Calibration TDS380 - Help me !

[chihaxinh]

Hi all

It'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 Manual
http://jumi.lut.fi/elko/TDS340A/tds340a_service.pdf

Thank so much !
Best Regards
Nam Nguyen Hai

[chihaxinh]

Hi everybody

I 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 .

Disconnect the DC calibration generator and connect the –1 V fast rise
output of a calibration generator to the CH 1 input through a 50R coaxial
cable and a 50R
  termination (Item 2).
15. Set the calibration generator to output a 1 ms, fast rise signal; set the pulse
amplitude to 50%.
16. Press SAVE/RECALL SETUP. Press the main menu button Recall Factory
Setup; then press the side menu button OK Confirm Factory Init.
17. Press AUTOSET. Then adjust the vertical POSITION control to center the
waveform on the screen so that the trigger arrow is at the center graticule, set
the VOLTS/DIV to 50 mV, and set the SEC/DIV to 250 ns. This should
result in a waveform similar to the one shown in Figure 5–2.

It's mean i need
1. 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 regards
Nam Nguyen Hai
Can anyone help me to pass step timming calibration ?

[tautech]

The SM will have a list of all equipment required to complete the calibration and while you can substitute some of them they should be close in spec to the listed equipment. I couldn't say for sure about substituting a probe for a 50 BNC connection but it seems to me this might be a problem especially if when in Cal mode the scope knows or expects a 50 input selection has been made. If you are using a probe as the connection the amplitude of the signal will not be what the scope expects to see.
Get a 50 BNC 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.

[chihaxinh]

The SM will have a list of all equipment required to complete the calibration and while you can substitute some of them they should be close in spec to the listed equipment. I couldn't say for sure about substituting a probe for a 50 BNC connection but it seems to me this might be a problem especially if when in Cal mode the scope knows or expects a 50 input selection has been made. If you are using a probe as the connection the amplitude of the signal will not be what the scope expects to see.
Get a 50 BNC 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.

Many thank tautech

I 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 support
Best Regards
Nam Nguyen Hai

[tautech]

I 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 support
Best Regards
Nam Nguyen Hai

So read section 5.1 of the Service manual again:

 Generator,
Fast-rise Step
tr ? 10 ns;
amplitude ? 1 Vp-p

The 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 why to the CH 1 input through a 50R coaxial cable and a 50R  termination is stated. Without a 50 connection and termination 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) 50 cable and 50 BNC termination.

I would not attempt to do this calibration step without them.

[chihaxinh]

Many tks tautech

After 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 said

Press AUTOSET. Then adjust the vertical POSITION control to center the
waveform on the screen so that the trigger arrow is at the center graticule, set
the VOLTS/DIV to 50 mV, and set the SEC/DIV to 250 ns. This should
result in a waveform similar to the one shown in Figure 5–2.

In 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 regards
Nam Nguyen Hai

[tautech]

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 50 termination to the scope end of the BNC cable, that should reduce the overshoot.