hybridfree/eevblog-posts huggingface dataset:
[SOLVED] Tek 2221A suddenly no power - Page 1
Forum section: electronics / repair

author: Fractal
author_rank: Contributor
timestamp: August 13, 2023, 04:51:24 am
content: Hey there, so my scope used to work fine till last night;today I press the power button and nothing happens; no fan spin, no light, no screen, no sound.I've checked the power cord, the fuse, all good.Opened up, seems like AC comes in past the power switch, but I can't figure it out past thatAny help?Thanks!

author: Fractal
author_rank: Contributor
timestamp: August 13, 2023, 12:19:23 pm
content: Ok update, there was actually a faint whining noise repeating every sec or so; probed around and found a shorted diode, CR907; removed it already, will go find a suitable replacement at my local electronics shop tomorrow

author: Fractal
author_rank: Contributor
timestamp: August 14, 2023, 12:50:32 pm
content: Okay replacing the diode didn't work out; started probing around for shorts in fets, found out Q946 and Q947 had short on 2 pins, removed them with the heatsink, but they now test find out of circuitShow up the short remains on the board, I'm getting it between TP950 and TP940 (42.8/43V?)This seems to narrow down the issue to the preregulator area, but now to locate it...I can't rely on my IR cam either as the unit only pulls 100mA pulses every secondAny help appreciatedCheers!__Yves

author: Fractal
author_rank: Contributor
timestamp: August 14, 2023, 04:16:04 pm
content: Well after facing crickets for the past couple days and since I have no idea what I'm doing I figured I'd just go the voltage injection way lolI sent 1A through the 43V rail with my bench PSU and immediately observed Q935 gobbling all the current on the IR cam.Removed it, reinstalled the inverter transistors and the diode, and sent power again.And what do you know, it powered on beautifully.I guess I'll just have to find a replacement triac; says MCR72 on it but seems long discontinued...will see to find a similar alternative.Service manual BOM says Thyristor, SCR:8A,200V,SENS GATE,TO-220W/LEAny suggestions welcome I guess

author: m k
author_rank: Super Contributor
timestamp: August 15, 2023, 09:58:04 am
content: It's just a crowbar, all similars are suitable.Maybe you should replace VR935 zener also.

author: Fractal
author_rank: Contributor
timestamp: August 23, 2023, 01:21:08 pm
content: Hey there friends!Just received the spare triac, a matching spec MCR72-8G from ONInstalled it, put my goggles on, pressed the power switch aaaand nothing happened.Turns out I forgot to plug back Q9070 lolTurned it off, plugged it back aaaaand... It lives!!!1111!No further damage to any components up or down the line, before or after the triac replacement. Very odd.But, super pleased that I can put it back to use, thank you for the tips!Cheers,__Yves
Tek 2225 trace disappears when DC voltage present at input - Page 1
Forum section: electronics / repair

author: shane321
author_rank: Newbie
timestamp: September 27, 2020, 03:51:25 am
content: Hello, hoping someone might be familiar with this sort of problem, I had a look around the internet, did find someone with same problem but no solution was presented.ProblemTek 2225 CRO Measuring AC ripple on 150 VDC supply, CRO is AC coupled.Ch1: unable to locate trace, pressing 'beam find' shows half trace near top of display, position control has no effect.Ch2: trace visible, shows AC ripple voltage just fine although trace wanders up a full division after 10-15 mins.Problem was intermittent before becoming consistent, it would be that the trace would display just fine before slowly wandering upward until it could no longer be brought back by position control. Upon shut down of the DC supply, as the DC voltage ramped down, it would return, slowing moving downward from 'off screen'.Without DC voltage present at the input, it works just as it should. I did replace the input coupling capacitor 0.022uF/630VDC but to no avail.Nice clean scope, worth trying to repair, any suggestions/help/advice is greatly appreciated.Thank youShane

author: bdunham7
author_rank: Super Contributor
timestamp: September 27, 2020, 04:08:06 am
content: If you change the channel coupling to 'GND' with the DC supply still connected, does the trace come back?Does the scope work completely normally on other signals?

author: shane321
author_rank: Newbie
timestamp: September 27, 2020, 04:17:58 am
content: Trace comes back with DC supply connected and input set to GND, yes.Works fine with all AC signals so long as no DC present.Thanks.

author: bdunham7
author_rank: Super Contributor
timestamp: September 27, 2020, 04:26:08 am
content: OK, then I think the thing to try is removing the attenuator board and cleaning the attenuator switch contacts with IPA. You can check the 500K resistors R3 and R5 and make sure the voltage at the input to U10 stays at 0 volts with the input disconnected and set to AC or DC, but that isn't likely to be the issue. The attenuator board is fairly easy to remove, but those switches are bit fiddly.

author: shane321
author_rank: Newbie
timestamp: September 27, 2020, 04:35:53 am
content: I'll give it shot, thank you.
Tek 2235 CRT shot or fixable?? - Page 1
Forum section: electronics / repair

author: Kidon
author_rank: Regular Contributor
timestamp: June 02, 2020, 03:14:00 am
content: Hi,I have this Tek 2235 that I got not too long ago, I decided to start using and went thru most of the essential calibration procedures(including all the CRT and power supply ones, minus the tube voltage (I do have a voltmeter that can handle up to 32kV, but not the optional HT probe).Anyhow, this is when I noticed this pb. The trace is thinner on the right hand side, and although it is straight when on the middle horizontal graticule line, the right side leans downwards when all the way up, and upwards when all the way down.Maybe it doesn’t show all that well in the pictures, but it’s clearly visible in person.So my question is: Is there a adjustment that can be made to rectify this, or is it shot and I need a new one?Thanks for your ideas.

author: helius
author_rank: Super Contributor
timestamp: June 02, 2020, 04:07:22 am
content: The pictures of the traces look perfectly normal.You should consider that any slight geometric issues at the extremes of the display are totally irrelevant for the intended purpose. If the trace is bright and the brightness control directly changes the brightness, the tube is fine. The sign of a bad (gassy) tube is when the brightness control doesn't affect the brightness of the trace, or makes it suddenly very fuzzy. None of your images show that at all.

author: james_s
author_rank: Super Contributor
timestamp: June 02, 2020, 04:50:07 am
content: Yeah I'm looking at those pictures trying to see what the problem is, it looks totally normal to me. CRTs are analog devices, even very good ones never had *quite* the perfect geometry that you get on LCDs.

author: Gyro
author_rank: Super Contributor
timestamp: June 02, 2020, 10:29:49 am
content: If you're really concerned, there's a trace geometry adjustment pot (R870) with adjustment procedure in section 5-5 of the adjustment section of the service manual. This adjustment is for trace straightness in the upper and lower portions of the screen. Note that it is a best compromise adjustment, so may already be set correctly.

author: David Hess
author_rank: Super Contributor
timestamp: June 03, 2020, 02:41:19 pm
content: That looks normal to me and within the specifications for geometry distortion. If it was damaged, I would expect it to be much much worse.
Tek 2235 Vertical Attenuator - Page 1
Forum section: electronics / repair

author: jdragoset
author_rank: Frequent Contributor
timestamp: October 21, 2019, 09:03:03 pm
content: Following removal (intermittent solder joint or contact in channel 1 on higher ranges) instructions, the coupling selector cams seem adhered to the coupling selection levers.Is this something that would have been repaired with adhesive or is there a release method?Thanks in advance.

author: jdragoset
author_rank: Frequent Contributor
timestamp: October 22, 2019, 12:27:48 pm
content: The coupling selector levers snap/click into and out of the coupling selector cams.
Tek 2236 aberrant trace - Page 1
Forum section: electronics / repair

author: dsw8191
author_rank: Newbie
timestamp: February 27, 2020, 07:48:24 pm
content: I've acquired a Tektronix 2236. It works but there is a distortion in the traces even when the inputs are grounded (see IMG_1095). The degree of distortion is dependent on Y position - worse when the trace is above mid CRT. Both channel traces superimpose when moved to the same Y position. The X position of the distortion is independent of time base setting.I've searched the forum for a similar problem without success. Hope someone wiser than I can provide an explanation for this.

author: pbarton
author_rank: Frequent Contributor
timestamp: February 27, 2020, 10:19:57 pm
content: My vote, CRT is damaged beyond repair, possibly the scope has been dropped.Good news, the X and Y electronics are fine.More advice if you scroll half way down this page...https://www.sphere.bc.ca/test/tek-parts/tek-info.htmland another one...https://www.eevblog.com/forum/repair/tek-2211-crt-weirdness/
TEK 2245A Start-Up Problem - Page 1
Forum section: electronics / repair

author: JdaleH
author_rank: Contributor
timestamp: November 12, 2023, 06:02:18 pm
content: When I press the on/off switch, most of the time the unit will not start up. I hear an ongoing click sound (relay?). I can usually keep pushing the button and the unit will turn on. Most aggravating. Can it be fixed?

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: November 12, 2023, 10:39:14 pm
content: Yes, sounds like a capacitor problem in the power supply as a guess but would require troubleshooting to the problem.Start with service manual and multimeter at a minimum, capacitance checker may help.Jeff

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: November 14, 2023, 01:11:07 am
content: Did you mean Tektronix 2445A?Jeff

author: Vovk_Z
author_rank: Super Contributor
timestamp: November 14, 2023, 05:05:01 am
content: Quote from: JdaleH on November 12, 2023, 06:02:18 pmQuite often that's a power supply problem (one or several dried electrolyte capacitors). The most efficient way to troubleshoot it when you have in-circuit ESR meter.

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: November 14, 2023, 08:31:27 pm
content: Go to PDF page 263 on the service manual here:https://w140.com/tekwiki/images/d/d1/070-7672-00.pdfdisconnect power supply output wires to completely isolate the PSU from the scope. If the 2245A uses PCB jumpers instead like traditional 22xx series scopes, desolder those. Measure voltages with a DMM and use a constant current load to measure the tripping current and make sure it matches up with the specs in the service manual.If the PSU trips under loaded, trouble shoot the PSU. If the PSU works perfectly fine, trouble shoot the rest of the scope by disconnecting power to some parts of the scope and see what makes the PSU trip. Isolate the problem and troubleshoot the suspect board/board area.Go to the Maintenance section of the manual and the sub section "Troubleshooting Techniques". Read that and then start your troubleshooting journey.
Tek 2246 channel 1 - Page 1
Forum section: electronics / repair

author: Tubesrule
author_rank: Contributor
timestamp: July 15, 2022, 02:57:07 am
content: Hi guys, I been putting this of since I'm not scope savy. But is time to get it done. I have two issues with the 2246, first annoying but workable the self calibration. The second is the real problem, channel 1, has no vertical movement at all, I can switch the ac/dc and it shows but no trace. The other three channels are "fine". I already check all voltages and checked fine from 5v-130v. Any input is more than welcome.Thanks

author: David Hess
author_rank: Super Contributor
timestamp: July 15, 2022, 05:36:59 pm
content: Quote from: Tubesrule on July 15, 2022, 02:57:07 amIt looks to me like channel 1 is not being displayed at all. To me that indicates a problem with the digital control of the analog sections. The 2246 uses TTL SIPOs like the 74164 to control things. Maybe a bit is stuck. The service documentation is comprehensive so it should be possible to track down with a multimeter.

author: Tubesrule
author_rank: Contributor
timestamp: July 16, 2022, 01:03:10 am
content: Thanks for that, yes you are correct not visible at all only the the beam find shows it(but I can't move it) vertical. Let's do some reading.

author: David Hess
author_rank: Super Contributor
timestamp: July 16, 2022, 02:54:25 am
content: Quote from: Tubesrule on July 16, 2022, 01:03:10 amThat changes things. If the beam finder shows it, then the trace is activated and either is not displayed because of a z-axis (intensity) problem, or the trace is shifted out of the viewable area. The later is likely the problem since the beam finder overrides the z-axis; somewhere in the vertical signal chain, there is an offset pinning the trace off screen. That also explains the calibration error.The diagnostic process is the same; the vertical signal path can be traced from the input to the vertical channel switch and likely find the problem.The input high impedance buffer or the input protection circuitry could have been damaged by an overload to cause this.

author: Tubesrule
author_rank: Contributor
timestamp: July 17, 2022, 02:23:12 am
content: Hi, A bit of an update after I read to this awful printout of the service manual, I decided to go back and check voltages and ripple. Dc voltages were fine, ripple on 58V was way up, north of 100 mV but one that I didn't check the first time was the 130v AC which right now is 97V I found the 130Ac going to the Dc restorer circuit, so that's where I'm at.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: July 17, 2022, 11:10:37 am
content: Did you check the ohms at the various inputs? with the unit off?

author: Tubesrule
author_rank: Contributor
timestamp: July 17, 2022, 05:02:40 pm
content: No I did not.
tek 2430 calibration procedure - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: January 02, 2022, 10:54:59 pm
content: Hi all,can anyone tell me how to calibrate this scope,or tell me where its described in the service manual,i gather i just need a few voltages to do it but cant find how to do it for love or money in the service manual,tia.

author: m3vuv
author_rank: Super Contributor
timestamp: January 03, 2022, 10:27:56 am
content: can no one help me with this?

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: January 03, 2022, 11:29:55 am
content: The service manual contains information on checking the scope pages 4-1 thru 4-35 and adjusting the scope pages 5-1 thru 5-11 all of the information is based on using the factory selected equipment. If using other equipment that you select it will require you to determine what, where and how that equipment is set and used to arrive at the same outcome. I have not calibrated a 2430 even though it is older than the others in that series all of which I have done and have the equipment for except a few pieces I have subsituted for better or what I had at the time. Say a calibrated leveled sine wave generator (SG504) replaced with an uncalibrated HP 8656B signal generator and scope (2440) and freq counters (7261A) and meters (8505A) (8050A) (8040A) to check settings and verifiy. Also if scope is an 05 option (TSG170A) may sub for R147A, R148.Jeff

author: m3vuv
author_rank: Super Contributor
timestamp: January 03, 2022, 12:46:17 pm
content: Well as you guys couldnt be of help,i did some hunting and found this site:http://k5jxh.com/Tektronix/TeK2430.html#freeJust thought it may be a help to any one facing the same issue,cheers all.m3vuv.
tek 2430A trigger stop - Page 1
Forum section: electronics / repair

author: denov
author_rank: Newbie
timestamp: May 31, 2020, 10:49:54 pm
content: all,i have a tek 2340A that was working great. then a few weeks ago i powered it back up and the trigger seems not to work anymore. at first i thought it was probably operate error but now i'm starting to think there's an issue with it.with nothing plugged in, and doing a program -> init panel after boot the trig'd light is solid. i have also notice that in the status screen it say 'completing acquisition 3364:30 HRS'. being a bit of noob still i'm not sure what this means but it doesn't seem right.i didn't seen any troubleshooting steps in the manual. i just found the service manual but that's going to take a sec to go through.i'd love any help getting this things back to normal.

author: David Hess
author_rank: Super Contributor
timestamp: June 01, 2020, 08:32:59 pm
content: Did you try resetting the 2340A using the menus?If the trigger light is stuck on and the 2340A is unresponsive, then that could be a diagnostic code.

author: med6753
author_rank: Super Contributor
timestamp: June 02, 2020, 12:31:31 pm
content: I once got my 2430 stuck in some weird trigger mode and I don't recall what I did to reset it. Tek didn't provide a master "panic" reset on these scopes.

author: David Hess
author_rank: Super Contributor
timestamp: June 03, 2020, 04:12:47 pm
content: The system or utility menu has a complete reset function.

author: med6753
author_rank: Super Contributor
timestamp: June 03, 2020, 11:36:24 pm
content: Quote from: David Hess on June 03, 2020, 04:12:47 pmReally? Perhaps the 2430A does. But I fail to find it on a 2430.Under Menu/Extended Functions. Bring up System.This is what's under "System". None of those functions bring up a reset.Edit, and just to be sure I RTFM the Operator's Manual again and no reference to a master reset.

author: David Hess
author_rank: Super Contributor
timestamp: June 04, 2020, 09:46:02 pm
content: Start by going to SYSTEM - PANEL - PWR ON, and configure it to INIT instead of LAST so the setings are reinitialized when the power is turned on.The COLD START function under the calibration menu will reset everything but requires an internal recalibration after.

author: med6753
author_rank: Super Contributor
timestamp: June 05, 2020, 12:45:11 am
content: Quote from: David Hess on June 04, 2020, 09:46:02 pmOK, if you want to call that a "reset" I'll go along with it.QuoteNot something you normally want to do. And you have to pull the "no cal" jumper. I've done it when I trashed a CCD hybrid. Luckily the re-cal sequence is not too difficult.
TEK 2440 cal - Page 1
Forum section: electronics / repair

author: cncjerry
author_rank: Unknown
timestamp: June 09, 2019, 10:10:01 pm
content: Hey there, not like I don't have enough scopes. A guy I met gave me a 2440 a few months ago for $25. I followed instructions widely posted and replaced the NVRAMS. It generally boots and runs the diags successfully with errors pointing to calibration. I do the Atten Gain and then next to is is "CHAN DLY" . I think the signal input signal for this calibration is supposed to be 120mv P2P at 100Khz. I cant find specific instructions and nothing is on the screen but I've tried a number of different input signals to both channels, including just leaving them off. When the "CHAN DLY" is pressed it runs "REPET Calibration #1" or something like that and then fails. I've tried running "REPET" cal from the main ext cal screen and that fails as well. I've checked all the voltages, etc, cleaned the hybrids, etc. Can't seem to get past this step. Interesting thing is that "REPET" turns on/off and looks fine under normal operation.I can calibrate the triggers and run the "CTE" cal using my input signal of 100Khz with a 10ns rise time. Just the REPET that is failing now. I'm digging in the manuals more now and wanted to get this up on the board incase someone has a pointer.Any ideas?Jerry

author: David Hess
author_rank: Super Contributor
timestamp: June 10, 2019, 02:54:41 am
content: The signal requirements for the channel delay calibration are not difficult to meet. I just used the fast rise trigger output from my function generator which was like 10 nanoseconds. But you need delay matched cables between the splitter and each vertical input.The service manual has full details.

author: cncjerry
author_rank: Unknown
timestamp: June 10, 2019, 04:29:09 pm
content: David, Thanks, yes, I have matched cables, etc. I have a couple of sources with less than 10ns rise time at 100Khz. I didn't see any other frequency listed than that.The primary failure is on the REPET calibration which it does first on the CHAN DLY cal. If it fails, the manual then suggests probing TP291 with REPET on. I can't get a solid trace there but when I turn on REPET when looking at relatively fast signals, it works fine. This test must have something to do with the phase of what is on TP291 and whatever clock is used for the REPET sampling.The gains, Trigger, CTE all pass. I'll keep screwing with it.Thanks.Jerry

author: cncjerry
author_rank: Unknown
timestamp: June 10, 2019, 06:53:56 pm
content: I went back to the manual and started the jitter debug as they suggest. You probe TP291 on the main board in REPET while looking at other signals. The interesting thing is that channel 1 wouldn't look with REPET turned on. Channel 2 did. I only see this on that signal though. Other signals I probe lock in REPET or not.So I'm going to keep going down this path and see where it leads me. The fact that channel channel seems to be ok gives me something to compare against.More to come.Jerry
Tek 2445 Broken transistors - Page 1
Forum section: electronics / repair

author: 20Ola02
author_rank: Contributor
timestamp: March 04, 2022, 08:08:11 pm
content: Hi,About 2 weeks ago I got my hands on a Tek 2445 and it was love at first sight!I got realy eager to try it out and forgot about the RIFA caps. Short story an X cap exploded and my room was filled with a wonderful smell!I ordered new RIFA caps and replaced the old ones.Then I put it all back together and everything was working except CH1 and CH2.At firtst I feared the hybrids was gone, but when I took a look at the board the resistor R144 was all black and white.The next natrual thing was to to see what this resistor does and seeing it is connected to the hybrids I think this is the reason CH1 and CH2 does not work.Probing around concluded the resistor was still around 6.8Ohm, but it did not have a voltage over it.Taking a closer look at the components linked around this part of the circuit I found the cracks in the transistor Q130 and Q131."The electrons are leaking!" as my boss said.These are the same PNP 92PU01AU51A a quick search does not give much information.Could I use a 2n3906 or do I need something more beefy since there is a heatsink on the originals?

author: MarkL
author_rank: Unknown
timestamp: March 04, 2022, 08:40:02 pm
content: The same pair of transistors and resistor got cooked on my 2465 due to a processor issue not driving that circuit correctly. Once that was resolved, I replaced the resistor and the transistors with 2N6727 (aka. NTE129P).You can get the NTE129P on Amazon for a premium.

author: Gyro
author_rank: Super Contributor
timestamp: March 04, 2022, 08:44:23 pm
content: It might be worth checking whether C130 is shorted too - it looks as if the transistors are only supposed to be pulsed, a shorted cap could turn them on permanently.
Tek 2445 issue with CH2 - Page 1
Forum section: electronics / repair

author: giosif
author_rank: Frequent Contributor
timestamp: December 30, 2024, 05:03:15 pm
content: Hi,Recently, I got my hands on a broken Tektronix 2445 scope which, at first didn't even power up.With help from people on this forum, I was able to fix the PSU and the scope is now turning on.However, CH2 has an interesting problem, where the signal I feed into it is showing at 50% vertical amplitude from the expected value.That happens with the channel set in DC coupling mode.In AC mode, the signal is displayed with the correct amplitude.Also, in DC coupling mode, the resistance I measure for the CH2 input is infinite, while CH1 is measuring the expected 1 MOhm.Looks to me I need to remove the CH2 attenuator assembly and check for any issues there.Would you agree or do you think I should do some other checks first?Thanks!

author: m k
author_rank: Super Contributor
timestamp: December 31, 2024, 12:39:34 pm
content: You can also check different termination and attenuation modes.Since AC is ok upper side of 1st and 2nd switches are ok.For lower parts you can check calibrator input, 0.2V for DC coupled 50 ohms load.If removing an attenuator is not a punishment you can also swap them and be sure.

author: giosif
author_rank: Frequent Contributor
timestamp: January 01, 2025, 07:04:23 pm
content: Thanks, m k!In the meantime, I decided to remove and disassemble the attenuator from CH2.I then proceeded to clean the contact pads on the ceramic substrate which make contact with the relay "fingers" (I very gently scratched the pads with some tweezers and under the microscope).I also cleaned the relay contact "fingers" using IPA.I reassembled and reinstalled the attenuator and now CH2 is working great.
Tek 2445 RIFA replacement - Page 1
Forum section: electronics / repair

author: dcmeigs
author_rank: Newbie
timestamp: July 25, 2025, 07:23:01 pm
content: My Tek 2445 was acting up a bit and fortunately removing and cleaning the cable connectors and pins satisfied that problem, but while I was in there I noticed that I have the original RIFA caps. I want to order new ones and replace them but I see now that if I want to stay with the proper lead spacing, I’m going to have to use the Kemet/RIFA brand. I’m reluctant because of their storied history of failure. What’s the best tack here? Trust that they are better now or fit in caps from another manufacturer with an alternate lead spacing?

author: wraper
author_rank: Unknown
timestamp: July 25, 2025, 07:47:29 pm
content: QuoteI don't know any reason to believe that. I've seen 2010+ RIFAs go bad.

author: dcmeigs
author_rank: Newbie
timestamp: July 25, 2025, 09:19:31 pm
content: I’ve ordered polypropylene caps from Wurth and TDK. The lead spacing is very close and I expect them to go in without issue.

author: David Hess
author_rank: Super Contributor
timestamp: July 26, 2025, 12:38:24 am
content: Quote from: dcmeigs on July 25, 2025, 09:19:31 pmThat is what I would do; the lead spacing only needs to be close enough. Make sure the ceramic or plastic replacements will fit within the area, which should be easy.

author: Tantratron
author_rank: Frequent Contributor
timestamp: July 26, 2025, 06:46:50 am
content: Quote from: dcmeigs on July 25, 2025, 07:23:01 pmAre these RIFA from the PSU block, how many of these need to be replaced ?

author: tggzzz
author_rank: Super Contributor
timestamp: July 26, 2025, 07:14:32 am
content: Quote from: dcmeigs on July 25, 2025, 07:23:01 pmMake sure you get the proper X/Y rating, of course.There's a useful guide to recapping 24x5/A/B scopes by Condor Audio, and the author sells kits of the exact components required.Be glad it is a 2445, not a 2445A/2445B, since those have other components that need replacing.

author: Kwakerman
author_rank: Regular Contributor
timestamp: July 26, 2025, 08:31:03 am
content: There can be up to five, I've also seen plastic ones (not epoxy) fitted from factory. There can be two on the mains input PCB and three on the other PSU board under the metal cover (three screws).
Tek 2445 Single Seq blank screen issue - Page 1
Forum section: electronics / repair

author: number6photo
author_rank: Newbie
timestamp: May 05, 2019, 01:52:22 pm
content: Hi all,I picked up a used Tek 2445 off eBay several months ago. It appears to work reasonably well for normal waveform measurement, but the other day I wanted to capture a switch bounce issue. I set the trigger to Single Seq, and theentiredisplay went blank. If I set the trigger back to Auto or Normal, the display is restored. Doesn't seem to matter which input channel is selected.I tried search the forum for this specific issue, but didn't find anything. Note, I'm a new member and perhaps did not search correctly. If anyone has seen this problem before and knows how to repair it, and/or can point me to the best part of this forum where I might find the answers, I would greatly appreciate it!Thanks!

author: Gixy
author_rank: Regular Contributor
timestamp: May 06, 2019, 02:17:26 pm
content: Hello,This is the normal behaviour. You have to set the trigger for the signal of interest then press the lower MODE button , which blank the display and illuminates the READY indicator. The sweep for each trace is controlled by Vertical MODE, A and B SEC/DIV and dt or 1/dt. Each sweep requires a distinct A-sweep triggering event. When the trigger condition occurs, sweep runs once, READY indicator commes OFF, scale illumination flashes and the readout display is written once to present the scale factors and other readout data. Press the lower MODE button to re-arm the sequence which illuminate the READY indicator again.This is from the Operator Manual (24x5A version, pages 2-5 and 5-20)

author: number6photo
author_rank: Newbie
timestamp: May 08, 2019, 01:40:38 am
content: That's very helpful, thank you! I used a 2430 a lot back in the day, and I just assumed the Single Seq procedure and display readout would be the same. That's really a strange HMI to have the whole screen go completely blank when you put the scope in that mode - it looks like something internally is shorted out.
tek 2445b repair problem - Page 1
Forum section: electronics / repair

author: jsblues81
author_rank: Contributor
timestamp: August 26, 2023, 09:29:44 am
content: In the process of testing and repairing this scope...according to the service manual in figure 5-1...I am to place my DMM on pin 13 of j119 they want you to turn the delta knob first ccw to get a negative voltage.(about -1.25v) and then cw to get a small positive voltage (about +1.25v). when I do this I get about .225v and the voltage never is negative. No matter which way I turn the delta pot...the voltage I get is positive. Has anyone out there have any ideas on this...what could be wrong? I will continue to investagate...

author: jonpaul
author_rank: Super Contributor
timestamp: August 26, 2023, 12:29:11 pm
content: Hello: Test is is for the DAC REF range, and must be approx _1.25V>>0>>+1.25V.Your result is typical of damaged A5 board due to leaky caps.Have not fixed 2445, but seems similar to 2465/7B:See long threasd on "2465B teardown" 79 pages.Check for A5 control board leaky SMP electrolytics.Also see groups.io>>tekscopes and tekscopes2 groups.Bon chance, Jon

author: jsblues81
author_rank: Contributor
timestamp: August 29, 2023, 07:37:47 pm
content: Thanks for your quick response. Changed all electrolytics and have found upon further investagating that the analog multiplexer switches need replacing...am changing all 5 4051's and all 4 TLO74 buffers...leave no prisinors..have been working on and off for almost a year on this...bought it non-working from ebay for $100. Wish me luck.

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: August 29, 2023, 08:11:34 pm
content: I had a similar scope with the same problem and it turned out to be a bad SMD resistor.The electrolyte is able to eat away at the resistors too. Might save you time and money to identify the broken parts instead of doing a shotgun approach.
Tek 2465A 50ohm input repair - Page 1
Forum section: electronics / repair

author: Gregory
author_rank: Regular Contributor
timestamp: November 08, 2019, 06:32:46 am
content: Hello guys! Recently I bought a Tektronix 2465A scope, it`s a really nice unit!I discovered that the channel 1 50ohm input was not working.I oppened tha atennuator module and saw that one of the RF resistors of the input 50ohm atenuator was blew.My only option was to solder two thruhole resistors to get the channel working again..I tested it with a frequency 400Mhz sweep and the channel response incredbly is similar to the original channel 2.I will test it with a fast pulse generator.. I was afraid that the inductance of the thruhole resistors would not give me a flat response, but..When I get the results of the pulse tests I will refresh this topic!
[Solved]Tek 2465A -8V -5V too low - Page 1
Forum section: electronics / repair

author: Galen
author_rank: Regular Contributor
timestamp: October 30, 2019, 11:37:50 am
content: I got a Tek 2465A, no trace. Sometimes, trace appear, but always 1 line, even I input signal.As first attempt, I measured J119 voltage, found the +10V is right to the point, and most others are also within limit, except the -8V and -5V, I got -4.7V and -2.9V respectively. As per the SM, should fix the -8V problem first. I checked the -13.1V (before regulated to -8V), it's -8.7V only.Anybody in this forum, has the experience to fix this problem, your advice is very appreciated. Thanks a lot in advance.Galen

author: tggzzz
author_rank: Super Contributor
timestamp: October 30, 2019, 11:49:10 am
content: You'll find the answer here:https://www.eevblog.com/forum/testgear/tek-2465a-8v-5v-too-low-216364/msg2761430/#msg2761430or here:https://www.eevblog.com/forum/repair/tektronix-2465a-repair-almost/msg2761440/#msg2761440Or use the search box at the top right.

author: Galen
author_rank: Regular Contributor
timestamp: October 30, 2019, 01:27:59 pm
content: dear tggzz, thank you very much. Calin in that post only say 3 caps were replaced, but not say which cap. Hope Calin can provide advice.Anyway, thanks again.Galen

author: tggzzz
author_rank: Super Contributor
timestamp: October 30, 2019, 01:36:17 pm
content: Quote from: Galen on October 30, 2019, 01:27:59 pmThere is a lot of information available on this forum (use the search facility) andelsewhere.There's no point in us wasting our lives repeating it - poorly.

author: med6753
author_rank: Super Contributor
timestamp: October 31, 2019, 03:14:18 am
content: If you are going to pull the Inverter/Regulator boards to perform the repair you might as well perform an entire re-cap of the supply at the same time. You'll find guidance here:https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102

author: Galen
author_rank: Regular Contributor
timestamp: June 01, 2020, 07:36:07 am
content: Fixed it long time ago. just close this topic.A rectifier diode, of the -13V, is bad. Used a multimeter measure it, can not find it's bad. After replace it, the -13V is right, then -8V also right. Scope fixed.

author: tggzzz
author_rank: Super Contributor
timestamp: June 01, 2020, 08:02:52 am
content: Quote from: Galen on June 01, 2020, 07:36:07 amProviding the solution is a courtesy to those that helped, and helpful to those that read the thread later.That is aided if the OP adds " " to the beginning of thread title.

author: Galen
author_rank: Regular Contributor
timestamp: June 02, 2020, 12:17:40 am
content: Thanks tggzzz, added the . I'm happy if it can help anybody.

author: Galen
author_rank: Regular Contributor
timestamp: June 02, 2020, 12:20:30 am
content: Quote from: med6753 on October 31, 2019, 03:14:18 amThanks med6753, yes, already recapped it in the repair.
Tek 2465A bootup - Page 1
Forum section: electronics / repair

author: zapvss
author_rank: Contributor
timestamp: April 26, 2019, 03:50:14 pm
content: Hi All,My Tektronix 2465A scope always boots up in Diagnostic mode screen after power up. I have to to push the "A/B Trig" button to get it out of Diag. mode then it works normally.It passes all of the tests at boot and everything works just fine after pressing the A/B Trig button.Is there a setting that can prevent this behavior and have the scope display the trace after passing the tests at boot time?ThanksDenis

author: alpher
author_rank: Frequent Contributor
timestamp: April 26, 2019, 06:41:21 pm
content: Are you sure that there are no test fail mesages? May have to tweak readout intensity ?

author: zapvss
author_rank: Contributor
timestamp: April 26, 2019, 07:04:43 pm
content: Hi Alpher,No error messages and readout intensity is up high enough to read anything that might show.

author: Andy Watson
author_rank: Super Contributor
timestamp: April 26, 2019, 07:10:33 pm
content: Have you tried forcing it to go through its diagnositc routines? It might show-up something that is being hidden by the boot process.

author: zapvss
author_rank: Contributor
timestamp: April 26, 2019, 07:14:23 pm
content: Yes I have and all 6 tests pass.

author: pbarton
author_rank: Frequent Contributor
timestamp: April 26, 2019, 08:31:20 pm
content: On power-up, the scope automatically performs a set of diagnostic tests.When the tests have completed, is the TRIG'D indicator on the front panel flashing?

author: edavid
author_rank: Super Contributor
timestamp: April 26, 2019, 09:18:26 pm
content: I think you just have to remove the CAL jumper:http://www.wb0smx.net/?p=2447

author: ArcticGeek
author_rank: Regular Contributor
timestamp: April 27, 2019, 01:23:32 am
content: +1 On the cal jumper.If you remove the cal jumper it will likely boot fine.

author: zapvss
author_rank: Contributor
timestamp: April 27, 2019, 12:24:30 pm
content: I checked the CAL Jumper and it is connected to the "No Cal" side. I tried removing it and the scope wouldn't boot up.

author: MarkL
author_rank: Unknown
timestamp: April 27, 2019, 01:14:52 pm
content: You might want to try clearing CYCLE MODE using EXER 03. It's described here:https://www.eevblog.com/forum/repair/tektronix-2465a-troubleshooting/msg2028619/#msg2028619This is from from the service manual page 6-18, under "CYCLE ERROR CLEAR". Cycle mode forces the scope into diagnostic mode on boot until it is cleared, and if I recall correctly, even if there are no more errors left to display.

author: zapvss
author_rank: Contributor
timestamp: April 27, 2019, 01:35:49 pm
content: Thanks MarkL,That worked like a charm. The scope now boots up properly.Thank YouDenis
tek 2465a noisy beamfind switch - Page 1
Forum section: electronics / repair

author: linux-works
author_rank: Super Contributor
timestamp: March 09, 2018, 06:20:07 pm
content: just bought a used 2465a in reasonably good/clean condition.the beamfinder switch seems to stick, though; maybe its just a matter of removing it and cleaning it? I hvae not opened the scope yet, just got it yesterday.it takes several wiggles and presses of that button to get it out of beamfind mode. so I'm hoping its just mechanical issues. worst case, I may just bypass it if I can't clean or replace it.while I'm on the subject, what else should I look for, to replace or check, when I have the case open?I went thru the 2465b model (that I bought a few years ago) and I replaced its battery backed dallas calibration module. wondering if the A model also has this or if its some other part.probably will have to replace the fan. is it the same as the B model? if so, I already ordered a fan for my older B and I'll just order another of the same one.thx

author: tautech
author_rank: Super Contributor
timestamp: March 09, 2018, 09:12:32 pm
content: You do know of this great thread and resource for 2465's don't you ?https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/Beam find are normally momentary switches so I'd expect it to be a mechanical issue.

author: Testtech
author_rank: Regular Contributor
timestamp: March 09, 2018, 10:18:48 pm
content: Just spritz a tiny bit of your favorite contact cleaner in from the rear of the switch...

author: martinr33
author_rank: Frequent Contributor
timestamp: October 27, 2019, 11:51:54 pm
content: That trick works. i put a drop of Deoxit red in there. To do this, you have to remove the main case but then the switch is accessible.
Tek 2467B inverter board problem - Page 1
Forum section: electronics / repair

author: aarons
author_rank: Regular Contributor
timestamp: June 29, 2025, 12:18:20 am
content: I was replacing the SRAM in my 2467B with an FRAM, and thought I might as well replace the 4 electrolytics on that board that are known to leak and corrode everything while I had it open. I had read someone used tantalum caps, so I did the same, but of course I accidentally put one in backwards and it pretty much instantly blew. Not a problem, I put the old electrolytic back in, but unfortunately the damage wasn't limited to that blown cap.I traced the problem to the inverter board. The most obvious problem was that R1071 was burning. I checked testpoint 78 above it, and instead of the nice square wave between 0 and +11V with a 24uS period it's supposed to be, it's some crazy noise at 238V 43kHz. I didn't get a capture of it, but I did get a capture of what I assume is the same basic idea at testpoint 77. Note that all this testing is being done with the inverter and regulator boards removed from the scope.So I'm assuming U1030 is dead at this point. and probably a bunch of other things if that 240V signal is running wild on the board. What should my approach be here?Also, the cap that I put in backwards failed short, putting a short between +5 and ground. And interestingly it was a 33uF cap (matched to what I removed) but the schematic specifies 47uF.

author: Kwakerman
author_rank: Regular Contributor
timestamp: June 29, 2025, 12:46:28 am
content: I assume you have built the dummy load for the PSU if it is out of the scope? I don't believe it will work properly if unloaded. The load is detailed in the fault finding tables in the service manual.

author: factory
author_rank: Super Contributor
timestamp: June 29, 2025, 10:23:39 am
content: The relevant details about the loads for testing the PSU/regulator boards, are in the other thread;https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg5431154/#msg5431154David

author: aarons
author_rank: Regular Contributor
timestamp: June 29, 2025, 10:17:17 pm
content: I didn't have the loads on it. I ordered the parts necessary for the dummy loads and then can follow along in the testing from the service manual.
Tek 24XX Series BNC replacement - Page 1
Forum section: electronics / repair

author: Fractal
author_rank: Contributor
timestamp: September 10, 2023, 02:23:05 pm
content: I just copped a 2565 locally but once again, a common issue I've found with old test equipment in Taiwan appears to be the BNC plugs getting oxidized over in this tropical environment.After spending 2 days in the ultrasonic bath it removed most of the shmoo, but the inner pin and outer surfaces remain significantly oxidized.I was able to read a part number; 28JR270-01, which appears to be a Tek proprietary part - couldn't find any sourceI've found a couple plugs at my local electronics shop, thinking the isolated part couldn't be that complicated and I could hack something up, but I don't get how to get the 3rd pin to workIt appears to me that:1- The signal pin goes straight through2- The ground goes from the outer ring through the chassis - solder pins are unused3- The 3rd pin "Probe-Coding Ring" according to the service manualQuoteHow is it connected within the connector? is it just an inductive ring isolated from both signal and GND?Are there any cutout views on how to reproduce it?Or any effective way to restore a worn-out BNC?Any tips appreciated!

author: calibrationfixture
author_rank: Regular Contributor
timestamp: September 11, 2023, 08:15:39 am
content: Hi Fractal,The Tek PN is 131-0679-02.Manufacturers:- Specialty Connector : 28JR270-01- Kings : KC-79-186- Tajimi Electronics Corp. : BNC340-BR-1Succes,Calibrationfixture

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: September 14, 2023, 08:12:38 pm
content: The Probe Coding Pin just goes to the probe part that connects to the scope. Inside the little probe adjust box, there is a resistor to ground. So not reactive, just a DC signal.The resistor in the probe will be different for each type of probe.e.g different for a 1X, 10X and 100X probes. This makes the scope able to tell which probe is in use. The probe 10X is calculated into the display. That is if you use the probes with the pin.A 10X probe without the pin would probably be taken as a 1X probe so the waveform displayed would be 10 Times Smaller.That is pretty bad corrosion,if you have nothing to lose, try Vinegar soak. or another acid.I do not think any of the commercial electronics cleaning sprays would help.
Tek 2754P display jitter and distortion - Page 1
Forum section: electronics / repair

author: russan
author_rank: Newbie
timestamp: January 13, 2025, 04:51:59 am
content: I am trying to repair a mostly-functional Tek 2754P spectrum analyzer. The letters and traces on the screen are distorted and jittery, and the whole image is compressed into the middle 50% of the screen in both dimensions.Going through the service manual, it appears that the only problem I can find is the 300V supply is very low: about 180-260V, and getting worse by the minute. I traced out the 300V power supply itself and measured all the components (diodes, caps, resistors) to be close enough to correct without pulling them out of circuit. The only other card I can find that uses 300V is the Z-axis card, and I don't see or measure anything obviously wrong with it. I don't see any way to tune the 300V rail voltage.Maybe the CRT is going bad? Charge pump capacitors are starting to fail? Looking for ideas. Thanks.

author: m k
author_rank: Super Contributor
timestamp: January 19, 2025, 07:09:41 am
content: My guess is that charge pump capacitors are weak.
Tek 2901 Time Mark Powr Supply Problem - Page 1
Forum section: electronics / repair

author: KK6IL
author_rank: Regular Contributor
timestamp: March 13, 2022, 10:41:22 am
content: Recently acquired Tek 2901 has a power supply problem. 120 Hz ripple on the -30V supply, which causes a ripple on the +3.6V supply also. Voltage drop on R430 is 0.155V, so 15.5mA current drain. Voltage on C430 drops from about -50V to -27V, which is more of a swing than I would expect with a 15mA load, but I'm mostly a digital engineer, so not up to calculating capacitor discharge rates.Power supply section of PCB is badly discolored. Photo hopefully attached.I would appreciate it if someone with a 2901 could measure the voltage across R430 and R411.

author: pbarton
author_rank: Frequent Contributor
timestamp: March 13, 2022, 11:47:04 am
content: We all know that an ink drop on blotting paper spreads uniformly in all directions with time.The center of the PCB discoloration appears to be that axial capacitor which is adjacent to the bridge rectifier marked as 152-0199.The right hand lead of that cap appears to be discolored.You could try replacing the cap.

author: tggzzz
author_rank: Super Contributor
timestamp: March 13, 2022, 11:55:54 am
content: I found the rectifier became excessively hot. The black connector behind it became very fragile.What are the ripple voltages? If they are too high, replace the relevant decoupling capacitor.I gave mine away since I found it boring and there are other ways of achieving the same objectives, so I can't measure anything for you. I wouldn't give my Tek 184 away, though, since the internal metalwork is to interesting

author: jonpaul
author_rank: Super Contributor
timestamp: March 13, 2022, 03:29:54 pm
content: First get Tektronix service manual off BAMA or tekwikiNext check electrolytics for C, esr, ripple, these 1970s vintage electronics usually neeed psu recapping.Several tantalum axial caps can go shorted on either top or bottom PCB.Tektronix harmonica connecters deplasticize over tge decades, DO NOT TOUCH they crumbleBurned PCB not unusual and unlikely to be the fault.The rectifier and series power resistance are underrated.G10 deplastocizes and after decades of high heat burnsIf you still need assistance go to groups.io tektronix2 or tektronix, many more tek experts.I found my 2901, works perfectly, PCBs clean and perfect no brown, rectifier normally hot but not excessive, all PSU caps ripple and V fine.We had replaced large tant next to rectifier. Voltage across 0.5 Ohm power R was ~ 0.5V so ~ 1A load.Comparing my unit and your pix, I think yours was left on 24/7 for years in a lab.Bon courageJon

author: KK6IL
author_rank: Regular Contributor
timestamp: March 16, 2022, 01:12:11 pm
content: The problem was indeed C430, 550 uF/50V. Voltage across the cap is 50V, so replacement with a higher voltage cap is desirable. Replaced with a 820 uF/200V Rubycon cap from the junkbox which was a very tight fit in the capacitor holder, so additional mounting hardware not necessary.C453 was slightly warm to the touch, but that seems to be heat from the bridge rectifier which is much hotter.