Tektronix 2430A halts  - Page 1
Forum section: electronics / repair

author: kavea
author_rank: Contributor
timestamp: May 28, 2016, 09:41:41 am
content: Hi all,I'have bought a Tek 2430A from ebay in order to repair it and get myself a digital oscilloscope. The problem with this scope is that it halts during (at the end of) the Self Test procedure (picture below). I have found a service manual for this version and there is actually a repairing procedure for this case (page 202, "System uP halts in power test"), however i still can't figure out what doesn't working .. What i have done:1/ Checked all voltages (except for CRT but it works), they are all ok2/ Visual inspection: nothing special, a part some traces of flux on some boards, i guess someone have already replaced some components3/ There is no Dallas NVRAM, it is an HM62256 and the battery is seems to be ok (3.5 V)4/ All caps seems good, i have desoldered two of them on a processor board and they where ok (all nichicon brand)5/ Replaced some logic and OpAmp: U940, U422, U4146/ Checked the ACQDN signal at U670, seems to be there (U670 is quite hot by the way, is it normal ..?)7/ Checked the Interrupting circuitry, seems ok8/ I noted that the waveform 3 (U942, pin 2) doesn't work, it still at 5V instead of dropping at 2.5V during the boot, but it still provide a good (high level) /RESET signal to the system uC (U640) , so i don't know..BUT.. since i have only an analog Tek 2225 i couldn't check the real shape of the waveforms because it doesn't trigger in almost all cases, so i could just check if there is some activity or not..If anyone have an idea of whats going wrong I would appreciate any kind of help to troubleshoot this scopeSERVICE MANUAL :http://kripton2035.free.fr/Resources/TEK2430A_serv.pdfVIDEO:

author: tautech
author_rank: Super Contributor
timestamp: May 28, 2016, 10:11:36 am
content: Welcome to the forum.There will be others that might have had this problem before so please be patient.In the meanwhile a little more study for you:http://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf

author: siggi
author_rank: Regular Contributor
timestamp: May 28, 2016, 08:01:43 pm
content: I don't have any experience with the 2430A, but I fixed a pretty far-gone 2430 at one point.First thing is that you MUST have a bench fan blowing over the hybrid heat sinks when you run'er open. You WILL otherwise damage the hybrids, which are getting pretty hard to find.Do you have a link to the service manual that you can share?The 2430 (and other scopes from the 2400-series) counts out the tests it's performing on the front-panel leds. I assume your 2430A does the same thing, as detailed in your service manual? Where does it stop? Does it always stop at the same place?Have you checked the LV power supplies for ripple as well as DC value? This is always first port of call, as if the supplies are wonked, just about anything can go wrong.There are several diagnostic aids in this scope, including a service jumper that cycles the CPU through the entire address space. This allows you to see whether the address bus is good, look at the address decoding logic, and to see - to some extent - whether the bus drivers are good.

author: kavea
author_rank: Contributor
timestamp: May 29, 2016, 09:28:50 pm
content: Quote from: tautech on May 28, 2016, 10:11:36 amThank you for welcoming and the pdf!Quote from: siggi on May 28, 2016, 08:01:43 pmYes, i turn on the scope for maximum 1 min when it's opened , just during the time i measure the voltages. Of course, here is the manual of the 2430A :http://kripton2035.free.fr/Resources/TEK2430A_serv.pdfActually the front panel leds doesn't show any error code sequence, but at the end when it halts the only led on is "+", and this behavior is always the same, it stops at the same step. The previous owner of this scope said that this problem has appeared progressively , it was stopping from time to time, but after off/on it was able to boot correctly. So i was thinking about capacitors, but they seems to be ok.I have just measured ripple on the voltage supplies (picture), and i found something interesting (thank you sigi for this advice to measure the ripple). The ripple of the '-5V Ref' is 450 mV (!) This ripple is a sinusoidal signal of around 1 MHz frequency... Unfortunately the ripple of the -5V Ref is not specified in the manual, but i think it's not normal

author: kavea
author_rank: Contributor
timestamp: May 29, 2016, 10:09:51 pm
content: I took a look on the circuit which generate -5V Ref, and all seems to be good. There is also a 'DC OK Sense' circuit which is LO when one of the power rail is out of spec (picture). In my case it's HI and voltages around the comparator are ok as well...

author: siggi
author_rank: Regular Contributor
timestamp: May 29, 2016, 10:17:12 pm
content: Quote from: kavea on May 29, 2016, 09:28:50 pmCool - I used a CPU case fan for my 2430 pointed at the underbelly of the scope. That seemed to work fine.Quote from: kavea on May 29, 2016, 09:28:50 pmThanks, and ugh - I've never worked from a MIL manual. I understand they're written to a slightly different audience than your usual Tek service manuals. The schematic diagram scans are excellent, though.Artek Manuals do have the 2430A on taphttp://artekmanuals.com/manuals/tektronix-manuals/if you get disillusioned with the MIL manual. Their scans are typically great, and they OCR the scans to allow searching.Quote from: kavea on May 29, 2016, 09:28:50 pmSee page 184, Fig 6-4 and the text around it. First all the TRIG LEDs should flash on, then they should count from zero up to the class of test going - is that not what you see?They are then supposed to flash out the number of the test that failed, though if the MPU is halting, they won't get there. If you see only the +TRIG light lit, I think that means the 8000-tests started, but the 9000 did not.Quote from: kavea on May 29, 2016, 09:28:50 pmPage 168, table 6-4 has the specs - 10mV peak-to-peak in 20MHz bandwidth. Finding a 1MHz sine on your -5V supply is highly unexpected - there'd have to be oscillation in the -5V regulation or some such.Good luck!

author: tautech
author_rank: Super Contributor
timestamp: May 29, 2016, 10:18:38 pm
content: If you look carefully at the 2 tables and compare yourlowripple measurements against the Teklimitsand some of the others look like they need investigation.Get all rails well inside the Tek ripple limits and you'll not have to revisit the PSU.FYIHigh ripple can be a sign of a rail being overloaded, there's many things that can cause excessive loadings, dried out remote caps, Tantalums.....Teck often have methods to isolate PCB's to assist finding the culprit/s.RTFM.

author: siggi
author_rank: Regular Contributor
timestamp: May 29, 2016, 11:25:12 pm
content: Quote from: kavea on May 29, 2016, 09:28:50 pmSorry - missed the "Ref" part the first go around.If you're measuring this with a 1X probe, it's possible that your probe capacitance is giving the Ref op-amp indigestion. Try measuring with a 10X probe, or with a bit of resistance in-line with the probe tip (1-10K should do it, I'm told).From the table of measurements, aside from the -5V ref - which almost HAS to be a measurement error (sorry:)) I don't think there's anything substantial wrong with your power supplies.Can you post a video of the front-panel as the scope starts up?

author: kavea
author_rank: Contributor
timestamp: May 30, 2016, 06:48:06 pm
content: QuoteOk, i have bought a small fanQuoteYes i have seen that page, but i can't find anything matching to my situation, even all trig led don't flash on, only three of them (all 5 leds are ok, they flash an error code when i disconnect one of the boards). You can see the video, i have inserted it in the first post.QuoteQuoteYou're right, in x10 there is no ripple, ~25 mV in 20 MHz (i have borrowed a TDS210 from the lab where i'm working which have 20 MHz BW limitation)QuoteI agree, i think it should be ok, it's a little bit out of specs, but.. considering the precision of my measurement tools..and 10mV of extra ripple should not disturb an old, good tekQuoteYes:I will take advantage of TDS210 to measure some digital signals, until tomorrow

author: siggi
author_rank: Regular Contributor
timestamp: May 30, 2016, 10:40:34 pm
content: Thanks for the video. I don't think your MPU is halted, IIRC the intensity pot is drive-by-wire, and you clearly manage to adjust the intensity. I think you'd need a fair amount of the digital stuff working for that.Maybe you have FPP connectivity issues - have you tried giving the scope a few extra minutes, see whether it clears the problem step?I couldn't offhand find another video of a good 2430A starting, and my 2430 is unfortunately not at hand, so I can't compare. Maybe we should try and take this over to the Yahoo TekScopes group - there's sure to be people there with a 2430A to compare against?

author: guido
author_rank: Regular Contributor
timestamp: May 30, 2016, 11:12:15 pm
content: The GPIB status led's stay off. On mine all three go on at boot for a few seconds. Than quickly only the middle and then left/right (hard to follow) and then all three on again for some more seconds. Then LOCK goes on during the rest of the self test. After this is finished, the SRQ led goes on.I have it connected to GPIB, but the computer with the card is powered down.Check around U754. Maybe it is broken and does also not reset gpib. If it is not selected it would be the main processor or address decoder. And it does more, maybe the other outputs are important hanging the system if not working

author: siggi
author_rank: Regular Contributor
timestamp: May 30, 2016, 11:49:05 pm
content: Quote from: guido on May 30, 2016, 11:12:15 pmHey Guido, can you post a video for comparison - ideally with the GPIB disconnected to eliminate that as a source of confusion?Quote from: guido on May 30, 2016, 11:12:15 pmIIRC the GPIB status lights have nothing to do with the GPIB interface chip at all - they're wired out from a register on the MPU data bus directly. Of course I can't find this in the schematic now, though...

author: guido
author_rank: Regular Contributor
timestamp: May 30, 2016, 11:57:47 pm
content: You are right. But Edited my reply already before yours. Page 346 of mil pdf. Buffer is controlled by system controller. But it has more outputs doing something. Seems to be dead or not driven in the video. Leds go on immediately after power up. Something is not right there. No need for comparisson video.Ps i'mnow

author: kavea
author_rank: Contributor
timestamp: May 31, 2016, 12:02:07 am
content: 2 guido and siggiI would like just tell that GPIB leds are working (flashing), but they have been disconnected. I will answer more tomorrow, it's late in Europe now

author: kavea
author_rank: Contributor
timestamp: May 31, 2016, 10:18:53 am
content: QuoteYes, the intensity is on FO-13 (p.313) then AOUT2 goes to the front panel uC (FO-8). But why there is a signal which appears when i touch the knob or the pin of AOUT2..QuoteIf FPP is the ribbon cables i will check them may be of of them are brokenQuoteHi guido, ok, i will check U754, but GPIB leds are working in my case, i forgot to reconnect the ribbon cable for a video. Can you tell me if your U670 (Time base controller, FO-16) getting hot ? I'am a little bit worry about this chip. And of course if you can post a video of booting i would appreciate, in order to compare all leds (gpib, trigs)I have checked the interrupting signal going to the system uC /IRQ and /FIRQ and they present some TTL signals which repetitively go from low and high. May be i should try to force them to high ?

author: metrologist
author_rank: Super Contributor
timestamp: May 31, 2016, 06:53:43 pm
content: I have the same scope and that is exactly one of the symptoms I was seeing (OP video). I replaced the two metalized paper capacitors on the supply input and it fixed it, sort of. My scope now boots up and works fine for about a minute, then the display goes blank and it is locked (I don't remember what the front panel LEDs are doing). I measured the supply test points and they seem fine, so I've been stuck.

author: kavea
author_rank: Contributor
timestamp: May 31, 2016, 07:16:34 pm
content: QuoteHi metrologist,Thank you for this information, you sayoneof the symptoms ? Which one exactly ?About capacitors, you are talking about two red caps (picture) ?

author: metrologist
author_rank: Super Contributor
timestamp: May 31, 2016, 08:05:00 pm
content: The caps will look something like this, and they are above the large blue filter caps between the metal framing and transformer (upper left area of your photo):http://www.tedss.com/stock/images/2020/2020043902.jpg2200 pFI replaced the same caps on another Tek 2213 and that completely fixed it.Mine was halting during self test and eventually showing the vertical bars. When I adjusted the horizontal, I could see a clipped waveform expand. I would get random self test errors. Most of the caps measured fine with an ESR meter, but I wonder if there is some leakage or other breakdown at higher voltage that I am not seeing.

author: metrologist
author_rank: Super Contributor
timestamp: May 31, 2016, 08:13:04 pm
content: And now that I'm looking at your photo, I'm suspicious of that larger yellow block at the base of your arrows. I've forgotten what that is - if it is the same type of construction cap? Those metalized paper caps seem to have a reputation that precedes the aluminum electrolytics... I think the plastic polymer type caps last longer.

author: Bud
author_rank: Super Contributor
timestamp: May 31, 2016, 10:02:51 pm
content: Did you re-seat the ICs, my 2430 got frozen during self-test and did all sort of funny things until i re-seated the ROMs and whatever i could find including interconnecting cables.

author: kavea
author_rank: Contributor
timestamp: May 31, 2016, 10:22:19 pm
content: QuoteThank you for the photos ! I have desoldered all of them , the red caps (68nF) seems ok , the paper caps are 3100 pF instead of 2200 pF and the yellow one (470 pF Phillips, mkt 344 hq, polyester caps) seems ok also. I will replace all of them to be sure.QuoteI will do some poke test on IC's after replacement of caps

author: lowimpedance
author_rank: Super Contributor
timestamp: May 31, 2016, 10:35:43 pm
content: I have an non 'A' 2430 which needed a power supply recap. After running for a bit it would also do weird stuff same as Bud's 2430 and the solution was to reseat the ROMs etc.So I would highly recomemd the "IC poking" too and in particular the ROM area.I find the 2430 an interesting beast and amazing how TEK crammed so many components in that casing!.Good luck

author: guido
author_rank: Regular Contributor
timestamp: May 31, 2016, 11:03:14 pm
content: Showing a video without saying the GPIB LEDs were disconnected is not usefull. Puts people that are trying to help on the wrong track. So no, the buffer is not suspect if the LEDs behave as i've described.There are already movies on the net, just search. E.g..I'm sure there will be more. You can also look out for similar models from the same range.Seems it is more trial and error what you are doing. Try to follow the service manual troubleshooting guidelines. I'm guessing you don't have GPIB available? That would be my first try if the front panel isn't responding. But then again, i have GPIB controllers available.Two caps left in the picture are evil. They will go bang. Not if but when. Red and yellow ones are normally ok.But it could be as simple as a bad contact indeed. I've reseated the ROMs in mine too. Not that it was needed, but it is rather manditory when reading them with a programmer. And replaced supply caps and batteries.When i look at your video you are already working on the controls when it is still testing. What happens if you just wait? Does it remain stuck in self test?

author: kavea
author_rank: Contributor
timestamp: May 31, 2016, 11:38:56 pm
content: QuoteThank youQuoteRead the first post, the troubleshooting procedure related to the problem (picture) have been done from the beginning. Voltages and interrupting circuit have also been checked, after that what else can i do except "trail and error" ...QuoteYes, i will replace the two left for the moment, their packages are cracked

author: kavea
author_rank: Contributor
timestamp: June 01, 2016, 08:06:44 am
content: To reseat the ROM's should i undo them from the sockets ? (i worry about the datas on these ROMs). I've bought all 5 caps and going to replace them after work

author: siggi
author_rank: Regular Contributor
timestamp: June 01, 2016, 11:00:37 am
content: One of those two caps went bang on my 2430.You're in general troubleshooting of a complex, multi-processor device. Observe what works, and what not. It seems pot scanning works, given that you have intensity control.This means your FPP is operational (check clock and key scanning).Your FPP is communicating with the MPU (exercise and observe FPP/MPU interrupt and registers).You have intensity control, which means the MPU DAC works (verify by observing DAC waveforms).Post a video where you exercise every front panel control. When you turn the vertical sensitivity & coupling controls, do relays click?A couple of more or less random suggestions to try:Re-seat anything in a socket, including ROMs, the waveform processor and the acquisition hybrids (careful, they're ESD sensitive)Set the service jumper that cycles the CPU through the address space, and see whether you find trouble in address decoding.There is a procedure to isolate and exercise the waveform processor, try that.Change the RAM chip. Those do go flaky sometimes, and can cause this sort of trouble.Sent from my iPad using Tapatalk

author: kavea
author_rank: Contributor
timestamp: June 01, 2016, 01:17:52 pm
content: Well... during the lunch time i've replaced all 5 caps (picture) by Vishay and Phillips, unfortunately it changed nothing. Then i've pocked all IC's, removed and reinstalled all ROM's = nothing. And finally i've decided to do what I've proposed earlier: desolder the U850 and install a DIP socket to force /IRQ to high (picture). After turning on, the scope didn't show any text and didn't respond to any button. Then i've repeated the procedure with fixing low level at /IRQ = same result. Then i reinstalled the U850 and turned it on ... and it booted up (picture) !! Then my lunch time have finished, so i will continue after work. There is some FAIL at Self Test, but at least it boots and i can navigate through the diagnostic menuIt isn't in the troubleshooting guide, but it worked. I don't really know what was the problem, solder joins at the U850 or putting high and/or low have changed something somewhere in the circuit.

author: BradC
author_rank: Super Contributor
timestamp: June 01, 2016, 01:40:42 pm
content: Awesome job! That checksum fail probably indicates it has lost its cal constants. Start with the Autocal and go from there.They're actually not that hard to cal with the right tools, and the leveled sine generator is only really necessary if you need to calibrate the CCD's. Most of what you need can be scrounged, made or borrowed excepting the fast rise pulse generator for triggering.I have a 2440M (I disabled the MATE board to make the GPIB do what the standard one does) and I love it.

author: siggi
author_rank: Regular Contributor
timestamp: June 01, 2016, 01:47:19 pm
content: Quote from: kavea on June 01, 2016, 01:17:52 pmAwesome, congrats!I remember a recent thread either here or in TekScopes where the problem was a bad CPU. Maybe yours is marginal in some dimension - like e.g. an output driver or some such.

author: kavea
author_rank: Contributor
timestamp: June 02, 2016, 07:50:22 am
content: Thank you, but there are still some problemsI can't perform the Self Cal, it halts again. Inside Extended Calibration i managed to calibrate "Triggers" , but "Attenuators" FAILs, and "Repet" halts .. so far, the better i could get are 6100 and 8700 errors (picture). Otherwise from time to time i can exit the extended calibration menu and use the scope (picture) but magnitudes are wrong and frequency counter too

author: siggi
author_rank: Regular Contributor
timestamp: June 04, 2016, 12:25:37 am
content: Here is the thread we're to MPU was badhttps://r.tapatalk.com/shareLink?url=http%3A%2F%2Fwww%2Eeevblog%2Ecom%2Fforum%2Findex%2Ephp%3Ftopic%3D46043&share_tid=46043&share_fid=25658&share_type=t.

author: kavea
author_rank: Contributor
timestamp: June 04, 2016, 01:04:03 am
content: Quote from: siggi on June 04, 2016, 12:25:37 amThank you , i have read it quickly.. and i think in my MPU is ok since everything working just fine except three points :1/ Self calibration halts2/ "Repet" calibration halts3/ "Attenuator" calibration FAILsIf one of the A0-A15 lines didn't worked it would be the same disaster like in mentioned thread.Today i've managed to get rid of NVRAM error (image), now i have only 8700 (attenuators) which should be related to 3/. I also measured attenuators TP, which are ok (image). There is also relays clicks etc. So i think the analog part is working. There is something in common between Repet and Self calibration which makes the scope halting. For the FAIL of the Attenuator calibration, i'm not pretty sure about my reference voltages which are 0.2V, 2V and 20V, if they are not precise enough this fail is normal (p. 244). The problem is that there is no tolerance to these voltages in the SM, and with my voltage supply and the DMM i have an error up to +/- 10mV, especially at 20V. But anyway, this "extended" calibration of attenuators should be done after the Self calibration.

author: siggi
author_rank: Regular Contributor
timestamp: June 04, 2016, 01:16:01 am
content: When you say "halts", what do you mean? Does the test or process fail, or is the scope becoming non-responsive?Sent from my iPad using Tapatalk

author: kavea
author_rank: Contributor
timestamp: June 04, 2016, 01:26:20 am
content: Quote from: siggi on June 04, 2016, 01:16:01 amThe process halts, when the cal process is launched (any cal process), there is "RUNNING" which appears and slightly blinking during the test. In the case of Self cal, there is a blinking for 1 sec, then it stop blinking and do nothing. Normally the cal time is about 10 sec (c.f. SM) , i have been waiting several times for 5 min or so and none of buttons are responsive except the display intensity knob. I know that the interruption system is ok, at each click on any button the "RUNNING" writing is blinking one time. I think the uC is waiting for something more important than front panel control. In the case of Repet cal, however , there is no any blinking, the process halts immediately. So i have to turn OFF/ON scope each time i do this.

author: siggi
author_rank: Regular Contributor
timestamp: June 04, 2016, 04:09:36 pm
content: The jitter correction ramps *might* be the problem. They're a time-stretching dual slope current switching machinery. On charge they measure the time from trigger to sample clock edge.The discharge time is measured with a zero crossing comparator and a counter. If the discharge current sink or the comparator are bad, maybe the REPET calibration would get stuck.Sent from my Nexus 5X using Tapatalk

author: kavea
author_rank: Contributor
timestamp: June 06, 2016, 12:09:21 pm
content: Quote from: siggi on June 04, 2016, 04:09:36 pmOk, i was measured some voltages on ramp current source (FO20, p.327) , and indeed there is a problem, SLAMP1 and /SLAMP1 signals should be at -1.6V , but i have -0.8V on one of them, so Q491 and Q492 are not driven in the same manner.

author: siggi
author_rank: Regular Contributor
timestamp: June 06, 2016, 02:07:05 pm
content: Quote from: kavea on June 06, 2016, 12:09:21 pmSLAMP1 & /SLAMP1 are complementary ECL-level signals. One should be at ~-0.8V, while the other is at ~-1.6V, and they should flip while the slow ramp is draining C491. It sounds like that's what you're observing, no?Are you seeing fast-up/slow-down ramps across C491 or at R495 as specified by oscillogram 84? I believe you have to be acquiring a triggered signal to get that same oscillogram.If you're getting a jittery fast-up/slow-down ramp, then probably there's nothing wrong with your jitter correction. Note that this was just a guess, but as you've had unexplained lockups with this scope already, it's perhaps more likely that the original cause persists.Did you re-seat all socketed components?

author: kavea
author_rank: Contributor
timestamp: June 06, 2016, 11:15:52 pm
content: QuoteWhere have you found the -0.8 and -1.6V ? Because on the schematic p327. both are -1.6V. But indeed i'm measuring -1.6 and -0.8 V. Yes, i have observed the ramp on 84, it was not triggered but i clearly see a ramp signal.QuoteOn the page 84 (Ramp switching) is said that during the calibration, the JIT1 GAIN is applied to the base of Q495, but i can't see any signal, only a DC value of -5.2 V during the normal operation or Repet Cal or Self Cal. And the MUX U651 (FO12 p.311) driving this BJT through U661A doesn't provide any kind of signal on all of its outputs (except one, with -1 V DC which is strange), whereas all input signals seems to be ok.QuoteYes, twice, unfortunately nothing changesOtherwise while the scope is stuck the output of the comparator U490 is 0 V, compared to 3.56V when it works

author: siggi
author_rank: Regular Contributor
timestamp: June 06, 2016, 11:41:59 pm
content: Quote from: kavea on June 06, 2016, 11:15:52 pmThis is "standard" ECL and the signals clearly need to be complementary in that circuit, as this is a current switch.Quote from: kavea on June 06, 2016, 11:15:52 pmThe signal is a DC signal, though it may wobble a little during self cal.Basically the DC voltage on the transistor decides how much current the slow "drain" current sink sinks. This in turn decides the time expansion ratio, and ISTR the service manual wants a ratio of 1250 between the fast and slow ramps.Quote from: kavea on June 06, 2016, 11:15:52 pmHow are you observing this - are you using an oscilloscope or e.g. a DMM?This sounds reasonably salient, though only if the ramp is also running, and this is a difference only in the output and not in the inputs. If the inputs to the jitter ramp are static while the scope is stuck, you need to look further "upstream".Interesting questions to ask and answer relate to how much of the digital circuitry is operational when the scope is stuck. We want to try and isolate the problem to a block in the block diagram or to a device in a schematic.Since you have intensity control, it seems the FPP works when the scope is stuck.I believe the intensity signal comes through the DAC and a mux from the MCU. This implies the regular interrupt works, the DAC works and the multiplexer in question works.Can you check those and report back?Can you post a video where you exercise *every* front panel control while the scope is stuck?In particular exercise the vertical channel controls and listen for relay clicks. Exercise the coupling controls and listen for same.Try shorting the BNC input sense ring to ground, and/or plugging in a 10X probe, see whether anything changes in the readout, and so on.

author: kavea
author_rank: Contributor
timestamp: June 08, 2016, 05:41:35 pm
content: QuoteOk, i didn't knowQuoteA DMM, but i will check it with a scopeQuoteYes, it would be great to isolate the problem, i will check these.Today i however have desoldered the MUX (U651) (which produces JIT-GAIN, GAIN-CAL and CH-BAL signals) since i had one, and without this IC the scope behave exactly in the same manner (!), no additional errors, i have signals on the screen and it halts when i'm trying to self calibrate, all this i found strange and was thinking that it's done, faulty U651... but unfortunately after replacing it by a new one, it changed nothing. I didn't look for the moment if there is something at its output.QuoteIn fact when it halts nothing except intensity knob works. No clicking from attenuators or other sounds. There is just RUNNING on the screen. But i will post a video, may be tomorrow.

author: offtrack2
author_rank: Newbie
timestamp: February 12, 2018, 06:19:02 pm
content: all it needs is a new NV ram battery. (just did this hours ago for same reason,)the book is clear, it says and I simplify, if CKsum fails, ignore all other errors !!! (that is because all amp offsets are lost and all self tests will fail)all 2430s do this and is a simple fix,replace the battery Keeper-II (early models, like mine is)or if no keeper bat there. (last models are)2430a , replace the Dallas Nvrams DS-nnnnn SRAM, they have a battery inside. I'm told some version have 2 Dallas NVram there, (look carefully for dallas)then remove the J156 jumperdo not run with case off, or use external fan to a10 board bottom or it will BURN UP,let the scope warm up for 10 minutes, the screen tells you that its not warm , wait for it ... then.....do the full diag (chapter 5-10 to 12 covers this the book is free from tek, need links?)then do the calibrate.last do the external CAL. using only an accurate PSU, variable power-supply, and good DMM 4-1/2 digits, (our meter today exceeds the old PG506 level gen by tekl. by 10 fold)I used a 10k ohm and 200ohm , low PPM resister pair (divider) to my 20vdc bench supply. (adjustable from 0 to 20v)then I did the external cal.levels. do the 3 dc levels as prompted. see it pass. ch1 and ch1 connected to sourcetriggers, do the 3 dc levels ext, trig 1 and both same time.repete (needs no inputs) its a all automatic.then when all 3 saypassed.turn off scope see chksum pass. on next power up.the remove J156.done.that halting is normal, it goes to cold start when CKsum fails for good reasons, not to do damage. with cal tables lost.on mine +5vd bus rail shored and I lost all cals.ribbon cable was cut by case, pin 1, +5vd, cure that and the blow fuse, and it cals prefectly. 32 years old running strong.as with any electronicswe check all supplies first for spec voltages and out of spec ripple. first.end 2340s , that all fail this way. all do and is not big deal at all.