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Re: TM500 Module Construction Details

Jim Ford
 

Well, I for one agree with you 100%, Glenn.   Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Glenn Little <glennmaillist@bellsouth.net> Date: 1/17/21 1:27 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] TM500 Module Construction Details If the part is beyond repair due to parts not being available and redesign being too costly, the repurpose of the item to aid in the repair of other equipment that can be repaired should be encouraged.In many cases the alternative is e-waste.This is my opinion, and mine alone.GlennOn 1/17/2021 4:22 PM, Roy Thistle wrote:> On Sun, Jan 17, 2021 at 08:41 AM, ebrucehunter wrote:> >>>> I recently picked up a 5A21N scope plug-in as a parts unit from which to build>> Jared Cabot's updated TM500 mainframe tester.>>>> Any thoughts?>>> Well if a thought can be a question... I have a question... It's not directed at Bruce.> I don't know why, on a forum, that is dedicated to helping people keep/restore classic Tektronix, we are discussing a project that could contribute to helping people destroy them.> > > > > -- -----------------------------------------------------------------------Glenn Little                ARRL Technical Specialist   QCWA  LM 28417Amateur Callsign:  WB4UIV            wb4uiv@arrl.net    AMSAT LM 2178QTH:  Goose Creek, SC USA (EM92xx)  USSVI, FRA, NRA-LM    ARRL TAPR"It is not the class of license that the Amateur holds but the classof the Amateur that holds the license"


Re: 2235 Horizontal Calibration Issue

 

On Sun, Jan 17, 2021 at 08:39 PM, Dave Peterson wrote:


Don't know if R740/R730 are easily accessible, but that's what seems to be
called for here.
Don't think so. It's not a problem of the amplitude (A sweep gain), because beginning-to end is ok, but a linearity problem. Amplitude corrections won't help. I guess there are some linearity adjustments for the highest sweep speeds but these (around 100 us/div) aren't.

Raymond


Re: P6137 scope probe repair

Tom Lee
 

Simple, Roy. If your post isn't helping Jared fix his probe, it's noise. Your constant irrelevant comments and meta-comments are prime examples of raising the noise floor.

As did Chuck, I am now pretty much putting you on my ignore list. My rant contains specific actionable information to help Jared. If you don't see it, I suggest that the problem lies with you.

Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/17/2021 13:54, Roy Thistle wrote:
On Sun, Jan 17, 2021 at 01:11 PM, Tom Lee wrote:

attempt at raising the SNR
I can't say with confidence that "rants" raise the SNR... perhaps they do... but, I'd need data.
In any case... it might be the case, one man's noise is another man's music... but, I don't have data on that.




Re: 564 AC ripple in beam intensity

Paul
 

Yeah, the HV supply works around 45kHz on this one, but this problem is definitely happening at line frequency. If I line sync the sweep the intensity banding is stationary.


Re: P6137 scope probe repair

Roy Thistle
 

On Sun, Jan 17, 2021 at 01:11 PM, Tom Lee wrote:


attempt at raising the SNR
I can't say with confidence that "rants" raise the SNR... perhaps they do... but, I'd need data.
In any case... it might be the case, one man's noise is another man's music... but, I don't have data on that.


Re: P6137 scope probe repair

Tom Lee
 

Read the posts, Roy.

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/17/2021 13:44, Roy Thistle wrote:
On Sun, Jan 17, 2021 at 01:11 PM, Tom Lee wrote:

What the hell's wrong with helping Jared *fix *his probe?
Well since no one that posted... as far as I can tell... explicitly said, "Jared, don't try" ... it's your claim that some people that did post are implying it. Is there data I missed to confirm that?




Re: P6137 scope probe repair

Roy Thistle
 

On Sun, Jan 17, 2021 at 01:11 PM, Tom Lee wrote:


What the hell's wrong with helping Jared *fix *his probe?
Well since no one that posted... as far as I can tell... explicitly said, "Jared, don't try" ... it's your claim that some people that did post are implying it. Is there data I missed to confirm that?


Re: TM500 Module Construction Details

Glenn Little
 

If the part is beyond repair due to parts not being available and redesign being too costly, the repurpose of the item to aid in the repair of other equipment that can be repaired should be encouraged.
In many cases the alternative is e-waste.

This is my opinion, and mine alone.

Glenn

On 1/17/2021 4:22 PM, Roy Thistle wrote:
On Sun, Jan 17, 2021 at 08:41 AM, ebrucehunter wrote:


I recently picked up a 5A21N scope plug-in as a parts unit from which to build
Jared Cabot's updated TM500 mainframe tester.

Any thoughts?
Well if a thought can be a question... I have a question... It's not directed at Bruce.
I don't know why, on a forum, that is dedicated to helping people keep/restore classic Tektronix, we are discussing a project that could contribute to helping people destroy them.
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@arrl.net AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI, FRA, NRA-LM ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"


Re: TM500 Module Construction Details

Roy Thistle
 

On Sun, Jan 17, 2021 at 08:41 AM, ebrucehunter wrote:


I recently picked up a 5A21N scope plug-in as a parts unit from which to build
Jared Cabot's updated TM500 mainframe tester.

Any thoughts?
Well if a thought can be a question... I have a question... It's not directed at Bruce.
I don't know why, on a forum, that is dedicated to helping people keep/restore classic Tektronix, we are discussing a project that could contribute to helping people destroy them.


Re: P6137 scope probe repair

Tom Lee
 

Lawrance and Roy, and a couple of others:

//Warning: Rant mode on. You'll want to power up your shields, 'cause photon torpedoes are headed your way.

What the hell's wrong with helping Jared *fix *his probe? Posts with vague or even explicit suggestions that his endeavor is doomed to fail are unhelpful, and technically just plain wrong. Adding irrelevant and sometimes wrong trivia, though perhaps interesting, just adds noise and distortion to the discussion. Here's my nth attempt at raising the SNR and actually point Jared to a solution.

It's been previously noted -- multiple times -- that probes use special resistance wire. If you've studied transmission lines at all, you will know that lines need to be terminated in their characteristic impedance in order to prevent reflections.

Probes are magic because they allow one to look at nodes whose impedances are uncontrolled, somehow without producing artifacts due to the inevitable reflections that must be occurring. How is this even possible? John Kobbe and Bill Polits had to solve this problem, or else Tek's efforts at making high-bandwith scopes would be the equivalent of inventing the phonograph without also inventing phonograph records. Kobbe and Polits understood that preventing reflections from misterminations is impossible. But they also understood that resistance is good at providing damping. In a 10:1 probe, you have a large attenuation anyway, so adding damping is relatively non-intrusive. Kobbe stripped some ordinary coax, connected resistance wire to the center conductor. As he pulled out the original lossless conductor, it pulled in the resistance wire. They tried it, and it worked. Thus was born the high-bandwidth probe. See US patent 2,883,619 (1959).

If you read anything at all of what I wrote to help Jared, you'll note that I made explicit mention of how his chances are a function of where the break is, the correct amount of damping being a function of length, among other factors. But contrary to what you implied, it's not a hyper-sensitive function of length. If you chop off an inch from the end of a 3ft cable, that 3% length reduction isn't abruptly going to trash the probe. Why would it? Suggesting that shortening would "most likely produce a semi-worthless probe" is a prime example of one of my pet peeves: Asserting an opinion without technical foundation (I'm guilty of it myself, but at least I'm aware that I have this problem). Worse, it's completely wrong. It only adds noise and distortion to the discussion. The "tuning" you speak of is not a sharp function at all. You can remove a small bit, and the effect will be a small bit. Think logically: Do you really believe that removing a nanometer instantly trashes the probe? Ok, how about a micron? A millimeter? When you acknowledge that maybe the deterioration is an analog, not binary, function of length, you will have made a cognitive leap forward. And if you have no clue at which point the amount removed is too much, that's a sign that you ought to keep your fingers away from the keyboard. The resistance per inch of probe conductor is typically  under an ohm. Jared has narrowed the general region of the break to about an inch from one end. If you think the removal of an ohm's worth of loss out of a 100 or 200 ohm total is going to produce a semi-worthless probe, show me your calculations or measurements that support such an assertion.

Better yet, how about not asserting unfounded discouraging things at all, and just let Jared try to fix his probe, instead of telling him he's going to fail? Or to "go buy another probe", as some Mr. Obvious suggested (do you really think that Jared is so thick-headed that he needs someone to tell him that)?

Next, your trivia about T-coils makes it sound like many probes use them. As far as I am aware, the total number is two: P6047 and the oddball 1kilohm P6048. If you are aware of any others, I would very much like to know their model numbers so that I can update my spreadsheet. T-coils are very much the /exception/, rather than the rule, in probes.

//Rant mode off. Photon torpedoes reset. For now.




--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/17/2021 06:29, Lawrance A. Schneider wrote:
On Sat, Jan 16, 2021 at 10:43 AM, Roy Thistle wrote:

The "coax" is not normal 50 ohm coax... on high performance/high frequency
probes.
It is usually a kind of "lossy" coax, which uses a shaped mono-filament
resistance wire for the center conductor. That wire is somewhat brittle
(compared to copper)... and shatters or cracks... when bent, mutilated, or
stapled.
After I wrote my missive about finding the break with a nanoVNA, I thought about the problem further. Last year, I started to explore why Tek Probes use t-coils - boy oh boy was that a fun project. And I then remembered the above. Why am I bothering to note this. I discovered the Probe is 'tuned' within and shortening the lead and reconnecting would most likely result in a semi-worthless probe. I believe Alan Wolke has a video about the wire within a probe. The wire looks like a mess.

larry




Re: 564 AC ripple in beam intensity

Harvey White
 

The ripple shouldn't be 60 Hz, more like 30 to 60 Khz or so.  Tek used oscillators to minimize HV transformer weight and size.  I've had issues with parts where the probe touching the circuit makes it work beautifully.  That turned out to be a floating lead that I hadn't connected (IIRC).  probe loading would make it look like ground for a bit.  Those would be the HV filter capacitors, so looking at them with an HV probe could be helpful.

The higher the frequency, the more effective a smaller value of cap will be.  Some old scopes that ran the CRT off 60 Hz high voltage used some very large (and nasty) filter capacitors to keep ripple down.

Harvey

On 1/17/2021 4:01 PM, Paul wrote:
Thanks Harvey -
I think my next step is to change out those few HV caps in the neighborhood. They're all pretty low value disc caps, which tend not to be components I suspect when looking for 60Hz ripple, but I'm running out of better ideas.

Paul





Re: 564 AC ripple in beam intensity

Paul
 

Thanks Harvey -
I think my next step is to change out those few HV caps in the neighborhood. They're all pretty low value disc caps, which tend not to be components I suspect when looking for 60Hz ripple, but I'm running out of better ideas.

Paul


Re: 465 55v regulated filter cap type.

adesilva_1999@...
 

The space there is very tight. I had to manipulate/bend the leads and put heat shrink on them to get it in there. I doubt an axial cap of sufficient value can be fitted there as it might be too tall. Also, in my case, I had to snip one end and take it out as I did it from the component side. Even the 4 uf I used was a little too big and hence the need to bend the leads and insulate them.

I got rid of the rest of the wet tantalums along with it but did not bother about the dipped tantalums other than the one under the HV shield. I could not get the exact same but went with the nearest in value for the critical caps on the power supply only. I also did not think of increasing the values because of the physical sizes and available space. Below is a list of what I replaced:

Mfr. #: USR1E470MDD1TP
Desc.: Aluminum Electrolytic Capacitors Radial Leaded 47uF 25V 85c 6.3x7 20% 2.5LS
#: 594222213836109 2pcs.

Mfr. #: MAL213836109E3
Desc.: Aluminum Electrolytic Capacitors Axial Leaded 10uF 25V 20%
#: 75TE1504E3 1pc.

Mfr. #: TE1504E3
Desc.: Aluminum Electrolytic Capacitors Axial Leaded 150V 5uF
#: 75TE1500E3 1pc.

Mfr. #: TE1500E3
Desc.: Aluminum Electrolytic Capacitors Axial Leaded 150V 1uF
#: 71RL07S361GTR 1pc.

Mfr. #: TE1208
Desc.: Aluminum Electrolytic Capacitors Axial Leaded 35uF 25volts
#: 594MAL212634102E3 2pcs.

Mfr. #: MAL212634102E3
Desc.: Aluminum Electrolytic Capacitors Axial Leaded 1000uF 10V 10x18
#: 5303AG1.5R 1pc.

Mfr. #: TVA1402
Desc.: Aluminum Electrolytic Capacitors Axial Leaded 150V 4.0 uF
1pc.

Hope this helps.


Re: TM500 Module Construction Details

Larry McDavid
 

What purpose do these pins serve?

The module card edge connector engages before the pins could; the mainframes I've looked at don't have corresponding tight-fit holes for the pins, only rectangular openings with clearance all around the pins.

Yet, all the modules I've looked at have at least one pin. These pins must not be for aligning the module and card-edge connector.

Would these pins prevent plugging a TM500 module into a 5000 scope?

Like in Jared's photo, all my modules without a back plate have the short bushing to space the pins out to compensate for the missing back plate thickness.

Larry

On 1/17/2021 9:21 AM, Jared Cabot via groups.io wrote:
I have noticed that the pins are the same with or without the back plate, with tubular washers used when there is no back plate to keep the pins at the same length. Some modules lack pins entirely.
I'm not sure what the ideas behind having a back plate or not are, except the usual airflow/EMI shielding assumptions.
Here's a photo of the pins with and without a back panel:
https://i.imgur.com/omQwaDF.jpg
--
Best wishes,

Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)


Re: 2235 Horizontal Calibration Issue

Stephen
 

On Sun, Jan 17, 2021 at 08:39 AM, Dave Peterson wrote:


Page 5-14 of the 2235 Service Manual:
https://w140.com/tekwiki/images/3/30/070-4206-00_2235_Service_Manual.pdf

1. Adjust Horizontal Amplifier Gain (R740 and R730)...c. ADJUST - A Sweep Gain
(R740) for 1 time marker per division over the center 8 divisions....e. ADJUST
- B Sweep Gain (R730) for 1 time marker per division.
Don't know if R740/R730 are easily accessible, but that's what seems to be
called for here. Should be accessible and easy since this is fairly routine
calibration. But I'm an armature, so take my advise with an appropriate level
of caution.
Dave
I have the manual, thanks.
R740 and R730 are just next to each other on the horizontal board.


Re: 2235 Horizontal Calibration Issue

Stephen
 

On Sun, Jan 17, 2021 at 08:13 AM, Ozan wrote:


As Raymond wrote this could be within the accuracy of the oscilloscope. Do you
see similar accuracy if you use B sweep?

Ozan
I haven’t checked sweep B. Good idea. Maybe they interact?


Re: 2235 Horizontal Calibration Issue

Stephen
 

On Sun, Jan 17, 2021 at 06:09 AM, Raymond Domp Frank wrote:


On Sun, Jan 17, 2021 at 01:40 PM, Stephen wrote:


The calibration procedure says to align the 8 middle pips. And they are as
best as I can do it on this scope, but the central one is always off...
Spec says +/- 5%, i.e. 0.1 division, so it's within spec. See SM,
"HORIZONTAL", "PROCEDURE STEPS", "1. Check Timing Accuracy and Linearity",
point "e.".

Raymond
Hi Raymond,
You’re right. But is bothers me because it’s the ONLY scope that has that issue. All the others are dead on.


Re: 2235 Horizontal Calibration Issue

Stephen
 

Hi Dave,

I also have several 400 series scopes. Some things are similar, and others are lacking (for me) on the 2000 series. Some adjustments are not on the 2000 series.
I have all the manuals. But thanks.


Re: 2235 Horizontal Calibration Issue

Dave Peterson
 

Page 5-14 of the 2235 Service Manual:
https://w140.com/tekwiki/images/3/30/070-4206-00_2235_Service_Manual.pdf

1. Adjust Horizontal Amplifier Gain (R740 and R730)...c. ADJUST - A Sweep Gain (R740) for 1 time marker per division over the center 8 divisions....e. ADJUST - B Sweep Gain (R730) for 1 time marker per division.
Don't know if R740/R730 are easily accessible, but that's what seems to be called for here. Should be accessible and easy since this is fairly routine calibration. But I'm an armature, so take my advise with an appropriate level of caution.
Dave

On Sunday, January 17, 2021, 11:14:09 AM PST, Ozan <ozan_g@erdogan.us> wrote:

As Raymond wrote this could be within the accuracy of the oscilloscope. Do you see similar accuracy if you use B sweep?

Ozan


Re: 2235 Horizontal Calibration Issue

Ozan
 

As Raymond wrote this could be within the accuracy of the oscilloscope. Do you see similar accuracy if you use B sweep?

Ozan

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