TDS744A: Hangs with 7-segment code ".L" or segment 'f' - Page 1
Forum section: electronics / repair

author: mssbid
author_rank: Contributor
timestamp: September 08, 2022, 05:16:43 am
content: When starting my 744A with all DIP switches (S1001) set to close (0b 0000 0000),it runs through the usual procedures which normally end in segments 'e' and 'f' flashingalternately when all is fine. Now, after turning off the front panel LEDs, it stops showingcode ".L" (see pic 744A_with_diag.jpg).When setting S1001 to 0b 0000 0100 (do not execute diagnostics) we see 'e' and 'f' toggle2 or 3 times but then only segment 'f' stays on permanently (see pic 744A_no_diag.jpg).In both cases ".L" can be seen occasionally for a few 100 ms during startup procedures.Don't nail me down on this but I think this wasn't the case earlier.So does anyone know what ".L" means? The dot means that some test has failed butno idea about the 'L' (it's not in the Service Manual).

author: TERRA Operative
author_rank: Super Contributor
timestamp: September 15, 2022, 05:36:39 pm
content: That's a weird one. You are correct that .L isn't in the service manual, attached is the page detailing the error codes.Is there any way you could make an adapter (or buy one from here) to attach the serial/parallel PCB to the console connector on the main PCB? (The edge connector to the right of the connector the serial/parallel PCB is normally connected).That way you can hook it to a terminal emulator on your PC (set to 9600 Baud, 8N1 with RTS/CTS flow control) and see the boot messages etc and it'll give us a much clearer idea of what's wrong.

author: mssbid
author_rank: Contributor
timestamp: September 17, 2022, 01:37:25 pm
content: Quote from: TERRA Operative on September 15, 2022, 05:36:39 pmYes, that's why I was asking here. Didn't find any reference for '.L' in the whole :-) Internet.QuoteI've already ordered two of them but it will take until they'll arrive. I will check the output and post it here.

author: m k
author_rank: Super Contributor
timestamp: September 17, 2022, 02:45:51 pm
content: Can it be a failed ID Register decoder of value b8 or 1d?

author: mssbid
author_rank: Contributor
timestamp: September 17, 2022, 02:50:48 pm
content: You mean that it's not .L indead but something else and some segments are missing?Well, I did that "Walk 7 Segment LED" test ( 0b10100010) and all segments were OK...

author: m k
author_rank: Super Contributor
timestamp: September 17, 2022, 03:17:49 pm
content: Not missing but off and dot being lsb or msb.

author: mssbid
author_rank: Contributor
timestamp: September 17, 2022, 03:22:32 pm
content: Sorry, I don't understand what you mean...

author: m k
author_rank: Super Contributor
timestamp: September 17, 2022, 04:21:28 pm
content: Last of first error code pdf is ID Register.There it states that nibbles are displayed.If that nibble display procedure swaps to alternative mode it can still display the whole 8 bit number using 7 segments and a dot as bits.Maybe some other machine using the same ID Register display procedure uses LEDs instead of 7-segment display.

author: mssbid
author_rank: Contributor
timestamp: September 17, 2022, 05:37:09 pm
content: OK, took a while but now I got it:Code:ID RegisterThe LED displays the A11 DRAM Processor/Display ID in hex: themost significant nibble (4 bits) first and then the least significantnibble.Now I am more lost than before. For this to apply I would expect two hex nibblesalternating (which would result in a 8 bit "A11 DRAM Processor/Display ID" -whatever that is) but no ".L".I have to admit that I don't understand the whole LED thing entirely. We haveCode:Table 1–26: Troubleshooting Procedure For LED DisplayandCode:Table 1–28: A11 DRAM Processor/Display LED (DS1)which are almost identical apart from that funky "ID Register" in table 1-26 andsome additional stuff in table 1-28.I think I will have to wait for the console adapter and see if this reveals anything...

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 18, 2022, 05:34:16 pm
content: I do not possess any non-suffix neither A or B serie oscilloscope. My return of experience is only TDSxxx/C/D serie.As for the 7 segments display, with C/D serie if all tests pass then there will be a permanent toggling of upper horizontal segment and lower horizontal segment flashing.Just for my own info, do you confirm that with TDS744A, once all tests are passed OK then segments 'e' and 'f' will flash ?Albert

author: TERRA Operative
author_rank: Super Contributor
timestamp: September 19, 2022, 04:18:41 am
content: In my C and D variant units, it's two of the vertical segments that toggle on and off.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 19, 2022, 04:23:26 am
content: Quote from: TERRA Operative on September 19, 2022, 04:18:41 amHum, what firmware do you use with your Cs and Ds, what TDS model ?Very strange because I've tested and/or repaired a total of 7 of these TDSxxx/C/D and all would have toggling on-off between top and bottom horizontal segments !

author: mssbid
author_rank: Contributor
timestamp: September 19, 2022, 04:25:13 am
content: Quote from: Tantratron on September 18, 2022, 05:34:16 pmNormally, when all is (was) fine, segments 'e' and 'f' flash alternately when bootingwas done and the device is running. This is what my 784A does and the 744A didbefore the error showed up.Now the 744A does what I described in my first post:When enabling diagnostics (leaving DIP switch 3 of S1001 in close position), thestartup ends with ".L".When disabling diagnostics (setting DIP switch 3 of S1001 to open) the startup endswith 'e' and 'f' flashing alternately a few times and stops with 'f' staying on.See also pics of my first post.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 19, 2022, 04:53:59 am
content: Quote from: mssbid on September 19, 2022, 04:25:13 amSorry but I still do not understand how you use then isolate the fault thanks to the S1001 switch, why choose 0000 0100 which does not corresponds to any know self-test choice.When I try to repair these TDSxxx/C/D (note that I've never had in hands any A or B), anyway I'll first choose 1000 0000 then try 1000 0001, after 1000 0010... to check and isolate individually all sub-systems.

author: mssbid
author_rank: Contributor
timestamp: September 19, 2022, 05:12:21 am
content: I made a small video which shows the behaviour without diag enabled.Since it can't be uploaded here, please checkhttp://tmp.dyn.g66.org/744a_no_diag.mp4The alternate flashing shortly before it ends is what would go on endlesslyif all was well...

author: mssbid
author_rank: Contributor
timestamp: September 19, 2022, 05:18:50 am
content: Quote from: Tantratron on September 19, 2022, 04:53:59 amWhen switch #3 is set to close (AFAIK the default), the device runs extensive diagnostics.This not only makes the startup take significantly more time, it also displays some funkystuff on the screen.When switch #3 is set to open, these diagnostics will be skipped:Code:Table 1–27: DIP Switch OptionsDIP Selection (8–1) Action...0100 0100 Do not execute diagnostics...I assume this was made to provide some kind of quick start when powering on the scope.

author: mssbid
author_rank: Contributor
timestamp: September 19, 2022, 05:56:28 am
content: Quote from: mssbid on September 19, 2022, 05:12:21 amQuoting myself :-) Here is the video showing what happens when diagnostics is enabled(sw #3 closed):http://tmp.dyn.g66.org/744a_with_diag.mp4I've read somewhere, that the 7-segment display is mainly used for low-level stuff (likewhen the boot ROM still runs). When the "real" FW has started, it only shows segments'e' and 'f' flashing.The diagnostics which is controlled by sw #3 is run from the FW. This is the long periodwhere we see 'e' and 'f' flashing. And in the end it shows ".L" since this error was detectedearlier...

author: m k
author_rank: Super Contributor
timestamp: September 19, 2022, 09:17:15 am
content: .8 1 2 3 4 5(g) 7 8 e [blinking -] I I- .L [blinking I] .L [blinking I] .L"I-" is probably just 'I' where last blink of '-' is visible.Generally previous value is still lit when next is already present.'5' has no time to be clean.Most likely L tries to be meaningful, if so then what, Loop?Maybe it's simply indicating that something is looping, its earlier blinks can indicate that.Those blinking segments have also some different timings.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 20, 2022, 03:19:05 am
content: Quote from: mssbid on September 19, 2022, 05:56:28 amAgain and again, as mentioned before you need to use the different S1001 testing positions for looping on each different tests to eventually find out or isolate during the complete sequence what could be wrong, at least find out what works. You are restricting yourself way too much on how the S1001 could help you solve the problem, otherwise let's wait what the Console Port will talk once you'll receive the adapter kit.Albert

author: mssbid
author_rank: Contributor
timestamp: September 21, 2022, 05:35:11 am
content: Quote from: Tantratron on September 20, 2022, 03:19:05 amWell, this does not reveal anything. Which is not of surprise since all those tests apparently arelow level tests checking some basic stuff on the processor board (presumably beeing done bythe boot ROM).Once the OS has kicked in, more diagnostics might be run (or not, depending on SW3). And thesecan be observed on the console (using that brilliant adapter from that guy in Italy which arrived now).With SW3 set to close (execute diagnostics) we get a rather detailed ouput with some interestingparts:Code:...calLibrarianDefaultCk .......... passdspForcedBus ................... passacqProcThermistor ..............ERRORID: 62 hardware error acq processor not responding***FAIL***..error details:ERRORID: 151 diagnostic test failure acqProcThermistoracq processor not responding** acqProcInit(ACQ_DIAG): Acquisition processor problemtrigGtlRegisterDiag ............ERRORID: 62 hardware error acq processor not respondingi=0 temp=ffff mask = 7ftrigReg=8a TRIGgtlAddr = 72c0800***FAIL***..error details:ERRORID: 151 diagnostic test failure trigGtlRegisterDiagacq processor not respondingRegNo: 0x72c0914fpDiagConf ..................... passoptDiagPM110Reg ................ passoptDiagFloppyCacheMem .......... passoptDiagFloppyControllerIO ......0x51ffea8 (tRootTask): duart portB write timeout, byte: a70x51ffea8 (tRootTask): duart portB write timeout, byte: 47passoptDiagFloppyDrive ............. passoptRS232DuartIO ................ UNTESTED...Smalltalk/V Sun Version 1.12Copyright (C) 1990 Object Technology International Inc.ERRORID: 62 hardware error acq processor not responding0x51efec0 (V main): duart portB write timeout, byte: a80x51efec0 (V main): duart portB write timeout, byte: 480x51efec0 (V main): duart portB write timeout, byte: a80x51efec0 (V main): duart portB write timeout, byte: 480x51efec0 (V main): duart portB write timeout, byte: a8...Thanks to the first error (acq processor) and that famous "component level diagnostics and repair manual"the rest was simple: The RX line of the 68HC05 on the acq board was quiet while the corresponding TXline of the UART on the cpu board was not. In the end it was a bad solder joint on that bus board whichconnects the two PCBs (the whole area around pin 85 looked suspiciously). After fixing that, the scopeis up and running.BTW, when setting SW3 to open (do NOT execute diagnostics), the error appears only at the end:Code:...Smalltalk/V Sun Version 1.12Copyright (C) 1990 Object Technology International Inc.ERRORID: 62 hardware error acq processor not responding0x51efec0 (V main): duart portB write timeout, byte: a80x51efec0 (V main): duart portB write timeout, byte: 480x51efec0 (V main): duart portB write timeout, byte: a80x51efec0 (V main): duart portB write timeout, byte: 480x51efec0 (V main): duart portB write timeout, byte: a8...So I can confirm what building (or buying) that console adapter is highly advisable and the7-segment LED should be considered only for that very early low-level stuff. I got attractedby that ".L", assuming it would represent any failure on the processor board, but I didn'thonour the fact that the OS was up and running already...

author: m k
author_rank: Super Contributor
timestamp: September 21, 2022, 09:21:56 am
content: Maybe one note for casual reader.Sometimes information is not as thorough as it is here.Here it is obvious that Thermistor or GtlRegister are not the cause.It's just that diagnostics happen to report the fault that way this time.

author: mssbid
author_rank: Contributor
timestamp: September 21, 2022, 10:28:34 am
content: Quote from: m k on September 21, 2022, 09:21:56 amWell, it also reports "acq processor not responding". So the probability that it'sreally the thermistor is not zero, but rather low :-).

author: m k
author_rank: Super Contributor
timestamp: September 22, 2022, 10:23:25 am
content: Then it would be more like something and thermistor.Other case could have stopped right after the first fault.It would also be a bit humiliating if Tek had a cryptic fault diagnostics.

author: mssbid
author_rank: Contributor
timestamp: September 22, 2022, 12:50:39 pm
content: Quote from: m k on September 22, 2022, 10:23:25 amTo be exact, it _is_ more, see "ERRORID: 151 diagnostic test failure trigGtlRegisterDiag"After fixing the problem, we can also see that diagnostic output has increased significantly.Here is the diff:Code:...calLibrarianDefaultCk .......... passdspForcedBus ................... pass-acqProcThermistor ..............ERRORID: 62 hardware error acq processor not responding- ***FAIL***-..error details:-ERRORID: 151 diagnostic test failure acqProcThermistor-acq processor not responding-** acqProcInit(ACQ_DIAG): Acquisition processor problem--trigGtlRegisterDiag ............ERRORID: 62 hardware error acq processor not responding- i=0 temp=ffff mask = 7f- trigReg=8a TRIGgtlAddr = 72c0800- ***FAIL***-..error details:-ERRORID: 151 diagnostic test failure trigGtlRegisterDiag-acq processor not responding-RegNo: 0x72c0914-+acqProcThermistor .............. pass+trigGtlRegisterDiag ............ pass+trigBtlRegisterDiag ............ pass+ch1LogicTypeComp ............... pass+ch2LogicTypeComp ............... pass+ch3LogicTypeComp ............... pass+ch4LogicTypeComp ............... pass+ch1EdgeTrigDiag ................ pass+lineTrigDiag ................... pass+dlyTrigDBETrigAfter ............ pass+dlyTrigDBTRunsAfter ............ pass+slewrateTrigDiag ............... pass+trigAttenSerialReg ............. pass+trigPreampSerialReg ............ pass+trigDTCSerialReg ............... pass+trigExtlSerialReg .............. pass+trigDacSerialReg ............... pass+TICountersDiag ................. pass+gtlBigCountersDiag ............. pass+trigBtlConfidenceDiag .......... pass+trigGtlCompRamDiag ............. pass+digRegisterConf ................ pass+digSpecialRegisterConf ......... pass+digPhaseLockLoopDiag ........... pass+digSpeedMemConf ................ pass+digAcqMemPatConf ............... pass+digDataFormatConf .............. pass+digAcqSubSampleConf ............ pass+digAcqPeakDetectConf ........... pass+digAcqHiResConf ................ pass+digAcqMemDataConf .............. pass+digAcqMemAddrConf .............. pass+digInterruptConf ............... pass+digA2DConnectsConf ............. pass+digHFStepConf .................. pass+digDspConf ..................... pass+glitchTrigDiag ................. pass+pulseWidthDiag ................. pass+digPixelatorConf ............... pass+trigNibDiag .................... passfpDiagConf ..................... passoptDiagPM110Reg ................ passoptDiagFloppyCacheMem .......... pass-optDiagFloppyControllerIO ......0x51ffea8 (tRootTask): duart portB write timeout, byte: a7-0x51ffea8 (tRootTask): duart portB write timeout, byte: 47- pass+optDiagFloppyControllerIO ...... pass...acqProcThermistor and trigGtlRegisterDiag are checked first and during this, the system detectsthat it is a communication problem (the cpu does not answer at all), spits out an additional message"acq processor not responding" and aborts the rest (as it would not make sense to go on).With SW3 set to close, the scope now needs considerably more time to start. I wasn't aware of thatsince I always had it in open position (so that all this diag is being skipped).

author: m k
author_rank: Super Contributor
timestamp: September 22, 2022, 04:12:49 pm
content: More messages but no more actual info, if not intermittent is not it.First acqProcThermistor is tested without an answer.Since diag continues there can be a Thermistor error with same result.Next trigGtlRegisterDiag is tested with the same no answer result.Now diag can assume it's something else since Thermistor and GtlRegister are too different.It of course can also be just a counter.

author: mssbid
author_rank: Contributor
timestamp: September 22, 2022, 05:03:12 pm
content: Quote from: m k on September 22, 2022, 04:12:49 pmI see a lot more actual info. Lots of stuff which wasn't tested before.QuoteSorry, I dont't understand.QuoteA broken thermistor will probably not stop the communication betweenthe two CPUs. It might come back with 0x00 or 0xFF (or whatever theADC range is) but not with nothing.QuoteYes, that's possible. It might say: When the first two tests (where the acq cpuis involved) fail so miserably, there must be something seriously wrong anddecides to not go on. It also might have kicked off trigGtlRegisterDiag beforeacqProcThermistor had come back.Honestly, I don't care ;-) Fact is, that console adapter and these error messageshelped me to find and fix the error within 30 minutes. Before I was too heavilyfocussed on that 7-segment display and that took me more than 30 minutes...

author: m k
author_rank: Super Contributor
timestamp: September 22, 2022, 07:18:52 pm
content: Quote from: mssbid on September 22, 2022, 05:03:12 pmAfter two similar incidents they can be treated as one non intermittent fault.That information was not available after first test so it can be treated as new information.

author: mssbid
author_rank: Contributor
timestamp: September 23, 2022, 04:01:13 am
content: Quote from: m k on September 22, 2022, 07:18:52 pmWell, if you like... For me the information was already available after the first test, since itwent like a phone call where the other side does not answer (instead of talking nonsense :-)).It would be a different thing if we had a bus (like I2C or whatever) where it's possbile thatone device is broken and others not. But in our case its a straight serial link with only twopeers and if the remote end does not talk to me regarding a thermistor it won't do that forother stuff as well (unless the software got confused).

author: m k
author_rank: Super Contributor
timestamp: September 23, 2022, 12:58:00 pm
content: Quote from: mssbid on September 23, 2022, 04:01:13 amFor you yes, but not for the diagnostics procedure.

author: mssbid
author_rank: Contributor
timestamp: September 23, 2022, 02:22:35 pm
content: Quote from: m k on September 23, 2022, 12:58:00 pmFor the diagnostics procedure as well, but it didn't honour it.

author: Tantratron
author_rank: Frequent Contributor
timestamp: March 23, 2025, 10:32:22 am
content: Quote from: TERRA Operative on September 15, 2022, 05:36:39 pmI've been offered a TDS784A earlier this week, the company wanted to throw it away to the junkyard because was unused for long.After some dust cleaning and different check prior powering up, it does boot under firmware FV:4.2.1e but will takehugetime to complete the normal run.So I've forced S1001 8-pin switch to 0b00000100 to skip diagnostics, this time the boot is much quicker.However in both cases, I do see for a few seconds the 7-segment code ".L" which is not reported in any service manual.After a few seconds, the ".L" wil disappear then alternate segment classic behaviour.