Repairing Tektronix TLA7012's failing flat panel display [SOLVED] - Page 1
Forum section: electronics / testgear

author: bracecomputerlab
author_rank: Contributor
timestamp: November 17, 2024, 12:46:12 am
content: My second posting here.Around the same time I ordered, what turned out to be a defective (Acquisition error code 321 issue), Tektronix DPO70804 oscilloscope, I also ordered Tektronix TLA7012 portable mainframe logic analyzer.The discussion about TLA714, TLA715, and TLA7012 about 6 years ago is part of the reason why I ended up purchasing TLA7012.Thank you for that great discussion.It was really helpful in making the decision to buy TLA7012.At this time, TLA7012 costs only around $500 on eBay including shipping and sales tax.It also came with one Tektronix TLA7AA4 module for free, and this one appears to be fully functional (passes diagnostics tests except the BNC related ones).The only "catch" of this TLA7012 unit is that LCD always go blank after about 2 minutes, particularly when Windows XP is loading.This was fully disclosed by the seller, so I do not have an issue with the seller.I plan to give a positive rating.A workaround suggested by someone else also selling the same unit (the same seller that gave me the advice to return the defective DPO70804) on eBay with the same LCD issue is to use an external DVI capable monitor.I tried it, and it perfectly works around the display issue for now.In other words, my TLA7012 appears to be fully functional except the built-in LCD.Looking at how TLA7012's LCD fails after a few minutes, the failure mode seems eerily similar to how an LCD monitor with busted aluminum electrolytic capacitors displays something for a few minutes, and then quits.If I shutdown the LA and turn the power back on, LCD does come back, but it goes bad again when booting Windows XP.Does anyone know how to fix this issue?Currently, eBay has several TLA7012 with the same issue, so it appears to be a fairly common issue.Any suggestions or advice will be appreciated.

author: nctnico
author_rank: Super Contributor
timestamp: November 17, 2024, 12:54:45 am
content: It could be a problem with the backlight inverter or the CFL tubes being worn and draw too much current.However, if you don't need the logic analyser to be portable, you are better off using it remotely because a bigger screen size really helps where it comes to using a logic analyser. Your PC probably has a much bigger screen compared to the TLA7012. I have my TLA715 high up a shelve with the probe cables reaching to the desk level; I use it remotely exclusively. IOW: the failing LCD panel doesn't have to be a showstopper.

author: colorburst
author_rank: Regular Contributor
timestamp: November 17, 2024, 02:33:53 am
content: When you say the LCD goes blank, do you mean the image goes to a black screen or does the backlight turn off as well?If you pause the boot process (e.g. BIOS setup or F8), does the display stay on? Or does it turn off after two minutes regardless? Could be a driver issue.

author: bracecomputerlab
author_rank: Contributor
timestamp: November 17, 2024, 03:33:19 am
content: nctnico,I saw your comments on TLA715 and TLA7012, and also about TLA7BB4 from 2017 to 2018.Those comments along with comments from TiN and lukier were instrumental in my decision to purchase a TLA7012, 2 units of TLA7016 (currently in transit to two different locations), 3 units of TLA7AA4 (varying state speed and memory capabilities), and 2 units of TLA7S16 PCI Express Gen 1/ 2 serial analyzer.I also bought P6716S PCI Express x16 interposer card kit so that I can finally see how PCIe devices work in practice.This is really my first "probes" I purchased.I brought the price down from $800 to $500.Of course, the original price is closer to $10K or maybe more.The kit comes with cables that attach to a PCIe interposer card.I do not currently have any real probes at this point, including fly lead type probe / cable for TLA7AA4.I think TiN is totally correct that probes cost more than the mainframe / analyzer module, especially P7500 series Tri-Mode active probe family for my ill fated purchase of DPO70804.Off topic, but I once got someone working for one of the Big 3 (Keysight, Tektronix, or Teledyne LeCroy; I do not remember which one.) to demo me at their expo booth to see how a multi-lane PCIe device initialize itself.This happened some years ago at a tradeshow called DesignCon, almost always held around end of each January at Santa Clara Convention Center (i.e., Silicon Valley).Many years ago, I implemented a few early LTSSM (Link Training and Status State Machine) states on my own using PIPE PHY for PCIe.I always wondered how a multi-lane PCIe device synchronized each lanes, so someone kind from one of the Big 3 demoed it for me.Basically, what happens is that each lane is not really guaranteed to be synchronized at a power up, but when a special packet set called SKP OS (Skip Ordered Set) is sent across all lanes (still not exactly at the same transmission timing at this point), all the lanes get synchronized against one another.From here on, all the lanes are transmitting TS1 or TS2 (Training Set) OS continuously at the same timing with an occasional SKP OS.The thing is, the PCIe base spec does not really specify how to handle this type of a situation, and without being to see a real implementation running, it is virtually impossible to test against this situation in one's verification environment (testbench) on an HDL simulator.From the previous Conventional PCI era, I have known that specs often leave out potential real world behavioral pitfalls, so visually being able to see how the spec is actually implemented in a real world hardware is really crucial in developing highly compatible hardware implementation.This type of a situation of having inconsistency between the spec and a real world hardware implementation is perfectly normal, unfortunately.It is still within the spec.I got a little carried away discussing my very few occasions that I got to witness how PCIe is working in the real world, but finally I own the hardware to see it for myself how it works, albeit with somewhat dated PCIe support (Gen 1 / 2).Sorry for the long OT blurb.I will reply to your comments about the LCD in another reply.

author: bracecomputerlab
author_rank: Contributor
timestamp: November 17, 2024, 03:54:09 am
content: Quote from: nctnico on November 17, 2024, 12:54:45 amYeah, I do not think this type of an equipment will casually use aluminum electrolytic capacitors like regular consumer grade electronics hardware.For this type of an equipment, I often see rather expensive surface mount tantalum capacitors being used fairly extensively , so "recapping" will likely not happen.I assume that when Windows XP starts up i915 graphics device driver, it switches from VGA upscaling mode to its native LCD panel mode.Likely the current draw is greater, hence, the outcome is a disappeared screen.Of course, the screen comes back instantly when I power cycle TLA7012 by shutting down the box and turning it back on right away.Based on this, I assume the CCFL still has some life left in it, so I suspect an issue with the inverter circuit.A rather old 19" Dell monitor with DVI input is sitting on top of my TLA7012 at this time as it's working monitor.I also ordered TLA7016 that should arrive in a few days.I plan to revive a little used Windows 7 Pro 64-bit that has not been turned on for about 4 years.I never dreamed going back to the Microsoft land in my life (I am myself sort of a hardcore Gentoo Linux user.), but I have no choice.

author: calibrationfixture
author_rank: Regular Contributor
timestamp: November 17, 2024, 05:41:55 am
content: Hi bracecomputerlab,Look at the RTC on your Monitor. Up to date? Very likely that the TLA7012 its MB Battery is flat and the BIOS is executing its Defaults. Local Flat Panel must be selected and saved. And yes Tektronix its TLA Series are extremely reliable. I came across dozens of these. Mainframes and Modules. All working perfectly. One exception: stay away from ALL TLA7ACx's. I myself have such a disaster, an acquintance of mine has two of these not working and on YouTube there is even a Repair Video on these. The Fails are all Memory related (the C).Calibrationfixture

author: bracecomputerlab
author_rank: Contributor
timestamp: November 17, 2024, 06:04:11 am
content: Quote from: colorburst on November 17, 2024, 02:33:53 amIt appears to be the backlight going out, but since most LCD panels really cannot display anything meaningful without backlighting, the distinction may be moot.Although I have not illuminated the LCD panel from the front yet, I have an LCD panel or two (different laptop computers) that can show extremely dim picture without backlighting.It appears at this point, display engine is still alive, but backlighting is going out.I will try tomorrow during the day to see how the LCD fares if I do not immediately boot Windows XP.Based on my recollection from the first time I operated the TLA7012, the LCD starts to dim in about 15 to 20 seconds after a power on.LCD appears to hold up somewhat for several minutes, albeit with dimmer screen brightness, if I stay within the BIOS setup or the Tektronix splash screen.I observed this because the CMOS RAM RTC coin battery inside the unit is totally drained, and I like setting the correct time and date before booting Windows XP.Hence, if I do this, along with customizing the BIOS settings to my liking, it can take a few minutes.During this time, I had the LCD screen, but it went bad during the Windows XP boot process.The LCD goes bad 100% of the time if I boot Windows XP.Restarting the computer, as opposed to shutting it down, does not appear to bring the screen back, although I am not 100% sure.I will test this as well.I know for sure that cycling the power definitely brings back the LCD.

author: calibrationfixture
author_rank: Regular Contributor
timestamp: November 17, 2024, 06:56:56 am
content: Hi bracecomputerlab again,All I posted is for TLA7012 Gen1 Models. Recently a Gen2 TLA7012 got a Flat MB Battery. In this case I saved Optimal Defaults in the BIOS Settings.Maybe usefull (Gen1):https://www.eevblog.com/forum/testgear/tektronix-tla7012-dim-screen/msg4778582/#msg4778582Calibrationfixture

author: bracecomputerlab
author_rank: Contributor
timestamp: November 17, 2024, 09:52:56 pm
content: Quote from: calibrationfixture on November 17, 2024, 06:56:56 amOkay, I turned on my TLA7012 this morning / afternoon, and yes, switching the LCD's brightness setting from "I2C" to "PWM" did the trick.Now the LCD is always on even when Windows XP is running.That being said, if the LCD is "warmed up" for 5 to 10 minutes or so, LCD barely appears to stay on even if the LCD brightness setting is turned back to "I2C".But, of course, the LCD stays fairly dim.I will also note that regarding the observations made by me in the earlier posting, I was not able to reliably reproduce them this time around (i.e., LCD will disappear during Windows XP boot thing), but this workaround discovered by Omicron mostly resolves the issue for the most part.Yes, I need to replace my CR2032 coin battery soon.If I were to elaborate a little more, attaching a DVI cable to the right side DVI port (facing the motherboard back I/O panel) appears to disable the LCD, but I was not able to get the left side DVI port to display anything at all on the external monitor.I will check the Windows XP display settings to see what is going on, but nctnico is right that using an external monitor makes more sense with TLA7012, unless there is a reason one needs to use the built-in LCD.Like if one brought out this TLA7012 for a demo, but forgot to bring an external monitor.Anyway, I do not think I could have figured out this by myself, so thanks Calibrationfixture to pointing to the solution.