condition and should
be capable of transferring the files directly to the hard disk without the
use of the flaky tape drive. It is not easy to obtain these original low
bite count floppies, because the 1.2 MByte high-density type became the
most widely used and are still quite available.

Gary

On Mon, Nov 23, 2020 at 4:27 PM Monty McGraw <mmcgraw74@...> wrote:

I'm making a little progress.

I transcribed the DDU service manual program to copy a tape file to a
floppy disk file - and copied all the System Verification tape files to a
floppy. I did run into problems with my DDU floppy drive - the spindle
drive motor won't start up correctly - so my temporary workaround is to
slightly eject the floppy, with causes the motor to start running, then I
reinsert the floppy and close the lever before the program attempts to
access the floppy. I got all the files copied onto a NOS floppy disk.

Then I wrote another program to copy every file on the floppy to the tape
drive. This program is much trickier to work with my bad floppy drive, and
fails after a couple of files copied to tape - but should work if you have
a working DDU and floppy drive (Gary :) )

I found a bug in my 4041 tape dump program - and modified it to make the
program to copy every file on the System Verification tape to disk -
however, you will need a 4041 with 512KB of memory to load the program :(

I haven't uploaded these programs to my github repository yet. Are there
any folks out there - ready to try these programs?

Monty






--
Gary Robert Bosworth
@grbosworth
Tel: 310-317-2247


Re: Resistor in series

SCMenasian
 

In my earlier days (pre 1970), I used to "trim" carbon composition resistors by carefully overheating them with a soldering iron to raise their values slightly. This may have also improved their stability by getting the early ageing out of the way (although I never verified this).


Re: 465 B sweep switch cam

Michael W. Lynch
 

On Tue, Dec 1, 2020 at 12:59 AM, Dave Peterson wrote:


I think JB Weld is a good solution for the B switch cam/shaft joint. It's slow
curing, and yeah, the knurling will make a great bonding surface. And I can
see where I need to be super careful about getting it into the spring portion.
But knowing what to avoid it should be no problem.
I have repaired a 465 (not "B") in this manner. Actually "reassembled" that little plastic part on the shaft from the pieces recovered from inside the drum. Tedious job, but JB Weld did the job. One thing that I will mention is that there are several designs of this mechanism within the 4X5 series. The 465 uses a couple of different versions, depending on serial number, I don't think that there will be interchangeability between the 465B and the 475, but I could be wrong.

--
Michael Lynch
Dardanelle, AR


Re: 7854 - No RO in SCOPE + WF modulates RO in STORED

Albert Otten
 

On Tue, Dec 1, 2020 at 01:54 AM, Ram wrote:

Thanks Albert. I'm wondering if the fact that there is absolutely no readout
in SCOPE mode (rather than a wobbly readout) would direct me to a different
starting point.
Best - Ram
No, in hindsight (after reading your messages once more) I see that your 'scope very likely has another problem.
After some searching in the manual I found U1720 at diagram 25, board A29. It would have been faster to search for U1720 in the old messages. There I saw it's 9 years ago that I looked at that schematic! At this moment I'd rather not repeat that because it's distracting me too much from other Tektronix "jobs" I'm doing.
Success,
Albert


Re: I give up.

Jean-Paul
 

Dennis has given information on how to pay by check

I used PayPal account with no issues, paid from my PayPal balance, not a credit card.

Jon


Re: 465 B sweep switch cam

Dave Peterson
 

I'm going to post the picture(s) I took of the disassembled Time/Div switch assembly.
D.


Re: 465 B sweep switch cam

Dave Peterson
 

I think JB Weld is a good solution for the B switch cam/shaft joint. It's slow curing, and yeah, the knurling will make a great bonding surface. And I can see where I need to be super careful about getting it into the spring portion. But knowing what to avoid it should be no problem.

I just took the setscrews out of the B time/div knob, and remember now what my big concern is here: it's just loooose. But it doesn't come apart. I'm very afraid of cracking something forcing it apart. And it doesn't come apart enough to get any glue into it. If there's any apparent theme to my newbie questions here is that I don't know what I'm dealing with. Once apart I'll know what the issues are. I know that most of the time things turn out fine and aren't as big an issue as I fret. But I like to know what I'm getting into before I go breaking things. Kind of like taking the CRT out. Freeking scary as heck, but turns out more easy than I could have imagined. Still, a very good thing to be concerned and careful about.

So anyone know what a broken B time/div knob looks like? Will I break the plastic trying to get it off the metal internals? I've been going through the photos and haven't seen a "naked" one yet.

Dave


Re: 465 B sweep switch cam

stevenhorii
 

Just a suggestion for gluing plastic to metal. I have found the slow-cure
epoxies to be generally stronger than the quick-cure ones. I bought some
"industrial" epoxy from Loctite (Hysol 1C - not cheap, cost me about $17
for 4oz). I used it to glue the hand loop of a pair of scissors back
together. The full-strength cure time was specified as 24 hours, but it was
reasonably hard in about three hours. However, I waited for 24 hours before
using the scissors. It was a pretty small contact area, but it has held
despite my using those scissors to cut through cardboard and the like. I
did not think it would hold through that kind of stress. My other use for
it is not for bonding stuff. It's for printing durable letters onto
surfaces. This epoxy is white.

The knurling on the shaft ought to provide a nice surface area for bonding
in your gluing task.

Steve H.

On Mon, Nov 30, 2020 at 9:49 PM Dave Peterson via groups.io <davidpinsf=
yahoo.com@groups.io> wrote:

Hi all,

I know this is a common problem, and have seen a nice description here:

https://forum.tek.com/viewtopic.php?f=568&t=138253&sid=c827508d3401e2cd90eb52f42415517a

In his fix he replaced some of the inner guts of the switch cam. In my
switch the shaft just spins in the cam. It doesn't come out, but just spins.

I found a listing for the part number, 105-0364-00, on eBay. It arrived
Friday and I just tried to install it. To my disappointment it's not a 1-1
match with mine. I'll reach out to the seller to see if we can't figure out
what's happened here, but when it comes to eBay I'm sure it's a sold as-is
thing, and buyer assumes all risk.

In frustration I went back to the old cam and tried to see if the shaft
would come apart, and with a little extra "encouragement" the shaft did
come out leaving all the attached innards inside the cam. The only thing
that came with the shaft was a ring-clip, which looks similar to the
picture in the above tek forum post. What's interesting is that in my case
there's just a lot of plastic powder filling the knurling where the shaft
used to bond to the cam.

My question is: can I just JB Weld the knurled part of the shaft to the
cam?

I'd clean the knurling of old decayed plastic, and make a bead of JB Weld
at the beginning of the knurling so it would spread as the shaft is
re-inserted to the cam.

Thing is, I have no idea what's going on inside the cam. There's obviously
some kind of spring mechanism for the pull release of the B-delayed sweep
time/div knob. Would the JB Weld just freeze all this up? I wouldn't go
nuts with the JB Weld. I really love that stuff and have fixed a lot of
hopeless cases with it. I think it might work in this case, but I'd prefer
to take the cam apart to re-bond the shaft to the inner workings directly.
But I have no idea how to disassemble the cam. Any ideas? I haven't found
anything here or elsewhere with a how-to for that part of the job.

And finally, is there any sharing of part numbers across models? Could
this "new" 105-0364-00 belong to something like a 475? I got the part
number from the 465 Service manual I have. I don't think my A7 board is any
different than other 465s. It's a high serial number 310XXX. I think it has
to be a different switch cam that got the wrong tag on it somehow
(nefarious or otherwise). It's an original looking Tektronix tag - old
paper, Tek logo, etc.

Thanks for any help or pointers to other threads that deal with this.
Dave






Re: 465 B sweep switch cam

Dave Peterson
 

I was showing my wife what happened and went through the 465B and 475 parts manuals from the Tek Wiki. To show her how similar the scope faces are, but also to look up the part numbers in the service manuals. They're all different. I think it's the 475 that has a similar part number, 105-0362-01 I think? Where the 465 is 105-0364-00.

After getting the shaft out (there's a joke there somewhere), I can pretty much see how this thing is put together. I'm going to JB Weld it and see how it goes. I really have nothing to loose at this point.

I also sent a note to the seller on eBay. We'll see where that goes!

I'm mostly curious about the knob attachment  to the metal body. I'm not convinced/ready to glue it yet. I would like to know if it should be removable.

Dave


Re: 465 B sweep switch cam

 

How similar is the 465's sec/div switch cam to the 475's, I wonder. I've got 3 "parts" 475s and could probably spare one of the switch cam assemblies. If you had a full drum and shaft assembly would you be able to disassemble it and replace the drum?

I haven't spent any time studying the sec/div knob in either the service manual or the physical units, but I'm going to be transplanting the front panel from one of the parts machines onto another one at some point, and I could harvest the drum and shaft assembly for you, if you would like.

-- Jeff Dutky


Re: 465 B sweep switch cam

Dave Peterson
 

Related:
The grey B time/div knob is supposed to be bonded to the metal part of the switch, right?
Mine is loose and only the "tails" of the setscrews in the holes are holding the plastic in position.
I ask because I'm all ready to JB Weld this thing together, but don't want to ruin an otherwise good knob - if it's supposed be this way. Or supposed to be able to come apart. Once I glue it it's never coming apart again!

This scope is physically in otherwise really good condition. What the heck are people doing to these switches!? This whole B sweep switch/knob has obviously been physically ripped apart.

Dave


Re: 465 B sweep switch cam

 

On Tue, Dec 1, 2020 at 03:48 AM, Dave Peterson wrote:


I know this is a common problem, and have seen a nice description here:
https://forum.tek.com/viewtopic.php?f=568&t=138253&sid=c827508d3401e2cd90eb52f42415517a
Just had a quick look at your post, Dave, but no time to read thoroughly: It's almost 4 AM where I live (Netherlands, GMT+1).
You seem to ask if you can just glue the aluminum shaft to the drum. If so, the answer is "yes". I did that for a friend of mine about 5 years ago and it's been posted somewhere in this group, because someone else asked. I used superglue, the water-like varitey, which just flows into the space between shaft and drum, being very careful to avoid glueing everything together. ISTR I covered part of a shaft with silicon grease to avoid stiction there but can't remember at the moment.
With care, it proved a lot easier than thought.

Raymond


Re: Horizontal Display switch shenanigans.

 

On Tue, Dec 1, 2020 at 03:44 AM, Dave Peterson wrote:


Just the internal plastic piece that broke.

Thanks for kicking me in the right place to jar my brain loose.
Glad and good to know it works on this mechanism too.

Raymond


465 B sweep switch cam

Dave Peterson
 

Hi all,

I know this is a common problem, and have seen a nice description here:
https://forum.tek.com/viewtopic.php?f=568&t=138253&sid=c827508d3401e2cd90eb52f42415517a

In his fix he replaced some of the inner guts of the switch cam. In my switch the shaft just spins in the cam. It doesn't come out, but just spins.

I found a listing for the part number, 105-0364-00, on eBay. It arrived Friday and I just tried to install it. To my disappointment it's not a 1-1 match with mine. I'll reach out to the seller to see if we can't figure out what's happened here, but when it comes to eBay I'm sure it's a sold as-is thing, and buyer assumes all risk.

In frustration I went back to the old cam and tried to see if the shaft would come apart, and with a little extra "encouragement" the shaft did come out leaving all the attached innards inside the cam. The only thing that came with the shaft was a ring-clip, which looks similar to the picture in the above tek forum post. What's interesting is that in my case there's just a lot of plastic powder filling the knurling where the shaft used to bond to the cam.

My question is: can I just JB Weld the knurled part of the shaft to the cam?

I'd clean the knurling of old decayed plastic, and make a bead of JB Weld at the beginning of the knurling so it would spread as the shaft is re-inserted to the cam.

Thing is, I have no idea what's going on inside the cam. There's obviously some kind of spring mechanism for the pull release of the B-delayed sweep time/div knob. Would the JB Weld just freeze all this up? I wouldn't go nuts with the JB Weld. I really love that stuff and have fixed a lot of hopeless cases with it. I think it might work in this case, but I'd prefer to take the cam apart to re-bond the shaft to the inner workings directly. But I have no idea how to disassemble the cam. Any ideas? I haven't found anything here or elsewhere with a how-to for that part of the job.

And finally, is there any sharing of part numbers across models? Could this "new" 105-0364-00 belong to something like a 475? I got the part number from the 465 Service manual I have. I don't think my A7 board is any different than other 465s. It's a high serial number 310XXX. I think it has to be a different switch cam that got the wrong tag on it somehow (nefarious or otherwise). It's an original looking Tektronix tag - old paper, Tek logo, etc.

Thanks for any help or pointers to other threads that deal with this.
Dave


Re: Horizontal Display switch shenanigans.

Dave Peterson
 

Just the internal plastic piece that broke. The only difficulty is managing the spring loaded catch that the four switches use to release the others when one is depressed, while simultaneously compressing both switch contacts while sliding the new button in. One of those three handed kind of jobs. Fortunately I have years of practice at that.

If you zoom in to the "bottom" button you'll see the end is just slightly different: tapered on all four sides, not just top and bottom.

Thanks for kicking me in the right place to jar my brain loose.
Dave

On Monday, November 30, 2020, 06:26:54 PM PST, Raymond Domp Frank <@Raymond> wrote:

Well done, Dave. Did you exchange the one switch? Or even just the broken plastic part? Can't see.

Raymond


Re: Resistor in series

Richard Knoppow
 

My own experience in the resistor business was long ago and did not include "mud" resistors. However, the only reason I can see that voltage might make a difference is if the resistor had a very high voltage coefficient of resistance. Composition resistors do have some while metal and carbon film resistors have virtually none. Nonetheless, the voltage at the terminals of a bridge or even a VOM should not make a significant difference.
   AFAIK the drift in composition resistors had to do with heat. The resistance element is made of many small particles of conductive material (carbon) embeded in an insulating material. As resistors age there tend to be fewer contact points between the small conductive particles so the resistance goes up. Excessive heat also causes this effect, again with an increase in resistance. I have observed resistors where the resistance has gone down. I don't know the mechanism but these were all very low value to begin with.
   I have not tried baking old composition resistors but if the original drift was caused by heat I don't see how baking would restore the original value. Perhaps if its due to moisture penetrating into the jackets it would.
    FWIW Allen Bradly made the Ohmite Brown Devil resistors, all came from the same place. Ohmite mentions this in their early advertising. I don't know why two brand names were used. In general, these seem to have been the best of the carbon composition resistors although I have no data on IRC resistors. I do remember being told when I was studying engineering to avoid IRC.
   The reason composition resistors were never available in tolerance less than 5% is that the heat of soldering could change the value more.
   These days, with cheap carbon film and metal film resistors easily available there is no reason IMO to use composition resistors. While at one time they were thought to have lower reactance at RF they provably do not. Supposedly composition resistors have some advantage for pulse use but I may be remembering that wrong.

On 11/30/2020 5:22 PM, Bob Albert via groups.io wrote:
I don't think the procedure for proper measurement of resistance would have an appreciable effect on a resistor that is grossly out of specification.  Maybe for nitpicking whether it's in spec or not, but not for gross errors.
Bob
On Monday, November 30, 2020, 04:39:57 PM PST, Roy Thistle <roy.thistle@...> wrote:
On Mon, Nov 30, 2020 at 11:48 AM, - wrote:

I have a large number of 40-ish year old Allen
Bradley carbon comp resisters...I have probed through the packaging and measured many of them and they're ALL well out of spec!
For A.B. "hot-moulded carbon composition resistors" (for Panasonic ones too) the effect of "moisture" ingress (a.k.a. gaseous water molecules = water vapour = moisture) is to always increase resistance.
According to several citations, this ingress is always reversible, with the appropriate time, temperature, and humidity conditions. (Older resistor manufacturing technologies might have used materials to comprise the resistance element which might have undergone strongly irreversible chemical reaction(s) with the ingressed "moisture...this perhaps causing a permanent change to the the resistor's nominal resistance.)
How one measures the resistance (for hot-moulded carbon comps) and compares it to their nominal value, depends on how the manufactures standardized their measurements... or that done in accord with the institutional standardizations the manufacturers adhered to. (Very generally, high values of resistance need to be measured at high voltages [without causing significant temperature increases]... and low resistance values can be measured at lower voltages. You have to know how the manufactures did the measurements.







--
Richard Knoppow
dickburk@...
WB6KBL


Re: Horizontal Display switch shenanigans.

 

Well done, Dave. Did you exchange the one switch? Or even just the broken plastic part? Can't see.

Raymond


Re: Horizontal Display switch shenanigans.

Dave Peterson
 

See the photos in https://groups.io/g/TekScopes/album?id=257214.

Something's finally fixed!

Thanks for the suggestion Raymond.
Dave


Re: OT: Analog Computer Comdyna GP-6

Wolfgang Schraml
 

Hi Steve,

You may find clues about what your Comdyna system is here: http://www.dvq.com/oldcomp/analog/comdyna.htm
Lots of pictures of various Comdyna computers and accessories.

Good luck, Wolfgang

--------------------------------------------------------

On Sun, Nov 29, 2020 at 12:39 PM, stevenhorii wrote:


I have what I think is an unusual Comdyna. It's a hybrid analog-digital
system. Half of it looks like most other Comdyna computers I have seen, but
there's another part on the bottom (the whole thing sits in an upright rack
of sorts) that has digital processing in it. I think it took the analog
output and digitized it, but it seems to do more than just A-D conversion.
It needs work and is on my "to-do" list, but I have zero documentation on
it. When I found this, the seller had two so I called a friend of mine and
he wanted one so I bought both and had one shipped out to him. He got his
working - I think his worked from initial power up. He's got several analog
computers - he also has the large Moog and Buchla analog synthesizers. He
has used the analog computers both for computing (he showed me his
implementation of the logistic difference equation on one of the analog
computers and the plot of the transition to chaotic behavior) and for
generating music. He has an EAI TR10 and pretty much rebuilt it -
capacitors were bad as were some of the transistors. He told me that for
the older analog computers (and synthesizers for that matter) that such
rebuilding would likely be necessary. Sounds like old Tek scopes.

Steve Horii

On Sun, Nov 29, 2020 at 1:37 PM Ed Breya via groups.io <edbreya=
yahoo.com@groups.io> wrote:

I also caught the analog computer bug a few years ago, and studied the
Comdyna stuff and lots of others from the old days. I started a project to
build a sophisticated analog computer with a wide variety of functions,
from scratch, with more "modern" components. I have it partly built, but
it's a long way to go, so it may never be finished. Instead of lots of
banana jacks, the plan is to use a number of those plastic plug in IC etc
prototyping plates, with the function circuits wired to the bottom, inside,
and programming with wire jumpers on top. It's very compact, and provides
hundreds of connection nodes.

Speaking of X-Y displays, there happens to be a somewhat related thread,
regarding possible uses for an old 528 TV waveform monitor. I suggested
making it an X-Y monitor, here:

https://groups.io/g/TekScopes/message/173941

You should view the whole thread for context.

Ed






Re: Resistor in series

Bob Albert
 

I don't think the procedure for proper measurement of resistance would have an appreciable effect on a resistor that is grossly out of specification.  Maybe for nitpicking whether it's in spec or not, but not for gross errors.
Bob

On Monday, November 30, 2020, 04:39:57 PM PST, Roy Thistle <roy.thistle@...> wrote:

On Mon, Nov 30, 2020 at 11:48 AM, - wrote:


I have a large number of 40-ish year old Allen
Bradley carbon comp resisters...I have probed through the packaging and measured many of them and they're ALL well out of spec!
For A.B. "hot-moulded carbon composition resistors" (for Panasonic ones too) the effect of "moisture" ingress (a.k.a. gaseous water molecules = water vapour = moisture) is to always increase resistance.
According to several citations, this ingress is always reversible, with the appropriate time, temperature, and humidity conditions. (Older resistor manufacturing technologies might have used materials to comprise the resistance element which might have undergone strongly irreversible chemical reaction(s) with the ingressed "moisture...this perhaps causing a permanent change to the the resistor's nominal resistance.)
How one measures the resistance (for hot-moulded carbon comps) and compares it to their nominal value, depends on how the manufactures standardized their measurements... or that done in accord with the institutional standardizations the manufacturers adhered to. (Very generally, high values of resistance need to be measured at high voltages [without causing significant temperature increases]... and low resistance values can be measured at lower voltages. You have to know how the manufactures did the measurements.