Agilent DSO80204 Trigger Fail.  - Page 1
Forum section: electronics / repair

author: sprit
author_rank: Regular Contributor
timestamp: March 12, 2025, 03:28:19 pm
content: Hello guys, hope you have a nice day.I have an Agilent 80204A. One fine day it suddenly wouldn't start. I opened it up and checked the power supply, I didn't find anything unusual. Then I closed it and tried to press the power button but there was no response. After some testing I realized if I unplug this green wire, the power supply will start but it won't boot. I removed the tu I took it apart and traced that green wire and found out it was the ps_on wire like on ATX power supplies, then I tried pinning it to GND and it booted up fine.The green wire is passed through a IC nám 74ACT32 On the power board below. And after the scope successfully started, I saw the software reporting Trigger errors on channels 2,3 and 4. When I apply signal to those channels, the waveform still appears normally but cannot trigger. The voltage levels are noted on the second power board I checked and they are correct. I don't know where to check, there are 2 TPs AVDD4 and VDD34 I measured 1.8V and 1.6V. Are those the correct numbers? I look forward to your help.Sincerely, Feng.

author: sprit
author_rank: Regular Contributor
timestamp: March 12, 2025, 03:49:07 pm
content: This is the photo that the software reported an error with.

author: sprit
author_rank: Regular Contributor
timestamp: March 13, 2025, 01:18:49 pm
content: Another day has passed and no progress. I don't know where to start, can you guys give me some suggestions?Thank you very much

author: tom66
author_rank: Super Contributor
timestamp: March 13, 2025, 02:41:16 pm
content: Does channel 1 still trigger OK?I would start by checking all of the power supplies, the scope will usually have 4 identical channels, so check across all of the decoupling capacitors for each of the trigger comparators and other analog components in that part of the instrument, and perhaps you will find the fault.It is also possible one or more of the DACs is not working correctly - does trace offset work OK?What happens when you run the built in self test?

author: sprit
author_rank: Regular Contributor
timestamp: March 13, 2025, 05:02:26 pm
content: Hi tom, hope you have a nice day.Other than channel 234 not being able to trigger everything works fine, at least I think so. There is no offset on any channel.When measuring 2Ghz frequency from my ESG, all 4 channels show correct frequency and amplitude. Only thing is that it cannot be triggered. I did the selftest and it passed. But when I switch to calibration mode it fails on all 4 channels. Now it can't boot normally, if I don't pin that green wire(ps_on) to gnd it can't boot. Could that be the main cause of the error? That ps_on pin is started by an ACT32 on the secondary power board. Is it possible that the IC itself is faulty causing it to not boot? Sorry my English is not good. Hope you don't mind.Sincerely,Feng

author: tom66
author_rank: Super Contributor
timestamp: March 13, 2025, 05:15:45 pm
content: What I mean, is can you adjust the offset (vertical position) of each channel, as well as the gain?I don't know why the PS-ON needs to be shorted like that. I guess there is usually a common fault but can't think of one right now.P.S. Your English is fine.

author: sprit
author_rank: Regular Contributor
timestamp: March 13, 2025, 05:53:54 pm
content: Hi tomYes. I can adjust the offset or gain on the remaining channels normally. Maybe my power supply is broken or has lost some voltage that I don't know about.In addition to the main working coil (the largest wire as shown in the photo), there are a dozen other wires going into the rectifier board below (I have attached the photo).I don't know their exact values. There are too many wires.

author: sprit
author_rank: Regular Contributor
timestamp: March 13, 2025, 06:13:33 pm
content: n my case, the PS_ON pin (green) is controlled by the 74ACT32 IC on the lower power supply board. When I press the power button, the IC refuses to pull it down to GND. I don't know if the cause is PS or IC. By the way, can you tell me what IC is equivalent to 74ACT32, this part is not available in my locality.SincerelyFeng

author: tom66
author_rank: Super Contributor
timestamp: March 13, 2025, 06:21:52 pm
content: 74ACT32 is just a quad OR gate, could be 74LVC32 or 74HCT32 replacement.However, don't assume because output is low, IC is broken. Maybe the inputs to it are wrong. If you know signal out is not high, have you checked both inputs to the OR gate are high? Refer to the datasheet and specifically truth table in that datasheet.https://www.mouser.com/datasheet/2/149/74AC32-180325.pdf?srsltid=AfmBOoqCU9AJyN53pcP7c8T9TcITuEaW03qvKbUhsc0NyzVjrJ6nuS2H

author: sprit
author_rank: Regular Contributor
timestamp: March 18, 2025, 01:22:07 pm
content: I just received the 74HC32 today to replace my old 74ACT32 which I suspected was faulty. After the replacement the scope started up normally. But the trigger error still remains, when I do the calibration (I use the sma cable as the software requires) but the trigger item still fails. Can anyone tell me if this model has a service manual, Or something similar? Hope you guys can help me. Thank you.SincerelyFeng

author: tom66
author_rank: Super Contributor
timestamp: March 18, 2025, 07:47:16 pm
content: I found this on Keysight's website.https://www.keysight.com/gb/en/assets/9018-05653/service-manuals/9018-05653.pdfNo idea how useful it is.

author: sprit
author_rank: Regular Contributor
timestamp: March 21, 2025, 05:47:06 pm
content: Hi, hope everyone is having a good day.Thanks tom for your help.Today I continued to repair it. After probing some TPs on the daughterboard, I realized that there was a broken rail. Specifically 2.5VREF. After some searching I found out the culprit is OPAM with code OP184. After replacing it with AD797, its boot problem was fixed. Now I can press the power switch to turn the device on and off normally. But the Trigger error still persists, The service manual of this device does not have much effect other than replacing the acquisition board. The strange thing is that when I do selftest, the Trigger item says passed while when I enable calibration it fails. I don't remember anyone saying that hidden menus can be enabled via command line or something. Does anyone have any information? Thank you so much.SincerelyFeng

author: sprit
author_rank: Regular Contributor
timestamp: March 21, 2025, 05:49:16 pm
content: Picture before and after replacing OP184. 2.5VREF is back and now scope boots normally.

author: sprit
author_rank: Regular Contributor
timestamp: March 21, 2025, 05:50:55 pm
content: selftest passed But when calibrating, it fails again. Haizzz

author: sprit
author_rank: Regular Contributor
timestamp: March 21, 2025, 06:16:49 pm
content: I just enabled the hidden menu on it and now I am trying calibration. I will keep you updated.

author: sprit
author_rank: Regular Contributor
timestamp: March 21, 2025, 07:03:58 pm
content: It seems like the trigger signal is getting interrupted or broken somewhere. I suspect one of these delay coils is broken. I tried checking the continuity of the coils and found that 2 coils have quite high impedance, the other coil is 100R. Or is it because I have I don't know if I did it correctly. Hopefully it's only here, otherwise it's likely the MC100 is in the ECL circuit.

author: sprit
author_rank: Regular Contributor
timestamp: March 21, 2025, 07:08:54 pm
content: It's 2am now. I think I'll continue tomorrow. Hope everything goes well.Wish everyone a peaceful day.SincerelyFeng

author: tom66
author_rank: Super Contributor
timestamp: March 21, 2025, 08:06:50 pm
content: See if you can trace where the trigger comparators are, you may need access to a slower scope, my suggestion is feed in say 2kHz AC sine wave on all 4 channels and get the trigger working, then use the other scope to see whether you can see that 2kHz signal. Then once you find the comparator you can check a few things, like whether the DAC reference is OK for the comparator, or whether the comparator is bad.

author: sprit
author_rank: Regular Contributor
timestamp: March 22, 2025, 12:41:28 pm
content: Hi bob, wish you have a nice day.Thanks for the suggestion. I am looking to test this delay line coil but not sure how to probe. Do you know how to test this, the datasheet of this one is not very clear to me.SincerelyFeng

author: sprit
author_rank: Regular Contributor
timestamp: March 22, 2025, 01:59:31 pm
content: I just reread the datasheet. I found out the 45ps delay coil is broken. (1 leg I put at pin 1 and did a continuity test at pins 1,3,4-9, 11-16 and found from pin 1 to pin 15 is broken and some more. I just googled it and can't find anywhere that sells this ic. Can anyone tell me what newer thing I can replace it with?Thank you very much.Sincerely,Feng

author: sprit
author_rank: Regular Contributor
timestamp: March 22, 2025, 04:02:14 pm
content: Update:I just tried connecting pin 1 to pin 15 using an old R&S 45ps delayline pcb with an impedance of 2R. After connecting and powering up, the scope starts but gives an Acquisition too long error. If I press "skip" the app still starts normally but no waveform appears even though I press autoset. I turned it off and removed the delayline board and the app returned to normal. I continued digging and found this transistor, I can't see the code very well but there is a graph of the voltage I measured below. It looks like the transistor (or something similar) is not working properly. Should it output -5V at pin 2 to the delayline coil? I really need your suggestions.In my opinion, I was correct in shorting the broken delayline but without -VDD the ECL/Acquisition circuit did not work properly. Although p Despite that judgment, I dare not risk injecting anything related to the source into this acquisition board. I wish someone had a scope like me and checked the TP there. Haizzz

author: sprit
author_rank: Regular Contributor
timestamp: March 23, 2025, 05:03:23 am
content: I have this idea I don't know if it works.Should I connect -5V via a 61Ohm resistor to pin 14, while connecting pin 15 to pin 1 via a 50Ohm resistor. I'm quite nervous about what I'm about to do. Any advice?SincerelyFeng

author: squadchannel
author_rank: Frequent Contributor
timestamp: March 23, 2025, 06:43:07 am
content: MS450D = Susumu GL2L5MS450D-Chttps://www.eevblog.com/forum/repair/agilent-infiniium-54855a-calibration-problem/msg3862130/#msg3862130attached datasheet.

author: sprit
author_rank: Regular Contributor
timestamp: March 23, 2025, 01:31:31 pm
content: Hi squadchanel, glad to see you again. How are you? Hope you have a nice day.There are some places I don't quite understand.Quote from: Aiy on December 08, 2021, 06:32:52 pmHow should I connect the resistors? I mean the position. Is it ok to connect the other broken pin 15 to -5V via a 50R resistor and connect pin 1 to pin 15 using a 61R resistor?My English is quite bad so I don't understand very well, sorry for that.

author: sprit
author_rank: Regular Contributor
timestamp: March 24, 2025, 03:10:47 am
content: My English is not good so I don't understand what he means. Sorry about that.

author: Aiy
author_rank: Regular Contributor
timestamp: March 24, 2025, 10:21:12 am
content: Hi Sprit,I'll try to help as best I can.You are probably experiencing the same problem I had with my Oscilloscope and you are on the right track.If one of the delay line is broken, you have to make the driver IC have ECL termination, so put 51 Ohm at the input pin on the broken side to -5V.At the output of the delay line, the broken side will be pulled to the termination voltage. There we patch 62Ohm to make a voltage divider to mid point for ECL differential pairI suggest that you use multimeter in continuity (beep beep mode), Oscilloscope OFF1. find U? in the picture, which IC is connected to DL2202 pin 2, 7, 10, 15. U2202, U2207 or U1502 are good candidates.2. When you find the IC, take photo of IC and resistors (R? in the picture) around so we see the resistors around it and the IC marking.3. Oscilloscope on. Find what is VCC in the picture, +5V? GND? -5V?

author: sprit
author_rank: Regular Contributor
timestamp: March 26, 2025, 02:30:19 pm
content: Hi ayi, I'm glad to see you here. How's going today.I will open it and check now. Glad you finally came.SincerelyFeng

author: sprit
author_rank: Regular Contributor
timestamp: March 26, 2025, 03:00:40 pm
content: Hi aiyi've attached the image with the measurment, hope it can helpSincerelyFeng

author: sprit
author_rank: Regular Contributor
timestamp: March 26, 2025, 03:05:32 pm
content: HiIn the picture, I connected pin 15 (broken) to pin 16 with a 51R resistor. Is that correct?

author: Aiy
author_rank: Regular Contributor
timestamp: March 28, 2025, 11:57:34 am
content: Hi Sprit,I see you have done a pretty good pin mapping, that helps us a lot.I see on KP11 that you find U2206/KP11 pin 7 -> DL2202 pin 2.There should be U2206/KP11 pin 6 -> DL2202 pin 15.I see that you have written 10 and 15 on left resistorI see that you have written 2 and 7 on second resistor from leftIf the delay is broken, I think that left resistor only has contact with DL2202 pin 10.I can take photo of my repair, but it will take a few weeks, I am on holidays.Best regards,

author: sprit
author_rank: Regular Contributor
timestamp: April 30, 2025, 02:01:51 pm
content: Sorry for the inconvenience but can you help me? I still haven't found the right direction.Sincerely,Feng

author: Aiy
author_rank: Regular Contributor
timestamp: May 02, 2025, 02:18:13 pm
content: Hi Sprit,I opened my Oscilloscope today and took photo around the area of the delay (see attachment).The modification on my Oscilloscope is at U282, KEP52 pin 1 (D+), new values "81A" = 681Ohm, and "39A" = 249OhmThis corresponds to your U2202. Please try to make the resistor change and see if calibration works.I may have done modification on the backside of my board, but it is a lot of work to take it out and look.Best regards,

author: sprit
author_rank: Regular Contributor
timestamp: May 04, 2025, 11:54:23 am
content: Hi AiyNice to see you again. I will try it now. Thank you very much for your help.SincerelyFeng

author: sprit
author_rank: Regular Contributor
timestamp: June 18, 2025, 01:48:13 pm
content: Hi ayi, hope you have a nice day.Today I took it out again to check again and try to measure again. At U2202, the resistors you mentioned are exactly the same as mine (unedited) 680 and 249 Ohm. I also checked the connection between pin 6 of KP11 and pin 15 of DL2202 and found it connected ok. What should I do next?SincerelyFeng

author: sprit
author_rank: Regular Contributor
timestamp: June 18, 2025, 01:50:53 pm
content: By the way, I also attached a picture of the bottom, hope it can help.

author: sprit
author_rank: Regular Contributor
timestamp: September 16, 2025, 11:45:02 pm
content: What a tough machine!Hello everyone, it's me again. I finally have some time today to continue my repair work. Now the old Mobo is broken, I have ordered some other mobo models from "Taobao" and local store to replace the old mobo. Their codes are different,Since finding the exact mobo with the same PN code as the old one was impossible, I had to use other mobos with the same architecture or newer but still no success. There are 2 cases that can happen, either the DSO will not boot if I insert the PCI to ACQ card, or it will boot but the driver for the Infiinium Board will not be able to install. I have a backup file of this model, then I do the trick to be able to boot that old OS on the newer mobo model without crashing Windows but the infiinum driver will still not be loaded properly.I have seen 2 people on this forum who have successfully replaced the motherboard on the HP54831D model and another one successfully in the DSO9000. I texted to get some more experience but have not received a reply yet. I'm wondering if Agilent put something in the BIOS file? I will attach the original bios file below. By the way, do you know where to buy Mobo code Intel D915GUX/GHA/PCM? I'm looking for it.There are some stores on Ebay that post the above code but it is not real. Mine uses 915 chipset, socket 775 while the one on ebay uses the older socket 370. Looking forward to receiving your comments. Thank you very much.