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@ kozard
That 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 -
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? -
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.
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Hi I noticed you are using an electrolytic cap
Try replacing it with a ceramic or non polarized
Poli cap as you need a fast rise 1ns on the 380
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Also, did you check all the small smd caps
On the main board. After you cleaned, there could be some dirt ,gunk ,underneath the caps
Putting 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.
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The capacitors are:
560uF Panasonic SEPC Series Aluminum Organic Polymer (Silver Can)
220uF Tantalum (Black)
22uF Ceramic 1206 X5R
10uF Ceramic 1206 X5R
1uF Ceramic 1206 X7R
The 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. -
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. -
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.
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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 chance
Jon -
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 numbers
Also 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 to
match your pulse . the setting have to be set first then the signal
The 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 be
all 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 >10ns
you 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
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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.
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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."? YES
Your screen MUST LOOK LIKE THIS . No exceptions
(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.
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
The Dallas can be blank when the scope boots it loads the setting into the VRam
PS yes your missing the bottom line the screen must show exactly as per the manual with the menu at the bottom
That should work the setting look good do the factory recall and make sure it says ok -
Quote from kozard
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."?
YES
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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.
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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.
Your Signal Looks 100% correct and is OK .
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.
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 acknowledgement
yours is not doing it . Not sure why . I think that the scope has still got another Problem .
Maybe a bad ceramic timing cap . -
Question what is this resistor bodged over channel 1 input . this may well be messing up your Cal
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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.
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If this is the case did you also check the relays as well . .. you defiantly have other problems with this scope
It 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 -
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. -
That is a different TDS380.
Ok 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 smd
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.
caps you have for sure got a few bad or cracked . I would recommend using in circuit tester . DER EE DE5000 LCR or similar
or 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 cracked
ceramic 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 15pf
cap 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 . -
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. -
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.
Please look at the schematics of the 380 and you will see .
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.
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
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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.)
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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 ..yes
have you checked the the resistance on the BNC it should read 1meg between center pin & ground . and 5volt from BNC outer to
the 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 as
the 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 again
Update edit replace that cap as well try 1.0 uf
Edit 2 typos sorry -
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. -
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.