Tektronix TDS 210 oscilloscope - Page 1
Forum section: electronics / general

author: luminol
author_rank: Newbie
timestamp: December 09, 2010, 11:45:04 am
content: Hi all,I'm Enrico from Italy !Congratulations Dave, yours videos are very interesting and help me to learn English language.I have bought a TDS 210 oscilloscope from Ebay few days ago, and I would know if it's a valid unit for our projects.It has also the FFT module, for advanced mesurements.Yesterday I noticed that this model of Tek's oscilloscopes is subject to a recall, because of an issue in the ground connection of the input BNC.Tek's document says:"In June 1998, Tektronix began the recall of its model TDS 210 and TDS 220 oscilloscopes. We initiated this voluntary program when it was determined that certain incorrect use of these products could cause the ground connection to fail, potentially exposing the user to risk of serious personal injury or death.This ongoing recall applies to TDS 210 and TDS 220 oscilloscopes with serial numbers falling within one of the following ranges:TDS 210:B010100 to B049399BU10000 to BU50199C010000 to C010879TDS 220:B010100 to B041059BU10000 to BU50199C010000 to C011174Tektronix has determined that certain incorrect use of our model TDS 210 and TDS 220 oscilloscopes (which are subject to the recall) may cause the ground connection to fail on these products, potentially exposing the user to risk of serious personal injury or death. If a user incorrectly connects a probe ground lead to a voltage source, or incorrectly touches the ground ring near the probe tip to a voltage source, a circuit board trace in the product's electrical ground path may open. Thereafter, the product may appear to function normally; however, the unit is no longer properly grounded. Subsequent use of the product could then result in a serious electrical shock to the user. We are conducting a recall to prevent this possibility of injury to Tektronix customers."My personal one should be sent for the modify, but I don't want that !!The modify consists to add a 1,5 mm copper wire between the ground of the input BNC and the ground of the IEC power connection.Can I do this operation myself ?

author: scrat
author_rank: Frequent Contributor
timestamp: December 09, 2010, 12:00:13 pm
content: Hello Enrico, this is Sandro, from Italy too. Welcome!This is an easy mod you can do yourself, since it does almost not affect the signal path. To be sure not to create additional paths to ground, I think the best way should be to run the cable near the existing shields or the metal case (if there is one), physically following the original way to ground.

author: luminol
author_rank: Newbie
timestamp: December 09, 2010, 12:36:52 pm
content: Hello Sandro !Thanks for the fast reply, I'll try follow yours advice !!I will let you know soon...

author: luminol
author_rank: Newbie
timestamp: December 11, 2010, 10:19:07 pm
content: Hi guys !I have successfully done the mod to my oscilloscope...What do you think ?

author: Unknown
author_rank: Unknown
timestamp: December 13, 2010, 10:06:52 am
content: Luminol, wasn't the circuit board grounded in the first place? I see no ground to the modded board directly from the IEC plug. Is that just the view angle?On a different note, the BNC connectors used on the main board of the TDS 210 and TDS 220 have a weakpoint. The shell of the BNC connector is soldered to the board with two pins that are part of the main connector. These break if force is applied when inserting a BNC probe. The connector itself is not solderable so to repair it you need a new connector. Be careful.After some research I found out a suitable replacement part that I list here if anyone has this issue.http://uk.farnell.com/jsp/search/productdetail.jsp?SKU=1654643

author: luminol
author_rank: Newbie
timestamp: December 13, 2010, 12:07:17 pm
content: Yes there was a main ground cable connected to the IEC with a hole in the circuit, you can see it in the first picture.Thanks for the link about the connector repleacement Alex !!.

author: scrat
author_rank: Frequent Contributor
timestamp: December 13, 2010, 04:32:12 pm
content: I guess the old connection to ground was the issue Tektronix warned for, since it is not so good to rely on a pcb track for the BNC connectors safety grounding.Maybe a mechanically weak connection between the BNCs and the board can be unsafe too, even if one can easily recognize such a case. Soldering a wire bridge between each BNC connector and then to ground should be safer, unless there isn't a solid metal contact between them through the front panel.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 13, 2010, 05:04:50 pm
content: Wouldn't that wire add a possible path for noise and possibly cause ground loops?

author: Unknown
author_rank: Unknown
timestamp: December 13, 2010, 06:09:04 pm
content: It seems the badly designed BNC connectors and Earth grounding using PCB traces was the reason for the recall.A ground loop is indeed formed. However it is in the same piece of equipment and both ends of the loop are connected to the same point: the IEC connector's ground. Therefore the loop would be very small and will be not generate significant noise voltage. In any case, you can place the second ground conductor close to the existing ground wire to minimise induced noise voltage.

author: scrat
author_rank: Frequent Contributor
timestamp: December 13, 2010, 06:59:25 pm
content: Although I'm not an expert, IMO a safe design would have had all the BNC connectors mechanically screwed together to the metal case, which would have acted as a shield. If the metal case exists, an option could be to connect BNCs only there. If the case is not made of metal, then the story is different, but connecting only one BNC to groud is not that safe, if they are easy to break.

author: 1955jetdriver
author_rank: Newbie
timestamp: September 09, 2015, 04:09:12 am
content: Firstly I have one of the "faulty" Tek TDS210's. I acquired this from the BAY where it was advertised for AUD $350 plus postage. It was then readvertised for $100 plus post when seller found that it was subject to recall and couldn't verify if it had been done. My lucky day.Upon receipt and having found these posts I dismantled the scope and found that there WAS NO CONNECTION TO THE EARTH PIN ON THE IEC RECEPTACLE. THE EARTH FROM THE SCOPE PCB ONLY WENT to THE PSU PCB. THIS WAS VERY DANGEROUS AS THERE WAS NO EARTH TO THE IEC ESRTH AT ALL. As someone earlier noted there is also a problem with the BNC connectorswhereby they fail and break away from the pcb thereby leaving no mechanical connection to earth at all.The solution I devised was to do the following.1. Connect both Channel 1 and Channel 2 BNC earths to a specific size earth cable as per Tektronix spec.2. Use a 300 mm piece of RG 6 with the dielectric and silver shield pulled out and the earth cable inserted in the wire shield inside the outer cover to offer some protection from interference from the new cable.3. Route this new cable to the rear of the IEC receptacle and solder to the earth pin.4. Not having some new BNC connectors to hand to replace ones with broken pins, I removed the broken ones and the external trig one which was not broken. Then cleaning them up and filing the broken ones where the pins had broken off and cleaning ISO and scrubbing around the pins and scratching around the broken pin areas, which is a must to remove the crap there, I then using a very hot iron soldered the whole bottom of the BNC pcb contact area. If you have cleaned the pin area properly you will achieve a total coverage of the bottom this is most important. Then scratch around the pcb area where the pins go thru andclean the contact area well and tin this area make sure the holes fill with solder.5. Using a fine point iron solder the BNC pin back into its hole, ensure that the BNC is tilted slight to the rear at this point as you should have a largish size solder pad where the pins were originally.6. Next using a very hot large surface area iron (about an area of 9 mm2) flat. Press down with the iron towards the rear of the BNC and it will heat the BNC quickly and you will see solder come out the sides.7. Maintain pressure with another metal object to remove the heat quickly, after removing your iron. Cleanup around BNC with a smaller iron.8. This will leave you with a very strong mechanical connection to the pcb if done properly. I am going to do this to the new BNC when they arrive also as the 2 earth pins are die cast and not very strong, especially if you remove your Ch 1 & 2 BNCs regularly as I do for RF work.9. I must STRESS that you must maintain correct and PRECISE alignment of the BNCs when replacing them, this is due to the fact that there is no space for them to be slightly out when replacing them in the plastic mounting area. SO BE VERY CAREFUL WITH THE ALIGNMENT. And don't distort the pcb either when soldering. It won't sit properly when replaced otherwise and Tek only mount them with the plastic clip which by now you will have become quite familiar with.10. I used some heatshrink at the ends of the wire to prevent any of the shield wires from touching anything also.11. If you use the external trig BNC I would suggest you supply an earth jumper to that from the CH 2 BNC.12. Make sure that the jumper wires go on top of the tin shield already attached and not to the front of the shield, there is no free space in front as this is where the pcb clips into the plastic frame.13. Run the new earth up onto the existing earth wire and across to the rear of the IEC cut to length and prepare wire end then solder to pin.14. If you are slightly out of alignment and I mean very slightly you can always Dremel the area where the BNC connectors sit in the plastic, it is because of this and for safety reasons it is good to totally dismantle the plastic housing of the scope pcb the power pcb and the screen itself. Leaving you with only the bare plastic. It's easier to handle when checking the scope pcb fit etc.In the photos supplied by Luminol who did his conversion he has soldered his earth to the external trig BNC, I don't recommend this as you are still relying on the pcb tracks for an earth. Done the way I have described you have a mechanical connection to the BNC earths that are the most important, the CHANNEL BNCs.I'm sorry I can't post photos of my repair but I have already reassembled and tested the TDS210.However if someone really wants to see some photos let me know and I will post some when I replace the BNCs when the new ones arrive.Peter

author: tautech
author_rank: Super Contributor
timestamp: September 09, 2015, 10:49:22 am
content: Welcome to the forum Peter.Yes these are common faults in the 210 and 220.Thanks for sharing your fix.One I fixed BNCs in, I also strapped the new ones with 1mm copper wire and soldered them to the adjacent GND plane.I'd add that around the BNCs the GND plane is substantial and IMHO a quite appropriate place for the mains GND connection. From the BNCs to the spade terminal where the PE connects AFAIK the plane is somewhat finer and fuses open, hence the general recall.

author: Nprod
author_rank: Contributor
timestamp: September 24, 2018, 04:41:54 pm
content: Does anyone have a more concise explanation on what the recall fix is exactly? 1955jetdriver's guide is pretty hard to follow without pictures and the way it goes off on a tangent about how to replace the BNC connectors (which i hear is another common fault with these)I have a "post-recall" TDS220 and from what i can gather the only modification is that they moved one end of the ground wire from the hole in the power supply board to the ground pin on the IEC socket. There is also a metal clip that connects a screw hole on the mainboard to the metal frame of the LCD, not sure if that's also part of the fix. It's held on there with enough pressure to bend the PCB which doesn't look like a good idea to me. I saw a video on youtube where they soldered the ground wire directly to the plated-through screw hole, but i'm looking at the PCB here and that part is mostly isolated from the large ground plane except for 4 small "tabs" which connect them.

author: tautech
author_rank: Super Contributor
timestamp: September 24, 2018, 07:16:35 pm
content: Quote from: Nprod on September 24, 2018, 04:41:54 pmAll that matters is that there is a mains ground link to the BNC'sandit's electrically robust enough to fuse/trip the mains supply in the case of a ground loop. Later units had the ground trace to the BNC's beefed up so it wouldn't fuse in such situations.