TEK TDS3014B defect - Page 1
Forum section: electronics / repair

author: StefanF
author_rank: Contributor
timestamp: April 09, 2020, 12:05:32 am
content: Hello,When scope is switched on, the start screen appears for half a second and then the screen becomes white.The fan is spinning and the scope responds when pushing the buttons zoom, delay, single seq, autoset, B-trig and coarse (leds turn on).Anyone who as experience with this fault?Thank you in advance

author: james_s
author_rank: Super Contributor
timestamp: April 09, 2020, 05:46:47 am
content: What happens if you press the Hardcopy button with a disk in the drive? Does it respond and write something to the disk? Since this is a B series I believe there is also a network port that hosts a webpage you can access. It's possible the problem is just something with the display or connection to it.

author: StefanF
author_rank: Contributor
timestamp: April 09, 2020, 08:02:31 pm
content: @ James: Thank you for the responseThe floppy however is not responding when i push the print button

author: james_s
author_rank: Super Contributor
timestamp: April 09, 2020, 09:22:53 pm
content: Assuming it is set up to harcopy to the floppy drive that implies that the CPU is crashing. First thing I'd do then is check the power supply voltages, these scopes are about the age where capacitors start failing.

author: StefanF
author_rank: Contributor
timestamp: April 10, 2020, 04:31:09 pm
content: @ james :I'm not sure the hardcopy is set to the floppy driveI don't think the CPU is crashed because the scope reacts normal when pushing autoset button (relays clicking)i checked the output voltage of power supply: 14,82V =okI measured the elco's on the battery board with RLC meter => okI checked the voltages on the tantalum smd caps near the 4 voltage regulators on the main boardc990: 4,91Vc940: 4,962Vc933: 4,976Vc905: 3,295Vc967: 3,296V2 other tantalumc725: 5,10Vc969: 5,10Vvoltages near regulators seems ok to me: 5V and 3,3V for the digital partsI'm not sure about the 5,10V . Someone can confirm?

author: james_s
author_rank: Super Contributor
timestamp: April 10, 2020, 04:41:15 pm
content: The service manual shows what the outputs of the power supply should be and the tolerances. Is that 4.91V supposed to be 5V? That seems a tad low. Can you test for ripple on the output? Maybe monitor the 3.3V line as you power up the scope?

author: StefanF
author_rank: Contributor
timestamp: April 12, 2020, 07:50:45 am
content: @ james: I didn't found voltage tolerances in service manual (only in the 3000 manual, not in the 3000B, plug is different) and also have no digital scope to monitor the power voltages when powering up.What i further did:Connecting with eScope : no connection.ping command directly to the UTP port with cross cable => no responseAlso checked the supply voltage on the ethernet chip (LXT905): ok 5,11VMeasured 3 clock oscillators: okI also found a topic on the Tek forum which discribed the same problemAnswer of a Tek engineer was that this issue is probably related to the main boardBecause there is no circuit diagram available, i begin to think to throwing in the towel

author: james_s
author_rank: Super Contributor
timestamp: April 12, 2020, 07:29:10 pm
content: It can be tough to track down a fault like this. You might look at the address and data lines, they are accessible in the expansion connector on the back. You also could try watching the serial port (LVTTL level) pins on that same connector and see if it spits out anything as it tries to boot. It's possible there's bad RAM or ROM causing it to crash, perhaps the firmware has become corrupted somehow. It's unfortunate that Tek never released any schematics for these, they're nice scopes but not easy to diagnose when something fails.If you do decide to give up I've been looking to buy a dead TDS3000 series because I have a fully working one that all the plastic has become very brittle and is cracking and crumbling apart but it might not be economical to ship that far.

author: StefanF
author_rank: Contributor
timestamp: April 13, 2020, 04:51:13 pm
content: Hi James, thank you for the time and effort you have put in so far.I opened a topic on the Tek forum. Maybe a Tek engineer can give more detailed info.In mine opinion the scope isn't crashed, because it reacts normal when pushing the autoset button (relays clicking)It looks like the I/O (screen, ethernet, floppy) is completely dead.I have no idea which IC on the main board is processing the I/O signals.The scope isn't mine, it belongs to the firm where i work. I can't sell it to you unfortunately.It looks like new. It was mounted in a cabinet of a laser inspection system in a plant of us in France.It was only used with remote access when we had a technical problem with the laser inspection system.Because we have 2 more TDS3000 scopes, we gonna keep this one for spare parts in case it's not repairable.

author: StefanF
author_rank: Contributor
timestamp: April 22, 2020, 01:19:29 pm
content: I have found the culprit.I made an effort to dismantle our 3034B and build in the 3014b display.Result was the same white screen.Now trying to score a display in China at a reasonable price.

author: daveyk
author_rank: Frequent Contributor
timestamp: April 23, 2020, 06:03:40 am
content: Hold on the “B-Trig” button as you power on the scope to reset it.

author: james_s
author_rank: Super Contributor
timestamp: April 23, 2020, 06:59:23 am
content: I bought a replacement display for mine a while back, I think it was about $80 including shipping, it came from a China seller and was a genuine NOS display. Watch out for sellers asking crazy money, the display is not a Tek part, it's a standard industrial TFT of the era.

author: daveyk
author_rank: Frequent Contributor
timestamp: April 23, 2020, 05:49:44 pm
content: "the display is not a Tek part, it's a standard industrial TFT of the era."It's the same display as used in the Krautkramer/GE Inspection Technologies "Phasor XS" and USN60 instruments.The biggest problem I've always had with them customers drop the instrument (USN60/Phasor XS) and breaks one of the back light tubes. When I was with them, I contacted NEC and got a NEC part number for the backlight tubes and were able to stock packs of two of them. At one time we ordered from some grey market vendor and got just the fragile tubes. I said "What the hell is this?" and returned them and found about 200 of the complete the backlight tubes boxes (2 per box). They got hard to get when NEC discontinued the display.I need to order one of those LED upgrade kits. They were about $130 with the PWM driver PCB and two strips of LEDs. I will have to find them again or have someone point me to a vendor again. I would love to see this NEC display with LED back lights. My one TDS3052 that I am shipping off today for calibration is a little dim when turned on, but after five minutes, the tubes warm up and the display looks good.

author: james_s
author_rank: Super Contributor
timestamp: April 23, 2020, 08:27:50 pm
content: While not for one of these specific displays, I always just ordered the bare tubes and installed them in the existing trays. I've also done LED conversions on similar displays, $130 seems WAY high, I think the last one I did was around $20.

author: MarkL
author_rank: Unknown
timestamp: April 23, 2020, 08:38:09 pm
content: Quote from: daveyk on April 23, 2020, 05:49:44 pmI thought my TDS3054 was getting a little dim until I replaced the CCFLs. It was like night and day (no pun intended). I had gotten used to the gradual degradation over the years.I rolled my own with bare tubes from ccflwarehouse.com, part #CC26153. At $9.95 per tube it's cheaper than the LEDs.The NEC slide-in replacements are 65LHS-3L. There's a pair on ebay right now (under NL6448AC20-06) for $52.25, but that's a bit much, IMO.If you do find the LED kit, please post. Maybe I'll end up there too next time around.

author: Synesthesiac
author_rank: Newbie
timestamp: April 25, 2020, 06:40:26 am
content: Quote from: StefanF on April 22, 2020, 01:19:29 pmHey StefanF,I just got a 3012B with the same issue. If you find where a good deal on the display could be found before I can, can you please post a link? Thanks!

author: StefanF
author_rank: Contributor
timestamp: April 25, 2020, 08:20:58 am
content: Quote from: daveyk on April 23, 2020, 06:03:40 amHello daveykThank you for the tip, but that didn't work

author: StefanF
author_rank: Contributor
timestamp: April 25, 2020, 08:29:00 am
content: Quote from: Synesthesiac on April 25, 2020, 06:40:26 amHello Synesthesiac,There is a large selection from ChinaSearch on Ebay for "NL6448BC20-08"I didn't order one yet

author: shakalnokturn
author_rank: Super Contributor
timestamp: April 25, 2020, 08:39:11 am
content: Are there any small P-MOS transistors for power sequencing on the LCD supply?