Topics

2235 horizontal sweep ripples wrong direction


Ilan Messing
 

This is my first post,, if i am doing something wrong, let me know.
I have recently acquired a 2235 from a university that was dumping their entire supply.
the sweep ripples in the wrong direction several times a sweep, out of phase with the sweep itself.
here is a video. skip to 1:25 https://youtu.be/v6NTnEvhzTM the probe is connected to the compensation.


here is another video
https://www.youtube.com/watch?v=DcQEsyPuBJY


Siggi
 

On Sun, Sep 3, 2017 at 19:33 izm9515@... [TekScopes] <
TekScopes@...> wrote:



This is my first post,, if i am doing something wrong, let me know.
I have recently acquired a 2235 from a university that was dumping their
entire supply.
the sweep ripples in the wrong direction several times a sweep, out of
phase with the sweep itself.
here is a video. skip to 1:25 https://youtu.be/v6NTnEvhzTM the probe is
connected to the compensation.


here is another video
https://www.youtube.com/watch?v=DcQEsyPuBJY
Hey there (Ilan?)

It would be nice to have a name or a nick to call you by :).
Congrats on your new scope, looks like she's in fair shape, though one of
the vertical channel skirts have been lost.
The first port of call is always to test the power supplies for value and
ripple. This looks like it could be due to dried out mains filtering
capacitors.
You need to grab a copy of the service manual to get the specs and
locations of the test points. This <http://w140.com/tekwiki/wiki/2235> may
link to a decent copy, or if you can't find a decent free copy, Artek
Manuals are sure to have a great scan for a little money.
Do you have access to a second scope?

Siggi


<https://www.youtube.com/watch?v=DcQEsyPuBJY>


 

On Mon, 04 Sep 2017 10:55:29 +0000, you wrote:

...

The first port of call is always to test the power supplies for value and
ripple. This looks like it could be due to dried out mains filtering
capacitors.
I am thinking we are seeing the ripple from the inverter instead of
the preregulator and that the problem is open capacitors on the
secondary side.

The horizontal CRT amplifier uses the +100 volt supply which only has
one capacitor, C954 shown on schematic 7, so that should be checked. I
believe that +100 volt supply is only used by the horizontal CRT
amplifier and the z-axis amplifier.

You need to grab a copy of the service manual to get the specs and
locations of the test points. This <http://w140.com/tekwiki/wiki/2235> may
link to a decent copy, or if you can't find a decent free copy, Artek
Manuals are sure to have a great scan for a little money.
The 2236 service manual could be used also.

Do you have access to a second scope?

Siggi
This might be one of those cases where the oscilloscope can be used to
check the ripple on its own power supply. Just make sure that the
probe ground lead does not touch *anything* except a ground. I would
not even use the probe ground lead at all.


Ilan Messing
 

You can call me Ilan. I have another analog scope, a TAS 455. I am in high school and have little education and experience, but I can replace capacitors. I do not have an isolation transformer or differential probes so i guess I will stick to the old ADD INVERT trick when measuring ripple. I may buy a paper service manual, since it is easier than trying to scroll to the right page and navigating the cut up schematics.


 

The important measurements right now are on the secondary side of the
power supply so an isolation transformer is not required. Care still
needs to be taken with the probe ground because it can short out
anything on the secondary side risking damage. For low frequency
measurements like this, I usually fasten the probe ground to the
chassis ground or a solid ground test point or disconnect the ground
lead from the oscilloscope probe to avoid accidents.

The inverter operates at about 20 kHz so some multimeters can measure
the AC ripple directly and this would be the safer because there would
be no risk of grounding something important.

On 04 Sep 2017 14:59:12 +0000, you wrote:

You can call me Ilan. I have another analog scope, a TAS 455. I am in high school and have little education and experience, but I can replace capacitors. I do not have an isolation transformer or differential probes so i guess I will stick to the old ADD INVERT trick when measuring ripple. I may buy a paper service manual, since it is easier than trying to scroll to the right page and navigating the cut up schematics.


 

That is not a meaningful display, except that it indicates a power supply problem.The direction the ripple appears to move is of no diagnostic value.Check the LV power supplies & you will find one or more which are grossly out of spec.
 HankC, Boston WA1HOS

[Non-text portions of this message have been removed]


Ilan Messing
 

Unfortunately my mom made me put the cabinet back on after 1 look at the 7kV warning on the CRT neck. The issue is minor, So I will wait another 3 years. See yall then!


John Griessen
 

On 09/04/2017 07:40 PM, izm9515@... [TekScopes] wrote:
Unfortunately my mom made me put the cabinet back on after 1 look at the 7kV warning on the CRT neck. The issue is minor, So I will wait another 3 years. See yall then!
Too funny!

Still, I recommend studying human body model, electrocution, circuit theory: kirchoff law, volts, amps capacitor discharge, time constant, etc. in the mean time... Don't take anyone's word for it when it comes to what risk of your life you take, derive it from basic principles instead.


 

I faced the same problem with my mom 64 years ago.  Fortunately for me, we had an uncle and a family friend who were electronics technicians.  She trusted them to mentor me as I learned the rules.  They taught me well enough that I was a TV repair technician by age 17.  My point is: Mom is right, but friends are always willing to help a precocious young man with a willing attitude.  

From: "izm9515@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Monday, September 4, 2017 7:40 PM
Subject: [TekScopes] Re: 2235 horizontal sweep ripples wrong direction

  Unfortunately my mom made me put the cabinet back on after 1 look at the 7kV warning on the CRT neck. The issue is minor, So I will wait another 3 years. See yall then!

[Non-text portions of this message have been removed]

#yiv9546336778 #yiv9546336778 -- #yiv9546336778ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv9546336778 #yiv9546336778ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv9546336778 #yiv9546336778ygrp-mkp #yiv9546336778hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv9546336778 #yiv9546336778ygrp-mkp #yiv9546336778ads {margin-bottom:10px;}#yiv9546336778 #yiv9546336778ygrp-mkp .yiv9546336778ad {padding:0 0;}#yiv9546336778 #yiv9546336778ygrp-mkp .yiv9546336778ad p {margin:0;}#yiv9546336778 #yiv9546336778ygrp-mkp .yiv9546336778ad a {color:#0000ff;text-decoration:none;}#yiv9546336778 #yiv9546336778ygrp-sponsor #yiv9546336778ygrp-lc {font-family:Arial;}#yiv9546336778 #yiv9546336778ygrp-sponsor #yiv9546336778ygrp-lc #yiv9546336778hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv9546336778 #yiv9546336778ygrp-sponsor #yiv9546336778ygrp-lc .yiv9546336778ad {margin-bottom:10px;padding:0 0;}#yiv9546336778 #yiv9546336778actions {font-family:Verdana;font-size:11px;padding:10px 0;}#yiv9546336778 #yiv9546336778activity {background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}#yiv9546336778 #yiv9546336778activity span {font-weight:700;}#yiv9546336778 #yiv9546336778activity span:first-child {text-transform:uppercase;}#yiv9546336778 #yiv9546336778activity span a {color:#5085b6;text-decoration:none;}#yiv9546336778 #yiv9546336778activity span span {color:#ff7900;}#yiv9546336778 #yiv9546336778activity span .yiv9546336778underline {text-decoration:underline;}#yiv9546336778 .yiv9546336778attach {clear:both;display:table;font-family:Arial;font-size:12px;padding:10px 0;width:400px;}#yiv9546336778 .yiv9546336778attach div a {text-decoration:none;}#yiv9546336778 .yiv9546336778attach img {border:none;padding-right:5px;}#yiv9546336778 .yiv9546336778attach label {display:block;margin-bottom:5px;}#yiv9546336778 .yiv9546336778attach label a {text-decoration:none;}#yiv9546336778 blockquote {margin:0 0 0 4px;}#yiv9546336778 .yiv9546336778bold {font-family:Arial;font-size:13px;font-weight:700;}#yiv9546336778 .yiv9546336778bold a {text-decoration:none;}#yiv9546336778 dd.yiv9546336778last p a {font-family:Verdana;font-weight:700;}#yiv9546336778 dd.yiv9546336778last p span {margin-right:10px;font-family:Verdana;font-weight:700;}#yiv9546336778 dd.yiv9546336778last p span.yiv9546336778yshortcuts {margin-right:0;}#yiv9546336778 div.yiv9546336778attach-table div div a {text-decoration:none;}#yiv9546336778 div.yiv9546336778attach-table {width:400px;}#yiv9546336778 div.yiv9546336778file-title a, #yiv9546336778 div.yiv9546336778file-title a:active, #yiv9546336778 div.yiv9546336778file-title a:hover, #yiv9546336778 div.yiv9546336778file-title a:visited {text-decoration:none;}#yiv9546336778 div.yiv9546336778photo-title a, #yiv9546336778 div.yiv9546336778photo-title a:active, #yiv9546336778 div.yiv9546336778photo-title a:hover, #yiv9546336778 div.yiv9546336778photo-title a:visited {text-decoration:none;}#yiv9546336778 div#yiv9546336778ygrp-mlmsg #yiv9546336778ygrp-msg p a span.yiv9546336778yshortcuts {font-family:Verdana;font-size:10px;font-weight:normal;}#yiv9546336778 .yiv9546336778green {color:#628c2a;}#yiv9546336778 .yiv9546336778MsoNormal {margin:0 0 0 0;}#yiv9546336778 o {font-size:0;}#yiv9546336778 #yiv9546336778photos div {float:left;width:72px;}#yiv9546336778 #yiv9546336778photos div div {border:1px solid #666666;min-height:62px;overflow:hidden;width:62px;}#yiv9546336778 #yiv9546336778photos div label {color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}#yiv9546336778 #yiv9546336778reco-category {font-size:77%;}#yiv9546336778 #yiv9546336778reco-desc {font-size:77%;}#yiv9546336778 .yiv9546336778replbq {margin:4px;}#yiv9546336778 #yiv9546336778ygrp-actbar div a:first-child {margin-right:2px;padding-right:5px;}#yiv9546336778 #yiv9546336778ygrp-mlmsg {font-size:13px;font-family:Arial, helvetica, clean, sans-serif;}#yiv9546336778 #yiv9546336778ygrp-mlmsg table {font-size:inherit;font:100%;}#yiv9546336778 #yiv9546336778ygrp-mlmsg select, #yiv9546336778 input, #yiv9546336778 textarea {font:99% Arial, Helvetica, clean, sans-serif;}#yiv9546336778 #yiv9546336778ygrp-mlmsg pre, #yiv9546336778 code {font:115% monospace;}#yiv9546336778 #yiv9546336778ygrp-mlmsg * {line-height:1.22em;}#yiv9546336778 #yiv9546336778ygrp-mlmsg #yiv9546336778logo {padding-bottom:10px;}#yiv9546336778 #yiv9546336778ygrp-msg p a {font-family:Verdana;}#yiv9546336778 #yiv9546336778ygrp-msg p#yiv9546336778attach-count span {color:#1E66AE;font-weight:700;}#yiv9546336778 #yiv9546336778ygrp-reco #yiv9546336778reco-head {color:#ff7900;font-weight:700;}#yiv9546336778 #yiv9546336778ygrp-reco {margin-bottom:20px;padding:0px;}#yiv9546336778 #yiv9546336778ygrp-sponsor #yiv9546336778ov li a {font-size:130%;text-decoration:none;}#yiv9546336778 #yiv9546336778ygrp-sponsor #yiv9546336778ov li {font-size:77%;list-style-type:square;padding:6px 0;}#yiv9546336778 #yiv9546336778ygrp-sponsor #yiv9546336778ov ul {margin:0;padding:0 0 0 8px;}#yiv9546336778 #yiv9546336778ygrp-text {font-family:Georgia;}#yiv9546336778 #yiv9546336778ygrp-text p {margin:0 0 1em 0;}#yiv9546336778 #yiv9546336778ygrp-text tt {font-size:120%;}#yiv9546336778 #yiv9546336778ygrp-vital ul li:last-child {border-right:none !important;}#yiv9546336778



[Non-text portions of this message have been removed]


Siggi
 

On Mon, Sep 4, 2017 at 20:40 izm9515@... [TekScopes] <
TekScopes@...> wrote:



Unfortunately my mom made me put the cabinet back on after 1 look at the
7kV warning on the CRT neck. The issue is minor, So I will wait another 3
years. See yall then!
Hey Ilan,

That's too bad, though your mom may well be right. You may still want to
get and study the service manual, as if you're of the bent, you're sure to
learn a lot from it. You may also want to read this doc: <
http://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf> and do
your own diagnosis on your ailing scope.

Keep your lasers handy!

Siggi


Ilan Messing
 

[in case you cant see any of the previous posts in this thread, here is a recap https://groups.io/g/TekScopes/message/139381 ]

Hey gang, it's been 3 years and I am currently studying for an Electrical Engineering major at university. Because of the pandemic, we have limited lab classes and the professor is having a hard time adjusting. So we're not learning a whole lot this semester. In addition, the IEEE student lab is closed. Anyway I may have another crack at my 2235 over winter break. I'm more confident in my soldering skills and I have a few more tools like a power supply and function generator. Even if I cant fix it's no sweat, more of an educational thing at this point. A possible setback is that my other oscilloscope, a TAS 455 isn't responding very well to front panel controls. Also I'm an idiot and never really fixed anything like this before. When finals are up I'll read through the service manual but I probably wont understand a lot of it with only a semester. I also found some other documents lurking around here with information for fixing these things. Some preliminary questions I had:
Before even doing the gritty diagnosing, Is it worth it to replace all electrolytic and/or tantalum capacitors? Someone on YouTube made a video that I've been trying to follow and he made a digikey cart with all the capacitors and some other parts. https://youtu.be/lrXCVg6T-ek and https://www.digikey.com/short/zf0m5b . Kind of a risky investment in my opinion, since it's a ton of parts for something that just might not get fixed. On the other hand, blanketly replacing those parts could fix an issue that I never would have found.
As previously pointed out, one of the vertical channel 1 "skirt" is missing, the little clear plastic ring with the volts per division labels. I always thought of it as the last thing to fix, but are there any creative solutions? 3d printing a ring and hand writing the numbers?
How much current do the low voltage power rails need? My power supply has dual 30v 2A channels. Can that replace the 43v, 8.6v or whatever other LV rails the scope has?
What method works for you for removing solder from these boards? Since they're older style I'm assuming they're more delicate. If I use leaded solder should I use a different tip than the one I use with lead free solder? What solder do you recommend?
I'll search through older threads on this forum to scrape more information to questions I don't even know I should be asking

Sorry for rambling in this very nice community, lemme know if I'm approaching this from the wrong angle or something.

-Ilan


Jean-Paul
 

Ilan:

BRAVO for your work and persistence!

A few tips: Avoid using external power in debugging, easy to have safety or do damage.

Suggest Do NOT replace all capacitors, can do damage in desolder and new caps may have different size/specs! Logical troubleshooting should reveal the culpret!

Ripple measurement is done with AC coupling and single probe not differential, beware of scope max input voltage, DO NOT check ripple on HV without proper percaution and proceedure.

Youtube: Avoid irrelivant music and try to stabalize, often a still photo is better.

Ripple on PSU would affect other parts of trace are you sure it is triggered properly?

Manuals and serive on TEKWIKI for free, no need to buy the Artech or Qservice.

TAS455: Have found a low cost analog scope much better to troubleshoot, picked up a hameg HM103 for EU7 at a flea market!

Best learing is practical experience, and tips from forums, suggst to post similar on EEVblog repair or test equipment

Network with local Amateur Radio clubs to get the best education, assistance and contacts

Just the ramblings of an old retired EE, in electronics since 1950s and EE since 1968!

BUT STILL LEARNING!

Bon journee,

Jon

Been electronics guy since