TEKTRONIX 2215 Issue - Page 1
Forum section: electronics / repair

author: Kidon
author_rank: Regular Contributor
timestamp: May 18, 2020, 10:35:52 pm
content: Hi,This is my very first post on this forum, so forgive me if this as been asked before, or if this is not the right place to ask these questions.I picked up 2 Tektronix osciloscopes yesterday for a very fair price. A 2335 and a 2215 (not 2215A).Not the main issue is with the 2215.Everything seems to work fine, the display is fine and bright, no dead spots or anything (on both).These are the first osciloscopes that I ever owned. But I’ve used many.That being said, I notice that the 500mV/1Khz calibration square wave On the 2215 is not showing a neat square wave at all.The « walls » are not straight. The waveform looks slightly like a pyramid. Meaning that the if you take the positive portion, it is narrower than negative at the top. Not my much, but it’s clearly visible. I’ve tried everything I know to correct it, but it just won’t let me.Now I don’t know if this is the generated signal that is « defective », or something else.I should be receiving my new frequency generator soon, and compare.Of course I have calibrated the probes.Any ideas as to what this could be due to? Is there a inside trim pot to adjust it maybe?I also was thinking of replacing all the electrolytic caps in the power supply. I noticed a 2x70Mfd 450V can capacitor.I measured the voltages across, and I have about 320-ish V. I have 2 100Mfd 400V caps. Unless there is a spike when powering up, I assume it’ll be safe to use them, correct?PS: Does Someone know where I can find schematics for these 2 units?Thank you for your help.

author: David Hess
author_rank: Super Contributor
timestamp: May 19, 2020, 01:09:48 am
content: Quote from: Kidon on May 18, 2020, 10:35:52 pmI have never noticed such a distortion in the calibration output signal however you might be seeing significant geometry distortion in the CRT which indicates a problem. Your frequency generator should allow a determination of which is occurring.QuoteThe 2213 is the same oscilloscope as the 2215 but without the dual delayed timebase so its manual can be used in most cases.The 2215 manual at Tekwiki may be pretty good:http://w140.com/tekwiki/wiki/2215Beware that the power supply of the 2213 and 2215 underwent a significant upgrade which is described in the later service manuals. My guess is that you have a later 2215.

author: Kidon
author_rank: Regular Contributor
timestamp: May 19, 2020, 08:39:47 am
content: Quote from: David Hess on May 19, 2020, 01:09:48 amI hope it’s not the CRT...If it is, is it fixable? Iris there a way to compensate?Quote from: David Hess on May 19, 2020, 01:09:48 amI may have the later 2215...I’m not knowledgeable enough to differentiate between iterations yet... I can’t really tell.All I know is that mine haveI have the manuals. I was more looking for the actual schematics...

author: Kidon
author_rank: Regular Contributor
timestamp: May 19, 2020, 08:41:18 am
content: Some pics...

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 19, 2020, 11:54:03 am
content: Why not use the calibration signal from the 2335 to test the 2215?

author: David Hess
author_rank: Super Contributor
timestamp: May 19, 2020, 02:36:56 pm
content: Quote from: Kidon on May 19, 2020, 08:39:47 amFirst determine where the problem is.If there is a geometry problem then the shape should change as the position control is adjusted.The calibration signal is made using a 741 so it should have a discernible slope but not as much as shown. My 2232 has effectively the same circuit (1) and I measured the slope at 0.06 volts per microsecond which is consistent with the performance of a 741 when the output is divided down 10 times as they did.Are the 0.5 volt and 1 kHz amplitude and frequency correct?(1) The only difference is a 5.1 volt zener diode across the output which to me indicates that at some point ESD damaged someone's calibrator output.

author: Kidon
author_rank: Regular Contributor
timestamp: May 19, 2020, 03:53:33 pm
content: Quote from: PA0PBZ on May 19, 2020, 11:54:03 amWhy didn’t I think of that?!!? Thank you!I just did, and it is indeed the internal signal generator that seems to be faulty for some reason.Thanks.

author: Kidon
author_rank: Regular Contributor
timestamp: May 19, 2020, 04:01:18 pm
content: Quote from: David Hess on May 19, 2020, 02:36:56 pmIt is in fact the signal generator that is defective.I have no clue whatsoever what you’re talking about. I’m not an expert on these at all.What’s a 741? Can I just replace it? Do you know the part number so I can order it?Thanks.PS: For good measure, I just recapped the entire Power Supply Section, and it works like a charm.

author: mawyatt
author_rank: Super Contributor
timestamp: May 19, 2020, 04:52:13 pm
content: The test signal on a Tek 2465 I got off eBay was hosed up, this was traced to a bad zener diode, as acustom marked Motorola device. A little circuit analysis and replace with a 1N4733A zener diode.Don't know if the 2465 test waveform circuit is similar to the 2213 or 2215, but here's what the defective waveform looked like.Best,

author: shakalnokturn
author_rank: Super Contributor
timestamp: May 20, 2020, 12:35:36 am
content: The "741" or μA741 is an old op-amp.http://www.ti.com/lit/pdf/slos094/Check it's decoupling capacitors before replacing.

author: Kidon
author_rank: Regular Contributor
timestamp: May 20, 2020, 02:28:18 am
content: Quote from: shakalnokturn on May 20, 2020, 12:35:36 amHummm.... I don’t see that chip anywhere on the board... And I’ve looked everywhere.I would really like to fix this issue...

author: jdragoset
author_rank: Frequent Contributor
timestamp: May 20, 2020, 03:17:16 am
content: U 535, Front Panel Board

author: Kidon
author_rank: Regular Contributor
timestamp: May 20, 2020, 07:53:31 am
content: Quote from: jdragoset on May 20, 2020, 03:17:16 amThanks.I thought so, but couldn’t clearly read the prints.I see 2 zener diodes beneath it.That board seems like a b... to remove...Could you tell me which ones are it’s coupling caps?Thanks

author: Per Hansson
author_rank: Unknown
timestamp: May 20, 2020, 03:14:00 pm
content: C531?

author: shakalnokturn
author_rank: Super Contributor
timestamp: May 20, 2020, 03:30:57 pm
content: No, C531 is part of the oscillators timing.I'm assuming there would be decoupling although it does not figure on that extract of schematic.Often decoupling capacitors are all piled together in one corner of a schematic and referenced to whatever they decouple.If they exist they'll be physically close to the 741a'd easy to find as they link to its supply pins.

author: Kidon
author_rank: Regular Contributor
timestamp: May 20, 2020, 04:14:36 pm
content: Quote from: shakalnokturn on May 20, 2020, 03:30:57 pmThat would be pin 4 and 7. I found C726 directly connected to pin 7. 0.1uF 20% 50vI’m just gonna change this one for now, until I find where the other one is...

author: Kidon
author_rank: Regular Contributor
timestamp: May 20, 2020, 04:41:03 pm
content: I changed C726 to pin 7 and no change....

author: Per Hansson
author_rank: Unknown
timestamp: May 20, 2020, 05:50:42 pm
content: What about C725?

author: Kidon
author_rank: Regular Contributor
timestamp: May 20, 2020, 06:34:43 pm
content: Quote from: Per Hansson on May 20, 2020, 05:50:42 pmYeah, it’s an electrolytic cap.It’s already been replaced as part of the recap job I did yesterday.But thanks anyway.

author: Kidon
author_rank: Regular Contributor
timestamp: May 20, 2020, 06:47:30 pm
content: Oddly enough, there is not coupling cap I can find on pin 4 -Vcc....I’m at a dead end here.Gonna grab a UA741 tomorrow at the store and change it.Could it be it? Would it even work at all if it was bad?Since I’m gonna change it, do you guys know of a direct replacement « upgrade »?Thanks

author: David Hess
author_rank: Super Contributor
timestamp: May 20, 2020, 08:08:36 pm
content: Quote from: Kidon on May 20, 2020, 06:47:30 pmIt could be the 741.QuoteThere are lots of alternatives however none are going to provide better performance in this application and the precision of the output voltage depends somewhat on the output saturation characteristics of the 741.Other parts I might consider are the TL071, TL081, LF351, and similar JFET parts because they have similar output characteristics and a wide differential input voltage range. These will provide much faster edges.Oh, a clever upgrade would be the old LM301A since it uses external compensation and no compensation is required in this application making it a performance upgrade. I wonder why Tektronix did not use it.

author: Kidon
author_rank: Regular Contributor
timestamp: May 20, 2020, 08:23:07 pm
content: Quote from: David Hess on May 20, 2020, 08:08:36 pmThank you. I’m gonna install a socket and try a couple.It’s gonna be a drag since I’m doing this without removing the board.I’m not even sure I’m gonna be able to do it.

author: David Hess
author_rank: Super Contributor
timestamp: May 20, 2020, 08:34:56 pm
content: Quote from: Kidon on May 20, 2020, 08:23:07 pmThat is what I would do for my own edification.QuoteI have worked on the 2213/2215 before but I never had to deal with the front board so I am not sure what is involved. It could be nasty.

author: Kidon
author_rank: Regular Contributor
timestamp: May 20, 2020, 09:49:58 pm
content: Quote from: David Hess on May 20, 2020, 08:34:56 pmYep, it seems to be. I’m not gonna remove it. It would be too much of a hassle.This my first time ever working on an osciloscope. I’m learning as I go, and discovering more small issues.For example I noticed a problem with the horizontal section. Meaning that the wave forms are getting narrower As you look further and further at the right side of the display. I didn’t notice that before. Or maybe I wasn’t paying attention. Could it be due to the electrolytic cap change on that board, and it now needs to be re-calibrated?Any ideas that would save me from going through pages and pages of Service Manual to find the answer (If there is even one)?

author: tautech
author_rank: Super Contributor
timestamp: May 21, 2020, 02:12:39 am
content: Quote from: Kidon on May 20, 2020, 09:49:58 pmSounds like sweep non-linearity.You might need another scope to examine the sweep ramp waveform.Study the sweep generation section in the manual.

author: Kidon
author_rank: Regular Contributor
timestamp: May 21, 2020, 02:20:26 am
content: Quote from: tautech on May 21, 2020, 02:12:39 amYes it does sound like it. I’ll post a picture tomorrow.I have another scope, but I have no idea how to do that, or where to even start.I’m a complete noob when it comes to these things. I’m still learning (the hard way apparently...)Which manual are you referring to? The Operator Manual, the Service Manual??

author: tautech
author_rank: Super Contributor
timestamp: May 21, 2020, 05:56:56 am
content: Quote from: Kidon on May 21, 2020, 02:20:26 amThe service manual should have waveforms and test points for those waveforms however they all are usually with a specific setup for the scope under test.Simply, the sawtooth from the sweep generator should be a perfect rising ramp that via the horizontal plate output drivers applies a rising voltage to electrostatically drive the beam from left to right across the display WRT the timebase setting. Any non-linearities will distort a repetitive waveform as it nears the right edge of the display.The problem could be anywhere on the horizontal circuit so you start at one end of the other and look for non-linearities until you find the part of the circuit that's gone haywire. Normally you start where you have reference waveforms like printed in the manuals.

author: Kidon
author_rank: Regular Contributor
timestamp: May 21, 2020, 09:10:29 am
content: Quote from: tautech on May 21, 2020, 05:56:56 amYes, I will definitely look into that. I’ve never done that before.I’m learning as I go.Here are pictures of what I’m talking about.Could it be the 4 cap change on the sweep board?

author: Kidon
author_rank: Regular Contributor
timestamp: May 21, 2020, 01:10:52 pm
content: Ok, so I changed the UA741 with a brand new one but that didn’t change a thing. That wasn’t it.I’m out of options and ideas...Coupling caps changed, chip changed...Could it just be a calibration issue of the entire unit from the start?Any TEKTRONIX experts???

author: Kidon
author_rank: Regular Contributor
timestamp: May 21, 2020, 02:42:11 pm
content: Quote from: David Hess on May 20, 2020, 08:08:36 pmI installed a socket, and I bought several of the OP-AMP you mentioned, and NONE of the 5 UA741 I tried solved the problem. And I was desperate when I decided to try one of the LM301A I got.I tried all the references you gave me.And low and behold, THEY ALL SOLVED THE ISSUE, and the wave forms were absolutely perfect!!

author: David Hess
author_rank: Super Contributor
timestamp: May 21, 2020, 06:18:46 pm
content: Quote from: Kidon on May 21, 2020, 02:42:11 pmThat is weird. My 22xx oscilloscopes have the same circuit but do not display that weird edge.QuoteThey should all produce a faster edge but the intention of the calibrator output is to compensate attenuating probes and to roughly check the oscilloscope's calibration so a faster edge is not really required.

author: Kidon
author_rank: Regular Contributor
timestamp: May 21, 2020, 08:22:42 pm
content: Quote from: David Hess on May 21, 2020, 06:18:46 pmYes, I imagine...Quote from: David Hess on May 21, 2020, 06:18:46 pmIndeed, but it’s still not “normal” for these edges to be that far “off”. I presume that if all the 2215/A had this issue, it would have been reported/documented by now...Anyway, this issue is somewhat fixed, or rather “compensated”.Now I have to focus on recalibrating the whole machine. And it scares the ... out of me...I guess it’s normal after recapping the whole thing. Voltages have probably changed, hence the issues...I hope to somehow succeed... I‘ll take this as a learning platform I guess.

author: tautech
author_rank: Super Contributor
timestamp: May 21, 2020, 09:12:29 pm
content: Quote from: Kidon on May 21, 2020, 08:22:42 pmYou shouldn't need touch calibration after recapping just the PSU and each PSU rail voltage is exactly to spec.

author: Kidon
author_rank: Regular Contributor
timestamp: May 21, 2020, 09:50:39 pm
content: Quote from: tautech on May 21, 2020, 09:12:29 pmMaybe it was a bad idea, but I also changed the 4 electrolytic caps on the sweep board.🤷‍♂️

author: tautech
author_rank: Super Contributor
timestamp: May 21, 2020, 09:56:57 pm
content: Quote from: Kidon on May 21, 2020, 09:50:39 pmTiming caps or something else ?Wholesale cap changes are not normally a good idea especially in areas where caps are not under stress like they are in PSU's and when in doubt always test before replacement.

author: David Hess
author_rank: Super Contributor
timestamp: May 21, 2020, 11:10:20 pm
content: Quote from: Kidon on May 21, 2020, 08:22:42 pmThere is a visible slope, which I measured, but yours had a kink in it which should not be there.Quote from: tautech on May 21, 2020, 09:12:29 pmI agree. Replacing the power supply capacitors should not affect calibration to any significance.Quote from: Kidon on May 21, 2020, 09:50:39 pmExactly which capacitors did you change? There is a matched set of axial film capacitors on the sweep board which look like electrolytic capacitors but are actually precision and matched oil filled film capacitors which are responsible for the sweep. If these were replaced with electrolytic capacitors, then I would expect severe sweep non-linearity which your 2215 does show.

author: Kidon
author_rank: Regular Contributor
timestamp: May 22, 2020, 01:37:22 am
content: Quote from: David Hess on May 21, 2020, 11:10:20 pmYep.Quote from: David Hess on May 21, 2020, 11:10:20 pmOk.Quote from: David Hess on May 21, 2020, 11:10:20 pmI obviously made that exact rookie mistake!!! You perfectly nailed it. I replaced the 4 capacitors I thought were electrolytics on the sweep board.Fortunately, I kept them and I just put them back. Everything is back to normal again!!Live and learn from your mistakes. I hope this whole experience will benefit someone else and prevent them from doing what I did.THANK YOU!!!PS: That still doesn’t explain why a UA741 has that steep a slope on my scope whereas I’m sure it’s fine on other 2215. I don’t know what chip is used on a 2205, but I saw a video the other day where the guy had one, and the calibration signal was perfect.

author: Kidon
author_rank: Regular Contributor
timestamp: May 22, 2020, 01:51:00 am
content: One more question. Is it supposed to have a fan? Because this one doesn’t seem to ever had one installed, and it get pretty warm/hot in there. Does anyone know where I can source one? I can’t seem to find a suitable one online in Europe. It’s an axial fan 50mm x 50mm, 48V (I think), correct?Thanks

author: David Hess
author_rank: Super Contributor
timestamp: May 22, 2020, 08:36:21 pm
content: Quote from: Kidon on May 22, 2020, 01:37:22 amIt is a good thing you kept them. The sweep capacitors would be very difficult to find replacements for except from another 2215 or similar oscilloscope. Those capacitors are not only high performance, but selected to make a matched set of decade values.QuoteThat is right; the sweep capacitors have nothing to do with the calibrator output signal. I do not know how to explain that all of the 741s you tested produced the same distorted output but the other operational amplifiers worked.Quote from: Kidon on May 22, 2020, 01:51:00 amNo, like most of the 22xx series, the 2213/2215 did not have a fan. The 2213/2215 are really their own separate series and prototypes for the 100 MHz 2235. Later the 2213A/2215A which were based on the 2235 replaced the 2213/2215. Later models which included a large multimeter and timer counter board (2236) or a digital storage board (2230/2232) drew more power and included with a fan.If you want to add a fan to your 2215, then I suggest running a 12 volt fan off of the +8.6 or -8.6 volt supply which is what was done in some of the later models.

author: Kidon
author_rank: Regular Contributor
timestamp: May 22, 2020, 09:48:03 pm
content: Quote from: David Hess on May 22, 2020, 08:36:21 pmWell,... as long as it’s fine now...Quote from: David Hess on May 22, 2020, 08:36:21 pmI see... I might do that eventually. I actually have a 2235 on the way.What is the real difference between a 2215 and a 2215A? TekWiki doesn’t really say anything....Are the 2215 inferior machines?

author: David Hess
author_rank: Super Contributor
timestamp: May 23, 2020, 01:04:02 am
content: Quote from: Kidon on May 22, 2020, 09:48:03 pmThe 2235 at least has the unpopulated circuits on the main board to support the fan. If you do add a fan to your 2215 or 2235, do not go overboard. It does not take much air flow to make a huge difference. The fans in my 2230s and 2232s are practically silent and they have to support the large increase in power required for their digital storage boards.The 2213/2215 originally used a very different thyristor based power supply which was upgraded to the off-line switching regulator used in the 2235. Construction was very different with wafer type switches while the 2235 had the cam type switches Tektronix used in contemporary products. Input capacitance was 30 picofarads instead of the 20 picofarads of the 2235.Except for issues with the early power supplies, I do not think the 2213/2215 is inferior in any significant way.The 50 MHz 2225 series is another separate series with a different power supply, construction, and input capacitance (25 picofarads).

author: Kidon
author_rank: Regular Contributor
timestamp: May 23, 2020, 02:11:12 am
content: Quote from: David Hess on May 22, 2020, 08:36:21 pmWouldn’t it be better to use a 220V-230V (in my case), and run it off the mains directly? That way there will be no interaction with the internal power rails.BTW, there are 2 unused lugs sticking out the board, very close to where the fan goes. I assumed they were the dedicated power supply for it. I’m not sure, but I think they deliver 48VAC or something, (don’t quote me on that)

author: james_s
author_rank: Super Contributor
timestamp: May 23, 2020, 03:55:06 am
content: Mains voltage fans tend to be noisy and expensive, as well as the machine is then locked to one line voltage.Why add a fan at all though? These scopes do not need one, the only thing a fan will do is make it noisier and suck more dust into it. I hate fans, in some equipment they are a necessity but 2215 scopes have lasted decades without one and are not known for running particularly hot.I wonder if the problematic op-amps were counterfeit? An original 741 does not offer remarkable performance, but it may exhibit faster rise and fall times than some random super cheap op amp. It's also possible that the replacement you found that works is superior to the original and able to mask some other fault with the circuit.

author: Kidon
author_rank: Regular Contributor
timestamp: May 23, 2020, 08:02:14 am
content: Quote from: james_s on May 23, 2020, 03:55:06 amGood points.Quote from: james_s on May 23, 2020, 03:55:06 amYes, this is also what I think. But Is this is the case, not that I’m an expert, but I failed to determine what it is.Do you have any clues?

author: David Hess
author_rank: Super Contributor
timestamp: May 23, 2020, 01:46:16 pm
content: Quote from: Kidon on May 23, 2020, 02:11:12 amSure you could use an line voltage AC fan assuming that you can find one small enough since they tend to be 120 millimeters square. You could also lower the speed somewhat by placing an AC film capacitor in series with it; values from 2 to 10 microfarads are common.QuoteThe off-line preregulator produces about 42 volts DC for the inverter. You could indeed use this for the fan supply however be warned that it is not isolated from the line input.

author: jdragoset
author_rank: Frequent Contributor
timestamp: May 23, 2020, 04:26:19 pm
content: I checked three 2215's and they all had slow rise/fall edges but a 2225 had sharp edges.The 2225 uses an LM 358 rather than a 741 and the rest of the circuit for the probe calibrator is nearly identical for each model.

author: Kidon
author_rank: Regular Contributor
timestamp: May 23, 2020, 04:43:19 pm
content: Quote from: David Hess on May 23, 2020, 01:46:16 pmYes, as I think it’s “better” to have the fan isolated from the internal power rails. Either that, or I’ll just drop the idea altogether.Quote from: David Hess on May 23, 2020, 01:46:16 pmYes, I knew it was in the 40ish volts, but couldn’t remember if it was AC or DC. What is the off-line preregulator anyway. (Can you tell I’m an expert?)

author: Kidon
author_rank: Regular Contributor
timestamp: May 23, 2020, 04:46:04 pm
content: Quote from: jdragoset on May 23, 2020, 04:26:19 pmLike mine had?Quote from: jdragoset on May 23, 2020, 04:26:19 pmWhen you say “nearly identical”, what is different?

author: jdragoset
author_rank: Frequent Contributor
timestamp: May 23, 2020, 09:06:09 pm
content: Architecture is identical but the resistance values are not.Will identify specific resistances when I have the circuit diagrams side-by-side

author: Kidon
author_rank: Regular Contributor
timestamp: May 23, 2020, 10:15:44 pm
content: Quote from: jdragoset on May 23, 2020, 09:06:09 pmCool.The ones you checked had the exact same slopes mine did before I switched the Op-Amp?

author: jdragoset
author_rank: Frequent Contributor
timestamp: May 23, 2020, 10:51:18 pm
content: Yes

author: David Hess
author_rank: Super Contributor
timestamp: May 24, 2020, 06:55:58 am
content: Quote from: Kidon on May 23, 2020, 04:43:19 pmThe 2215 and 2235 power supply design is unusual by modern standards. The preregulator stage steps the rectified line voltage, so 170 to 340 volts DC, down to about 42 volts and then an inverter which is modified for linear regulation produces the isolated and regulated output voltages. The implementation of the preregulator is the part which was changed during production of the 2213/2215.

author: Per Hansson
author_rank: Unknown
timestamp: May 24, 2020, 11:01:48 am
content: Quote from: jdragoset on May 23, 2020, 10:51:18 pmI was so sure when reading this thread that it is not normal.Now I checked my 2215 and it looks basically the same tooFirst picture is 0.5v & 200µS per divisionSecond picture is main sweep at 0.2v & 200µS and delayed sweep at 10µS per division.Probes are set to 10x, it is those cheap China P6100 probes but found at Elfa Sweden with partno 300-44-246 as a spare part for another instrument.Here you can also see another thread about a user troubleshooting delayed sweep using the calibration signal in his linked video.https://www.eevblog.com/forum/repair/tektronix-2215-delayed-timebase-fault-()/

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 24, 2020, 11:08:10 am
content: I decided to build the calibration circuit from scratch to get an idea what is going on here. I used a really old (TI) 741 and had to put some resistors in series to get to the correct value:It looks better than the pictures on page one, the risetime is about 6 uS according to my scope:Not sure if this is conclusive or not...

author: Per Hansson
author_rank: Unknown
timestamp: May 24, 2020, 05:07:22 pm
content: In my previouslycropped part of the schematicit is shown a measure point 34.Here is that from the manual:In the photos in my previous post above it can be seen that the risetime is 12µSAs previously mentioned though it is just a calibration signal for the probe.And all that is really required is to be able to see the peaks well...Was it very difficult to replace the chip Kidon? Got any photos of the work?

author: Kidon
author_rank: Regular Contributor
timestamp: May 24, 2020, 07:42:57 pm
content: Quote from: David Hess on May 24, 2020, 06:55:58 amSince the power supply of the “A” models are more modern, and probably “better”, is there a point in modifying the older ones to meet these new specs? Is it even possible or even worth it?

author: Kidon
author_rank: Regular Contributor
timestamp: May 24, 2020, 07:44:52 pm
content: Quote from: Per Hansson on May 24, 2020, 11:01:48 amThank you. I will check it out.

author: Kidon
author_rank: Regular Contributor
timestamp: May 24, 2020, 07:47:56 pm
content: Quote from: PA0PBZ on May 24, 2020, 11:08:10 amInteresting. Are the resistance values you used to get that result are the same values used on the 2225 @JDRAGOSET mentioned earlier in the thread?

author: Kidon
author_rank: Regular Contributor
timestamp: May 24, 2020, 07:53:01 pm
content: Quote from: Per Hansson on May 24, 2020, 05:07:22 pmNo, it wasn’t very difficult without having to remove the board, because the chip is actually located at the very top and very accessible. And there is plenty on room to install a socket. I wouldn’t call it “easy”, but definitely doable.And I don’t regret doing it.I’m not gonna open in now, but I’ll try to post you a picture when I do. Probably tomorrow.

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 24, 2020, 08:07:48 pm
content: Quote from: Kidon on May 24, 2020, 07:47:56 pmI followed the schematic that Per Hansson posted in reply #13

author: jdragoset
author_rank: Frequent Contributor
timestamp: May 24, 2020, 10:05:03 pm
content: When I looked at the 2225 (LM 358 instead 0f 741 calibrator op amp) on X10 sweep Mag, it appeared to be 3 us rise/fall time as opposed to 10-12 us in the 2215.Probably splitting hairs as to whether it is worth the trouble.

author: james_s
author_rank: Super Contributor
timestamp: May 25, 2020, 12:41:48 am
content: I don't really think it matters either way, as long as the rise and fall times are symmetrical and the top and bottom edges are flat then it should be fine for the intended purpose. The calibrator is only there to set the probe compensation and you don't need super fast rise and fall times for that.

author: tautech
author_rank: Super Contributor
timestamp: May 25, 2020, 07:58:09 am
content: Quote from: james_s on May 25, 2020, 12:41:48 amI agree and finally had some time to check this today.First screenshot is a collection of fast and slow edges, ch1 being BNC connection from my ARB, 2 and 4 via 10x probes. Rise times listed but too fast as they are in ns ranges.This shows ch3 connected to the scopes probe compensation output and the other 3 channels to my ARB and all in more typical us ranges.Probes compensated fine with any of these rise times.

author: David Hess
author_rank: Super Contributor
timestamp: May 25, 2020, 09:40:30 am
content: Quote from: Kidon on May 24, 2020, 07:42:57 pmThe 2235/2213A/2215A power supply is essentially identical to the "late" model 2213/2215 except for being part of the main circuit board instead of a separate circuit board.The original 2213/2215 power supply had some issues of which the major one was that the CRT heater voltage was too high causing short CRT life. Tektronix published a change notice to fix this which involved removing a turn from the transformer.

author: Kidon
author_rank: Regular Contributor
timestamp: May 25, 2020, 09:57:21 am
content: Quote from: David Hess on May 25, 2020, 09:40:30 amMy 2215 has a power supply board on top of the main board, and is connected to it by four wires (I didn’t look into what they are exactly). That makes it a “late” mode then, correct? So it should have the CRT issue, I guess.Except for changing the caps, I didn’t really took a closer look at the power supply itself. I did notice a triac mounted on some sort plastic holder, and a small ceramic plate on top of it, holded by another plate with a wire (I think to ground).

author: Kidon
author_rank: Regular Contributor
timestamp: May 25, 2020, 10:30:37 am
content: Quote from: james_s on May 25, 2020, 12:41:48 amYou are absolutely correct. I guess it was just my OCD kicking in.... I guess I must like when things are kinda neat lookingOn the other hand, it’s interesting, IMHO, to understand why this happens on these particular scopes.

author: Kidon
author_rank: Regular Contributor
timestamp: May 25, 2020, 10:32:20 am
content: Quote from: tautech on May 25, 2020, 07:58:09 amThank you for taking the time to share this.

author: Per Hansson
author_rank: Unknown
timestamp: May 25, 2020, 08:03:12 pm
content: Quote from: Kidon on May 25, 2020, 09:57:21 amDepending on the serial number the fix may already have been done on your unit, but you should check it.Here is a post where the SUP3010 change document is attached:https://www.eevblog.com/forum/testgear/tek-2215-never-been-used!/msg1824551/#msg1824551Do read my posts further down also, or else you might soon need to make a new thread about fixing the power supply.That poor little MOSFET in the plastic holder is really not having an easy life in this instrument!

author: tautech
author_rank: Super Contributor
timestamp: May 25, 2020, 08:36:53 pm
content: Quote from: Per Hansson on May 25, 2020, 08:03:12 pmYes you've made some valuable contributions that offer clarity to what's happening with the switching MOSFET.We explored it in this thread too, P4 and on:https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/

author: tautech
author_rank: Super Contributor
timestamp: May 25, 2020, 08:38:48 pm
content: Quote from: Kidon on May 25, 2020, 10:32:20 amNo worries, was a wet day and what else do you do other than play with your toys ?

author: Kidon
author_rank: Regular Contributor
timestamp: May 27, 2020, 12:32:43 am
content: Quote from: Per Hansson on May 24, 2020, 05:07:22 pmThere you go.

author: Kidon
author_rank: Regular Contributor
timestamp: May 27, 2020, 12:38:37 am
content: Quote from: Per Hansson on May 25, 2020, 08:03:12 pmAs you can see from my initial pictures, the serial number on mine has been scratched off for some reason... Maybe in was stolen at some point in its life. Who knows...But I will definitely look for the “01” on the transformer. If not present, I will follow the instructions to make the modification myself per the doc you pointed me to.Thanks.

author: Kidon
author_rank: Regular Contributor
timestamp: May 28, 2020, 01:45:57 pm
content: Quote from: Per Hansson on May 25, 2020, 08:03:12 pmI did follow the procedure from that document, as mine didn’t have the “01” on the PT; just “00”.Pretty easy stuff. That weird part came when I went on and did the “Performance Check Procedure” As they suggested, and referred to the manual. The 1st thing to check for is the +4.2V to +4.4V. So I did and read +5.23V. The problem arose when I wanted to adjust it to the correct +4.3V... Mine does NOT have any R952 variable resistor. It’s actually jumpered from the factory... I can see it written at the back of the board itself, but on the other side there is just nothing...So what now...? Should I go ahead and install one??I adjusted the -8.6V to specs though. It’s perfectly at -8.6V.I checked all the other Voltage Test Points, and everything else is within specs, but this one, which at +5.23V, is 1V above what it should be.

author: Kidon
author_rank: Regular Contributor
timestamp: May 28, 2020, 03:07:25 pm
content: Since I don’t have the right value (2K VR),I removed the jumper and tried different resistors within that range.It had absolutely no effect whatsoever.... I’m puzzled...

author: Per Hansson
author_rank: Unknown
timestamp: May 29, 2020, 05:36:58 pm
content: You have the wrong service manual.Or one that is not new enough.Check this:Quote from: tautech on May 25, 2020, 08:36:53 pmThe SUP3010 mod was what lead me to it, when I did the performance check you are supposed to leave it on to warm up for 15 minutes or what it says in the service manual.That is what killed the poor MOSFET, it did not have proper cooling after being removed.That is why I did not link that thread directly, as I added in the details about the thermal compound in that other threadQuote from: tautech on May 25, 2020, 08:38:48 pmWet toys?I umm, nevermind

author: Kidon
author_rank: Regular Contributor
timestamp: May 30, 2020, 08:01:34 am
content: Quote from: Per Hansson on May 29, 2020, 05:36:58 pmI think I do have the right Service Manual. Your first picture is in it, but in section 5-5, and the second in section 5-4. It still doesn’t make sense to me that the manual says both these things, but only one is doable because R952 is just not there...

author: Per Hansson
author_rank: Unknown
timestamp: May 30, 2020, 08:52:06 am
content: What I meant is you do not have R952 because your unit has the external preregulator board A18 (43VDC power supply)Therefore your unit does not have potentiometer R952, that will only be there if the unit has the current limit board A19.And what it says in that change notification I posted is to skip that section that speaks about R952 if you have the preregulator board.I posted some pics below of me doing the SUP3010 mod of my unit, I never think I posted these before.It is funny because the very next picture in the series from the camera is the repair of the preregulator board, as I wrote in my previous post

author: Kidon
author_rank: Regular Contributor
timestamp: May 31, 2020, 06:13:51 pm
content: Quote from: Per Hansson on May 30, 2020, 08:52:06 amI got it.I did everything by the book and adjusted the grid bias, and it was indeed a bit off.I didn’t check the +4.3v again, but I guess it should be better (hopefully).I also followed almost all the calibration procedures, and it looks to be just fine now.Thank You again for your time and patience.PS: I’m now struggling with the calibration of my 2235. I’ve been trying to calibrate the horizontal amp for 3 days without success. But I will start a new post about it if I can’t figure it out.Thank you again for everything.