TDS210 recall mod - Page 1
Forum section: electronics / testgear

author: gkmaia
author_rank: Frequent Contributor
timestamp: February 10, 2020, 07:32:16 pm
content: I am curious about the recall mod. I am aware the issue is the PCB trace from the BNCs GND to IEC Earth is too weak, therefor a mod is required improve this connection.I've had several TDSs 210 and 220. The only part that is not listed on the OEM exploded view is a little clip that shorts the main PCB ground to the LCD chassis. I suspect that was the recall mod.From factory the LCD chassis is shorted to the metalized case by the conductive pad #16. There is also a braided tube #12 does short the lower shield (that has pretty strong connection to BNCs) to the metalized case.So if the intention of the little clip mod was to short the PCB GND to the case that is redundant as the braided tube does the same.Also there is no connection between the metalized case and the IEC ground or the PSU. So makes no sense to short it to the case as there is no path between the case and the ICE.As I said I've probably 20 of these TDS in my hands (some within recall range, some out of the recall range) in the past and I have seen some with that extra clip and some without.Nothing else... no soldered wire between the PCB ground and the IEC as some suggested.So I am wondering... what is that mod about? Or how this clip can somehow ground the PCB GND to earth if there is no route to the IEC earth from there?!

author: tautech
author_rank: Super Contributor
timestamp: February 10, 2020, 08:14:24 pm
content: I had a TDS210 too and IIRC there was a general recall in which the main PCB was replaced as in early ones a trace could fuse before mains supply in the event of a mains ground loop. Yes a heavy earth link could be connected to repair or prevent the PCB trace from fusing I suppose but it's a bit of an ugly bodge.If the SN# is after the recall and there's continuity between BNC's and IEC plug earth it should be safe, if not provide a mains earth path !The LCD grounding clip maybe just an evolution of design/manufacturing to meet later regs where all metal parts (LCD frame) need be grounded for safety. As the LCD frame is not really accessible, is the clip really needed ?

author: tautech
author_rank: Super Contributor
timestamp: February 10, 2020, 09:11:14 pm
content: And oh, they talk about Siglent chassis rust but WTF:Not the first Tek I've seen with rust !

author: gkmaia
author_rank: Frequent Contributor
timestamp: February 10, 2020, 09:24:35 pm
content: That is actually Sharp's fault. The rusted bit is the LCD chassis.

author: Caliaxy
author_rank: Frequent Contributor
timestamp: February 10, 2020, 09:38:23 pm
content: Also, keep in mind that we are very likely seeing a ~24 year old oscilloscope stored who knows where.

author: gkmaia
author_rank: Frequent Contributor
timestamp: February 10, 2020, 09:40:54 pm
content: I've emailed Tek to find out more about it or other ways to identify the mod apart from the label.Lets see if they reply...

author: lowimpedance
author_rank: Super Contributor
timestamp: February 10, 2020, 09:42:07 pm
content: Quote from: Caliaxy on February 10, 2020, 09:38:23 pmIt does certainly appear to be the result of 'some' fluid ingress.

author: wraper
author_rank: Unknown
timestamp: February 10, 2020, 09:48:29 pm
content: Quote from: lowimpedance on February 10, 2020, 09:42:07 pmActually there are water drops under display glass.

author: tautech
author_rank: Super Contributor
timestamp: February 10, 2020, 10:15:17 pm
content: Quote from: gkmaia on February 10, 2020, 09:40:54 pmIs that not clear here:https://www.tek.com/service/safety/tds210-tds220

author: ataradov
author_rank: Super Contributor
timestamp: February 10, 2020, 10:27:52 pm
content: Is not this from the scope that got dragged through a mud race? For that the condition is pretty decent.

author: gkmaia
author_rank: Frequent Contributor
timestamp: February 10, 2020, 11:03:26 pm
content: Quote from: tautech on February 10, 2020, 10:15:17 pmNot really. According to this page the only way to identify is they have been modified is by the external label. But the label fades, gets removed etc...If the fix is a replacement PCB the replaced PCBs will have a different identification code. That is what I asked them. Also asked them if there are any other visible clue apart from the label that suggests is had been modified.If the fix is something else and not a PCB replacement.

author: gkmaia
author_rank: Frequent Contributor
timestamp: February 10, 2020, 11:07:21 pm
content: Quote from: ataradov on February 10, 2020, 10:27:52 pmExactly! And even after that the main logic and acquisition still worked. The only thing that failed were probably the LCD/drivers.

author: tautech
author_rank: Super Contributor
timestamp: February 10, 2020, 11:18:25 pm
content: Quote from: gkmaia on February 10, 2020, 11:03:26 pmThe fix was a PCB replacement. Period.Anything else was a user bodge job......which if you know what you're doing would be safe anyways.I remember at the time researching the one I had finding various sites where it was discussed ad nauseum and everyone recommended they be sent back for the new PCB. I didn't have to as my SN# was later than the recall although I had to replace the 2 post BNC's as they commonly bust free and are suspended by only the center conductor.I beefed their mounting up some with a copper strap over them soldered to the ground plane and the only way they would bust after that was to break the PCB !Luckily scope manufacturers have learnt from Tek's error and now mostly use bulkhead type BNC's properly secured to the chassis with a nut.

author: Nprod
author_rank: Contributor
timestamp: February 11, 2020, 01:06:24 am
content: The clip is just there to connect the LCD's metal frame to the mainboard's ground. I personally don't like it because it bends the PCB quite a bit, so i soldered a screw-terminal lug to the frame and ran a wire directly from the IEC connector to it.

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 11, 2020, 04:11:14 am
content: You can always just solder a stonking great earth wire to the PCB like I did once.