Upgraded TDS340 to TDS360  200Mhz @ 1GSa/s. For Any One Interested .Plus TDS380  - Page 1
Forum section: electronics / repair

author: Labrat101
author_rank: Unknown
timestamp: December 28, 2020, 09:33:59 pm
content: Hi,First I know this subject came up about 3 years ago and there was never any conclusion how it turnedout.Well being bored and had too much time on Hand etc.I decided what the heck I will revamp and old TDS340 and give it a new lease of Life and Kill a few hours.The whole project took about a day including research and studying the service manual .And doing it with minimal parts OK what I had at hand .The only Parts I did not change in the List were the four 270nH inductors as I didn't have and guessedif all went to plan I would order them .L203 ,L204,,L205 & L206 Need to be replaced for 27nH 100Mhz Q )Changed 7 resistors ,All 1%R208 2.21k changed to 2k ( important )R240 10k (added)R241 3.3k (added)R246 222 to 10R247 222 to 10R248 222 to 10R249 222 to 10Removed 1 cap C125 (AE1 15pf) located under the shield near C219Removed 2 bridge links R651 & R653 0.0(green)The exact location of the parts are Marked on the Photo,s as coloured dots.Next Plug it inLong Pause .It Booted up just fine with the new screen TDS360It then needs to be recalibrated .. Utility .. Cal .. wait for about 5 minutesO yer all passed with flying colours .If any one else is interested in this nice easy upgrade Please Enjoy .The scope must be functional as A TDS340 and not showing any error . Before upgrading .This project is, as is . I will not be responsible if you get it wrong .If this Helps someone please just say THANKSIf you Do need Help Please feel free to Ask .Also I know How to do a full Calibration of these TDS easy way If you should loosethe cal . and get Stuck . You will Require a Calibrated Meter Accurate to 4 Digits ie uv (Updated )Read the entire Blog

author: Labrat101
author_rank: Unknown
timestamp: December 28, 2020, 09:41:35 pm
content: Few more PicturesUpdate : If someone has the newer firmware 1.05 that would make a great addition to this.I have been looking for it without any joy so far .So if some one could throw some light on where to find it .would be more then welcomed

author: Labrat101
author_rank: Unknown
timestamp: December 29, 2020, 01:33:55 pm
content: Just another update .That might be required for fine tuning if there is a small problem with the wave form .varies from device to device .C230 & C231 are normally fitted on the TDS360 By Default ::CERAMICMLC;1PF,+/–0.25PF,50V

author: james_s
author_rank: Super Contributor
timestamp: January 13, 2021, 12:32:40 am
content: Quote from: Labrat101 on December 28, 2020, 09:33:59 pmI just noticed this part. Between a friend and myself we have three of these things that have all lost their calibration. I've been successful in calibrating the voltage and trigger but I have not managed to get the timing calibrated, and I'm not spending $20k on the instrument they suggest using to calibrate it.

author: cheapskate
author_rank: Contributor
timestamp: January 13, 2021, 06:29:16 am
content: The TDS380 is also really similar, I wonder if it would be possible to upgrade further and unlock 2GS/s mode. It seems that the four FISO inductors of the 340/360 are replaced with some high speed NPN transistors so probably not.The firmware is likely stored in U602, U603, and U607 with calibration values stores by U605. The address and data busses for those chips are present at the GPIB/Parallel/Serial options board but aren't connected in their entirety to the GPIB or UART controllers. Unless someone figures out how to boot the MC68331 CPU from an external source or the firmware includes some secret features, I don't think it is possible to extract the firmware without desoldering the flash memory. Perhaps OC3, OC4, and OC5 on J608 are some sort of debug UART?

author: james_s
author_rank: Super Contributor
timestamp: January 13, 2021, 07:03:24 am
content: I know with certainty that the calibration values are stored in the Dallas NVRAM because dead batteries is the reason the scopes I have need calibration.

author: Labrat101
author_rank: Unknown
timestamp: January 13, 2021, 01:20:17 pm
content: Quote from: james_s on January 13, 2021, 07:03:24 amHi James ,First you don't need to spend $20K unless you feel like giving me a BD present..If you Have lost the CaL . The battery must be replace if not already done so. as they some timesdie short circuitIf you managed to do all the voltage calibrations OK . Though the 50ohm terminator . you guessed thatwhen it ask for 1v you have to set the function gen to 2v so the scope see 1v @ 50(Example)When it ask for the fast rise pulse this also must be doubled so the scope see 1v pulse @ 50. (example)If using a UTG 962 set to 50ohm load the out put voltage is doubled .corrected for 50put a bench meter on the function gen on the DC 1.0000v and measured what the voltage error isfrom the function Gen (example) set dc level to 1.0000v Meter read 1.0010 . so minus the error on thefunction gen . So when set to 2.0000 volt - 0.0020 to correct . (use a RG cable with BNC to Banana )Don't measure with single jumper wires .then set function gen to pulse and the corrected voltage and all should be good.The TDS has built in ref voltages & frequencies these have to be matched before it will load them backinto NVRam again .If this still fails then you may have a few out of tolerance caps . See photo above the Blue caps wereout on my one. these were caps I replaced 1% mylar Good enough and this solved that .I guess you don't need NASA spec's . After Cal I checked with a Leo Bodnar GPSDO .. less than 1% error.Or you can raise or lower the signal voltage by just a few uv will do it as well to compensate for wear and tear.The one Most important thing that I found that this scope is very fussy on noisy connections during Cal setupthe connections MUST Be 100% good connections including the grounding.As any voltage drop on the cable will result as a failDid it to me as well .The Battery MUST be replaced or you will be recaling every other day .or never unplug it from the mains .If you use the UTG962 Set to 50ohm Load the voltage will be correct Set@987mv =1.9990vScope sees after terminator 1.0005v Adjust to match cable losses (updated typo)Did this Help or did I miss understand something with the Question

author: Labrat101
author_rank: Unknown
timestamp: January 13, 2021, 07:11:25 pm
content: Quote from: cheapskate on January 13, 2021, 06:29:16 amUpdate The NVRAM (U605) consists of a single nonvolatile memory IC. This RAMprovides storage of front-panel settings, waveforms, andcalibrationconstantsTDS 360 to 380 does not need a firmware update Only the Sampling chip is changed and 4 buffer transistors the inductors are removed completely . and a few links & capsI am not going into this . There is a flash point and its Not via GPIB .Only If the newer chip was already installed on the 360. and its the B version MB then you have aProject . other wise there will have to be a few additional jump wires .I am already pushing my upgraded 340/360 to 1.2Ghz BW which is maxing the sampling chip.with some custom made caps .

author: Labrat101
author_rank: Unknown
timestamp: January 14, 2021, 05:21:43 pm
content: Don't forget to remove the Cal Jumper J609 first ..I have made a bad drawing of the connection . (Not as good as Dave's Cad)All lead Must be the same Length 50cm MAXThe Terminator at the scope Must be a Straight Though 50Terminator .All cables Must be high quality 50and no loose connectionsA Banana Plug to BNC required for the Meter Fluke or similarThis is the only correct way if you don't want the failed Message on xtrigger

author: Labrat101
author_rank: Unknown
timestamp: January 15, 2021, 01:18:04 pm
content: Cal update The Trigger Cal when the scope ask for itis done as Per Photo.Please note checking all connection this way and you will know that all is goodAlso you can check final voltages that the scope SEEsWill help those who are having trouble getting the scope to recognise the voltages etc Asked forIE Connecting the Fluke instead of the scope to the 50ohm load . and adjust your voltage ref to the correct voltageon the Fluke when your happy with your setup and all is correct . The calibration will go easier .Good Luck . And If this Helps you Please enjoy . and Say thanks .If it made you Laugh that is also GoodSorry I must be the worst teacher on the planet . I just Know how to do . But explaining how I did it issome thing else .Still confused .Built My first all Tube scope when I was 10 yrs Old (Early 60s )

author: james_s
author_rank: Super Contributor
timestamp: January 16, 2021, 07:18:57 pm
content: Cool, thanks for the info. Yes I replaced the battery no problem, that's when I ran into the issue trying to calibrate the timing. So you did it using a cheap Chinese function generator? I was becoming convinced that something much more exotic was required. I have a 33120A which is supposed to do better than 20ns rise/fall, I don't know offhand how that compares. Seems like the Tek manual specified something under 10ns for calibration but maybe it doesn't actually matter. I'll have to take another crack at this later.

author: Labrat101
author_rank: Unknown
timestamp: January 16, 2021, 09:07:07 pm
content: Quote from: james_s on January 16, 2021, 07:18:57 pmI sent you a PM before I read this .I was sure I used 1khz @ less than 10ns rise . as I said in the PM I think the manual has a TYPO .Only Thing you need is an accurate voltmeter that can read uv (4 place of decimal )Remember 25 years ago there was no such thing as cheap Chinese function generatorsMy new Project is HP54645A .. Hehe ..I have got my sticky little hands on the original A1 Blueprint ..

author: cheapskate
author_rank: Contributor
timestamp: January 21, 2021, 11:32:00 pm
content: The TDS300 programming manual includes an undocumented "PITBULL" command. On the TDS500+ "PITBULL" is used as a password to allow unrestricted memory reads and writes. I wonder if this command is somehow similar. It is only mentioned in the reserved words listing, there is no associated documentation. I don't have a null modem adapter for the serial port yet so I haven't tried it out.

author: Labrat101
author_rank: Unknown
timestamp: January 22, 2021, 09:05:15 am
content: Quote from: cheapskate on January 21, 2021, 11:32:00 pmHi Cheapskate I found this in My Archive .I did not Pull this and I can NOT verify Firmware version etc .If you want to open it and mess with the coding Enjoy .I Do NOT work with Software . I am a Hardware engineer . I let others play with the BIN codesSo Use at your OWN risk . If you do figure out an easy way to update the software Lets us Knowhow you got on.But I am a big believer in If it aint broke Don't Fix itPS . I am sure of One thing you don't have to mess with the firmware to take itup to 2Ghz Sampling . as the the input section on these scopes are 400Mhzrated and the current firmware recognises the faster speeds if the sampling chipis replaced . If your scope was original TDS360 the transistor place footprintsare under the 4 inductors . If it was Made AS a TDS360 they should be alreadyinstalled . And just follow the custom sheet I put Above earlier#7 on: January 13, 2021,Plus Look on the schematic Diagram Last section it will show the Links to be removed or added .Have Fun Enjoy.

author: Labrat101
author_rank: Unknown
timestamp: January 23, 2021, 10:15:44 am
content: Just an UpdateThis is the Cal Frequency Screen . as per the ManualThe Cal jumper Removed ..Recall Factory setup first .. MustPlease note that if the settings are not exact as shown the screen on the scope Will notSnap to this . As all the references Must match the Internal settingThe Square wave is NEGATIVE (1ms) 1Khz @ -200mvTrigger is set to -102mv .. MUSTTime base 200 MS/s 250 ns .. MUSTVolt / Divide 50mv .. MUSTAll these setting have to be as is .

author: kozard
author_rank: Contributor
timestamp: February 26, 2022, 05:42:14 pm
content: I have been sending messages back and forth to the thread opener as I made the modifications to a "For Parts" TDS 340 I bought from eBay. The thread opener suggested that I post.Originally I first bought a TDS 380 from eBay and it arrived with a blown attenuator. As far as I can tell that is not practically fixable unless you sacrifice another TDS 380 and are really capable of desoldering the ceramic hybrid. [The preamp IC is damaged and drags down the DC offset input to -7V and saturates the preamp output (clips).]I compared photos from the non-functional TDS 380 (400 MHz) to the "for parts" TDS 340 (100 MHz) and TDS 360 (200 MHz). Originally I bought the TDS 340 to salvage the attenuator as a spare part to repair the TDS 380. However I found that the TDS 340 and TDS 360 have a different attenuator inside. The part number on the preamp IC is different. As a result my plan changed to modifying the TDS 340 to perform as close to the TDS 360 (or even better).Based upon the attached TDS 380 photos (with 10 Ohm resistors and no bandwidth limiting filter/inductors) I decided to use the same values on the TDS 340 upgrade to achieve what I hope will be the maximum possible bandwidth upgrade.Note that the TDS 380 also has four SOT23 marked R2 which I believe are SMD versions of the 2N3906. I don't plan to make a tiny PCB board with four 3906 buffers but I guess that is possible if you want to get the absolute maximum bandwidth.I followed the instructions in the first post however I made a couple of modifications:I did not install 27nH inductors in place of the 270nH inductors. Instead I used 0 ohm 1206 resistors. (Since the TDS 380 has no bandwidth limiting filter/inductors.)I did not have a 2k 1206 resistor so I soldered a 22k on top of the existing 2.2k to achieve 2k equivalent.The TDS 340 now boots up with a display that says "TDS 360". I ran signal path compensation and it passes.Photos are in the following posts.

author: whatboy
author_rank: Regular Contributor
timestamp: February 26, 2022, 06:58:04 pm
content: Maybe your photos are too big, try resizing to lower resolution..

author: Labrat101
author_rank: Unknown
timestamp: February 26, 2022, 07:22:28 pm
content: I used PNG for most of my clips here .I believe its Snip in windows or Screenshot in Linux with Grab area .I only use Linux .. Anti Bill thing

author: kozard
author_rank: Contributor
timestamp: February 26, 2022, 07:53:16 pm
content: These are pictures of the TDS 340 after the upgrade.

author: kozard
author_rank: Contributor
timestamp: February 26, 2022, 08:05:08 pm
content: Here are the TDS 380 photos.In the attenuator photo you can see that the preamp chip is not the same chip that is in the TDS 340 and 360 attenuators. Originally I bought the "For Parts" TDS 340 to fix the TDS 380 that has a blown attenuator. [The preamp IC is damaged and drags down the DC offset input to -7V and saturates the preamp output (clips).] If anyone has any ideas on how to fix it please let me know. I think it is perhaps too much even for MacGyver since any little replacement PCB for the preamp chip needs to do the DC offsets (H Position), HF adjust, three attenuation levels, balanced output and be close enough to the original hybrid to pass calibration and signal path compensation. As far as I know the preamp chip and the hybrid are both unavailable. I have also read that removing the brittle hybrid is not easy.In the zoomed in photo you can see the R2 (MMBT3906?) buffers which presumably are needed to get the highest bandwidth (400 MHz) in the TDS 380.In the TDS 380 the resistors are 10 Ohms and there are no bandwidth limiting filters (the inductors which are 270nH in TDS 340 and 27nH in the TDS 360). Presumably it is the inductor combined with the input capacitance of the IC is what forms the bandwidth limiting filter. That is why I used zero ohm 1206 resistors in place of the inductors and 10 Ohm resistors when I upgraded my TDS 340.

author: Labrat101
author_rank: Unknown
timestamp: February 26, 2022, 08:16:53 pm
content: Nice . I am glade every thing went well . Saved another TDS . The photos look good .I notice your Dallas chip has still got the original battery . you may have to replace it in the near future .

author: kozard
author_rank: Contributor
timestamp: February 26, 2022, 08:22:00 pm
content: If anyone would like to see what a real TDS 360 looks like inside I have attached photos from a scrap TDS 360 that I bought for spare parts.As you can see the TDS 380 PCB is not the same as the TDS 340 and TDS 360 PCB.The TDS 340 and TDS 360 share the same PCB and appear to be only slight BOM/Bill-Of-Materials (parts list) changes.The TDS 340 and TDS 360 use the same attenuator. The TDS 380 uses a different attenuator with a different part number on the preamp chip that is soldered to the ceramic attenuator hybrid.In this post you can see the 27nH inductors that are used in the bandwidth limiting filter (200 MHz) of the TDS 360. I used zero ohm jumpers in the hope of getting a bandwidth between that of the TDS 360 (200 MHz) and the TDS 380 (400 MHz).

author: kozard
author_rank: Contributor
timestamp: February 26, 2022, 08:39:38 pm
content: Yes, I do need to replace the DS1644. I just bought a DS1744 off of eBay from a US seller and it has a 2020 date code. I am hoping that the DS1744 will work in the TDS 340/360 as a replacement for the DS1644.I am planning to use ChipQuik Tin-Bismuth low temperature solder to remove the existing DS1644. I don't know how to backup the DS1644 inside the scope. I am hoping to remove the DS1644 without too much heat and I hope I can still read it afterward. I hope it will not be corrupted or destroyed.[See the attached picture of the Arduino Mega 2560 programmer with the DS1744 installed.]If someone else needs a DS1644/DS1744 reader/writer mine is based upon the following Arduino EPROM programmer. [It is very easy to make but a little slow. Don't forget to put a pull up on the Write Enable pin! In my case when I try to read the DS1644 removed from the scope I will have the Write Enable hardwired to the Vcc pin just to prevent that chance of corruption.]Here is the link for the Arduino EPROM programmer that I found online:http://danceswithferrets.org/geekblog/?page_id=903Finally for completeness I have attached pictures of the unmodified TDS 340 just in case someone needs to see an unmodified TDS 340. The inductors are 270nH I believe.

author: Labrat101
author_rank: Unknown
timestamp: February 26, 2022, 09:30:37 pm
content: If you copy the calibration from the Dallas after upgrade 340 to 360 I have a feeling that the cal will be out and you will stillhave to do a full re calibration . I had to do a calibration after I replaced the battery with the drimmel out job .Then again after the upgrade I found my one was out again . Re ran a full calibration again . Maybe Luck of the draw . would beinteresting if the Cal holds true after upgrade as the new ranges won't have a cal point .UpDate Edit :: What I mean is that the Calibration flag is still set as OK . when 340 mode now after the Upgrade to 360 the Cal flag wont necessary be changed and now with Bandwidth changed etc . I would be inclined tocheck / verifyother wise you maybe doing some tests on a future projectand be led down a Rabbit hole look for false error . I would personally feel safer re: doing a full calibration or at least a partial .Yes I know its a pain in the Ass but could save a futureCal!Out!!

author: kozard
author_rank: Contributor
timestamp: February 28, 2022, 04:23:37 pm
content: Finally made progress on fixing the real TDS 380. [Funny how that happens immediately after I upgrade a "For Parts" TDS 340 to a TDS 360.]There is (hopefully) some useful information here for others.For example, in the photos you will see that I replaced the DS1644 with a DS1744. I can confirm that this works. (I could not find an answer to that question when I started.) I expect it will also work in the TDS 340 and TDS 360 in place of the DS1644.Another important fact is that assuming your scope is not damaged (and thus can be recalibrated) you can install a blank DS1744 (or blank DS1644) into the TDS 380 and start the calibration. You don't need to save the data from the old NVRAM. I would prefer to save the data myself but the TDS 380 arrived interriblecondition. (See the last photo for what I received from eBay!) Note that attenuator damage (such as burned resistors on the ceramic hybrid or over voltage damage to the MAXTEK preamp chip on the ceramic hybrid) will cause calibration attempts to fail.Next I tried to build a number of voltage calibrators and the Calibration Voltage Reference always failed. (Error message "Cal error, CVR source gain".)Here are some hints to make it work: Listen CAREFULLY and observe the timing between the individual voltage calibration steps. If it quickly moves to the next step then you know that it has already failed. Make a note of that step and improve your calibration voltage source for that voltage step! Otherwise you will go through all eight steps and not know where the failure occurred. In my case it passed with a battery powered home-made calibrator with a battery powered meter attached. (Not necessarily a good idea to leave the meter leads (antenna) attached but it worked in this case.)Now you can build a relatively low-cost calibrator. I finally got it to pass when I used a battery (3x18650) and op-amp buffers to drive the 50 Ohm terminator. Each op-amp buffer has an RC filter at the input using a 0.47uF polypropylene capacitor. Note do not use electrolytics for the noise filters due to leakage current. The final step is 15.0mV which isn't very much.I did not have the ideal rail to rail op-amps available. I really needed low offset voltage and low input bias current precision op-amps that are rail to rail at least to the negative rail on input and output. I did not have those so I had to be extra careful about using low resistance dividers due to the problems cause by the input bias currents. I don't recommend that you use the op-amps I used. If you must build your own calibrator try to make your life easier with a good precision reference and good quality precision rail to rail op-amps that are low input bias current. I recommend battery power.I used 3x18650 followed by LM7805 followed by a TL431 to generate 2.5V Vref. (The TL431 is not great but that is what I had. Try to get something better.)Then I used a resistive divider, RC filter and op-amp buffer to generate 1.5V from the 2.5V Vref.Then I did the same with a resistive divider, RC filter and op-amp buffer to generate 0.3V from the 2.5V Vref.I could not successfully generate a sufficiently stable 80mV and 15mV from the 2.5V Vref.So I used the buffered 0.3V with a low impedance resistive divider, RC filter and op-amp buffer to generate 80.0mV.Finally I used the buffered 80.0mV with a low impedance resistive divider, RC filter and op-amp buffer to generate 15.0mV.I could not get it to work with relatively low noise HP supplies, resistive dividers and RC filters. I suspect it was a combination of going to battery power and op-amp buffers (with RC noise filters) which made it finally work.I am not saying my calibrator is the way to do it. Just that it worked and I was able to build it without buying anything. I am sure there are much better ways to do this, especially if you are willing to buy more expensive parts and/or equipment.I have attached pictures. Note the last two pictures. The second to last is this TDS 380 as it is today. The last picture is the TDS 380 as it arrived from eBay! (With apocalyptic damage done inside by someone else.)I placed this here in this thread because I believe it might possibly help others calibrate a TDS 340 upgraded to TDS 360, for example. Such as the "For Parts" TDS 340 that I just upgraded to TDS 360.

author: Labrat101
author_rank: Unknown
timestamp: February 28, 2022, 06:33:15 pm
content: @ kozardThat is an amassing clean up job you did on that TDS380 . Along with that ninja surgery job on the MC68331 chip .I have to take my hat off to you . Who would have thought the old girl would have bounced back to life .I am sure there will be others interested . Saved 2 more from landfills .Well done

author: kozard
author_rank: Contributor
timestamp: March 01, 2022, 11:35:42 pm
content: Calibrating the external trigger went smoothly with nothing more than a 50 Ohm termination and an HP power supply (with 10 turn potentiometer) providing the +/-1V and +/-10V.The timing calibration seems to be challenging. I tried using a 74AC14 to clean up the edges but it appears that the inductance/length of the ground and Vcc leads in the DIP-14 package prevent acceptable performance. (Too much ringing, etc.)Has anyone successfully done the timing calibration on a TDS380/360/340? (With DIY level equipment?)I also tried generating the square wave from a surface mount (less inductance) microcontroller (M328) and the waveform was improved (less ringing) but the timing calibration still failed.Any experience/suggestions?

author: kozard
author_rank: Contributor
timestamp: March 02, 2022, 09:52:32 pm
content: My first attempt at timing calibration/compensation of the TDS 380 failed with a DIP package 74AC14.So I tried again with a SN74LVC1G14 SOT23 package Schmitt Trigger... ...and it failed again.I have attached photos of the construction, the setup prior to running the calibration and then after failure. After it fails it shows the waveform with a 5ns time base. (Last photo.) The construction photos are prior to the addition of a 47pF 51 Ohm snubber on the output of the 1G14.Any suggestions? I think I set it up right. (Factory recall and then setup as shown in the fourth attached image which looks like what is shown in the manual.)Does anyone know how (DIY) to make a cleaner looking waveform? Making a PCB and using a SiGe comparator is a little pricey for a DIY project.Does anyone know of a (driver/output) schematic that makes a nice clean pulse? I have some PN5179, BF245, BF998, 3904/3906... I know there are classic old discrete generators out there that made nice clean pulses without ringing, etc.

author: Labrat101
author_rank: Unknown
timestamp: March 03, 2022, 08:52:47 am
content: Hi I noticed you are using an electrolytic capTry replacing it with a ceramic or non polarizedPoli cap as you need a fast rise 1ns on the 380..Also, did you check all the small smd capsOn the main board. After you cleaned, there could be some dirt ,gunk ,underneath the capsPutting them out of spec .If you look at my photos of the main board, you will see a load of blue caps . I found about 8 that were failing out of spec.I used an in circuit cap checker .After the amount of cleaning, you had to do.Just a thought.

author: kozard
author_rank: Contributor
timestamp: March 03, 2022, 12:46:48 pm
content: The capacitors are:560uF Panasonic SEPC Series Aluminum Organic Polymer (Silver Can)220uF Tantalum (Black)22uF Ceramic 1206 X5R10uF Ceramic 1206 X5R1uF Ceramic 1206 X7RThe SOT23 Schmitt Trigger is soldered on top of the 1uF 1206 Ceramic capacitor.Do you think the Panasonic SEPC Series Aluminum Organic Polymer would cause a problem?Does anyone know if an old Datapulse 101 (< 5nS rise time) pulse generator would be clean enough for this calibration? I noticed you said < 1nS but the service manual says < 10nS rise time on page 5-1.

author: Labrat101
author_rank: Unknown
timestamp: March 03, 2022, 04:48:32 pm
content: About the cap you are using, you will have to check the specs.The timing I used a 2ns rise when I did my 340/360 . The 380 has a higher BW . 10ns seems too slow . It's not uncommon for typos in manuals . If you're having trouble with what you are doing now , It's too slower to rise. Try 5ns; see if it gets any results.Also make sure it's a 50/50 square.

author: kozard
author_rank: Contributor
timestamp: March 03, 2022, 06:17:43 pm
content: I added a ferrite bead to the power supply line and a 10nF capacitor. (First three pictures.)That improved the ringing but the timing calibration still fails.Then I added 10pF to the attenuator (junction of the 1.2kOhm and 50Ohm) and the timing calibration still fails. (Next three pictures.)I think the calibration signal waveform looks pretty reasonable now? It is exactly 50% duty cycle.The last photo shows something that might be a clue. The last five power on cycles it no longer shows the error "Cal error, timing - Check Signal Source". It is still failing the timing calibration but is not adding that error to the error log anymore. Does that mean the waveform is ok but the scope is truly failing the calibration? It appears to be operating very well.The last five power on cycles might be when I switched over from the 74AC14 (DIP package) Schmitt Trigger to the SOT23 1G14 Schmitt Trigger.Not sure what else to try at this point. I wonder if there is any sort of ham radio club in New Jersey/Central New Jersey where some kind soul might own a real pulse generator that could be used to try the calibration. It only takes a couple minutes to hookup the BNC cable, recall factory setup and run the timing calibration.I might need to put this aside for a bit until a new idea or plan comes up.

author: jonpaul
author_rank: Super Contributor
timestamp: March 03, 2022, 06:46:47 pm
content: Suggest to post on Groups.io Tekscope and tekscopes2 forums, many EX TEK experts.I recall that the freq, duty cycle and levels must all be precise to do that cal.There are old threads for 2465/A/B but may be similar CAL requirement for your model.Bon chanceJon

author: Labrat101
author_rank: Unknown
timestamp: March 03, 2022, 07:06:44 pm
content: OK that error log is saying that there is an error with the original Factory defaults .You will have to go into setting there is an option to set to default setting .You could also have a bad connection on the Ram chips were the original setting are stores .The chip were you ran the patch lead across to the left top chip . Sorry being lazy and not look up numbersAlso on all those photos nun of them have got M 250ns Ch1 . the setting must be as per the manual don't try to adjust the scope tomatch your pulse . the setting have to be set first then the signalThe numbers on scope screen setting are as per the manual no deviation is allowed .First do a full factory restore . make sure the cal jumper is removed .Set the scope to the correct setting shown in the manual . also look carefully at my photo and the yellow squares these have to beall correct . apply the signal . The scope may show multiple cycles leave to settle, it should snap to this half cycle .if it does not settle try adjusting the timing just a little and back to the correct setting .If it does not Snap .Yes my manual is also printed Less than >10nsyou have ::A Your signal pulse is too slow or the voltage is wrong .B You still have a problem with your scope maybe a bad ceramic caps .C your Dallas chip is not excepting the new sampling rates so you will get a conflict of Factory & NULL .These are correct setting As per manual . Make sure your screen looks the same . Including Recall Factory Setting @ bottom . & Recall Has been Done ..OK Pressed >>https://www.eevblog.com/forum/repair/upgraded-tds340-to-tds360-200mhz-1gsas-for-any-one-interested/?action=dlattach;attach=1156060;image

author: kozard
author_rank: Contributor
timestamp: March 03, 2022, 07:34:29 pm
content: Do you mean "Press the front-panel button SAVE/RECALL, the main-menu button Recall. Factory Setup, and then the side-menu button OK Confirm Factory Init."?(I did do that. The calibration jumper is removed.)The other time base settings are just to show what the calibration signal looks like. I have started the calibration on the correct 250ns. The below image is one example with M 250ns Ch1. (Does that one look correct or am I missing something?)I believe the message "Factory timing cal constants invalid" is due to the fact that the DS1744 was installed totally blank. This TDS380 arrived with the DS1644 sawn through by someone with a dremel. I believe I can only fix that error message by performing the timing calibration successfully. Or do I need to use a programmer to load the new DS1744 with someone's backup NVRAM dump before I can run the timing calibration step?I believe that read/write to the new NVRAM is ok since it read/writes successfully for the other calibration steps and also for save and recall of user setups.

author: Labrat101
author_rank: Unknown
timestamp: March 03, 2022, 08:01:27 pm
content: Quote from: kozard on March 03, 2022, 07:34:29 pmYour screen MUST LOOK LIKE THIS . No exceptionsThese are correct setting As per manual . Make sure your screen looks the same . Including Recall Factory Setting @ bottom . & Recall Has been Done ..OK Pressed >>https://www.eevblog.com/forum/repair/upgraded-tds340-to-tds360-200mhz-1gsas-for-any-one-interested/?action=dlattach;attach=1156060;imageThe Dallas can be blank when the scope boots it loads the setting into the VRamPS yes your missing the bottom line the screen must show exactly as per the manual with the menu at the bottomThat should work the setting look good do the factory recall and make sure it says ok

author: Labrat101
author_rank: Unknown
timestamp: March 03, 2022, 08:15:26 pm
content: Quote from kozardDo you mean "Press the front-panel button SAVE/RECALL, the main-menu button Recall. Factory Setup, and then the side-menu button OK Confirm Factory Init."?YES

author: kozard
author_rank: Contributor
timestamp: March 03, 2022, 10:11:59 pm
content: The first three images are just double and triple checking the frequency, duty cycle and amplitude. The duty cycle should be extremely precise since the 1kHz is derived from 4kHz divided by two 74ACT74 flip-flops setup as divide by two each.The fourth image is after recalling the factory setup. Cal jumper is off.The fifth image is the calibration waveform prior to starting the calibration side by side with the calibration waveform example from the manual. I believe it is exactly as per the manual.The sixth image is after the timing calibration fails again.This time I used battery power (3x18650), LM317 power supply and 74ACT74 just in case there were any issues with noise or duty cycle. The previous attempts used a line powered HP power supply.

author: Labrat101
author_rank: Unknown
timestamp: March 04, 2022, 08:03:54 am
content: Quote from: kozard on March 03, 2022, 10:11:59 pmYour Signal Looks 100% correct and is OK .But I did notice that your scope screen is not actually responding to the signal .During the actual Cal the scope should flash up the reading of the signal on the top right of the pulse ..Ch1 200mv PK- PK This shows the reading of cal acknowledgementyours is not doing it . Not sure why . I think that the scope has still got another Problem .Maybe a bad ceramic timing cap .

author: Labrat101
author_rank: Unknown
timestamp: March 04, 2022, 12:03:43 pm
content: Question what is this resistor bodged over channel 1 input . this may well be messing up your Cal

author: kozard
author_rank: Contributor
timestamp: March 04, 2022, 01:01:31 pm
content: That is the other TDS380, not this one. That other TDS380 arrived with two burned out attenuators. But with a working DS1644.I was able to "fix" one attenuator by soldering in a 50 Ohm resistor to replace a 50 Ohm resistor burned out on the ceramic hybrid. (The black square showing up from under the blue film is the burned resistor.)The other attenuator is beyond hope because the preamp chip is damaged. (Always clips/rails the horizontal position control voltage/offset.) I don't think I can get that MAXTEK chip and I likely cannot remove or replace it on the ceramic. I was hoping the TDS340 attenuator would be suitable but it is a different part number (as seen on the preamp chip). I originally bought the "For Parts" TDS340 to get parts (attenuators) to fix the TDS380. But instead I fixed the TDS340 and upgraded it to TDS360(+) bandwidth.I don't think I can fix that other TDS380 because I cannot find attenuators for sale.However the TDS380 that I am calibrating has good attenuators and passes SPC.The attached photo shows the good attenuators in this TDS380 that I am trying to calibrate.

author: Labrat101
author_rank: Unknown
timestamp: March 04, 2022, 01:47:14 pm
content: If this is the case did you also check the relays as well . .. you defiantly have other problems with this scopeIt will never pass this cal if there are any problems with the inputs .you may have to live with it as is or do a major hunt for all the possible damaged parts in line

author: kozard
author_rank: Contributor
timestamp: March 04, 2022, 03:01:59 pm
content: That is a different TDS380.I am not trying to calibrate the TDS380 with damaged inputs.I am trying to calibrate the other TDS380 that does not have damaged inputs.

author: Labrat101
author_rank: Unknown
timestamp: March 04, 2022, 05:03:18 pm
content: Quote from: kozard on March 04, 2022, 03:01:59 pmOk But the scope you are trying to Cal has also a got another problem as well .. As I mention before you need to check all the smdcaps you have for sure got a few bad or cracked . I would recommend using in circuit tester . DER EE DE5000 LCR or similaror you are going to be running in circles.Do first a quick test by using a led light over all the caps with a microscope or big Magnifying glass and see if there are any crackedceramic caps they fail at the ends . (not always)When upgrade my last one it also failed when I first got it . It had about 8 or so bad ceramic caps . I replaced them with though hole caps and just bent the wires short to fit the smd space . They are all the blue caps seen in my photo on previous page .Also on the other scope you said you put a 50 ohm over the burnt one .. There are no 50 ohm resistors there . It should be a 15pfcap that you put a resistor over . the scope input only has small ceramic caps the brownish one is Not a resistor . its a hi voltage ceramic or similar .

author: kozard
author_rank: Contributor
timestamp: March 04, 2022, 05:15:13 pm
content: The resistors are deposited on the ceramic, then laser trimmed and covered with the blue coating/film. The ceramic attenuator hybrids contain quite a few laser trimmed resistors under that blue coating.If you probe across the SMD cap you can measure the resistance of the connected resistor. (On a good attenuator.)If you look at the photo of the repair/resistor soldered to the SMD capacitor you can see nearby a black mark where the film resistor (on the hybrid) burned up. The black spot is not seen on the other hybrid/attenuator.I will look into how to check the capacitors on the board. Right now I don't have an in-circuit tester. But perhaps I can find/make something.

author: Labrat101
author_rank: Unknown
timestamp: March 04, 2022, 05:40:19 pm
content: Quote from: kozard on March 04, 2022, 05:15:13 pmPlease look at the schematics of the 380 and you will see .I think from memory it 1.0uf & 0.022uf . I can a sure you there is only one resistor there and its a 1.00k

author: kozard
author_rank: Contributor
timestamp: March 04, 2022, 07:01:11 pm
content: I don't think you can see from the schematic since I think the schematic does not show the contents or schematic of the ceramic attenuator hybrid.None of the laser trim resistors deposited on the ceramic are shown in the schematic. In fact there is only a box labeled "AT205 H2565". The technical manual that I have does not include the schematic/insides of "AT205 H2565" at all.The schematic I have (attached) treats the ceramic attenuator hybrid as a black box. It says nothing about the contents of the attenuator such as the laser trimmed resistors, MAXTEK preamp chip or relays.Do you have a different schematic that shows the contents/schematic of the inside of the "AT205 H2565" ceramic hybrid? I was under the impression that Tektronix did not publish that.In my second picture you see the burn spot over the resistor. (Black rectangle with the red box around it.)

author: Labrat101
author_rank: Unknown
timestamp: March 04, 2022, 07:28:46 pm
content: I have the same diagram . I will look to see if I have another .I don't think its 50 ohm though . as its coming from the center pin ..yeshave you checked the the resistance on the BNC it should read 1meg between center pin & ground . and 5volt from BNC outer tothe probe sense ring .It does Not make sense that its a 50ohm across a decoupling cap . It may well be a 1.2Meg ohm would make more sense asthe input impedance is 1 meg @ 13pf apx .because when you put a 50ohm terminator on this would read at the scope about 25 ohm and the cal would fail due to bad signal.I would replace that resistor for a 1 Meg ohm . and try againUpdate edit replace that cap as well try 1.0 ufEdit 2 typos sorry

author: kozard
author_rank: Contributor
timestamp: March 04, 2022, 07:42:35 pm
content: I measured 50 Ohms on the other attenuator. (The attenuator on the other channel.) When I get a chance I will check on two more attenuators that I can measure in the other TDS380.With the 50 Ohm installed all ranges work properly/read properly on that attenuator now.Right now on the other TDS380 I am going to try getting rid of the invalid factory timing constants by removing and copying the contents of the DS1644 from the other TDS380. (The one that can not be fixed.) Then I will see if it calibrates properly. If not I will likely just live with it. The measurements look very good. Later I can try to do more detailed comparisons with a 2465, TDS360 and then the upgraded TDS340. But so far the TDS380 appears to be performing very well strangely enough.

author: kozard
author_rank: Contributor
timestamp: March 04, 2022, 09:27:56 pm
content: Success! Finally!The Tektronix TDS380 timing calibration passed the first time I tried it with the DS1644 that I desoldered from a different unrepairable TDS380. (I used ChipQuik low temperature Bismuth solder to remove it. I thought it was not going to come out but eventually it did.)I am leaning towards the conclusion that the timing calibration routine will fail if the scope reports "Factory timing cal constants invalid" when it boots. Perhaps those factory timing calibration constants are stored in the DS1644 NVRAM and are wiped out if the NVRAM battery dies. [Perhaps the timing calibration routine can not work without those calibration constants.] So make sure to not let that happen. This would be consistent with someone else's struggles I read about online who also tried to calibrate with a blank brand new NVRAM. I can not be sure that these conclusions are correct but I do know that the scope now calibrates.So I thought my MacGyver homebrew/DIY signal generator was the problem, but it was not.In case it helps someone else a binary image of the DS1644 is attached. (Straight binary file, not HEX file.) You will have to run the other calibrations such as Calibration Voltage Reference and SPC. (They will be different for each scope.)On the other topic: I measured the resistor (built into the ceramic hybrid) on two more attenuators (on a different scope) and they both measured 47.8 Ohms.

author: Labrat101
author_rank: Unknown
timestamp: March 04, 2022, 10:37:51 pm
content: I am pleased that you are now a Happy camperPut the circuit diagram of your MacGyver homebrew/DIY signal generator so it may help some else .I have replaced a lot of those Dallas Chip batteries with a Drimmel and replaced the battery on many scopes and never hada problem re calibrating them . It is possible that that the memory was corrupted I had that once . and the clock showed weirdletters & symbols for the time . I just did a few hard resets and it cleared .I also do have a Fluke Calibrator for scopes Now which does Help .. Got it from a local Lab that closed down . needs repairing .Its Murphy, what can happen will happen its all to confuse us.Anyway pleased all is well .

author: uspeakers
author_rank: Newbie
timestamp: April 27, 2022, 02:54:31 pm
content: Hi Labrat.I see you have lot more experience with the TEK TDS scopes.In this case the TDS350.I replaced the NVRAM battery but, long story short seem to have wiped it.Soledring iron with hot nife was grounded to chasses , so when it touched the + of the battery shorted it to ground sec or two,,,,Now the scope lights come on, but does not boot!!Will the "Maxim Integrated 1Mbit 120ns NVRAM, 32-Pin EDIP, DS1245Y-120+" RS stock no.:189-9196 work?Or am I waisting my time here?Your help will be appreciated.Regards Willie"Labrat"Hi First I haven't worked on a TDS350 . I have only refurbished the TDS340 . THE 350 IS A 200Mhz scope and it a slightly different .I have changed the NVram batteries in HP scopes and the TDS340 . shorting the battery terminals I have done this with no ill effect . Just removing the battery willerase the memory But the NVram ONLY holds the calibration & the Time . There is a bigger possibility that your soldering Iron is not ground protected and you some howput an static pulse on the board . The Boot up is held in EEProm or Eprom which must have got damaged .Or you have another problem .. Try doing a hard reset . There is some times a test point marked RST , if not you will have to study the service manual ..Ask in the forum their is bound to be someone who has more knowledge on the TDS350About the other question."Maxim Integrated 1Mbit 120ns NVRAM, 32-Pin EDIP, DS1245Y-120+" RS stock no.:189-9196 .. Have no never used one .I have always replaced just the batteries in the NVRam never had any other problems .I always use an Isolated soldering Iron .Good Luck sorry I could not help more ."uspeakers"Thanks for reply.I did ground the soldering Iron directly to the scope chassis.I just opened the battery on top for neg and a little on the side to get to the positive.The battery neg also measured 0 ohm towards the chassis so static maybe but very little chance .."Labrat"Grounding the iron to the scope chassis is not a good idea . the scope should be not connected to any thing while underservice . only ground .as in mains if your in the UK or US .I work with an isolation transformer .& or Battery powered ceramic iron .Open a new Post add all your info and what you have done so far . I am sure there is Help .The TDS 300 series the NVram will not stop it booting . it will should boot with a lot of error of cal .The battery maybe shorted and locking the system from booting which is possible remove at least one connection on the battery and try to boot it upThe iron must be grounded to Mains Earth only

author: kozard
author_rank: Contributor
timestamp: April 27, 2022, 03:14:25 pm
content: You might look into seller "qservice-electronics" (ebay). They might have the DS1630.I have not bought from them. I just found it with a search.Perhaps try a google search for "Tektronix 156-3870-00 Genuine Dallas DS1630AB-120 Partitionable NVSRAM"

author: Labrat101
author_rank: Unknown
timestamp: April 27, 2022, 06:29:01 pm
content: @ uspeakers Welcome to the ClubOk, The photo Looks good.. The Black wire Neg .. Looks very close to the OLD Cell Case.Make 100% sure it DOES NOT make contact with the OLD Cell casing .Also Please Note that "PM's" meaning is "Private Message " Its OK I don't care this time .. But another member maybe unhappy being quoted direct from a PM .

author: uspeakers
author_rank: Newbie
timestamp: April 28, 2022, 02:59:15 pm
content: Hi LabratI thought it will be better to add your replies as not to go over those points again in this post..sorryI soldered the wire onto the negative tag and positive case of battery and then lifted the neg tag off were it was spotwelded..So the negative tag was 0 ohm to ground before and not anymore.Measure 2.1v between old bat neg and new bat neg ( old battery was 0.9V)So old bat is not in circuit anymore..

author: uspeakers
author_rank: Newbie
timestamp: April 28, 2022, 03:14:07 pm
content: Hi Kozart.I saw the add on EBAY.I'm still thinking about that route,,Might just do more damage taking that nvram out.Thanks

author: kozard
author_rank: Contributor
timestamp: April 28, 2022, 04:15:35 pm
content: They are hard to remove. I removed a couple using ChipQuik (Bismuth) Low Temperature Alloy and lots of flux and patience. I ended up being able to reuse them. (These are DS1644 from TDS340/360/380.)First use solder wick to remove as much of the Tin-Lead solder. Then use lots of the ChipQuik. Then patiently heat and gently pull. (Takes quite a bit of time.) I used a Hakko knife edge tip.After removal I remove as much of the ChipQuik as possible with wick (and you need flux too). Then I use a stainless needle to clear the holes.If you remove the NVRAM carefully you can clean-up the original leads and test it in a programmer to see if it is working with your new battery. That might tell you if something else is damaged. But removal is a difficult process.

author: Labrat101
author_rank: Unknown
timestamp: April 28, 2022, 05:33:28 pm
content: Quote from: kozard on April 28, 2022, 04:15:35 pmThat sounds like a lot of hard work . I would just cut the legs at board level with small snips and then bend the chip up an do the back .Then there is enough contacts to push into a side holder . or top plug over . then the Nvram is less likely to be damaged by excess heat.An then pull the leg tips from the MB one by one less chance of damaging the PCB .That's Me .I would prefer to loose a chip than screw the PCB tracks pin holes

author: kozard
author_rank: Contributor
timestamp: April 28, 2022, 05:45:37 pm
content: It is indeed difficult and a bit risky. But if you can remove the NVRAM and test it in a programmer you might gain information on what is the problem. If the NVRAM works then that suggests something else was damaged during the work.Both of the NVRAM that I removed were ok and still worked. I was able to read the data and program a new NVRAM

author: Labrat101
author_rank: Unknown
timestamp: April 28, 2022, 05:52:14 pm
content: Quote from: uspeakers on April 28, 2022, 02:59:15 pmBottom, Line you have not said whether it Boots up ??Is it a ya or a Na

author: uspeakers
author_rank: Newbie
timestamp: May 02, 2022, 08:22:21 pm
content: Hi LabratTook a brake and just got back home.. needed it.No the scope does not boot ..only the lights come on , stay on and some relays click.. thats it..Does anyone know to hard reset it..there is a couple of points ..J608 or TP601Cheers

author: Labrat101
author_rank: Unknown
timestamp: May 03, 2022, 10:20:13 pm
content: Hi I have dropped the service manual . unfortunately I can not find a schematic diagram for the TDS350.I only have for the TDS340 360 & 380 .There are differences on the TDS320 & 350 not really sure what . But I do know that on some TDS350 they used adifferent version of the Dallas Non volatile Ram . It was the partitioned type RAM to ROM .Question did it boot before you messed with it ?If yes . Check the legs on the Motorola chip that you did not splash solder on any of the pins . Etc.2) Check the 3 Flash chips to the Left of the Dallas NVram Make sure all the Legs are clean and no bad connections.3) remove the Cal jumper . (Cal Jumper J609 Middle left hand-side)4) try again to reboot .If No it did Not Boot before . You properly have a power supply problem or missing voltages .As I don't have a TDS350 or a schematic diagram I can't really say what the differences are .Load up a photo of the entire board hires .The service Manual gives you all the voltages to check etc .

author: Labrat101
author_rank: Unknown
timestamp: May 04, 2022, 07:38:41 pm
content: Quote from: uspeakers on May 02, 2022, 08:22:21 pmTP602 /601 are a manual reset ..J608 is "" For Diagnostic Test ""Follow the manual ..

author: kozard
author_rank: Contributor
timestamp: May 04, 2022, 08:11:45 pm
content: It probably is not this, but just in case:I have an old TDS 380 with lots of screen burn and when I first booted it with a new NVRAM I thought it was damaged since I saw the LEDs on the front panel turn-on but nothing on the screen.It turned out that it was actually working but too dim to see. I had to turn the room lights off and then I could barely see the display. Then I could go into the display menu and select "bright" for the graticule and text.

author: Labrat101
author_rank: Unknown
timestamp: May 04, 2022, 09:06:16 pm
content: I also said its was not the NVram .. As this has nothing to do with the boot sequence . Unless the NVram data lines are shorted or has an internal short.the Data in the NVram Dallas only holds the Time of any saved screens & time/Date & the Cal . I have the TDS 340 upgraded to 360 was running it without the Batterywithout any problems other than Cal error . On boot the default factory Cal settings are loaded.@ kozardGood point about the brightness easy over looked

author: Darthyson
author_rank: Newbie
timestamp: November 29, 2023, 12:48:53 pm
content: Hi kozard,thanks for sharing your progress building your Ultra Low Cost Calibrator.My tds360 has failed on me with lost calibration data due to a old/defect Dallas DS1644-120 NVram (production year 1996).So right now I'm in the progress of building your Ultra Low Cost Calibrator.Quote from: kozard on February 28, 2022, 04:23:37 pmI have started to rebuild this in eagle (300mV, 80mV, 15mV still missing).Maybe you can take a look at it, since I don't know much about op-amps myself? I am especially unsure about the cut-off-frequency/values of the RC filter (R5, C8) and value-range of thelow impedanceresistive divider for the 80mV and 15mV.

author: kozard
author_rank: Contributor
timestamp: November 29, 2023, 03:40:29 pm
content: The upper half of the last divider was 200 Ohms (metal film) in series with a 100 Ohm 20 turn trimmer. The lower half was 50 Ohms (metal film).I used a 47uF low ESR capacitor to bypass each divider output. You want a good quality capacitor with good (low) leakage current. I like Panasonic.After each bypassed divider I put a 100 Ohm (metal film) & 0.1uF Polypropylene RC low pass filter. (Between the output of the divider and the input of the op-amp buffer.)Each stage has a divider, filter and op-amp buffer.If you are going to the effort of making a PCB keep in mind that my design was something "very quick and dirty" to try to fix a scope which I did not really know if it could be fixed.So if you are putting the effort into a PCB I suggest that you consider looking at the temperature coefficients (of drift) for the initial voltage reference and of the op-amps. The offset of the op-amps is not as big a deal as the drift. Since each stage is trimmed with a 20 turn trimmer what you want is very low drift of the offset.You want to pick a low drift reference and low offset drift op-amps. Also you should pick an op-amp that has low input bias currents (and offset and drift) and generally precise input offset characteristics.It is not a great op-amp but I had on-hand many LM258A:The input offset voltage drift of the LM258A is 15 µV/°C.The LM258 is a low-power dual operational amplifier that has a low input offset voltage of 2 mV, low input offset current of 2 nA, and low input bias current of 20 nA (temperature compensated).The LM258 is pretty noisy however.The fairly low offset voltage drift and input bias current (offset) worked out ok for my one time use calibrator. If you are building a PCB spend some time picking your reference and op-amp carefully. (I assume you are building a PCB because you want to own a calibrator that is not one time use.)

author: kozard
author_rank: Contributor
timestamp: November 29, 2023, 03:44:59 pm
content: Also consider checking out KiCAD for PCB layout.Also if you are not aware JLCPCB has very good prices on prototype PCB. Such as 10x10cm or smaller. If you get into a situation where the PCB costs too much to ship they have thinner options. I often order 10x10cm prototypes (two layers) with a thinner option to reduce the weight. Certain thinner options do not increase the cost for 2 layers but reduces the shipping weight.

author: Darthyson
author_rank: Newbie
timestamp: December 01, 2023, 02:18:12 am
content: Thanks for your fast response and helpful infos. Now my breadboard starts looking like yours.I now get all voltages (1.5V, 0.3V, 0.08V, 0.015V). But I think I'm still missing something about the 50Ohm output resistor.As I'm applying the 50Ohm (R20 in attached schematic), the op-amps output voltage (1.5v) drops to ~0.8V.The dropoff starts at applying ~100Ohm. Raising the op-amps VDD to 12V the dropoff starts at ~85Ohm.As op-amp I'm using TLC271, as I'm like you, had them laying around. Hopefully reading the datasheet correct, they shouldn't be worse then your LM258A.I just draw the schematic in eagle to understand your writings and most importantly to understand the function. Not sure maybe I create a PCB while waiting for my new Dallas NVRAM to arrive.I'm aware of JLCP and KiCad. KiCad is on my learning list, but as a ~20 year eagle user, i often have other things todo

author: kozard
author_rank: Contributor
timestamp: December 01, 2023, 02:45:55 am
content: The 50 Ohm is not on the output of the op-amp. The 50 Ohm is part of the divider before the op-amp. The divider consists of an upper half (resistor) comprised of one metal film resistor and a 20 turn trimmer in series. The low half of the divider consists of one metal film resistor (which is 50 Ohms on the last stage). The output (of the divider, not the op-amp) is bypassed with an electrolytic and then filtered by the RC low pass filter. Then the op-amp buffers the output. This is one stage. The output of the op-amp unity gain buffer feeds the next stage.So each stage is: Input Voltage >>> Trimmable Resistive Divider >>> Electrolytic Bypass >>> RC Low Pass >>> Unity Gain Op-Amp Buffer >>> Output VoltageEach stage is similar except the resistor values get lower and lower. Each stage has lower and lower resistor values since otherwise the currents through them will get lower and lower relative to the bias currents for the op-amps.

author: Darthyson
author_rank: Newbie
timestamp: December 01, 2023, 03:02:01 am
content: Quote from: kozard on December 01, 2023, 02:45:55 amOK, thats how I understood your last post, then checked with your breadboard picture and changed it back to a decoupling capacitor.Regarding the 50 Ohm, I meant the 50 Ohm terminating resistor which needs to be applied at the channel 1 input BNC of the oscilloscope which is the op-amps output of each stage?

author: kozard
author_rank: Contributor
timestamp: December 01, 2023, 11:51:03 am
content: Is your op-amp going into current limit? Perhaps that is the problem. Which output voltages give this problem? What is the current (Vout/50 Ohms) at the output voltage where you see this?Is your power supply capable of providing that output current? (What is your power supply?)

author: Darthyson
author_rank: Newbie
timestamp: December 06, 2023, 07:14:07 pm
content: Sorry for the late response. I had to wait for the delivery of a few parts.My op-amp was current limited by VDD, just as you suspected. I had to increase VDD to 10V and was successful on the first try.Thanks again. Now comes the difficult timing calibration...

author: kozard
author_rank: Contributor
timestamp: December 06, 2023, 07:24:46 pm
content: Great. The voltage calibration does not seem so hard in the end. Even that TLC op-amp can do it. It is noisy but at least it is low input bias current.Hopefully you have a suitable clean and fast-edge generator for the timing calibration. Mine were all too old and slow hence the DIY circuit I built into a 50 Ohm connector housing.

author: Halmir
author_rank: Newbie
timestamp: January 17, 2024, 03:08:04 pm
content: Hi,I am about to buy a TDS 360 offered as defect.The seller povided the following screenshot with the error messages:Do you think this can be fixed by changing/modifying the NVRAM chip, or is there more and I shouldn't buy it ?regards, Halmir

author: kozard
author_rank: Contributor
timestamp: January 18, 2024, 02:15:46 pm
content: I think it is possible. However carefully examine the scope inside and out before you start. For example, one that I worked on turned out to have additional damage to the attenuators. Another I bought and opened up turned out to have physical damage around the NVRAM because someone else have previously tried to remove the NVRAM. At this age many being sold are in quite poor condition with multiple problems.Also make sure that you have the necessary equipment to generate the calibration voltages and to do the timing calibration.Finally make sure you can get a good/genuine NVRAM before you start.

author: Halmir
author_rank: Newbie
timestamp: January 19, 2024, 05:48:10 pm
content: Thanks for the reply. I carfully read the hole post and came to the conclusion to build the DIY DC calibrator as you and Darthyson described. For the timing calibration I will likely buy a UNI-T 962E waveform generator. This generator can also output adjustable DC levels - would it be possible to do also the DC calibration with this unit ? Regarding the Dallas chip: I plan to leave the origin chip in place and do the 'mod' with replacing the battery ?

author: kozard
author_rank: Contributor
timestamp: January 19, 2024, 06:50:22 pm
content: I don't know anything about the UNI-T 962E waveform generator. From a brief glance I would be concerned that it might not have the resolution to produce low mV calibration voltages. Maybe someone who has used the 962E could comment but in general I would not expect to use such a waveform generator for voltage calibration.Also you should carefully check the Tektronix calibration procedure and look at the rise time requirements for the generator. Then check the specifications for the UNI-T 962E waveform generator to make sure it is suitable.

author: Halmir
author_rank: Newbie
timestamp: January 20, 2024, 01:20:14 pm
content: I came to the decision with the UNI-T 962 because Labrat101 described it in the post ? I read the Tek instructions in the service manual carefully, but couldn't find any specs regarding the rise time ? It would be very appreciated if you could provide me with a step by step instructions how the calibration procedure has to be done.

author: kozard
author_rank: Contributor
timestamp: January 20, 2024, 01:57:54 pm
content: Do you have the manual "TDS 340A, TDS 360 & TDS 380 Technical Reference"?The required equipment listed in 5-1 is the "Wavetek 9100 Calibration System with Option 250". Specifications are tr ≤ 10 ns, amplitude ≤ 1 Vp-p, Variable amplitude to ±10 V, accuracy to 0.05%. (From table Table 5–1: Adjustment equipment.)Chapter five goes through the process step by step.

author: Halmir
author_rank: Newbie
timestamp: January 24, 2024, 03:24:59 pm
content: I just received my TDS 360 and played around a bit. I set the actual date and time and strangely enough it keeps it. So I do not understand why it has lost all the calibration data ? All in all it is in very good condition, but I now don't know if i should going to 'repair' / replace the DS1644.