Date   

Re: MEMBERS PLEASE READ: Our annual Group.io payment is due in 2 weeks.

Charlie Conger
 

Dennis thanks for all you do. $25 payment has been sent.


Re: Tektronix 2245a Flickering Trace

KB6NAX
 

Hi Bill,

Sounds like Panos has a clue. Switch in the 20 MHz bandwidth filter to see if the erratic triggering stops or lessens. Too much bandwidth can be a problem in a noisy environment. If the triggering in 20 MHz mode still acts up there's something noisy in the triggering circuits.

Arden

-----Original Message-----
From: guitardad1967@gmail.com
Sent: Thursday, January 02, 2020 5:58 AM
To: TekScopes@groups.io
Subject: [TekScopes] Tektronix 2245a Flickering Trace

Hey guys, newbie here. First of all I want to say thanks for what a great resource this place is! Made my donation two days ago.

I have a Tektronix 2245a, which I bought about a year ago. This is my first scope, and I’m still learning how to use it. I have replaced all the power supply capacitors, and all the voltages test out OK., and the unit runs OK when I first power it on. After about 10 minutes though, I start to get ghost traces and a jumpy, flickering image. Here is a link to a video I made of the unit. https://youtu.be/j6Dqke1CIRE

It is usable for what I do, which is just viewing a signal after it’s gone through a tube amp, but I would like to track down the issue. Any suggestions on where to look?

Thanks everyone, Bill


Re: Push-push switch repair (need some theory of operation)

Greg Muir
 

Reference Tek Lubrication Kit Instructions 070-0496-01

Wow. Tek actually recommended WD40 even to use on pot resistive surfaces.

Granted the penetrant in WD40 does permeate between tiny interfaces and the lubricant will serve its function but I’m really leery about it otherwise unless I can remove it promptly after applying. And i doubt if anyone has done any research into the long term effects of it on resistive elements or other sensitive materials.

I’m wondering if the specifying engineer had any regrets afterwards making this decision. On the other hand any problems resulting from the use of WD40 apparently has not been significant enough as to cause poor operation of the equipment. And the continual upgrade (purchase) to new equipment by the first users left us on this site dealing with the long lost after effects if any are lingering.

As it has been said in the past “You pays your money and takes your chances” sort of akin to driving at high rates of speed on icy roads. Most of the time it will be successful.

Greg


Re: Push-push switch repair (need some theory of operation)

Mlynch001
 

A vast majority of these switches which I have encountered seem to stop working because they get dried out (no lube) or full of congealed lubricants or just plain old crud. The 2213 and 2215 come to mind as I have bought several as "non-working". All they needed was the power switch cleaned and proper lubrication to restore them to function. On occasion, one sees corrosion damage due to some well meaning individual using a cleaner which leaves a reactive film or residue. This is the exception to the rule, at least in my experience. I have repaired many an instrument that simply needed a switch or two properly cleaned to restore primary functions.
--
Michael Lynch
Dardanelle, AR


Re: 130 LC meter

Dave Wise
 

Not the OP's problem but it's about the 130. I want to document some interesting symptoms and their causes.

I calibrated it using Albert Otten's 2016 topic "Tpe 130 L-C meter calibration using only a 300 pF cap", https://groups.io/g/TekScopes/topic/7656928#126515 .
It's much easier than acquiring an S-30, all you need is one good close cap and a frequency counter. Few labs had counters when the 130 was born.
Since I had the counter connected, I decided to try calibrating C7, Resistance Compensation.

SYMPTOM: Not possible to match readings 1M vs 100K, C7 at minimum still too big.
FIX: Reducing R8 helps. I put in 680K instead of 1M.

NOTES:
Carbon film and metal film have less parasitic C than carbon comp at these values and frequencies.
This helped, but still some tubes work in V4, some don't. I can't predict it.
Fewer fail after the mod.
You can substitute 6GH8 and 6EA8 in place of 6U8.
All my 6EA8s work; the Amperex 6GH8 fails. So does at least one 6U8.
It doesn't matter how it tests; some weak tubes work and some strong ones fail.
I measured my 1M/100K parasitic C with GR 1656 at 10kHz.
It's about the same as 1kHz.
I used Conductance mode with AC excitation, and an external variable cap on the bridge arm to balance out the parasitic.
Then measured the variable cap. You have to push it through an equation to get the true C instead of a multiple due to the ratios.
Old black Welwyn 1% spiral-cut carbon? film resistors in my junk box which happen to be the type used in early production of S-30: 100K is 0.4pF, 1M is 0.5pF .
So I adjust R8 so 1M reads 0.1pF higher than 100K.

SYMPTOM: C99 and C100. Tek installed them backwards, they're
drawn backwards on the schematic too.
FIX: Probably EVERY 130 needs them replaced, with anode facing positive voltage.

SYMPTOM: 10pF reads high on 30pF range.
CAUSE: Dielectric Absorption in C92 .0047/400 charge pump cap.
This is the first failure I've ever seen that was traceable to DA.
It makes the cap appear larger than it should be, and changing with frequency,
so readings that are low on the scale pump too much charge and get skewed upwards.
NOTES:
You can measure C92, C93 etc in-circuit if the 130 range switch is OFF.
The cap is not leaky.
It's a Sprague 160P DiFilm. (Plastic/paper dielectric.)
Use GR 1680-A to measure C at 1kHz and 400Hz.
Should read 4.7nF, but I see 6.5nF at 1kHz, 7.5nF at 400Hz. Yep.
An ideal cap will be constant C, a cap with DA will increase with decreasing f.
Later I tested it using the soak-discharge-wait-measure method. Significant rebound,
over 10V after 100V soak. That will mess up a charge pump!
FIX: Replaced with polypropylene. Also replaced C93 .015/400 10pF range because
it had some DA too.
Joke's on me - now 10pF on 30pF range reads a bit low where it used to read high.
I bet those 160P caps had some DA when new, and Tek drew the meter scale to fit.
Maybe I should have used something with more DA. Oh well, |error| is smaller now at least.
LESSON: Replace all paper/plastic caps in positions sensitive to Dielectric Absorption,
even if they test good for leakage.

HTH,
Dave Wise


Re: Push-push switch repair (need some theory of operation)

ROLYNN PRECHTL K7DFW
 

"Siggi" <siggi@undo.com> wrote:
This <http://w140.com/tekwiki/images/8/87/070-0496-01.pdf>; one?
====================================================================


Affirmative.


Rolynn


WTB: Tektronix TDS3000 handle hubs

Tom B
 

Hello All,

I am looking for 2 Tektronix TDS3000 handle hubs, part number 401-0785-00.  These hold the handle on the TDS3000 series oscilloscopes.  I  could also use one or 2 of the hub covers, part number 200-4394-00.  Please let me know if you have these parts available or where I can get them at a reasonable price.

Tom Bryan
N3AJA


Re: Push-push switch repair (need some theory of operation)

Siggi
 

This <http://w140.com/tekwiki/images/8/87/070-0496-01.pdf>; one?

On Thu, Jan 2, 2020 at 1:21 PM ROLYNN PRECHTL K7DFW <k7dfw@clatskanie.com>
wrote:




What was stripped from the email was a pdf of the instructions for the
Tektronix Lube Kit.


TEKTRONIX LUBE KIT INSTR 070-0496-01.pdf (3902Kbytes)

Maybe you can find it on the www.


Rolynn
Tek Bvtn and Sunset 1966-1971




Re: Tektronix 2245a Flickering Trace

Panos
 

Hi Bill,
Is this disappear if you will use one of the freq rejection filters, or hold off setting?


Panos


Push-push switch repair (need some theory of operation)

ROLYNN PRECHTL K7DFW
 

What was stripped from the email was a pdf of the instructions for the Tektronix Lube Kit.


TEKTRONIX LUBE KIT INSTR 070-0496-01.pdf (3902Kbytes)

Maybe you can find it on the www.


Rolynn
Tek Bvtn and Sunset 1966-1971


Re: Push-push switch repair (need some theory of operation)

ROLYNN PRECHTL K7DFW
 

very correct in regards to not using WD40 for switch (and potentiometer) cleaning/lube.

=========================================================================================

From this I gather that you think that the Tektronix engineers were daft when they wrote the contents of the attached.


Rolynn
Tek Bvtn and Sunset 1966-1971


Re: Push-push switch repair (need some theory of operation)

greenboxmaven
 

WD-40 can be a superior solvent to loosen up hardened grease and petroleum based crud. However, it can only be used as a first part of the cleaning process, and then must be promptly flushed out once it has done it's work. It does indeed leave a residue that is difficult to remove. DeOxit or comparable products use oxalic acid as one of their main ingredients. It is quite effective in removing oxides and tarnish from contacts.

Bruce Gentry, KA2IVY

On 1/2/20 12:31 PM, Greg Muir via Groups.Io wrote:
Bob Krassa is very correct in regards to not using WD40 for switch (and potentiometer) cleaning/lube. When used the light volatile carrier eventually evaporates leaving a heavy sticky Cosmoline type grease film that loves to collect crud. As a demonstration spray some WD40 on a tool, don’t wipe it off and leave it for a few weeks and see what happens.


Greg



Re: Push-push switch repair (need some theory of operation)

Greg Muir
 

Bob Krassa is very correct in regards to not using WD40 for switch (and potentiometer) cleaning/lube. When used the light volatile carrier eventually evaporates leaving a heavy sticky Cosmoline type grease film that loves to collect crud. As a demonstration spray some WD40 on a tool, don’t wipe it off and leave it for a few weeks and see what happens.

One first has to flush the switch with a compatible solvent (I see that Tek recommends IPA in their switch repair document) followed by a suitable lubricant and/or deoxidant. Many lean towards the Caig DeoxIT products as have I in the past but eventually came upon a product made by MG Chemicals called “Super Contact Cleaner” that has mysteriously similar characteristics as compared to the Caig products but at a considerably lower cost for larger quantities (I am not affiliated with either manufacturer or product offering). I have never had a problem using it on any switch or pot.

In all, it is not recommended to “goop up” switches and controls with those household products that don’t list use on delicate electronic devices. I always cringe when I open a piece of previously doctored equipment where the “doctor” used a non-recommended cleaner & lube and end up either cleaning all of the controls or having to replace them.

Greg


Re: MEMBERS PLEASE READ: Our annual Group.io payment is due in 2 weeks.

Hugh Vartanian
 

Hi Dennis,

Thank you and Michael for all your moderately profuse information
transmission, modulation and noise (reduction) in your duties as moderator,
bringing moderation and great knowledge to the more-than-moderately fun and
informative tek group.io group!

Best for the new year to all,
Hugh


Re: TDS3044B repair

Tom B
 

Hello All,

I finally had time to get back to fixing the TDS3044B with no display.   The problem turned out to be a bad solder joint on a surface mount choke that supplied Vcc to the display.  The crack was so small it could barely been seen on a microscope.  So, the problem was not the display.  For those that need a display for a TDS3000B, the real part number is NEC NL6448BC20-08E.  The other thing that was helpful in troubleshooting the display was a Hirose connector part number DF9A-31P.  This gave me some more room to probe the display connections on the main board.  Now I need to find the hub bits that hold the handle on the scope.  If someone knows where to get those please let me know.

Tom Bryan

On 11/7/2019 10:00 PM, Tom B wrote:
Hi Dave,

If you look at this video https://urldefense.com/v3/__https://www.youtube.com/watch?v=Z_gvjmKHN4Y__;!b9GWhakWANQ!wEpfxjysOXjFgv3ZjJzwPT00sPf81J7-h9F-OyCNJMU1-f5Y3AG4Mbyun-yU$ it shows a part number on the back of the display as 65BLM04 and on the front of the display the tag says NL6448BC20-08.  If you search each of these part numbers on ebay, the price is very different when they are actually the same part.   The cheapest price I could find for the 65BLM05 is $158.74 (used), while the cheapest price for the NL6448BC20-08 is $88 for a new part. These appear to be exactly the same part.  Any idea if there is any difference?

Tom

On 11/7/2019 2:28 PM, David Kuhn wrote:
https://urldefense.com/v3/__https://www.youtube.com/watch?time_continue=261&;v=iVU0YPIeovM__;!b9GWhakWANQ!wbXzExaWmEY10yA6ddr1j7dzMVPNV7j4iMLI9u6paEFuQ5tXhS6mqOV8S_HN$

https://urldefense.com/v3/__http://lcdparts.net/UBDetail.aspx?ProductID=3796__;!b9GWhakWANQ!wbXzExaWmEY10yA6ddr1j7dzMVPNV7j4iMLI9u6paEFuQ5tXhS6mqCtAAjYv$

Looks like a perfect solution for the NEC on the TDS3000 series and in the
NEC 65BLM05 Display (virtually the same display as the one TEK uses) in the
instruments I do a lot of work on.

Unlike the video, I would not remove the paper exposing the glue when
installing the strips.  I don't want those LED strips permanently in my
LCDs in case they fail.

Dave

On Wed, Nov 6, 2019 at 11:40 PM Harvey White <madyn@dragonworks.info> wrote:


Re: Push-push switch repair (need some theory of operation)

Mlynch001
 

Definitely use a "plastic safe" lubricant. Also one that has proven non-corrosive characteristics. The vast majority of these switches are simply dried out, gentle cleaning and lubrication will restore most to service.

--
Michael Lynch
Dardanelle, AR


Re: Push-push switch repair (need some theory of operation)

bobkrassa
 

This swithc looks similar to the one in the Sencore PR57 AC Powerite. The basic operation is that pushing the button has to cause the latch bar to move sideways. In these switcches that as done by pushing on a fairly steep, small ramp. Looks like the ramp is on the little star wheel. Using small steep ramps to get lateral motion requires a bit of lubrication to keep the ramp smooth and working. In the Powerite, the ramps are on tiny plastic pieces.

I suggest taking the board out but before you unsolder the switch from the board, try flooding the switch with your favorite plastic-safe combination cleaner-lubricant and gently moving the parts back and forth. As a preventive measure, when these switches start to become difficult, do not use force, instead take them out and clean and lube. Do not use WD40.

73 Bob Krassa ACØJL


Tektronix 2245a Flickering Trace

William Schuler
 

Hey guys, newbie here. First of all I want to say thanks for what a great resource this place is! Made my donation two days ago.

I have a Tektronix 2245a, which I bought about a year ago. This is my first scope, and I’m still learning how to use it. I have replaced all the power supply capacitors, and all the voltages test out OK., and the unit runs OK when I first power it on. After about 10 minutes though, I start to get ghost traces and a jumpy, flickering image. Here is a link to a video I made of the unit. https://youtu.be/j6Dqke1CIRE

It is usable for what I do, which is just viewing a signal after it’s gone through a tube amp, but I would like to track down the issue. Any suggestions on where to look?

Thanks everyone, Bill


Re: MEMBERS PLEASE READ: Our annual Group.io payment is due in 2 weeks.

Joe Laffey
 

Sent in a donation PayPal from my other email address. I don’t need credit per se. So no worry.

Thanks for all the hard work.

--
Joe Laffey

On Jan 2, 2020, at 10:24 AM, Victor via Groups.Io <vmcfer=aol.com@groups.io> wrote:


Hi Dennis,
I just read your message and sent you my contribution of USD20.00.Thank you for the great job and effort you are doing all the year.This is a fantastic group. Love it !!!Wish you a Happy New Year 2020.Victor(vmcfer@aol.com)

-----Original Message-----
From: Dennis Tillman W7PF <dennis@ridesoft.com>
To: TekScopes <TekScopes@groups.io>
Sent: Tue, Dec 31, 2019 4:42 am
Subject: [TekScopes] MEMBERS PLEASE READ: Our annual Group.io payment is due in 2 weeks.

Hello everybody,
In a few minutes it will be 2020. This is much further into the future than
I thought I'd ever see. Years ago I was sure someone would have developed a
tiny ultra-thin LED display that can be imbedded into a credit card by 2020.
It would display your current outstanding balance every time the card was
inserted in a reader. If my non-futuristic credit cards only had this
imbedded into them I would certainly not be in my present predicament. I
maxed out both cards and my wife took them away. I found this puzzling
because the cards still look the same even though they don't work anymore.
It is clear to her that she can't afford to keep me. She has made this very
clear to me often in the past 2 weeks.

Since we moved to Groups.io I have been paying the annual fee they charge to
host us. I did this for two reasons:
* It was expedient when we first joined because the demise of Yahoo seemed
imminent and this was the fastest way to get up and running on Groups.io.
* Later when I asked for suggestions on alternate ways to pay for Groups.io
I didn't see anything I liked. I thank you for all of them, they were all
fine. It seemed as if they would create extra work and, more importantly,
consume more of my time (which is in very short supply). I kept each of your
suggestions for future consideration.

In 2 weeks the total amount I will have paid will be $340. This is
significant enough that I have to do something about it, and more
importantly, I need to get back into my wife's good graces. So I am asking
for small contributions via PayPal if possible to be sent to
dennis@ridesoft.com. If you include a note along with each contribution
saying it is for Groups.io that will make it easier to track. See the
postscript at the end of my post for a no-fee way to send money with PayPal.

If PayPal doesn't work for you my address is 13808 NE 26th Place, Bellevue,
WA 98005 USA. If you have an extremely rare or unusual 7000 series plugin
that is definitely an acceptable form of payment but I must advise you I
probably already have it so contact me first.

I plan to give an accounting of the total to the group once the
contributions stop. Anything over $340 will be set aside. I will find out if
Groups.io will let me pay for the following year (or years) so we don't have
to worry if I get hit by a truck. I will press them hard to let me do this
at the old price of $110/yr.

This is the Groups.io billing summary for TekScopes:
Invoice Date Plan Payment Method
Amount Paid By
#3055 01/13/19 Premium Visa XXXX XXXX XXXX 7319 USD $110
dennis@ridesoft.com
#814 01/13/18 Premium Visa XXXX XXXX XXXX 7319 USD $110
dennis@ridesoft.com
#793 12/13/17 Premium Visa XXXX XXXX XXXX 7319 USD $10
dennis@ridesoft.com
The next payment of $110 is due 01/13/2000. NOTE: It appears the annual
price for the Premium Yearly Plan will go up the first of the year to $220.

Dennis Tillman W7PF

P.S. This is a way to send money via PayPal with minimal or no fee:
NO FEE PAYMENT METHOD FOR USA TEKSCOPES MEMBERS
* Choose "Send and Request".
* By default the Send tab will be chosen for you.
* In the "Send Money" field enter dennis@ridesoft.com.
* Next PayPal will ask you: "Sending to a Friend" or "Paying for an invoice
or service"?
* Choose "Sending to a friend".
* Enter the amount.
* Press next and choose your bank account to avoid the PayPal fee.
* Press the "Send the Money" button.
* Include your email address and TekScopes ID in the Notes section.
MINIMAL FEE PAYMENT FOR FOREIGN TEKSCOPES MEMBERS
* Chose "Send to friends and family internationally".
* Select the country you are sending to (USA).
* To keep the fee to 1% where it says "Select your delivery method" choose
"Send to a PayPal Balance".
* Under "You Send", enter whatever amount in local currency converts to the
correct US currency.
* Press next.
* The email account you will be sending to is dennis@ridesoft.com.
I can't help you after this point in PayPal because I was not outside the
USA to see what happened next.
* Include your email address and TekScopes ID in the Notes section.



--
Dennis Tillman W7PF
TekScopes Moderator






Re: 577D1 itching issue - Haven't touched since, currently in storage

Chuck Harris
 

Dennis,

It is a very bad idea to short out a turn on a transformer.

But it is a very good idea to load a turn or two on a transformer...
after all, that is the transformer's job.

Here is what your variac's brush really is:

Turn1 <--Resistor---+
Turn2 <--Resistor---+-----Brush terminal
Turn3 <--Resistor---+

The voltage between turns is around a volt on most variacs.
The resistance of the brush material is chosen so that its
the power dissipation will be 1 or 2 watts, for a typical
variac.

If it is essential that a variac go all the way to zero, there
will be a metallic landing pad for the brush to land on after
it falls off of the last turn.

Absent the landing pad, the lowest voltage will be on the
order of 1/2 turn's voltage.

The variac was originally designed to be a lamp dimmer for
theater use... it replaced the very wasteful carbon pile
rheostats originally used.

This curve tracer application is forcing an oval peg into
a round hole. It sort of fits... if you force it.

-Chuck Harris

Dennis Tillman W7PF wrote:

Chuck, Bruce, and Arden,
All my life I assumed there was little more to learn from how a Variac works. They appear to be pretty simple and a very clever. This has accounted for their incredibly useful life spanning more than 85 years.

The practical side of me says it is a very bad idea to short out a turn on a transformer with 120 (more or less) turns and 120V across it. So tomorrow I will test this by intentionally hooking a short piece of wire from one turn to its neighbor while I am holding the wire in my hand. If you are right the wire won't get hot and I will learn something new. If I am right I will get burned and never trust the three of you again. Either way you have nothing to lose. :)

I will report the results either way.

Dennis Tillman W7PF

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