Calibration TDS380 - Help me ! - Page 1
Forum section: electronics / repair

author: chihaxinh
author_rank: Regular Contributor
timestamp: November 26, 2016, 10:40:58 am
content: Hi allIt's bad day , to day i desoldering NVRAM of TDS520B and reading content. Everything OK , and i thing backup TDS380 it's good ideal .After desoldering DS1644 Dallas NVRAM of TDS 380 and read content in progamers . All data i have it's rubbish, i thing nvram fail, after that i solder socket to pcb , and put nvram go back.Power on TDS380 display calibration fail... I reading server manual and runing step by step, but i don't understand about DC Signal ?Calibration need DC Signal for DCV Calib . Need -1.5V +1.5V -0.08 + 0.08V and -0.015 , +0.015V.I try using signal generator have DC out signal and even try DC Power Source ( E3632A ) not help . Allway display fail calibration.How to calibration TDS380 , what equipmenti need for calibration ?Link for TDS 380 Service Manualhttp://jumi.lut.fi/elko/TDS340A/tds340a_service.pdfThank so much !Best RegardsNam Nguyen Hai

author: chihaxinh
author_rank: Regular Contributor
timestamp: November 26, 2016, 03:49:15 pm
content: Hi everybodyI finish calibration 3 option . Signal Path , VDC Reference , External Trigger ... But cant pass Compensate Timing .I reading carefully but don't understand in service guide .QuoteIt's mean i need1. Signal generator have PWM negative ?2. 1ms meaning 1khz ?3. Why in guide we need setting -1V ( but in guide show 50mV / Div - Have 4 Div like about 200mV ) ? What it's 50R bnc terminal ? I dont have 50R BNC and i using osc probe and switch to x10 mode.I have Tabor 8022 FG have square , positive square , negative square generator. But i thing it's not fast enough for pass step.Many thank so much !Best regardsNam Nguyen HaiCan anyone help me to pass step timming calibration ?

author: tautech
author_rank: Super Contributor
timestamp: November 26, 2016, 06:35:31 pm
content: The SM will have a list of all equipmentrequiredto complete the calibration and while you can substitute some of them they should beclosein spec to the listed equipment. I couldn't say for sure about substituting a probe for a 50BNC connection but it seems to me this might be a problem especially if when in Cal mode the scope knows or expects a 50input selection has been made. If you are using a probe as the connection the amplitude of the signal will not be what the scopeexpectsto see.Get a 50BNC to BNC cable, they're not expensive.Also you need to check the rise time of your FG is similar to the Service manual specified signal source. Not hard if you know what the instrument is, just Google for its specs and compare with the FG you have.

author: chihaxinh
author_rank: Regular Contributor
timestamp: November 27, 2016, 05:25:35 am
content: Quote from: tautech on November 26, 2016, 06:35:31 pmMany thank tautechI thing problem in rise time of FG , i make some caculator with formular BW = 0.35 / Tr , my osc have 400Mhz BW , so Tr need multiple ten time ==> Tr need 4Ghz .With caculator , i need Tr - rise time around 87ps . My FG have only 10nS rise time in 250ns Time/Div.Ok , if i have good FG i can calibration , but i using for mearsurement audio, i thing Compensate Timing calibration fail it's not critical .I thing hard in calibration step it's rise time + negative pulse (all schematics diy project on internet talk about square pulse - not negative pulse ).Many tks for your supportBest RegardsNam Nguyen Hai

author: tautech
author_rank: Super Contributor
timestamp: November 27, 2016, 06:34:27 am
content: Quote from: chihaxinh on November 27, 2016, 05:25:35 amSo read section 5.1 of the Service manual again:Generator,Fast-rise Steptr ? 10 ns;amplitude ? 1 Vp-pThe Wavetek 9100 is specified as it can do many things like the waveforms required and the precision voltage sources. But your generator meets the rise time spec.It is my belief the -1V is a misprint, it should read the amplitude as stated above.But more important is the signal fidelity, that is whyto the CH 1 input through a 50R coaxial cable and a 50R terminationis stated. Without a 50connectionandtermination any fast rising edge will ring and any probe used for connection will cause the ringing to be excessive.More reading on correct termination for pulses and square waveforms is in this thread:https://www.eevblog.com/forum/testgear/show-us-your-square-wave/Please, save yourself more trouble and get a ~3ft (1M) 50cable and 50BNC termination.I would not attempt to do this calibration step without them.

author: chihaxinh
author_rank: Regular Contributor
timestamp: December 01, 2016, 08:08:09 am
content: Many tks tautechAfter buy BNC 50R termination , and using 50R coaxial . I can't pass timming calibration .I thing i have wrong setting , you said 1V pk-pk , but i try setting not help . In service manual saidQuoteIn Figure 5-2 display only 4 div - like about 200mV peak peak .But when setting to 200mV peak peak - i can't pass . Relay sound click click on 2Ghz sample rate and fail .I thing my FG not accurate and rise time don't fast like requirement .Do you have any diy project to create square wave with fast rise time ?Thank so much !Best regardsNam Nguyen Hai

author: tautech
author_rank: Super Contributor
timestamp: December 02, 2016, 04:03:22 am
content: All I can suggest from what I see in your photos is to follow the instructions more carefully. Waveform amplitude matches the scope OSD, scope settings and the FG settings and the OSD scope risetime shows the rising edge to be more than fast enough to meet the required Calibration risetime spec.I do know some scopes are "touchy" if you don't follow the Cal sequence step by step.Try from the start again after some study to check that you are not making a mistake.Also move the 50termination to the scope end of the BNC cable, that should reduce the overshoot.