hp 54200D DSO Troubles - Page 1
Forum section: electronics / testgear

author: 6E5
author_rank: Regular Contributor
timestamp: April 13, 2014, 03:49:41 pm
content: Hello,Recently, I purchased a hp 54200D digitizing oscilloscope. The cover is missing and it is generally dirty. I powered it on to find this error message:ERROR In Controller Command_______LLO MTADoes anyone know what this means and if this is repairable?Here is a link to the manualhttp://www.home.agilent.com/agilent/techSupport.jspx?pid=54200A:epsg:pro&pageMode=MN&lc=eng&cc=GBThanks for you help,Paul

author: merox
author_rank: Regular Contributor
timestamp: April 13, 2014, 05:32:47 pm
content: Quote from: 6E5 on April 13, 2014, 03:49:41 pmLLO means "Local Lockout" and MTA stands for "My Talk Address".This error-message relates to the GPIB-Controller inside the scope, basically telling you that the controller received an malformed command via the GPIB-Bus. Have a look at the back of the device and search for the GPIB-Connector (or whatever its called, it looks a bit like the centronics-port at older printers). Maybe something shorts out some pins at the connector, making the scope believe that it received a commands.It could also be possible that the controller-chip itself or his buffer/driver ICs are broken. They should be nothing special.But before fiddeling around with the internals of the scope, you should perform a "Key-Down Power-Up Reset". Corruption of the Cal- and Settings-RAM can lead to various issues and misbehaviour. To perform the reset, switch the device off, then press and hold any key and turn the device on again while still holding that key. You may release the key after a few seconds.Edit:You might also have an issue with the EPROMs holding the firmware... In my 54200A one of them went bad, making the device hang while starting up (only the grid was shown, nothing else happened). After replacing them with "new" ones, the scope is now working fine again.

author: 6E5
author_rank: Regular Contributor
timestamp: April 13, 2014, 09:27:59 pm
content: Hi,The IEEE-488 connecter looks fine. I tried the key down power up routine and was greeted by the same message. I looked at the back up battery and it looked crusty, and it measured 3.4v compared to the marked voltage of 3.9v. While no components looked damaged by it, as it was leaking, I removed it. There was no change in behavior.I was able to take several high speed shots of the start up processes, and there are 2 message before the ERROR message.1. Power-Up Complete_____LLO MTA2. Status: Acquired Frame 00000LLO MTA3. ERROR in Controller CommandLLO MTAWhere were you able to purchase new EPROMS?Thanks,Paul

author: merox
author_rank: Regular Contributor
timestamp: April 14, 2014, 04:45:53 pm
content: Quote from: 6E5 on April 13, 2014, 09:27:59 pmI hope you held down the key until the power-up-chime was completed? Sorry for not mentioning that in my last post, i seem to have skipped that sentence when reading the manual.Quote from: 6E5 on April 13, 2014, 09:27:59 pmThe two messages that appear on your screen before the ERROR don't look suspicious to me, my 54200A shows them too.Quote from: 6E5 on April 13, 2014, 09:27:59 pmI guess the voltage of your battery shouldn't have caused any problems, my battery reads 3.1 volts and the scope still keeps it's settings. But since your's was leaking, desoldering it was a good choice.Quote from: 6E5 on April 13, 2014, 09:27:59 pmI didn't purchase new EPROMs, I was just lucky to find some EPROM-dumps on the net. I got them burned into some old (used) EPROMs somebody had lying around on a german forum.Quote from: 6E5 on April 13, 2014, 09:27:59 pmToo bad, but i guess that would have been too easy. I'm still suspecting something within the IEEE-488-circuitry to be broken, because normally the LLO gets cleared after a power down and has to be reactivated via the IEEE-Bus. Maybe its one of the buffers, maybe its the TMS9914 interface-chip itself. Here is a datasheet of that chip:http://www.physics.brocku.ca/~edik/gpib/TMS9914.pdfSince they are all relatively close to the leaking battery, maybe the leakage actually led to some corrosion in the inner layers of the board?

author: 6E5
author_rank: Regular Contributor
timestamp: April 14, 2014, 09:45:37 pm
content: Hi,Unfortunately, by desoldering that battery, I may have worsened the situation. The scope now shows a power up failed message, which I'm fairly sure means that the calibration data was lost. However, I was able to find a battery replacement and solder that in. The old battery was leaking slightly from the top, and no residue had reached the board. I'm fairly certain corrosion can be ruled out.1. After I fix this IEE-488 problem, can I assume that a simple self calibration can fix this error?2. I did hold the button down until the power up chime had finished and the screen had booted up.3. At this point do you think it would be wise to try to replace the TMS9914? It is fairly inexpensive, only $5 or so. Are there any other suspect chips that you would recommend replacing?Thank you for you help. I am thankful for the time you have spent. I am not knowledgeable in this era of digital circuits, as I tend to stick mostly to analog.Regards,Paul

author: echen1024
author_rank: Super Contributor
timestamp: April 15, 2014, 02:19:31 am
content: Replacing the battery and doing a self-cal will not help the situation, at least I don't think. YOu have lost all constants in the volatile memory, but I may be wrong.

author: merox
author_rank: Regular Contributor
timestamp: April 15, 2014, 03:13:21 pm
content: Quote from: 6E5 on April 14, 2014, 09:45:37 pmI don't know if the self calibration will fix this error but i'd give it a try. However, there was a service floppy for that oscilloscope, but since the manual lists it only in the section for the screen adjustment i'm not thinking that it is really needed.Maybe someone who is reading this can get a hold of that floppy, it was contained in the support kit 54200-69501 and has the part number 54200-12001. I'd like to have it in case i need it for my oscilloscope one day.I also don't know if replacing the TMS9914 would be a wise step, it's just a part of the circuitry i would suspect when my oscilloscope would show this error. The TMS9914 will definitely be connected to some bus tranceiver-chips which interface between the TMS9914 and the IEEE-Bus. They are close to the TMS9914 and are labeled with HP-Numbers:1820-3518 = DS75162AN1820-3431 = DS75160ANI'd check them before replacing the TMS9914 because they are sitting between him and the bus. So if something was damaged by e.g. ESD, then it's most probably them.

author: 6E5
author_rank: Regular Contributor
timestamp: April 15, 2014, 03:24:27 pm
content: Quote from: merox on April 15, 2014, 03:13:21 pmHi,The power up fail message appears for only a second or so, and then the standard Controller Error message pops up.I would have no way of connecting the floppy to the scope anyway, I don't have any hp drives or computers. Do you happen to have a method?I will order those chips today, thought they will take some time to be delivered from China to the US. It's good luck that HP-IB became standard IEEE-488, all these chips are mass produced and inexpensive!Regards,Paul

author: merox
author_rank: Regular Contributor
timestamp: April 15, 2014, 03:41:04 pm
content: Quote from: 6E5 on April 15, 2014, 03:24:27 pmThe floppy (or a floppy drive) isn't connected to the oscilloscope, it runs the software it contains on a secondary "PC" which connects to the oscilloscope via the IEEE-Bus. The software is written in HP Basic (at least that's what i understand from reading the manual) and is intended to run on an ancient HP Series 200 Machine:http://www.hpmuseum.net/display_item.php?hw=4But as far as the manual describes it, it seems only be used for adjusting the brightnes etc. of the screen. So I guess there is no real need for that floppy but it would only be a "nice to have" for me.

author: 6E5
author_rank: Regular Contributor
timestamp: April 15, 2014, 05:08:25 pm
content: Hi,On US eBay right now there is a hp 200 series computer for about $600. This is way over budget for me, and as you said, the software is rare as hen's teeth.I was able to get screenshots of the error messages.1. ERROR Power-up FailedLLO MTA2. CAL Factor LossLLO MTA3. ERROR In Controller CommandLLO MTAFrom this the loss of calibration can be confirmed. I'm fairly certain a self calibration will solve this. Also, with LLO and MTA appearing as soon as the machine starts, I have a hunch that your broken IC theory is correct.Also, screen brightness is adjusted using a pot on the CRT driver board. I'm not sure what you mean by using the floppy to adjust it.Paul

author: merox
author_rank: Regular Contributor
timestamp: April 15, 2014, 08:43:43 pm
content: Quote from: 6E5 on April 15, 2014, 05:08:25 pmThe software on that floppy is only needed to plot some specialized adjustment-patterns on the screen, normal adjustment jobs like brightnes etc. it's not needed. If you want more information about this, it's in section 10-5 "Display System Adjustmant" of the manual (the floppy seems to be mentioned only in that section). So there is no need for buying that old PC, especially since there exist modern interpreters for the software stored on that floppy (so you could run it on a modern PC if there was a need for that).

author: Stray Electron
author_rank: Super Contributor
timestamp: April 18, 2014, 11:55:57 pm
content: 6E5,Where are you located? I have a bunch of old HP 2xx/3xx computers that are still operational. I have HPL, Basic, RMB and Pascal for them. Located in Orlando. Might want to PM me so that I don't overlook your reply.