Elenco s-1325 slanted trace - Page 1
Forum section: electronics / testgear

author: jmctech
author_rank: Contributor
timestamp: July 07, 2014, 04:49:41 am
content: Hi everyone, this is my first post I apologize if it is in the wrong spot. I got my first scope an Elenco s-1325 off craigslist. It came with 2 probes. When I hook either probe up to the calibration pin my square wave is slanted. This is what it looks like with time set at .5 mS and volts at .5. Cal pin says 2v P-P.If this a fixable issue or did I get taken. I paid $50 for the scope. It shows the same on both channels. Thanks for any help you guys can provide.Jason

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2014, 04:57:09 am
content: did you try to adjust the trace rotation? or does that rotates the whole signal?right in the middle of Intensity and FocusEdit: Then again it could be something to do with the deflectors on the actual CTR that got dislodge during shipping but be careful there is high voltage in there. Even if unpluged you gotta be careful.

author: jmctech
author_rank: Contributor
timestamp: July 07, 2014, 05:01:28 am
content: The trace rotation does the whole signal.

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2014, 05:53:15 am
content: Looks like the vertical deflection is tilted. Maybe someone else can chime in.I couldn't find any pictures of the insides of your scope specially the coils around the CRT tube.I couldn't find a service manual either, just the user manual.

author: tautech
author_rank: Super Contributor
timestamp: July 07, 2014, 07:25:16 am
content: Quote from: miguelvp on July 07, 2014, 05:53:15 amCRT Oscilloscope's don't use defection coils.I've fixed a few CRT scopes but have never seen one with a negative rise time.But the display seems to displaying as it should, however an incorrect signal.Have you any manuals for the scope?This will surprise many and I for one will be very interested in the progress of this thread.C'mon Super Contributors give us some clues.EditOP could this be a combination of incorrectly compensated probe and trace rotation?To check, adjust trace with no signal input and a fine focus setting to match graticule lines.Then adjust probe.

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2014, 07:30:38 am
content: Maybe not coils around the CRT neck but it looks like the vertical deflection (even if it's inside the tube) is tilted.(image from:http://www.ic.sunysb.edu/Class/phy122ps/labs/dokuwiki/doku.php?id=phy124:lab_2)That's the only thing I can think that will make this happen.edit:QuoteThat can't be because the falling edges are aligned.

author: Richard Head
author_rank: Frequent Contributor
timestamp: July 07, 2014, 07:31:59 am
content: What you have discovered is proof of the existance of tachyons! This scope is indeed displaying signals traveling backwards in time.The square wave generator must contain a flux capacitor as its timing capacitor.

author: tautech
author_rank: Super Contributor
timestamp: July 07, 2014, 07:35:30 am
content: Quote from: Richard Head on July 07, 2014, 07:31:59 amBeautiful.

author: tautech
author_rank: Super Contributor
timestamp: July 07, 2014, 07:44:46 am
content: @miguelvpYes the deflection plates may have been bent by way of impact to the scope, though it seems unusual that they seem bent both the same amount.@jmctechJason, are there any signs of impact on the case?

author: tautech
author_rank: Super Contributor
timestamp: July 07, 2014, 08:15:37 am
content: JasonSupply asawtoothtest waveform and photograph the result for us please.

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2014, 08:18:13 am
content: It can also be whatever is controlling the vertical deflection that is acting up somehow.So it might not be the deflection plates themselves but something related to the control of the vertical trace being out of sync.

author: tautech
author_rank: Super Contributor
timestamp: July 07, 2014, 08:25:03 am
content: @miguelvpI suspect scope is displaying a "reverse" sweep.That is: the horizontal plate wires have been reversed.A great trick to play on a buddy.

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 07, 2014, 08:37:54 am
content: I think it is just trace rotation and a sloppy calibration signal. Set the input to GND, use trace rotation to make the line horizontal and then use a better signal to see what it looks like.

author: AlfBaz
author_rank: Super Contributor
timestamp: July 07, 2014, 09:21:03 am
content: Has this scope got XY mode?If so place a signal in one channel and then the next. You should should get a small horizontal line in one channel and a vertical in the other.By rights the vertical one should be slanted

author: leppie
author_rank: Frequent Contributor
timestamp: July 07, 2014, 09:56:09 am
content: Got a big magnet or speaker next to the scope?I know my variable SMPS causes my TDS340 to go ape-shit when next to it.

author: Joule Thief
author_rank: Regular Contributor
timestamp: July 07, 2014, 03:29:29 pm
content: To check trace rotation, place the CH1 coupling to GND position and place the trace line over one of the horizontal graticules. The trace should stay on the graticule across the entire CRT screen. Trace rotation will correct anylineardeparture from the graticule line.To check for reversed horizontal sweep. set the HORIZ SWEEP SPEED to a low speed and observe the "dot" trace move left to right across the CRT. If the "dot" moves right to left, then the trace direction is reversed - maybe the CRT is upside down?

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 07, 2014, 03:53:35 pm
content: Quote from: Joule Thief on July 07, 2014, 03:29:29 pmNo, rotating the picture 180 will not make it look any better.

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 07, 2014, 03:55:51 pm
content: Even mirroring does not do the trick.

author: AlfBaz
author_rank: Super Contributor
timestamp: July 07, 2014, 04:17:59 pm
content: Neither does embossing

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 07, 2014, 05:53:48 pm
content: Quote from: AlfBaz on July 07, 2014, 04:17:59 pmHey there, I'm just trying to tell that the tube is not upside down or that the plate connections have been swapped, you are just bragging about your embossing talent

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2014, 05:56:26 pm
content: Maybe the OP could open up the unit and take pictures of the tube neck and control boards around it.

author: jmctech
author_rank: Contributor
timestamp: July 07, 2014, 05:57:41 pm
content: So I used an arduino and a 1uf cap and it still shows negative rise time.I did get the service manual with it but do not have the equipment to calibrate it. I don't have a waveform generator.Here is a pic of the inside,

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 07, 2014, 06:04:44 pm
content: Do you have a horizontal line without input (or set to GND)?

author: jmctech
author_rank: Contributor
timestamp: July 07, 2014, 06:09:32 pm
content: Yes, it's the same on both channels

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 07, 2014, 06:14:31 pm
content: Quote from: jmctech on July 07, 2014, 06:09:32 pmHmm, I do get the idea that the X-position is somehow getting distorted by the Y-deflection.If you decrease the X sensitivity, does that give you a lesser negative effect?You say that you have the service manual, so start by checking the power supply.

author: Andy Watson
author_rank: Super Contributor
timestamp: July 07, 2014, 06:29:58 pm
content: Can you see any evidence that the yellow coil - half-way along the tube - has been jarred out of its correct position? You could try disconnecting the coil - follow the white and red wires.

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2014, 06:33:34 pm
content: BTW here is some info for the CRT:http://tubedata.milbert.com/sheets/186/d/D14363GY123.pdf

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2014, 06:43:09 pm
content: Quote from: Andy Watson on July 07, 2014, 06:29:58 pmThat would be the trace rotation coil affixed with resin, it would affect the whole signal.

author: jmctech
author_rank: Contributor
timestamp: July 07, 2014, 06:48:52 pm
content: Coil looks good, it has 4 epoxy spots that are solid

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2014, 07:11:26 pm
content: Note 2 of the CRT pdf linked aboveQuoteEdit, but careful we are talking about 2KV here.Also the CRT has astigmatic correction, I wonder if that has a front know control and if it will affect the signal's orthogonality as mentioned in note 9 of the above doc.Quote

author: jmctech
author_rank: Contributor
timestamp: July 07, 2014, 07:16:35 pm
content: I tested all power supply leadsManual shows 140 meter showed 150Manual showed 12 meter at 12.6Manual showed 16 for two they were at 16.89 and 16.04Manual showed 31 and 6.3 on the isolation for the crt was at 7.14 and 34.8

author: jmctech
author_rank: Contributor
timestamp: July 07, 2014, 07:31:31 pm
content: This is what displays when in x - y

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2014, 07:50:44 pm
content: Quote from: miguelvp on July 07, 2014, 07:11:26 pmMore about note 9Angle between x and y traces 90 ± 0.5° (note 9)

author: tautech
author_rank: Super Contributor
timestamp: July 07, 2014, 09:07:26 pm
content: Next test should be the ramp generator for the sweep.You will want to see a cleanlinearsawtooth waveform.You will need another scope for that test.

author: rob77
author_rank: Super Contributor
timestamp: July 07, 2014, 09:21:40 pm
content: just an idea Guys....if the there is a common supply for X and Y deflection... can't it simply be that the power rail is weak and causing this ? or there is some other interference between X&Y amplifiers ? because for example: once Y starts to deflect the beam and it puls down the voltage for the X deflection... then it would produce similar effect (X goes backwards)... and similarly for the the falling edge - Y decreases deflection of the beam and the voltage for X raising back to "normal" (X goes forward faster than should).

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2014, 09:47:32 pm
content: A picture of the controller board from the back (the board tilted about 13 to 19 degrees) might help to see how the g2,g4 and g5 are connected.

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2014, 10:26:36 pm
content: Since you mentioned that you have the service manual, can you find where the astigm and geom pots are if anywhere?and post pictures of the schematic that connects to the CRT?for example something like this:Edit: Again a reminder to be careful, because there are very high voltages there. Maybe if you have a friend that repairs TVs they might be helpful.I would only try to adjust them with the power off myself and only with a plastic tool and my free hand in my pocket, high voltages scare me.I have no idea on your level of confidence dealing with 2,000 Volts.

author: jmctech
author_rank: Contributor
timestamp: July 07, 2014, 10:44:28 pm
content: Here is the other board you asked about

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2014, 11:12:07 pm
content: Can you check in the manual if VR822 is the astigmatism adjustment? and were is it located in your board?I believe is the one on the upper left of this image you posted earlier next to that 3 pin connector that I'm guessing it connects to the CRT board but I can't see it from the picture you posted.Edit: linking to your image didn't work so here is the section I'm talking aboutIs the connector labeled P802 and is that pot labeled VR822?And does the manual refer to it as the Astigmatism adjustment?It might need to be adjusted or the cap C808 is doing something funny. (Edit: if that is a cap at all, looks blurry to me)Edit: This is an educated guess, someone please chime in if you think this will fix the orthogonality between x and yEdit again: The red cable on that connector should trace all the way to pin 13 of the CRT connector.

author: AlfBaz
author_rank: Super Contributor
timestamp: July 08, 2014, 12:14:21 am
content: Quote from: jmctech on July 07, 2014, 07:31:31 pmIn that picture you have a signal to both channels in XY mode?I was curious to see what the vertical trace looked like.Checking the horizontal is easy, ground the input and you should have no vertical deflection or rotation and can be seen by looking at the line and comparing it to the graticule.To do the same for the vertical you need to apply a varying voltage on the vertical but eliminate the internal horizontal sweepSo in XY mode , if you put the signal to only one channel at a time, on one you should get a nice horizontal line and the other a nice vertical line, or in this case a line slanted back, thereby concluding that it is actually the deflection plates/circuit.

author: AlfBaz
author_rank: Super Contributor
timestamp: July 08, 2014, 12:20:31 am
content: Quote from: PA0PBZ on July 07, 2014, 05:53:48 pmLOL, I've been waiting for an excuse to post one for ages

author: tautech
author_rank: Super Contributor
timestamp: July 08, 2014, 12:55:52 am
content: Quote from: jmctech on July 07, 2014, 07:16:35 pmYour measurements show ALL voltages above spec.2 questions:Is your meter accurate?Is the scope mains input selector set for the correct mains voltage in your location?

author: jmctech
author_rank: Contributor
timestamp: July 08, 2014, 01:33:22 am
content: Yes I check that it is set for 120

author: tautech
author_rank: Super Contributor
timestamp: July 08, 2014, 01:56:48 am
content: Quote from: jmctech on July 08, 2014, 01:33:22 amI strongly suggest you change the mains input voltage selector to a lower voltage.All components in the scope will be subjected to higher than design voltages with the existing input selection.

author: jmctech
author_rank: Contributor
timestamp: July 08, 2014, 01:58:07 am
content: The only options I have is 120 and 240

author: jmctech
author_rank: Contributor
timestamp: July 08, 2014, 02:01:09 am
content: This is what the vertical looks like

author: jmctech
author_rank: Contributor
timestamp: July 08, 2014, 02:06:06 am
content: Quote from: miguelvp on July 07, 2014, 11:12:07 pmVR 822 is the astigmatism adjustment.Manipulating it makes no difference in the slant though.

author: miguelvp
author_rank: Super Contributor
timestamp: July 08, 2014, 02:34:20 am
content: That's odd since it's connected to g2, g4 and g5 it should change both the geometry and the astigmatism.At least it should make the traces wider on the bottom or narrower depending on the direction. Maybe there is something with that part of the circuit. Still not sure what C808 is, Anyone knows if the NPN transistor Q805 could cause this problem? or the capacitors C809 and whatever C808 is? (looks like a blob to me)BTW here are the notes of the CRT documentQuoteand the link again to said document:http://tubedata.milbert.com/sheets/186/d/D14363GY123.pdf

author: jmctech
author_rank: Contributor
timestamp: July 08, 2014, 02:40:59 am
content: I belive what I am going to have to do is buy a waveform generator and calibrate it from the service manual to see if that helps. Looking through the manual it shows that there is VR for the power supply which sets all voltages that I measured earlier. It does also talk about a vertical and horizontal amp adjustment. Could either of those have anything to do with it? I want to thank everyone for their input so far also.

author: miguelvp
author_rank: Super Contributor
timestamp: July 08, 2014, 03:03:45 am
content: Good luck with your repair. Even if it's slanted it's kind of usable for square waves.I find it strange the astigmatism doesn't do a thing.Otherwise it could be something to do with note 2 above since g5 g2 and g4 are connected the x and y potentials have to be symmetric, but VR 822 not doing a thing looks suspicious to me.

author: tautech
author_rank: Super Contributor
timestamp: July 08, 2014, 03:14:08 am
content: Quote from: jmctech on July 08, 2014, 02:40:59 amQuoteYou will not be able to do a proper cal with WG or FG. Maybe an AWG for a scope like this.A simple ramp gen will do to check sweep results.Somebody might like to offer a circuit?QuoteVR meaning adjustment or voltage regulator?QuoteUnlikely IMO.There is a fault with one of the core parts of the scopeYour pics show correct amplitude, timebase and display parameters.I suspect the linearity of the sweep generator.

author: jmctech
author_rank: Contributor
timestamp: July 08, 2014, 03:18:58 am
content: The power supply has a variable resistor.

author: tautech
author_rank: Super Contributor
timestamp: July 08, 2014, 03:33:55 am
content: Quote from: jmctech on July 08, 2014, 03:18:58 amOften CRT scope multi-voltage regulated supplies are referenced from 1 adjustable supply.Check your manual for the adjustment procedure, follow it and the critical V+ rails should come to spec.There will be some V+ rails that are unregulated, and the manual usually has a wider V+ range for their spec.

author: Joule Thief
author_rank: Regular Contributor
timestamp: July 08, 2014, 06:51:45 am
content: Am I getting anywhere near understanding of this issue?Let us take a slight liberty with rise / fall times for the sake of argument and say point B and point A should be DIPSLAYED as the same time per the horizontal graticule. How do we interpret a part of the waveform to exist at the same time as another part of the waveform? Visual interpretation from the PHYSICAL position of the waveform along the HORIZONTAL graticule.During the rise of the voltage level from point B to point A, the electron beam striking the CRT moves very little along the horizontal axis but makes a significant jump upward due to significant voltage changes on the vertical deflection grids. The vertical change in the position of the electron beam causes the beam to change its position relative to the top and bottom area of the horizontal deflection grid.Assume the black line labeled CB (horizontal grid bottom) and GT (horizontal grid top) represents one of the damaged (tilted) horizontal deflection grids. As the electron beam changes position to a higher position within the horizontal grid (point A), and since no significant voltage change occurs on the horizontal (time) grid during the A to B transistion time, the electron beam should remain the same distance away from the horizontal grid. The electron beam does remain in the same position relative to the horizontal grid but if the horizontal grid GB –GT tilts to the left, the electron beam will also travel to the left as the beam rises vertically. The end result is the physical placement of the beam “back in time” along the horizontal time axis.

author: miguelvp
author_rank: Super Contributor
timestamp: July 08, 2014, 07:25:26 am
content: Sounds right and that will apply to note 2 of the CRT document. The thing is that the astigmatic adjustment has no effect as per the OP, maybe he didn't turn it too much to be conservative but it should have done something instead of no effect unless that wasn't the right pot (should be labeled VR822 but it's not in view from the picture he posted).But if it's not that pot, then inote 2 implies that the problem is a discrepancy between the x and y potentials since g2, g4 & g5 are connected according to the schematic he posted.

author: Joule Thief
author_rank: Regular Contributor
timestamp: July 08, 2014, 07:43:50 am
content: I know this is not the issue, but did we ever try the trace rotation controljust to see if it was operational? Sometimes a problem is isolated by first finding out what does function as expected.

author: miguelvp
author_rank: Super Contributor
timestamp: July 08, 2014, 07:49:18 am
content: Quote from: Joule Thief on July 08, 2014, 07:43:50 amPost #2 and OP's reply post #3It rotates the whole signal, no pictures posted i'm afraid.

author: Joule Thief
author_rank: Regular Contributor
timestamp: July 08, 2014, 08:10:55 am
content: Thanks. Was not sure if he had confirmed proper operation of the trace rotation or was just putting forward his understanding the whole trace would be affected and not just the "tilt".

author: miguelvp
author_rank: Super Contributor
timestamp: July 08, 2014, 08:13:35 am
content: A good picture of the back of the CRT neck connector will help.Maybe the connection between pin 12 and pin 13 is disconnected and that's why the pot has no effect since it's only driving g4 and not g2 and g5 if the connection is not there.Edit: that came out at pretty low res, adding the layout picture from the doc.The way I understand this, pins 5, 6, 12 and 13 should be all connected in that connector board.

author: onlooker
author_rank: Frequent Contributor
timestamp: July 08, 2014, 12:39:01 pm
content: The pinouts and diagrams shown are not consistent?Anyway, if vr822 has no effect, then check if q805 is working properly:-- the160V power rail. Is this the same one also labelled 140V?-- the base voltage. Does it change with vr822 with enough swing?-- the emitter voltage. Does it follow the base voltage?Then, check in xy mode, the votages btw gnd and y-, y+, x-, x+ respectively.These are just to check if the oscope is still in spec as described in those notes.

author: miguelvp
author_rank: Super Contributor
timestamp: July 08, 2014, 02:29:07 pm
content: Quote from: onlooker on July 08, 2014, 12:39:01 pmcareful where the 2000 Volts are if you are going to check this,you need high voltage probes too.Myself I would leave that to a shop or someone that works with high-voltages.Also what type of DMM do you have as in brand/model, might not be good for these kinds of measurements. (yeah i'm being overcautious but this is a dangerous area to be poking around)The pinouts on the diagram are looking from the back of the connector btw so they do match.

author: Electronics-Repairman
author_rank: Contributor
timestamp: July 08, 2014, 03:03:03 pm
content: Hope you solve it , beware if you stick your hand inside it may bite, remember it's a case of one hand in your pocket , and NO metal work like rings or chains, I know it's boring stuff, but it's the boring stuff that keeps you alive.

author: PointyOintment
author_rank: Frequent Contributor
timestamp: September 14, 2014, 03:49:22 am
content: Quote from: Joule Thief on July 08, 2014, 06:51:45 amI disagree. Both horizontal deflection plates being tilted the same amount should make no difference to the horizontal deflection of the electron beam. The E-field is uniform between them (across the width of the tube), so the electrons being closer to one plate than the other at the top or bottom wouldn't matter. If just one plate was tilted, then the E-field would be stronger between the closer ends of the plates, but it would be stronger in both directions, causing the horizontal deflection to be greater both right and left (from the center) at the top or bottom, which would look like the effect of the keystone adjustment on a projector. The only way plate position/angle could cause the effect shown is if the vertical deflection plates were rotated together (as a group) about the axis of the tube.

author: George Kaplan
author_rank: Newbie
timestamp: May 19, 2019, 10:30:50 pm
content: I realize that this is an old thread, but the subject pops up from time to time on the web, with lots of well-meaning, but wrong, advice. This post is for the next person who searches for a solution.If an undeflected baseline or the tops of a square wave are flat, then it isn't a trace rotation problem. A magnetized shield could cause odd geometric distortion, so degaussing it is always a good thing to try. One needn't fear damaging the CRT (unless you physically strike the glass; just don't do that).If the problem persists, you'll have to look deeper."Bent deflection plates" seems to be a popular guess, but it's the least likely explanation. Anything capable of bending plates would almost certainly destroy the jug. In any case, if the plates had broken loose, it would be easy to verify -- tapping the scope would affect the deflection in a very obvious way. But the guess, wrong as it is, does point in the right general area. There are many electrodes inside a CRT and they can all affect deflection. In many (but not all) CRTs there is one appropriately called the geometry electrode, which affects linearity over the entirety of the deflection area. When it's biased wrongly, a square trace would appear trapezoidal. And that's what most often causes the slanted trace problem (once trace rotation is correctly set). A poster already brought up this possibility but the thread sort of explored a larger space.In many scopes with this problem, the wiper of the trimpot ontrolling the geometry electrode voltage has simply gotten a bit dirty, and giving it a back and forth tweak will set things right. In other cases, a bypass cap has shorted, or another resistor has failed. Just look for a trimpot labeled something like "GEOM" and sniff around that region. The fix is usually trivial.In the case of this particular scope, the schematics don't show any provision for adjustment of the electrode voltage in question. However, the OP did note that the power supply voltages were high by a relatively large amount. Fixing that problem should be the first order of business, as supply voltage errors can cause a variety of confounding symptoms.

author: msat
author_rank: Regular Contributor
timestamp: March 13, 2021, 11:46:12 pm
content: Once again reviving this old thread just in case someone else in the future is looking for S-1325 schematics. It shares significant commonality with the 30MHz BK precision 2120B (the original 2120 is different!), for which I was able to find schematics for here:http://www.ko4bb.com/getsimple/index.php?id=manuals