Date   

Re: TM506

Dave Daniel
 

ISTR that when I recapped my TM-501 the voltage selector jumper pins were labeled with the various line voltage ranges such that if I knew the line voltage in my lab I could set the jumper correctly without having to refer to the manual.

DaveD

On Jul 22, 2020, at 17:05, Dennis Tillman W7pF <dennis@ridesoft.com> wrote:

Stephen,
Be sure the input voltage selector jumper inside the TM506 is set to the proper voltage range your electric utility provides. If they do not match your power line voltage the three AC voltages and the three DC voltages of the TM506 will be ~15% higher or ~15% lower than they should be.

Dennis Tillman W7pF




--
Dennis Tillman W7pF
TekScopes Moderator



Need help with 11801 delay jitter #photo-notice

lccavalheiro@...
 

Hi everyone,

I recently purchased a 11801B with an SD-26 module. Because I haven't used one before, I'm trying to understand if the behavior I'm seeing is expected or if the equipment is compromised. I'm using the Bodnar edge generator for this, and when I acquire as close as I can to the trigger (delay ~ 49ns), the edge looks fairly good, but when I add a bit more delay (delay ~ 11us), it seems that the jitter noise makes the measurement very unreliable and noisy. I've uploaded 2 images of what I'm referring to, and I'm hoping someone that also has this scope can tell me if this is the normal behavior or whether I mine has a problem.
The link to the pictures is: https://groups.io/g/TekScopes/album?id=250925

PS: This looks the same if I use the 11801 internal clock output.

Looking forward to getting any feedback.

Cheer!


Re: 11801 diagnostic help

lccavalheiro@...
 

I have a similar issue and I think your post is sort of answering the post that I just made. You can take a look at the comparison between the edges I get when the delay is very short to when the delay is long. I think it's likely the delay jitter not these Tektronix that are not very controlled, I'm guessing that as soon as you start going being the microsecond range, you will start seeing a large increase in jitter also causing the signal to look very noisy. I wasn't sure if my unit was faulty (because I just purchased as well and I've never used a 11801 before), but give that many people are saying they've seen this before, I'm starting to think that this is really just the normal jitter you'd expect when adding enough delay (from the trigger point) to the waveform acquisition.

You can take a look at the picture here: https://groups.io/g/TekScopes/album?id=250925


Re: TM506

Stephen
 

On Wed, Jul 22, 2020 at 10:05 AM, Dennis Tillman W7pF wrote:


Stephen,
Be sure the input voltage selector jumper inside the TM506 is set to the
proper voltage range your electric utility provides. If they do not match your
power line voltage the three AC voltages and the three DC voltages of the
TM506 will be ~15% higher or ~15% lower than they should be.

Dennis Tillman W7pF




--
Dennis Tillman W7pF
TekScopes Moderator
Yes, I agree. But the thing is, as I said earlier, I see where the jumpers are, but I don’t see any indications anywhere as to how to change that.
On the power cord retainer outside there is a little passive ring that says 220. But it can be changed to 240. However, inside there are only 2 jumpers that read 220V and 120V... And nothing else...


Re: TM506

Ke-Fong Lin
 

Hi Stephen,

4) that you have transistor failures suggests that at least one plugin
has a supply problem, and that you may have put in the transistors
wrongly.
Indeed. That much I understand. Now which one or ones...? I yet have to
figure that out.
What I understand, it’s a never ending story. You make the 506 work on
it’s own, than as soon as you plug in a module, if it’s bad, things will
go sideways all over again. If I had produced codes or network designs with
flaws like that, and no failsafe, I would’ve been out of a job very fast.
But maybe I’m wrong and don’t yet grasp the whole concept.
Yes, maybe you're wrong. Hardware is not software, you cannot always crash, fix, restart, and continue.
With software, with the advent of Internet and ubiquous connectivity, you can basically ship bugged software and provide fix patches.
With hardware, mistakes can just mean complete destruction of the device.

The TM5xx series of mainframes, your TM506 included in particular, are basically passive devices.
Providing 2x 25VAC per slot almost direct from the transformer, and shared filtered VDC voltages and 17.5VAC.
Hence, just a DMM (AC, DC, and diode tester to check the pass transistors) and perhaps a scope (to check the ripple of VDC) should be enough to make sure the mainframe works.

The TM5003, TM5006, and TM5006A are more modern (beginning of 80s) and have regulated DC voltages.
The regulated DCs have overcurrent protection (the failsafe you mentioned). There's even a "power good" pin (6B).
However, it's a switch-mode supply, much more complicated to fix than your TM506. Just compare the components count!

The point I'd like to make, is that your TM506 was designed in the 70s, where linear supplies were the "standard".
Electronic components were rather novel and expensive, but much simpler. Integrated circuit were not so common (even the TM500x have discrete switch-mode power supply).
Hence, protections we are used to (overcurrent and overvoltage) on our modern devices, were not implemented.


Best regards


Re: TM506

 

Stephen,
Be sure the input voltage selector jumper inside the TM506 is set to the proper voltage range your electric utility provides. If they do not match your power line voltage the three AC voltages and the three DC voltages of the TM506 will be ~15% higher or ~15% lower than they should be.

Dennis Tillman W7pF




--
Dennis Tillman W7pF
TekScopes Moderator


Re: 485 Cordwrap Feet

Roy Thistle
 

On Tue, Jul 21, 2020 at 12:30 PM, Jeff Davis wrote:


Would greatly appreciate anyone who could shed light on this mystery
If you look at the back of a horizontal 475, lying on a table top... (not standing on its feet)... it looks, by your pics... that the intact foot in those picture... is one of the two feet, on a 475... that would be closest to the table top.
By the crafty design, of that/those particular foot/feet (no doubt the work of a devil)... it has a rectangular shape to the "bottom" of the foot (as in your pics)... rather than the 1/4 pie shape of the two other feet. By the bottom of the foot, I just mean the part that touches the surface the scope would be standing on.
Perhaps, as Dennis pointed out... the rectangular shape, versus the 1/4 circular shape, helps to hold/store the cord.


Re: TM506

Stephen
 

On Wed, Jul 22, 2020 at 09:06 AM, Steve Hendrix wrote:


At 2020-07-22 04:03 PM, Stephen wrote:


Is it ok to replace those two 0.27R 10% resistors that blew with 0.33R 5%?
How about using 0.33 ohms in parallel with 1.5 ohms, for 0.27049 ohms?
Certainly closer than the resistor tolerances.

Steve Hendrix
You’re absolutely right. I’ll see what I have in my stash.
Thanks for pointing that out.


Re: Tek R561B on CL in Austin

greenboxmaven
 

I am interested in the scope and plug-ins. I have been looking for one of these for a while, and have a definate use for it. I am in Syracuse, New York, so picking it up is not possible. I have an account with Fedex, so shipping would be easier for you.

Bruce Gentry, KA2IVY

On 7/22/20 4:03 PM, John Griessen wrote:
This one *IS* mine! It comes with 6 plugins, and works.

2A63
2B67
3B3
3A3
3A74
3A74

They can be shipped, but after ?Aug 10th? and probably $85 shipping.

I'd like $30 for all that picked up locally, or added to the shipping, and paid by check or cash.

Will sell separately for $20 per piece + shipping.



Re: TM506

Steve Hendrix
 

At 2020-07-22 04:03 PM, Stephen wrote:


Is it ok to replace those two 0.27R 10% resistors that blew with 0.33R 5%?
How about using 0.33 ohms in parallel with 1.5 ohms, for 0.27049 ohms? Certainly closer than the resistor tolerances.

Steve Hendrix


Re: TM506

Stephen
 

On Wed, Jul 22, 2020 at 07:37 AM, Mlynch001 wrote:


On Wed, Jul 22, 2020 at 01:16 PM, Stephen wrote:


I checked the voltages on all slot between 1A-1B and I have around 26.2VAC
in
all of them. But
These AC voltages always seem to read high without a load. I believe that
24.8V is the fully loaded specification. Also depends on the RMS converter
and calibration of the meter. You are close enough.

--
Michael Lynch
Dardanelle, AR
Yes, you’re right. There is no load at the moment.
Any other pins/voltages I should check before calling it good?


Re: TM506

Stephen
 

On Wed, Jul 22, 2020 at 07:19 AM, Harvey White wrote:

Ok, then see if you can find one of the Tektronix breadboard systems. 
They were boxes with a substantial blank area and a power supply
module.  I think you could also find one that's simply a frame and a
plugin with a breakout.  Worst (not that it is) case is to find an old
plugin card with the appropriate number of pins.  You might also
consider buying a known bad, parts only, TM500 module, and instead of
fixing it, make it into a test fixture.
I’ll see what I can find, and if it’s not costing an arm and a leg.

First modules I'd test out would be the ones that don't use the external transistors, if there
are any.
How do I know that? The ones I have so far are:
1- PS503A (which was working fine until the 7.5A fuse blew)
2- SC502 15Mhz Scope
3- AM503 Current Probe Amplifier
4- FG502 Function Generator (the one that blew 2 resistors because of the shorted collectors)
5- DC503 Universal Counter (It has issues, but I don’t think they are power supply related. But I’m no expert)
6- SG503 Leveled Sine Wave Generator. (That one worked also perfectly)

If you had a variac, you could monitor voltages as you bring up the
power slowly. 
Unfortunately I don’t have one.

Is it ok to replace those two 0.27R 10% resistors that blew with 0.33R 5%? That’s all I could find.
If so, would it be wise to change the two others that didn’t blow, to match them?
I probably should check the rectifier and the capacitor on that side as well.


Tek R561B on CL in Austin

John Griessen
 

This one *IS* mine! It comes with 6 plugins, and works.

2A63
2B67
3B3
3A3
3A74
3A74

They can be shipped, but after ?Aug 10th? and probably $85 shipping.

I'd like $30 for all that picked up locally, or added to the shipping, and paid by check or cash.

Will sell separately for $20 per piece + shipping.


Re: 485 Cordwrap Feet

Roy Thistle
 

On Wed, Jul 22, 2020 at 11:39 AM, Dennis Tillman W7pF wrote:


Somehow we
all end up with more of them than we can possibly use.
Yes!
Around here, they do toss good usable Tek equipment into the dumpster... but, they always keep the power cord. I'm not sure of the thinking (One could need a 1 dollar power cord; but, not an expensive oscilloscope?) I get it for the probes; but, not the cords. Anyway, yes! ... barrels of the things.


Re: 485 Cordwrap Feet

 

Hi Jeff,
It was not unusual for the design engineers at Tek to pay attention to
product details (known as Human Factors Engineering in those days) just like
this one. This was one of the things that distinguished Tek from many other
companies. The 485 was a portable scope which meant things like a power cord
had to have a secure place to be while it was being moved from one place to
another. The logical way to carry the scope was by the handle with the scope
in an upright position so there would need to be feet on the rear of the
scope. Why not kill two birds with one stone and design a foot that would
also secure the power cord?

There are some things that the mechanical engineers at Tek never seem to be
satisfied with and cord wraps are one of them. The cord wrap evolved
constantly. It was almost as if the mechanical engineers saw each new
portable scope as an opportunity to improve on the design of the previous
instrument. My 453 (the 454 and 453 were the original portables Tek designed
to meet the needs of the IBM Field Engineers) had fairly simple rear feet
which the power cord could be wrapped around. I think there was a chance the
power cord could become undone from around the rear feet while travelling
with the 453 scope. By the time the 485 appeared the cord wrap foot was just
about optimal: It holds the power cord securely, and it communicates to the
user, by its unusual shape, what its intended purpose is, without the need
for any further explanation.

In other words its unusual shape tells you what it does. Donald Norman in
his book "The Psychology of Everyday Things" coined the term "affordances"
for the properties of objects which show users the actions they can take.
Users should be able to perceive affordances without having to consider how
to use the items. A simple example we all encounter every day is the handle
on a door leading into or out of a store. The shape of the handle should
communicate to you whether you should push or pull it to open the door.
Instead most of them are so poorly designed that it is necessary to include
a sign saying "Push" or "Pull".

With the advent of the IEC power connector standard in 1970 many instruments
gradually started using power cords that could be unplugged from the
instrument which created a totally different problem of what to do with the
proliferation of these power cords now that they are everywhere. Somehow we
all end up with more of them than we can possibly use.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jeff
Davis
Sent: Tuesday, July 21, 2020 12:30 PM
To: TekScopes@groups.io
Subject: [TekScopes] 485 Cordwrap Feet

I had a customer approach me about developing a replacement cord wrap foot
for the Tektronix 485. He sent me one of his that was mostly intact - but it
led to some questions that I'm now posing to the group.

The 485 service manual shows that the cord wrap looks a lot like the cord
wraps on a 2465, i.e. two assemblies, one right side and one left side, that
extend from the bottom to the top, and the cord wraps around the two of
them.

On the other hand, what my customer sent to me looked more like a foot from
a 465, i.e. 4 pieces, one on each corner, with flanges to hold the cord. The
cord wraps around the four pieces located at each corner.

Did early and later versions of the 485 have different cord wraps? If so,
are they interchangeable? I can only find one version of the service manual,
and it shows the 2465-like cord wraps.

Would greatly appreciate anyone who could shed light on this mystery.

Thanks,
Jeff / N0DY
www.n0dy.com





--
Dennis Tillman W7pF
TekScopes Moderator


Re: TM506

Mlynch001
 

On Wed, Jul 22, 2020 at 01:16 PM, Stephen wrote:


I checked the voltages on all slot between 1A-1B and I have around 26.2VAC in
all of them. But
These AC voltages always seem to read high without a load. I believe that 24.8V is the fully loaded specification. Also depends on the RMS converter and calibration of the meter. You are close enough.

--
Michael Lynch
Dardanelle, AR


Re: TM506

Harvey White
 

Interleaved:

On 7/22/2020 1:28 PM, Stephen wrote:
On Wed, Jul 22, 2020 at 04:21 AM, Harvey White wrote:

The NPN and PNP transistors for each slot are completely independent of
anything.  They're nothing but transistors connected to socket pins.
I'd suggest the following:

1) using one of the adaptors you bought, make a plugin to bring out the
wiring for each slot.  You're interested in the power supply voltages,
and the BEC junctions of the transistors.  Using a transistor tester
(the cheap ones built with a PIC or MEGA ought to be fine), test each
transistor. The advantage here is that the tester identifies which lead
is which.
Yes, but these adaptors will arrive late August or mid-September. I’m not gonna wait that long.
Ok, then see if you can find one of the Tektronix breadboard systems.  They were boxes with a substantial blank area and a power supply module.  I think you could also find one that's simply a frame and a plugin with a breakout.  Worst (not that it is) case is to find an old plugin card with the appropriate number of pins.  You might also consider buying a known bad, parts only, TM500 module, and instead of fixing it, make it into a test fixture.



2) Check the power supply voltages.  The bulk DC supplies are fused.
The AC windings are not fused,

3) Make a supply tester, that at least breaks out the voltages to banana
jacks or something like that.  You want to check each slot.  For now,
the current available may not be a factor, but you want to make sure
that all the voltages are where they should be.
Since I removed the bottom land top of the 506, I can easily check each slot individually with my DMM.
Same goes for debugging the plugins. Of course it’s not ideal, but that’ll have to do for now, I guess.
That'll do for inadvertent grounding.


4) that you have transistor failures suggests that at least one plugin
has a supply problem, and that you may have put in the transistors
wrongly.
Indeed. That much I understand. Now which one or ones...? I yet have to figure that out.
What I understand, it’s a never ending story. You make the 506 work on it’s own, than as soon as you plug in a module, if it’s bad, things will go sideways all over again. If I had produced codes or network designs with flaws like that, and no failsafe, I would’ve been out of a job very fast. But maybe I’m wrong and don’t yet grasp the whole concept.
Nope, cascade failure, shorts killing things.  First modules I'd test out would be the ones that don't use the external transistors, if there are any.  Next, I'd look at ones that don't use the AC voltage, not that there was a problem with those.  Then go to the other ones.  There's no really easy way other than a smart extender that allows you to monitor current, or put in a fuse (if possible).

However, without the plugin in the frame, if it does use an external frame transistor, the output part of the supply will be isolated and the input will be.  It's somewhat as if you removed the regulator tube from a tube supply.  You could test the bulk supply to the tube, then test the load, and in either case, see if there are any shorts.

If you had a variac, you could monitor voltages as you bring up the power slowly.  All the supplies are linear supplies, so there's not as much possibility of damage as there would be in a switching supply.




An ohmmeter cannot really tell the difference between the BE
and BC junctions, a beta test or transistor tester can.  If you have the
C and E leads reversed, you generally get a transistor with very low
beta, but it'll be a transistor.
I have a transistor tester on my DMM.
I'd be looking at that, then.


5) note that you have discovered that using plugins as test loads is not
the best idea.  A dedicated tester rig makes a lot of sense.
Tell me about it...! 😂
I admit though, that was stupid.
Everybody makes that kind of error every now and then.

Harvey




6) that tek-wiki article on the test module for the TM500 series frames
makes a lot of sense.


Harvey


Re: TM506

Stephen
 

On Wed, Jul 22, 2020 at 02:38 AM, Stephen wrote:


On Wed, Jul 22, 2020 at 02:34 AM, Michael W. Lynch wrote:


On Wed, Jul 22, 2020 at 07:42 AM, Stephen wrote:


No voltage at pin 1 on any of the slots. Schematic shows 24.8V RMS.
Are you checking this voltage between 1A and 1B of the back plane connector?
It appears to me that the 24.8VAC source at each slot is supplied by
independent winding in the Main XFMR, It seem unimaginable that every one
of
these windings in the main XFMR would have shorted out. However, I am
certainly no expert on the TM506, I suppose it is possible? You can check
the individual windings at each slot by connecting an ohmeter between 1A and
1B and looking for continuity of about 1.6 ~1.8 Ohms and then between each
contact and the chassis for no continuity. I just did this test on my
TM506,
so you should see something similar on yours.
--
Michael Lynch
Dardanelle, AR
Will do when I get back. At the store at the moment.
This is very strange. I even thought for a minute that I had wired everything
backwards. I checked, and rechecked, and re-double checked against the
schematic and the pinouts, and I don’t see any problems...
So unless my unit is, for some obscure reason, wired differently, all should
be ok. But it’s not...
I’ve fixe the transistor to ground issue by inserting plastic sheets between the screws and the baseplate. No more collector shorts to ground. Although I bought a few extras, I left the same transistors for now. I only replaced 3/10.
I checked the voltages on all slot between 1A-1B and I have around 26.2VAC in all of them. But my unit is set for 220V, and I have 232VAC from the wall.... that could explain the higher voltages. I saw the jumpers to switch the input voltages, but nowhere did I see in the manual how to set it up.


Re: Cleaning the screen of a TDS744A ?

David Slipper
 

Thanks, I used a few drops of baby shampoo in warm water (very very dilute) and applied it with a barely damp lint free pad then dried with a clean microfiber cloth. Worked a treat.
Dave

On 21/07/2020 17:10, Roy Thistle wrote:
On Tue, Jul 21, 2020 at 01:35 AM, David Slipper wrote:

What is the best way to get greasy finger prints off the plastic sheet that is
in front of the CRT

From page 6-5 in Zenith's scan of the "TDS 684A & TDS 744 Service Manual" on Tekwiki at
http://w140.com/tekwiki/images/d/d6/070-8992-02.pdf

"Clean the light filter protecting the monitor screen with a lint-free cloth dampened with either isopropyl alcohol or, preferably, a gentle, general purpose detergent-and-water solution."


It appears... looking at the mechanical parts drawing... the "light-filter" is not a separate numbered component (not listed as such, in the "Mechanical Parts List") but is part of/comes with the front panel assembly? or with the display frame? So how do you remove it? So what's the "plastic filter's" material? could be acrylic or polycarbonate? ... and it's hard to tell the difference between between acrylic and polycarbonate, just by looking.

For the nervous, who want to do de-fingerprinting service... I'd start with the lint-free (supposed to be really lint free, and anti-static is better too... like Kimwipes)... I'd start with the general purpose detergent (a.k.a., mild dish detergent) and lint-free cloth... and then move up to the alcohol...if detergent doesn't work.
For fingerprint "grease" (fingerprint "grease" isn't just grease)... a detergent, and water, solution works better than the alcohol, in my opinion... in the following way. If you can remove the plastic filter?, clean it with the detergent solution, and then flush the soapy filter with distilled water... preferably, from a squeeze bottle... so you get a pressurized stream... this flushes the hopefully emulsified, and dissolved, fingerprints from the plastic filter.
Other solvents are a big no-no... they are probably going to damage the plastic... so no acetone, naptha, et. al.



.


Re: TM506

Stephen
 

On Wed, Jul 22, 2020 at 04:21 AM, Harvey White wrote:


The NPN and PNP transistors for each slot are completely independent of
anything.  They're nothing but transistors connected to socket pins.
I'd suggest the following:

1) using one of the adaptors you bought, make a plugin to bring out the
wiring for each slot.  You're interested in the power supply voltages,
and the BEC junctions of the transistors.  Using a transistor tester
(the cheap ones built with a PIC or MEGA ought to be fine), test each
transistor. The advantage here is that the tester identifies which lead
is which.
Yes, but these adaptors will arrive late August or mid-September. I’m not gonna wait that long.

2) Check the power supply voltages.  The bulk DC supplies are fused. 
The AC windings are not fused,

3) Make a supply tester, that at least breaks out the voltages to banana
jacks or something like that.  You want to check each slot.  For now,
the current available may not be a factor, but you want to make sure
that all the voltages are where they should be.
Since I removed the bottom land top of the 506, I can easily check each slot individually with my DMM.
Same goes for debugging the plugins. Of course it’s not ideal, but that’ll have to do for now, I guess.

4) that you have transistor failures suggests that at least one plugin
has a supply problem, and that you may have put in the transistors
wrongly.
Indeed. That much I understand. Now which one or ones...? I yet have to figure that out.
What I understand, it’s a never ending story. You make the 506 work on it’s own, than as soon as you plug in a module, if it’s bad, things will go sideways all over again. If I had produced codes or network designs with flaws like that, and no failsafe, I would’ve been out of a job very fast. But maybe I’m wrong and don’t yet grasp the whole concept.

An ohmmeter cannot really tell the difference between the BE
and BC junctions, a beta test or transistor tester can.  If you have the
C and E leads reversed, you generally get a transistor with very low
beta, but it'll be a transistor.
I have a transistor tester on my DMM.

5) note that you have discovered that using plugins as test loads is not
the best idea.  A dedicated tester rig makes a lot of sense.
Tell me about it...! 😂
I admit though, that was stupid.


6) that tek-wiki article on the test module for the TM500 series frames
makes a lot of sense.


Harvey

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