hybridfree/eevblog-posts huggingface dataset:
Tektronix 2235 issue - Page 1
Forum section: electronics / repair

author: belzrebuth
author_rank: Frequent Contributor
timestamp: September 26, 2019, 01:35:37 pm
content: Hi,I was trying to troubleshoot a function gen (3312A) and after a while I realised that it was actually my scope that had the problem not the generator.The issue is that square waves of about 10kHz and on are showing like in the attached picture.(10kHz square and 100kHz square generated by a rigol dg1022z)The problem affects both channels so it should be probably before the input section.Although it's now showing at the pictures I'm using standard 50ohm bnc cables so it's not a probe problem.The scope used to work fine because I specifically remember viewing waveforms in the upper kHz range with no problems but as I mostly work with audio this problem can be easily over six months old without me noticing.

author: mzacharias
author_rank: Frequent Contributor
timestamp: September 26, 2019, 04:26:33 pm
content: "Thou Shalt Check Power Supplies"

author: belzrebuth
author_rank: Frequent Contributor
timestamp: September 26, 2019, 05:24:01 pm
content: DC Voltages are within spec. (5.2V is a little low at 5.08 but still within spec)Tested as per the service manual instructs on pg 5-4.Seems like CH2 is different than CH1.Here's what a 20kHz square looks like on CH1 vs CH2.edit: Should I mess with the attenuator compensation capacitors for each channel?The scope seems in a good working order overall so I don't want to mess with its calibration setting unless absolutely necessary.I mean I could maybe make the problem go away if I tinker with the adjustment capacitors but if there's an actual fault there I may need to calibrate it all over again..

author: rf+tech
author_rank: Frequent Contributor
timestamp: September 27, 2019, 02:49:09 am
content: Yes, thisisa "probe problem."A 50Ω cable, attached to a 50Ω signal generator output, must be terminated with 50Ω at the scope end.Basic transmission line theory.RF+ Tech

author: belzrebuth
author_rank: Frequent Contributor
timestamp: September 27, 2019, 09:19:00 am
content: This is not the issue here I'm afraid.The problem persists even If I terminate the bnc.I will go through the adjustment procedure up I think.Something I've noticed is that when I'm in the mV range the squares look infinitely better than when I'm in the volt range.The calibration steps for the square wave are also in the mV range..But my problem manifests in the volt range.

author: 2N3055
author_rank: Super Contributor
timestamp: September 27, 2019, 09:31:04 am
content: You need to put additional 50ohm terminator resistor on scope side when using BNC cable. Your scope is 1 MOhm input..

author: shakalnokturn
author_rank: Super Contributor
timestamp: September 27, 2019, 11:48:39 am
content: After replying to the other post, I started thinking: If both channels were wrong in the same way, any chance it is the vertical amplifier frequency response that needed readjusting rather than input amplifiers?I haven't looked at the S.M.
Tektronix 2235, no triggering - Page 1
Forum section: electronics / repair

author: teus
author_rank: Contributor
timestamp: December 23, 2019, 05:55:20 pm
content: Hi all,at work I adopted an old Tektronix 2235 that was supposed to be faulty. Plugged it in, worked fine. Took it home. It seemed to work okay, but struggled with triggering on high speed signals. I couldn't trigger on a 12mhz crystal. After a lot of fiddling, I noticed how I could set the volts/div a bit lower: the scope would trigger on the clock signal, but could only display the center part of the clock. Raising the volts/div to show the entire clock signal would cause the triggering to fail. It seemed a bit smeared out across the entire screen, like the entire display being dimly illuminated.After some time, it stopped triggering. Turning the scope off/on would help for a little bit. I could calibrate the probe, but the signal would go away when trying to trigger on a clock signal.I took the scope to work. Seemed to work just fine there. Damnit.Took it back home. Scope doesn't trigger on any signal anymore. Beam find still works. When I gently press the B/W limit button halfway, the signal appears on the display for a fraction of a second.I'm digging through the service manual, but I'm nervous to ruin the scope. Looking at the troubleshooting flowcharts, I should ""turn CRT bias adj r851 fully clockwise". I haven't found R851 yet, but I figured I would first ask here for some help. Maybe someone has an idea.Find the service manual here:https://www.tek.com/manual/2235-service-manual

author: teus
author_rank: Contributor
timestamp: December 23, 2019, 08:44:33 pm
content: this thread magically got bumped:https://www.eevblog.com/forum/repair/tektronix-2235-no-trace/pressing P-P auto actually made the squarewave display, for calibrating a probe. it's flickering badly. I disabled it again, and managed to display the squarewave by carefully setting the level.the scope seems to be working somehow again. a sound card producing a 20 000hz sine sometimes shows the signal twice: once in phase, once in counterphase, overlapping each other. the scope trace isn't flickering but is bouncing around quite a bit.maybe this info helps.
tektronix 2235 AN overheating - Page 1
Forum section: electronics / repair

author: kapo16
author_rank: Newbie
timestamp: July 07, 2023, 05:20:43 pm
content: Hello from AthensI purchase a 2235 UN in very good condition(cosmetic), but after 2 hours of working, ' a smell like plastic getting hot' came to my attention.Inspecting the board noticed that the TL594 was replaced with the same type, and Q9070 is irf710.1.Is it ok to replace the irf 710 with this mosfet: QorvoUF3C065080T3S as it has 100mh RDson?2. What caps in the power supply would you suggest replacing?. All the caps seem original.Thanks in advance.Panos

author: lucittm
author_rank: Newbie
timestamp: July 09, 2023, 04:13:48 am
content: Your Tektronix 2235 could have been manufactured in 1983 or 1984. This means it is about 40 years old. Electrolytic capacitors have a useful life expectancy of 25-30 years. I would replace all the electrolytic capacitors, if possible. Especially the ones in the Power Supply. It would be good to have a schematic to assist with part identification.The Service Manual is here:https://tinyurl.com/4chvr997Mark

author: tunk
author_rank: Super Contributor
timestamp: July 09, 2023, 10:15:47 am
content: Also see if there's any Rifa caps, they could be the source of the smell:https://youtu.be/MW_p8HzVAlY

author: Gyro
author_rank: Super Contributor
timestamp: July 09, 2023, 07:21:15 pm
content: QuoteSpecifically PME271 Metalized Paper capacitors - Kemet (formerly Evox Rifa) make other film dielectric types that are absolutely fine with age.
Tektronix 2235 upgrades - Page 1
Forum section: electronics / repair

author: MrElectric
author_rank: Contributor
timestamp: February 23, 2020, 08:09:14 pm
content: Hi,I have purchased a Tektronix 2235, and am wondering about the 050-2242-03 upgrade. According to the Tektronix document, the upgrade is for Tek 2235 Serial numbers B010100 - B041675. However, all B* serial numbers are USA made scopes. My oscilloscope starts with a 2, (203790), which means it was made by Tektronix UK.Will this upgrade be appropriate for my scope?

author: bd139
author_rank: Super Contributor
timestamp: February 23, 2020, 10:19:03 pm
content: Datasheet here:http://hakanh.com/dl/docs/kitinstructions/050-2242-03.pdfI would not touch it unless it's broken. The 223x power supplies are a complete sod from end to end. I have a thread here on one which decided to explode:https://www.eevblog.com/forum/testgear/tektronix-2235-repair-thread/.

author: george.b
author_rank: Frequent Contributor
timestamp: February 24, 2020, 05:02:24 am
content: Quote from: bd139 on February 23, 2020, 10:19:03 pmAnd I would second that.

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 24, 2020, 01:01:18 pm
content: If you really want to get your hands dirty, I have the info for this upgrade in my crappy video on the restoration of my 2235.

author: wizard69
author_rank: Super Contributor
timestamp: February 25, 2020, 02:43:47 am
content: Quote from: TERRA Operative on February 24, 2020, 01:01:18 pmThanks for the great video. I have an old 2230 that I need to repair, when I get around to it, hopefully there are some similarities. Unfortunately it is more of a not working variety so may require more work than you had here.

author: MrElectric
author_rank: Contributor
timestamp: March 01, 2020, 01:33:49 pm
content: Thanks! I have now tested the oscilloscope more, and I think everything works, except for the intensity control for the B channel, which does not do anything. Turning the main intensity control seems to affect both channels.
Tektronix 2235 Volt/Div Malfunctiog on Some Settings - Page 1
Forum section: electronics / repair

author: gmcjetpilot
author_rank: Newbie
timestamp: October 14, 2024, 11:40:15 pm
content: Channel A on 1, 2 and 5 volts/div are ok.Not working is 20m, 50m, .1, .2 .5, 10, 20 and 50 volts\/div is not working, zero volts. Again 1, 2 and 5 volts are OK.Channel B is fine.Unrelated may be is the probe connection is intermittent when wiggled. Dirty? Bad probe connector.I have owned it for 15 yrs always reliable, clean, but not used for many many years. Always stored inside home. I noticed this issue last year but only needed one channel. Recently needed two channels and got the job done on 1 volt/div... However I like to fix it.Ideas. I read other threads... Is the service manual on line?

author: George Edmonds
author_rank: Frequent Contributor
timestamp: October 15, 2024, 04:28:54 am
content: Service manual is herehttps://w140.com/tekwiki/wiki/Main_PageG Edmonds

author: David Hess
author_rank: Super Contributor
timestamp: October 15, 2024, 07:00:59 am
content: When you say not working, what do you mean?Are they the wrong sensitivity? Is there no signal? Is the signal corrupted?My guess is that the cam switches are not making good contact anymore. The leaf for each cam switch can be bent with tweezers to restore good contact.

author: gmcjetpilot
author_rank: Newbie
timestamp: October 15, 2024, 01:04:01 pm
content: WELL WELL I did something.I opened it up, removed the cover over the front board, which requires removing one header (yellow wire aft) and saw the Channel A Volt/Div selector mechanism. Contacts clearly visible. I blew compressed air around to dust it out (it was pretty clean).I rotated the selector and saw contacts open and close on traces. Decided to apply a little squirt of D5 Deoxit on contacts that were open and exercised selector, repeating for each set of positions. I put it back together.No trace now on either A and B. Beam finder works. Back light, it powers on. Just no trace. I did all the usual things with intensity and position to find the trace. Again scope working except channel A, 5 of 8 volt/div positions not working (reading zero volts when signal applied), but OK in 3 position (1, 2, 5 v/div).I am going to let it dry out over 48 hours and hope it will self heals.I am 99.9% sure I put the header back correctly. I was careful, but clearly I did something wrong. I never had D5 go sideways. I applied sparingly. D5 is great in contacts and no doubt some got on board, but it is safe in my opinion. We are talking about a 20-30 yr old piece of test gear.If you have ideas or want to admonish me feel free.... . I am sure there is a thread somewhere that says never clean the contacts with D5. Ha ha.

author: David Hess
author_rank: Super Contributor
timestamp: October 15, 2024, 04:09:37 pm
content: The cleaning of the contacts is done by closing the contact on a piece of non-clay paper, like a 3x5 card, soaked in solvent and drawing the paper out. Spraying with anything will make a mess.
Tektronix 2235A power problem - Page 1
Forum section: electronics / repair

author: xbunnyraptorx
author_rank: Newbie
timestamp: February 07, 2025, 10:22:02 pm
content: Hello,I just took my scope into school to do a demo and it was working fine. I took it back home and now it wont turn on. The power is oscillating between on and off as shown in the video, you can see from the LED and from the sound. I must have bumped it or something in transport. I have basic diagnostic equipment (multimeter, another scope) if probing is needed, although I don't have a strong sense of what I am doing so I'm inclined not to touch anything right now. Any ideas appreciated, thanks.Video -2235 manual -https://download.tek.com/manual/2235_sm.pdf?_gl=1*1153gll*_gcl_au*MTcyMjk0NjE5Mi4xNzM3NDg0MjIx*_ga*MjA3ODc5MDIxMC4xNzM3NDg0MjIx*_ga_1HMYS1JH9M*MTczODMwMTQ5NC4yLjAuMTczODMwMTQ5Ny41Ny4wLjA.

author: D2236
author_rank: Regular Contributor
timestamp: February 07, 2025, 10:38:40 pm
content: It appears that something is putting the PSU in an over-current situation. Follow the procedures starting pg 6-7 to isolate some of the supply feeds. You can also check with the unit off, the resistances between GND and each of the supplies mentioned in Table 6-4. You may find a low resistance (short) on one of these supplies.

author: xbunnyraptorx
author_rank: Newbie
timestamp: February 07, 2025, 10:59:05 pm
content: Thank you. I just came across this document too which says the same. I'll have to take a look at that.https://www.hakanh.com/dl/docs/troubleshooting_tips_on_2200_ps.pdf

author: m k
author_rank: Super Contributor
timestamp: February 08, 2025, 07:13:49 am
content: TP940 is familiar.Seems to be the same power as for 2215A, possibly others also.If memory serves you can use external 42V current limited supply.Disconnect Q9070 and maybe something else, can't remember, and connect 42V to TP940.There were also an external PSU kit back then.Q935 and VR935 is an overvoltage crowbar, it can kick in too early.If so then you should have all secondary voltages pulsing.
Tektronix 2246: no crt... and maybe more - Page 1
Forum section: electronics / repair

author: 8962
author_rank: Newbie
timestamp: July 05, 2025, 05:19:20 pm
content: Hello everyone,I am new as user, but quite old as guest... first of all I d'like to say a big THANK YOU to all the people sharing their knowledge here...I clearly can remember when a place to find informations like in here was just a dream...But let's talk about troubles:I recently got a Tek 2246 MOD A sn B10xxxx (early ones) with nothing displayed on crt...I did some check:- Voltages in J1204 were slightly high and are now ok after little adjustment- CRT blinks something just in case of switch off and on again immediately- Test point 7A seems ok, but 7B is quite bad (see photo)- Neon bulbs in HV section stay off during operation, they all just blink a little when powering off-Q701 and Q702 are quite hot... around 90°CAny suggestion?Thank You

author: frantisek
author_rank: Regular Contributor
timestamp: July 08, 2025, 11:20:37 am
content: Does the power supply and all its voltages match the manual?

author: 8962
author_rank: Newbie
timestamp: July 13, 2025, 03:07:09 pm
content: Yes, voltages were a little high, I did a little adjustment and now they look ok.I have some ripple (about 20 mV) on 55 and 130 vdc

author: ondraN
author_rank: Regular Contributor
timestamp: July 14, 2025, 07:40:09 am
content: Try disconnecting the wires to the CRT deflection plates. Set the brightness to minimum and increase it a moment after turning it on. If a dot appears, the HV circuits for the CRT are probably fine. Then I would connect the vertical amplifier and see if the position of the dot changes when moving the Position potentiometer. If that is OK, then continue with the X amplifier in X-Y mode. And according to the results, look for a fault in the specified circuits.
Tektronix 2252 - repair and preventive maintenance - Page 1
Forum section: electronics / repair

author: 22euu
author_rank: Newbie
timestamp: June 15, 2023, 08:35:24 am
content: Hi all,Recently I am the happy owner of an oscilloscope wanted since childhood - Tektronix 2252. The oscilloscope arrived in pretty good shape but when I turned it on, I noticed a few things I didn't like:1. What is displayed on the screen seems to have a slight flicker (a kind of visibly annoying "refresh rate") and the display is not sharper like my old 2215A Tek.2. When I turn it off, the waveform remains on the screen and gradually fades out, focusing on the middle of the screen (like old CRT TV).3. The fan sounds very noisy.4. I opened it and in the high voltage area, traces of "smoke - high voltage burnt dust" can be seen on the cover and underneath. I google it and comparing with the photos of other oscilloscopes, the area should be clean...Relying on your knowledge in troubleshooting Tektronix oscilloscopes, please help me to solve the above problems and also please indicate, based on your experience which components should be changed as preventive maintenance and to extend the life of the oscilloscope.Thanks.

author: David Hess
author_rank: Super Contributor
timestamp: June 15, 2023, 04:42:43 pm
content: Quote from: 22euu on June 15, 2023, 08:35:24 amThe single beam is time multiplexed to produce the readout which causes flickering in the waveform display. The readout can be shut off to prevent this. Some oscilloscopes have a mode where the readout is only generated between sweeps, but I do not remember that any of the 22xx or 24xx series support this.QuoteBoth of mine are almost completely silent, so your fan bearings might be worn. Oiling them (motor oil is good) will likely improve the situation.QuoteThe high voltages electrostatically collect smoke and dust from the environment. This likely indicates many hours of operation and is not something to worry about.

author: 22euu
author_rank: Newbie
timestamp: June 16, 2023, 06:55:26 am
content: Quote from: David Hess on June 15, 2023, 04:42:43 pm
Tektronix 2252 scope fuse holder "cap" replacement - Page 1
Forum section: electronics / repair

author: vaizki
author_rank: Newbie
timestamp: January 25, 2022, 09:38:32 pm
content: Had my Tek 2252 out of the house for a day and then shelved it for a few months.. Now putting it back on the bench noticed that the fuse and cover have gone missing and nowhere to be found.I opened up the scope and seems like getting to the power supply will be a real pain if I need to replace the fuse holder. Since this less than 30 years old, I'm hoping a replacement cap can be sourced instead. It's clearly a spring-loaded bayonet push-n-turn type which most probably is flush with the back panel.The tube is smooth on the rim (no keying or cutouts). The contacts are on the bottom (in) and sides (out) and there is no spring. So the spring is in the cap. The fuse must be a 5x20 type.Any help in identifying the part MUCH appreciated, I want to train my kid (10yo) on this.

author: vaizki
author_rank: Newbie
timestamp: January 25, 2022, 09:52:33 pm
content: Right after posting I realized Tekwiki must have images and they do. Seems to be a gray cap.

author: jdragoset
author_rank: Frequent Contributor
timestamp: January 25, 2022, 10:13:39 pm
content: check with qservice-electronics on ebay.

author: vaizki
author_rank: Newbie
timestamp: January 26, 2022, 09:05:21 am
content: Quote from: jdragoset on January 25, 2022, 10:13:39 pmI've ordered from them, thanks again. My ebay-fu is not what it used to be...

author: TERRA Operative
author_rank: Super Contributor
timestamp: January 26, 2022, 03:38:26 pm
content: Here is the part:https://www.schurter.com/en/part/0031.1666FEK 0031.1666
Tektronix 22xx 4-pin 270uF capacitor adapter - Page 1
Forum section: electronics / repair

author: moldy
author_rank: Newbie
timestamp: January 13, 2021, 06:36:43 pm
content: Hi,I'm new to the forum, but I literally spend nights reading the repair stories of the cool equipmentSome of the topics were also super useful to repair my Tektronix 2232 (particularlyhttps://www.eevblog.com/forum/repair/tektronix-2232-scope-in-need-of-a-doctor/). Now, I would like to share back my experiences, maybe they will come useful to someone.1) 270uF 4pin capIn any case, when recapping my Tek, I wanted to replace all power supply capacitor including the 4pin 270uF one. Unfortunately, it's not that easy to source a correct size capacitor in Europe. After seeing an adapter for 7xxx series (https://github.com/peekpt/tekcaps), I decided go quickly draw an adapter for my case (and it should also fit Tektronix 2235 and 2246A and probably more). Here's the repo with Kicad files and gerbers for everyone to use:https://github.com/dymczykm/22xx_tek_cap_4pin/See in the attachments how it looks (the cap was not soldered yet). Aaand it nicely fits, without colliding with the black plastic line filter cover.2) Digital mode unreliable, after few minutes the screen was just blank (but the analog mode worked fine)It really sounded like a powers supply issue and indeed the light grey connectors (J9011 on the digital board) turned to be cracked and brittle. I attached a picture of the brittle connector.I have desoldered the connector on the digital board and soldered the wires directly and crimped a new connector/pins on the other side:- Molex 0008650115 gold-plated pins- Molex 0009508081 3.96mm 8pin housingHope that helps someone with the 22xx family of scopes!
Tektronix 2335, similar to 2336YA etc... - Page 1
Forum section: electronics / repair

author: Spectrum
author_rank: Regular Contributor
timestamp: April 10, 2021, 01:36:34 pm
content: Hi, I bought this not working scope which has a BJT on the HV board in short. The transistor is Q161 (2SC2527) one of the tr switching of the HV trafo. All the other voltages are of correct value (+5 -5 +10 -10 +40 unreg). Someone knows if this board could have some other issue, or some other componenti faulty before give power ?I found R115 burned but not interrupted, Q115 C 116 and Q116 ore OK.

author: bob91343
author_rank: Super Contributor
timestamp: April 10, 2021, 07:11:22 pm
content: I realize English isn't your first language but I really can't understand your message.

author: Spectrum
author_rank: Regular Contributor
timestamp: April 12, 2021, 08:26:30 am
content: I replaced Q161, the scope worked for 10-15 minutes and then the F89 fuse blown again. This happened two times after 10-15 minutes. There is something that absorbs too much after 15 minutes of operation. After replacing the F89, the scope works for 10-15 min. The voltage of 102 V is ok as the others. Could be the HV transformer ?
Tektronix 2335 - Page 1
Forum section: electronics / repair

author: renato.pierri
author_rank: Newbie
timestamp: March 01, 2025, 11:55:32 pm
content: Hello, I am restoring a Tektronix 2335.Initially, it had an issue with the High Voltage and CRT board because the transistors Q163 and Q161 were burning out.After replacing these transistors, some capacitors and the U130 HV module, I could get the trace back as shown below.The problem now is that when I move any one of the traces to the lower part of the screen, the signal gets distorted as shown belowHere you have a link to a YT short I did:https://youtube.com/shorts/eS0JAjEjIaE?si=aSZFvTcPaPXQ0Yt1Any tips and hints will be very welcomed.Thanks

author: ondraN
author_rank: Regular Contributor
timestamp: March 02, 2025, 08:01:46 am
content: I think the only way to identify such a problem is to trace the signal path of the vertical amplifier to the point where the distortion is occurring. Before that, I would measure all the power supply voltages rails and the voltages at the anode and cathode of the CTR.

author: benj38
author_rank: Frequent Contributor
timestamp: March 02, 2025, 01:27:53 pm
content: It does not look like the problem has anything to do with the CRT.

author: awesomechapro
author_rank: Contributor
timestamp: March 02, 2025, 09:45:12 pm
content: Since you said it happens on both channels, I would suspect a problem with the final vertical amplifier. According to the service manual, U54 is the final vertical amplifier chip. I would start by measuring U54's 40V supply rail on pin 1. If that is low, has too much ripple, or is non-existent, that could definitely be causing your problem.

author: renato.pierri
author_rank: Newbie
timestamp: March 07, 2025, 09:19:50 pm
content: Hello everyone!First of all, I’d like to thank you all for your comments on what could be causing this issue.In short, here’s how I managed to fix it (the steps are not ordered):I considered all suggestions and applied the powerfull RTFM tool and performed all the necessary adjustments and checks related to vertical deflection.I recapped the oscilloscope—replacing the electrolytic capacitors in the power supply and the key capacitors in the HV board and vertical amplifier.After the recap, I got some magic smoke on power-up. A few unrelated capacitors failed and had to be replaced. Even a capacitor from the probe compensation signal generator went bad.I replaced those, and this particular issue stabilized. The oscilloscope is now working.The main culprit was the capacitor A15C191 (2µF x 150V).It was faulty and prevented the +102V supply (TP320) from regulating properly.See <9> High Voltage & CRT Tek 2335 Service Manual for reference if you want know more.The oscilloscope still has an issue related to the delay time position, but I’ll start a new thread to address that.I really appreciate all support received.
Tektronix 2336 Scope Sec/Div Switch Issue - Page 1
Forum section: electronics / repair

author: TimeBandit
author_rank: Regular Contributor
timestamp: February 14, 2022, 10:52:18 pm
content: My 2336 started acting up today while I was using it to monitor a 1kHz sine wave. I've attached a link to a short video showing what I'm seeing. As I decrease the sweep speed, the sine wave starts acting wonky (technical term). I've never had to do any work on this scope, but I'm ready to dive in with some direction.https://youtu.be/1P13kJ4kDmU

author: bdunham7
author_rank: Super Contributor
timestamp: February 14, 2022, 11:05:16 pm
content: Looks like you aren't triggering properly. Can you show the whole front of the scope?

author: TimeBandit
author_rank: Regular Contributor
timestamp: February 15, 2022, 12:17:35 am
content: Sure. Let me know if this isn't clear enough.

author: bdunham7
author_rank: Super Contributor
timestamp: February 15, 2022, 12:36:25 am
content: I meant with everything connected, turned on and set so that the problem is happening.What I suspect I'll see is that you have it in AUTO trigger mode but the trigger indicator light is not on. You likely need to adjust the trigger level until the light is on, which should be somewhere in the middle of the adjustment if the scope is working properly. Unlike many other Tek scopes, this model does not have the AUTO P-P feature which sets the trigger level automatically, so the AUTO trigger mode is 'dumb' and just triggers so you have something to see. You will almost always want to use this scope in the NORMAL trigger mode.

author: TimeBandit
author_rank: Regular Contributor
timestamp: February 15, 2022, 03:18:50 am
content: Sure enough that was it. Thanks for saving me from myself.
Tektronix 2424L Oscilloscope Repair - Page 1
Forum section: electronics / repair

author: Tomorokoshi
author_rank: Super Contributor
timestamp: April 26, 2019, 02:36:47 am
content: I got a Tek 2424L that had been in service for many years somewhere in an industrial building. It is loaded with an accumulation of dust mixed with oil.It was relegated to the scrap metal bin because it stopped working. Upon retrieval, the first noticeable symptom was chirping of the power supply. A search for a 2424L manual was not successful. In fact, most anything about it was not forthcoming. Therefore I tried to use the Tek 2430A service manual. The more I got into it, the more it seems the 2424L is a down sampled version of a 2430A. The A16 power board appears to be identical.Various measurements and sequential disconnection of various boards narrowed it down to the A16 power supply once everything else was disconnected. This included unstable DC outputs. When powering up, it would chirp 3 or 4 times before finally running the fan, if it made it at all.I made a list and measured all the electrolytic capacitors in circuit for capacitance and dissipation. As it happens the problem was in the first capacitors I measured. A16C305 was 326 pF at D = 0.2, while the identical A16105 was 673 uF at D = 0.16. Out of circuit was similar. These are specified as 680 uF at 200 V.After a cursory reassembly I was able to get almost full functionality. Cleaning, replacing RIFA capacitors, etc. will happen later.
Tektronix 2430 Oscilloscope - Page 1
Forum section: electronics / repair

author: wanderer404
author_rank: Newbie
timestamp: January 07, 2022, 07:56:44 am
content: Hi all,one of the ribbon cables on my Tektronics 2430 Oscilloscope has been munged (technical term) by the case.Can anyone identify what sort of connector and cable I can use to remake it? I'm not having any joy searching for part numbers in the service manual. I looks much more solid than standard ribbon cable.The cable goes from Board A10 J113

author: shakalnokturn
author_rank: Super Contributor
timestamp: January 07, 2022, 09:05:21 am
content: You may have found that by yourself but original manufacturer is Amphenol.I had no luck either with original references.You should find something easily enough on Mouser in "FFC & FPC Connectors" or "FFC / FPC Jumper Cables" then refine search by manufacturer, number of contacts, pitch...

author: m3vuv
author_rank: Super Contributor
timestamp: January 07, 2022, 09:15:54 pm
content: surley you can repair it?,looks like an easy job.

author: BrokenYugo
author_rank: Super Contributor
timestamp: January 07, 2022, 10:34:34 pm
content: Looks like at least one contact is destroyed, so they'll need parts at minimum.Also looks to me a lot like an ordinary 0.100 inch/2.54mm pitch pin header connector.

author: wanderer404
author_rank: Newbie
timestamp: January 08, 2022, 12:51:29 am
content: Thanks for checking. It’s the first time I’ve seen a solid wire flat ribbon cable being used so I’m not sure of the current capacity requirements for the connector. Pitch seems pretty standard. Elsewhere on the scope standard multi strand ribbon cables are used so there must be a specific reason for using solid here. The connectors have exposed solder pins which is unusual but may make it easier for fixing.It’s annoying because I’ve recently renovated the entire HV section and PSU section of the scope and was all working until I slid it back into the case and it caught the cable.

author: wanderer404
author_rank: Newbie
timestamp: January 08, 2022, 12:53:59 am
content: Thinking about it more I wonder if they use standard multi strand ribbon where IDC connectors can be used but solid ribbon where solder connectors are used.
Tektronix 2432 with vertical failure? - Page 1
Forum section: electronics / repair

author: weakbit
author_rank: Newbie
timestamp: April 05, 2020, 09:45:08 pm
content: Hello,the failure is if i turn the time base A to 50us/div the horizontal line (beam) can never adjust vertical.If the time base is turned to 100us/div the beam (horizontal line) is normal and the oscilloscope is working normal.From 50us/div and under the vertical disturbance is shown in the signal and the beam is in the middle of the screen but I can't move it up/down. This is under this time base not possible anymore!I change all Electrolytic caps in the power supply but the problem is not gone away.Where Is should search? I've download the service manual. Also the Battery is defect maybe this is a miss align problem. Did someone have the same problem? The failure is in all faster timings (time base 20us and faster) the same. If I turn the vertical position the signal is changing from down the line to upper the line but the line is not moving. What can that be?Thank you and Best Regardsweakbit
Tektronix 2432A noisy trace - Page 1
Forum section: electronics / repair

author: gerdy
author_rank: Newbie
timestamp: February 23, 2023, 07:16:29 pm
content: Hi, I have a Tek 2432A scope. It works well except it has a bit of a noisy trace. Grounding the input channel(s) does not change that, still noisy.Anyone experienced this before? Any clues where I have to look to fix this?

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: February 23, 2023, 11:52:41 pm
content: That actually looks kinda normal. Go down to 2mV and check it. I have a 2430 and a 2440 and they both pretty much do the same.

author: David Hess
author_rank: Super Contributor
timestamp: February 24, 2023, 10:54:56 pm
content: Didn't we just cover this?The Tektronix 2400 series DSOs are pretty noisy because of their CCD technology, but that looks pretty normal to me, and is actually not bad for a 300 MHz bandwidth, but check at the most sensitive vertical sensitivity to make sure.
Tektronix 2432A noisy trace - Page 1
Forum section: electronics / repair

author: gerdy
author_rank: Newbie
timestamp: February 17, 2023, 03:36:42 pm
content: I have a TEK 2432A that works well, except for the trace(s) which are slightly noisy. This is as well on 1 of the channels as on on both channels, even if I ground the channel(s). Anyone having a clue where I have to start looking to repair this?

author: TheDefpom
author_rank: Frequent Contributor
timestamp: February 17, 2023, 09:40:49 pm
content: Re-cap the power supply, I have done some videos on this unit.Mine also had issues with Tantalum caps failing (because of the main power supply ripple getting excessive), so you may want to get onto that sooner rather than later.A point to note, if you power it up without the cover on make sure you have a fan blowing air across the hybrid modules... you don't want them to overheat and blow up.

author: Bud
author_rank: Super Contributor
timestamp: February 19, 2023, 02:51:17 pm
content: It looks normal to me.@TheDefpom do you still have yours? Can you post a photo of yours traces?

author: David Hess
author_rank: Super Contributor
timestamp: February 19, 2023, 04:51:14 pm
content: That looks about normal to me also, and reasonable for a 300 MHz bandwidth. The 2400 series DSOs are known to be pretty noisy because of their design.What does the noise look like at maximum sensitivity at the different bandwidth settings?

author: TimFox
author_rank: Super Contributor
timestamp: February 19, 2023, 05:59:49 pm
content: How does the noisy trace change when you use the bandwidth-reduction switch?

author: Bud
author_rank: Super Contributor
timestamp: February 19, 2023, 07:09:48 pm
content: These are hybrid scopes, there is digitization and multiplexing involved and part of the noise is because of digital artefacts. You can use averaging to smooth the trace but as it is it looks normal to me.

author: David Hess
author_rank: Super Contributor
timestamp: February 20, 2023, 12:34:44 am
content: Quote from: Bud on February 19, 2023, 07:09:48 pmThe 2400 series DSOs are not multiplexed. In Tektronix terms they were "real time" with a separate sampler and acquisition record for each channel. I do not remember if the digitizer is shared but it would not matter because it operates at low speed.I am not sure what you mean by "hybrid". They use hybrid circuits but these DSOs have no analog mode like the 22xx series.

author: BradC
author_rank: Super Contributor
timestamp: February 20, 2023, 12:50:45 am
content: I'm with everyone else. That looks pretty normal.I did have a strange noise issue on my 2440 back in 2017 (it's archived on the Tekscopes2 list), but that was resolved by letting it warm up for a couple of hours and running an auto-cal.That fault was characterised with extra noise on the Ch1 trace. Yours looks consistent on both and about what I normally see.
Tektronix 2445 repair using home made HV module - Page 1
Forum section: electronics / repair

author: Forward Bias
author_rank: Newbie
timestamp: January 25, 2023, 02:21:45 am
content: https://youtu.be/Uo5oABz9FisI got this Tektronix 2445 for repair with a blank screen. Opening it up revealed so many issues repair process was tedious and long but the end result was worth it.. I love old oscillocopes. Please turn on closed captions for english subtitles

author: Forward Bias
author_rank: Newbie
timestamp: January 25, 2023, 02:54:16 am
content: https://youtu.be/f7KCOZVPU8A

author: inse
author_rank: Super Contributor
timestamp: January 25, 2023, 11:14:01 am
content: Amazing repair job

author: Forward Bias
author_rank: Newbie
timestamp: January 27, 2023, 06:36:06 am
content: Thankyou..
Tektronix 2445A with problems - Page 1
Forum section: electronics / repair

author: fant
author_rank: Contributor
timestamp: January 29, 2023, 02:55:51 pm
content: A company gave me a Tektronix 2445A just for nothing after many years not powered.At power on appears the diagnostics error as the following picture.Indicating TEST 04 FAIL 13 errorAfter few seconds it disappear end the scope is working, but on the readout bottom row, the data are mixed with?, as the following picture.Any idea what to search?I have the user and service manual.Thank you in advance

author: factory
author_rank: Super Contributor
timestamp: January 29, 2023, 03:37:32 pm
content: Calibration data has bad checksum according to the manual, test 04, LED CH4 lit, error 1x.David
Tektronix 2445B Screen fault. - Page 1
Forum section: electronics / repair

author: ekremc
author_rank: Newbie
timestamp: December 08, 2022, 04:39:42 pm
content: Hi all,My 2445B screen bottom side many ? ? ? ? ? ? ? sign.How solve this problem.Thx all

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: December 08, 2022, 07:54:42 pm
content: My 2467B did that when it lost its calibration.

author: 807
author_rank: Frequent Contributor
timestamp: December 09, 2022, 12:24:37 am
content: Yep. It means it needs to be calibrated. When the internal jumper is set to calibration setting the question marks will change to dots.Did you get any error codes as the scope booted up?

author: tggzzz
author_rank: Super Contributor
timestamp: December 09, 2022, 12:39:25 am
content: Execute the self tests as described in the manual, and see the results.When the battery inside the "non-volatile" RAM is exhausted, the calibration constants are lost. The remedy is to replace the RAM and recalibrate. Note that the "non-volatile" RAM stopped being manufactured a long time ago, so any "new" devices on fleabay will probably have a nearly depleted battery.Workarounds are discussed elsewhere in this forum, and on the tekscopes groups.io forum.

author: 807
author_rank: Frequent Contributor
timestamp: December 09, 2022, 01:09:15 am
content: Quote from: tggzzz on December 09, 2022, 12:39:25 amAre there 2 types of A5 boards on the 2445B like there are with other 2445/2465 variants? The older through-hole board having a separate battery, while the newer SMD board had the Dallas chip with inbuilt battery?
Tektronix 2455B CRT Trace issue (video included) - Page 1
Forum section: electronics / repair

author: 11mrjones
author_rank: Contributor
timestamp: August 19, 2025, 08:20:47 pm
content: Hi all- my 2455B scope has recently developed an issue where the crt beam trace and screen readout are very much out of focus at turn on. The focus adjust works but will not bring the trace into focus during this initial stage. Waiting for maybe about a half hour the trace will eventually "snap" into focus. Alternatively I can bring it into focus immediately by turning the beam intensity to maximum the backing it down to a normal level. At this point everything work fine ; beam trace is sharp as is screen readout, focus works perfectly, intensity adjustment, screen illumination works fine.I haven't opened it up and done visual inspection and rails check etc, yet. This will be my first scope repair and i am a little leary of poking around in the HV area. Guessing something in the high voltage supply, a cap? If someone has seen this before any advice is greatly appreciated.See the video below, one can skip to timestamp 1:00. Shows the scope starting up. At the end I max out the beam intensity to snap it into focus.https://youtube.com/shorts/bgIj-9VeWY4Thanks for any ideasVictor

author: Kwakerman
author_rank: Regular Contributor
timestamp: August 19, 2025, 10:08:59 pm
content: Don't think it is an actual focus issue (I think its the effect rather than the cause), that seems to be a very long time for the CRT to come up to full emission. I'd be tempted to look at the HV (A9 board IIRC) and also check the heaters.

author: Runco990
author_rank: Frequent Contributor
timestamp: August 20, 2025, 01:36:59 am
content: I'd agree with that. Check the power supply, in particular the heater voltage.

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: August 20, 2025, 06:33:48 am
content: It is highly likely to be one of the carbon comp resistors in the high voltage section.

author: 11mrjones
author_rank: Contributor
timestamp: August 20, 2025, 05:08:38 pm
content: Thanks guys- looks like I have some reading/studying of the HV section of the service manual to do in the next few days.V.
Tektronix 2465 Calibrator Broken - Page 1
Forum section: electronics / repair

author: mawyatt
author_rank: Super Contributor
timestamp: May 07, 2020, 03:46:08 pm
content: Hello,New here and thought about posting a success repair for restoring the Calibration function. I purchased a couple 2465 off eBay, each had their problems. I've replaced many of the usual power supply capacitors (waiting for a few others) as indicated by many others, but the Calibrator waveform is not correct as you can see. I traced this out and after a little circuit analysis thought the cause was a defective zener diode, this is a special Motorola part. I replaced the Zener with a 1N4733A zener and this fixed the Calibrator waveform.Best,Mike
Tektronix 2465 - Beam Intensity too bright when more than 1 channel is active - Page 1
Forum section: electronics / repair

author: Terraqua
author_rank: Newbie
timestamp: December 20, 2022, 01:55:56 pm
content: Hello EEVblog folks and Tek 24xx ownersMy Tektronix 2465 is having a problem with the beam intensity.If I adjust the intensity to a normal brightness when 1 channel is active, it becomes too bright when I activate a second channel. If I activate a third, it remains the same, and when I activate all 4 the intensity becomes really bright...All PSU voltages are within spec, DAC ref in spec. I replaced U650 (just to check).... the problem is located somewhere elseDoes someone have an idea where I should start the troubleshooting? My old tekky and I will be gratefull if you could point us in the right direction...Here a video of the problem (brightness adjusted to 4 active channels, if I disable a channel, I can't see any traces (unless I increase the intensity)https://youtu.be/n9u6L1K3P8Q

author: bdunham7
author_rank: Super Contributor
timestamp: December 21, 2022, 06:55:34 pm
content: Can you post a photo of the entire front face of the scope showing how the controls are set? Is this something that just happened suddenly after working normally or is the scope new to you?

author: tggzzz
author_rank: Super Contributor
timestamp: December 21, 2022, 08:21:20 pm
content: Those are sensible questions!If you need to go inside the scope, the traditional places.to start are with the PSU voltages/ripple, SMD caps on the control boards, and voltages near the DAC. All are well described on this forum and elsewhere.A good 2465 is a delight to use

author: Terraqua
author_rank: Newbie
timestamp: December 21, 2022, 08:39:51 pm
content: I have this scope for a while now, but it was in storage in a box with silica gel granules to keep it dry (don't know if that's the right name in English for that stuff)Now I have a seperate room for my hobbies, and more space, so I thought to recomission my old scope again.It still works all right, apart from the brightness problem... the PSU voltages and ripple are within spec, that's the first thing I checked...It seems cumulative. If I adjust the brightness when 1 channel is on, it is too bright when 2 or 3 channels are active, and blasts away the fosfor on the screen when I activate all 4 channels...Here a picture of the settings on the front panel:
Tektronix 2465 different shematics? - Page 1
Forum section: electronics / repair

author: 97paul
author_rank: Contributor
timestamp: October 05, 2025, 01:06:03 pm
content: Hello everyone,I'm currently repairing a 2465. A Rifa capacitor in the power supply exploded and fried a resistor. Now I'm looking at the circuit diagram (board A2A1) and notice that some parts, such as R1014 and R1015, are different (75K). According to the circuit diagram, they should be 36K. A few other resistors also don't match. Does anyone know if there were different revisions? I can't make out the color code of the burned-out resistor (R1018), and I'm not sure if the labels in the circuit diagram are correct.

author: Kwakerman
author_rank: Regular Contributor
timestamp: October 05, 2025, 07:02:46 pm
content: Yes, I've seen different values on different models. When you say 2465 is that the non A or B (with toggle switches)?

author: 97paul
author_rank: Contributor
timestamp: October 05, 2025, 09:36:20 pm
content: Exactly, I have the 2465 without A and B.

author: 97paul
author_rank: Contributor
timestamp: October 05, 2025, 09:39:12 pm
content: Here you can see the burned resistor and exploded RIFA.

author: MarkL
author_rank: Unknown
timestamp: October 05, 2025, 09:57:18 pm
content: Quote from: 97paul on October 05, 2025, 01:06:03 pmTektronix documented changes by serial number. Attached is the parts list from the service manual showing the two values in question for R1014 and R1015. In the list is also the burnt resistor, R1018, 30 ohms, 5%, 0.5W.

author: 97paul
author_rank: Contributor
timestamp: October 05, 2025, 10:00:55 pm
content: Thank you so much! This helps me a lot.
Tektronix 2465 Input Issues - Page 1
Forum section: electronics / repair

author: mawyatt
author_rank: Super Contributor
timestamp: May 07, 2020, 04:21:59 pm
content: Hello,New here and thought about posting a success repair for restoring the Input functions on channel 1 and 2. I purchased a couple 2465 off eBay, each had their problems. I've replaced many of the usual power supply capacitors (waiting for a few others) as indicated by many others. Both channels 1 and 2 had multiple problems with ground erratic and not working, 50 ohms, range and such. After some study of the schematics and single tracing the problems were localized to the 2 input hybrid modules. Replacements were expensive, even in surplus removed from trashed scopes, so decided to try and repair the hybrid.These were removed and disassembled (use a heat controlled soldering iron on the hybrids as it's easy to "leach" the surface and ruin the hybrid), everything seemed OK except the ceramic hybrid relay contacts were suspect. These modules use the substrate as the contact area for the input open type relays. Evidently these contact areas were oxidized and maybe coated with something, possibly tobacco smoke. Used a rubber soft pencil eraser to carefully clean the contact area, then thoroughly clean any residue.After hybrid reassembly and reinstalled the 2465 has now be revived and back to proper working order, beautiful scope !!!Note: Bottom image should be at top.Best,Mike

author: BravoV
author_rank: Super Contributor
timestamp: May 07, 2020, 04:46:52 pm
content: Wow .. thanks for sharing this, really appreciate it.

author: mawyatt
author_rank: Super Contributor
timestamp: May 08, 2020, 01:08:24 am
content: Hopefully this will help some folks, and they won't need to replace the input hybrids. Believe these hybrids are used in a few different scopes.Best,Mike

author: jdragoset
author_rank: Frequent Contributor
timestamp: May 08, 2020, 01:58:48 am
content: Also very applicable to earlier cam-operated contacts used in vertical input attenuators in 2235's and others.Not at all easily accessed but do-able, with patience.Almost like working on a Jeager, Atmos clock.