Tektronix 2465A - Trace Horizontal Position and SEC/DIV dependency - Page 1
Forum section: electronics / repair

author: YO3DIX
author_rank: Newbie
timestamp: August 18, 2018, 07:33:47 pm
content: Hi,2 weeks ago I've bought from eBay a 2465A Tek. All ok, in very nice conditions, inside almost no dust, exterior looks very fine.10k duty hours, serial number B011715. Price 225$.First of all I've changed the fan with a new one.Then, backup LI-Ion battery with a new one (the old it was from 1986 and the new bat it's from Jan 18)Still, I discover one issue:When turning the SEC/DIV knob clockwise, then shifts the trace to the right, and vice-versa.I added some pictures. (All the time, button for horizontal position was untouched -- middle position.)any idea?many thanks in advance.73!

author: JimS
author_rank: Contributor
timestamp: August 19, 2018, 12:07:54 am
content: Hi:I took one of my 2465B's off the shelf and set it up as you did.I see the same thing on it.I then checked my 2467B that I use and it also does that.Nothing to worry about, it's normal behavior on these scope's.

author: YO3DIX
author_rank: Newbie
timestamp: August 19, 2018, 12:30:49 am
content: Hi there,thanks a lot for the answer. I also have a BK Precision 2120B (30 Mhz bandwidth) and on that scope I don't have that behavior.Even if it is normal is still unpleasant. It's like the horizontal sweep is not centered on the center of the screen.I've checked all the voltages through the power block and all okay.Just wonder: ... is not there a setting that would make the horizontal sweep longer (enough to sit in the screen)? or maybe centering the trace on the screen at 10 or 5 ns?many thanks again & have a great day!Gabriel

author: Johnny10
author_rank: Frequent Contributor
timestamp: August 19, 2018, 03:23:06 am
content: That is definitely not normal.If that was the norm you would be changing the Horizontal position knob all day long.I am sitting in front of my 2465A right now channel 1 connected to calibrator and this is not happening on my scope.I even changed trace position by 1 division so I could watch the left position while changing Sec/DivYou have a setup or trigger setup issue.I went back and looked at your setup...Are you connected to a source? The calibrator or a signal generator?You may see a display such as this with no signal.Do you have this problem with a signal applied to Channel 1 ?

author: particleman
author_rank: Regular Contributor
timestamp: August 19, 2018, 06:05:22 am
content: I don't think your trace is shifting I think at the faster speeds it is becoming dimmer. It looks dim for 7ns or so. There is a blanking pulse when the CRT retraces. Its taking longer than 5ns to recover from that.

author: floobydust
author_rank: Super Contributor
timestamp: August 19, 2018, 06:46:50 am
content: There are a bunch of calibration trimpots that affect the CRT/scope performance, around Z-axis switching. To name a few:Horizontal Dynamic Centering R3401.Z-axis Transient Response R4335.CRT Grid bias R1878.

author: YO3DIX
author_rank: Newbie
timestamp: August 19, 2018, 08:15:58 am
content: Hi,Thank U a lot to everybody for reply.Next week I have few days off from the office and I'll read the procedure of cal. But, many thanks @floobydust - at least I can accelerate the process, looking direct on possible part where to check.Now, I'll add some picture below, with sine signal applied on CH1, 70 Mhz and different positions of time/div.many thanks again to all,Gabriel

author: Johnny10
author_rank: Frequent Contributor
timestamp: August 19, 2018, 12:28:56 pm
content: I set my scope with 70.5MHz signal and Horizontal position knob all the way left and these are my results.

author: YO3DIX
author_rank: Newbie
timestamp: August 19, 2018, 12:35:40 pm
content: Yes, that I want to say.You have knob on the left clockwise and in this way you can see all trace at 5 nS.But when you move time/sec at 10 ns or 20nS, the image go to the leftif you want to keep in screen, you have to rotate horizontal position (knob) to the right ...and it's not normal.Maybe it's something with calibration ?(if you'll set the horizontal position button on middle position" you'll see that figure will be 50% outside of the screen, in right side)

author: Johnny10
author_rank: Frequent Contributor
timestamp: August 19, 2018, 03:31:39 pm
content: And then with the horizontal position in center position.

author: YO3DIX
author_rank: Newbie
timestamp: August 20, 2018, 12:19:39 am
content: Hello,As you already know, I've changed the fun.Then I've changed Li-Ion backup batteryMow, plan it's to recap according the attached list.(xls)After that, I will keep informed about the progress.if it will be the case, I will do some calibration after that.

author: JimS
author_rank: Contributor
timestamp: August 20, 2018, 06:05:12 am
content: The first post was with out any signal input.As another poster said the trace at higher sweep rates does get dim on the left side.The horz sweep is adjusted using a marker generator.The X1, X10, and center is set during horz adjustment step 5.I attached screen shots from my 2467B with a 70Mhz sine wave input at 5ns.Along with the pictures showing the horz position range at 100ns.The last picture is again at 5ns and with the 70Mhz signal and the horz is at mid range.I turned the intensity turned way up to show the far left of the waveform.Sorry for the fuzzy picture's.But they should be good enough to show what I see.Probably the scope would benefit from a full adjustment.But most of what I see from your pictures is normal for these scopes.Edit>OOps I attached 2 full right pictures.Added correct one below.

author: YO3DIX
author_rank: Newbie
timestamp: August 20, 2018, 07:05:09 am
content: Hi,thank you very much !keep in touchhave a great week!

author: YO3DIX
author_rank: Newbie
timestamp: August 24, 2018, 09:28:52 pm
content: Hi folks!As I told you, I've changed cooler and backup batery. These days, I just ordered some cap and my plan was to change as many cap in scope.For now, I did only for source.I've attached here a list and now I want just to make some correction: there are 2 cap which in tek scheme are 180 micro/40V and I've changed with 330 micro/50V.Surprise..on the screen I get some "dots" arranged in place in which there are trace and readout characters..it took some times until I catch about this. I think that anyway, if there are in a filter (low pass) it's ok. But charge it counts and 330 micro was too much.So, I put back 180 micro and all okwith this occasion, I will put for all rest the value in Tek scheme (even with some increase of voltage - not more than 30-50%) and temp at 105 Celsius.So, the correction it's to say that if somebody want to re-cap source, better to keep same values like Tek in scheme.below, there are values which are correct:C1016 .068 µF 275 Kemet X2 SuppFilmC1018 .068 µF 275 Kemet X2 SuppFilmC1021 290 µF 250 Nichicon PWC1022 290 µF 250 Nichicon PWC1110 250 µF 35 Panasonic EBC1111 250 µF 35 Panasonic EBC1113 180 µF 50 Panasonic EBC1114 250 µF 35 Panasonic EBC1132 250 µF 35 Panasonic EBC1116 180 µF 50 Panasonic EBOn the other hand, that "issue" for which I've open this post remain... I'm not sure if Tek make a project in which when turning the SEC/DIV knob clockwise, then shifts the trace to the right, and vice-versa....maybe somebody knows if it's normal.. (Many thanks Jim - exactly same issue I have, I can live with it but maybe it's a way to fix it..)

author: YO3DIX
author_rank: Newbie
timestamp: August 24, 2018, 09:34:47 pm
content: By the way, for whom don't know.The fan, it's on 7.7 V when you start scope, then, depending on the temp from inside, the voltage it's increased automaticaly...I start it, 1 hour ago, with 7.7 Vnow, there are 9.28 V almost stable.also, on that famous U800, for around 5 hours, I just put my finger from 30 in 30 min to check temp.It's hot but I can keep my finger on it -- so all ok, in my opinion it's not necessary supplementary cooling...

author: YO3DIX
author_rank: Newbie
timestamp: September 02, 2018, 09:21:04 pm
content: Hi there,regarding the issue (When turning the SEC/DIV knob clockwise, then shifts the trace to the right, and vice-versa.) , digging, on the other place, I found next explanation:"The scope may have a Y bandwidth of 400MHz, but X and Z bandwidths are 10 times less, only about 40MHz. This means that acceleration at left edge of screen cannot and should not be displayed. The reason beam isn't displayed is because the intensity axis amplifier cannot turn the beam on fast enough, which is just as well because the start of the sweep would be non-linear. The appearance of the shift is a consequence of that."next comment was:"I once had the same effect, but much worse, on a Tek 647.In this case, the bootstrapping circuit of the Z amp was defective,resulting in a slow response (risetime)."and in the end, another person said:"I'd think that starting each sweep with the beam deflected offscreen to theleft by the equivalent of a division or two would be one way to get aroundthe linearity and intensity problems. It could complicate thesynchronization a bit at <= 1 ns/division, though. More dynamic range fromthe X-deflection circuitry would've been needed, and the delay line wouldneed to be somewhat longer.I'm sure that if there were any genuinely trivial fixes, Tek would'veincorporated them, because I've always found the effect pretty annoying andI'm sure their engineers did too."One friend of mine, which have a similar scope (2465A) told me that the deviation on his it's only 1 mm on the screen.So, because on mine the deviation it's about 1.5 cm it's possible to be something wrong with Z axis amp.Think to change it...any opinion?