TDS3014 fails aquisition and SPC  - Page 1
Forum section: electronics / testgear

author: Abel
author_rank: Newbie
timestamp: November 15, 2021, 11:11:31 pm
content: Gentlemen,Got this scope for decent price; came to me as described above. After further examination it shows that CH2 is not working (no trace movement when exercising Position) and signal shows on screen only for 10 mV and bellow, distorted (clipping).I disassembled the scope (I'm familiar with this family) and started a cold verification, measuring resistance toward GND of the pins of the hybrid modules.There seems to be a key for pin #1, looking from the solder side, at the left, lower side when BNC inputs are close to you and Timekeeper is somewhere at 12 o'clock (pad of that pin #1 shows square, opposed to round for all others).I'm counting 26 pins on the left side, 8 at the top and 26 other pins on the right (not all are populated, but for consistency...)Long story short, pin 22 and 28 are 696 ohms to GND, both; these pins are shorted (assumed on PCB) for all modules, but resistance supposed to be around 18K (as that for for all other modules); furthermore, from each pin there is a resistor going somewhere to the IC. From pin 18, the other side of the resistor shows 159 ohms (again, around 18k for all other modules), so, bad IC on the module 2. The hope is that this is the only issue (value of the two resistors, in hundreds of ohms, should protect a potential output from another silicon device, worst case current is bellow 10 mA).I have a TDS3012 that has a vertical line on the right side of display (assumed a bad memory location, an entire row or column?) that I'm prepared to sacrifice for the greater good; problem (not issue) is how could I remove the module from the donor? I can completely sacrifice the one on 3014, as definitely not good, but the whole task seems close to impossible. I read here and there that people have tried this (no mention about success) but I'd like to hear how they've done it.For the hybrid module a vacuum de-soldering station is certainly a must (I don't have, have to find); but removing the bracket that holds BNCs... not easy: some soldering points are under the hybrid and hybrid pins are under the bracket.Hope to hear your opinion and guidanceAB

author: coromonadalix
author_rank: Super Contributor
timestamp: November 16, 2021, 01:22:30 am
content: you have episodes 564 and 565 who could help ?

author: voltsandjolts
author_rank: Unknown
timestamp: November 16, 2021, 02:17:52 pm
content: Quote from: Abel on November 15, 2021, 11:11:31 pmI replaced a TDS3034B input hybrid module some years ago.As you say, desoldering is the tough part but only on the donor scope, where damaging the motherboard is not a problem. Just don't damage the module, check every pin is loose before pulling the module.On the scope to be repaired, just cut all the (broken) module pins, then desoldering individual pins is easy.IIRC I used a TDS3014 (non-B) module in the TDS3034B, and a had to put a wire link across one pair of pins of the new module. (hazy memory).

author: Abel
author_rank: Newbie
timestamp: November 16, 2021, 03:08:57 pm
content: Thanks to those that have answered; coromonadalix, I've seen those two episodes (and probably everything related to TDS3000 family, both on YouTube, here, on this forum, and also on TekScopes). Unfortunately there is nowhere any details about removing the modules.voltsandjolts, thanks for confirming that it is possible; you may be right about the wire link, I believe it's about what model the scope is; I noticed myself differences in resistance readings from module to module (and I mean those modules that seem to be working fine in the scope - maybe I didn't verify if AC and DC make a difference, e.g.) - possibly some default settings for CH #1 that are not the same for other channels. Should be interest, I could publish my readings here."On the scope to be repaired, just cut all the (broken) module pins, then desoldering individual pins is easy.", agree with that, but I was hopping I could go by without removing the iron cage around the modules.If someone else could provide additional information I would be more than interested to see it; at this moment I'll start preparations for the procedure (it'll take a while).Thanks everybodyABP.S. Interesting fact, on this scope, module for CH #1 is different than those for other channels in that the two relays close to the bottom edge have a blue colour; the third one and all relays on the other modules are whitish; not sure about significance of that... And the scope is an early SN

author: voltsandjolts
author_rank: Unknown
timestamp: November 17, 2021, 10:07:30 am
content: Quote from: Abel on November 16, 2021, 03:08:57 pmSounds like CH1 module has been replaced sometime in the past.For some odd reason, when doing slightly dodgy probing with a single channel, I use CH4 instead of CH1.My logic is that I would find a broken CH4 less annoying than a broken CH1Purpose of each relay explainedhere.

author: Abel
author_rank: Newbie
timestamp: November 17, 2021, 02:35:08 pm
content: There is no sign of work done in the past to module for Ch#1 (certainly would be visible).I made measurements on every pin on all four modules; and thanks for the link with explanation of purpose for each relay (I missed that post, didn't look for TDS3034...).I started a list with "to do..." before doing anything and, for sure, it's a long roadAB