Repair Help: Issues with TIME/DIV on Hameg HMO3524  - Page 1
Forum section: electronics / repair

author: paulscout550
author_rank: Newbie
timestamp: January 02, 2025, 10:14:35 pm
content: Hi,I recently bought a faulty Hameg HMO3524 for a relatively low price. The seller mentioned that no channel could display an input signal, so I initially assumed there might be an issue with the input stage, possibly the A/D converter. However, I was wrong.When setting the TIME/DIV to 50ms or above, the input signal appears, but the measurement is incorrect. For example, when I input a 5MHz signal into one channel and set the scope to 50ms TIME/DIV, I can see the signal. It looks identical to how it would appear on a working scope set to 100ns TIME/DIV. However, when I measure the signal manually or automatically, the scope shows a frequency of approximately 25Hz. If I set the scope to anything below 50ms TIME/DIV, the signal disappears. Additionally, if I set the scope to anything under 50ms, turn it off, and then back on, there is a frozen signal line that disappears as soon as I change the TIME/DIV setting.Scope set to 50ms, with a 5MHz sine wave at the input and auto measure.Scope set on 10ms with a 5MHz signal at the input.Scope set on 50ns with a 5MHz Signal at the Input after restart, the signal is frozen.The trigger appears to be working fine. When observing the trigger frequency, it consistently measures the correct input frequency. Auto set defaults to 50ns TIME/DIV, where no signal is visible since it requires a setting of 50ms or higher.5MHZ Signal with Trigger frequency measurement.It seems to me that the TIME/DIV functionality is somehow "shifted," if that’s the correct term. Has anyone encountered a similar issue or have any idea what could be causing this? My first thought was that it might be a software problem and that uploading new firmware might resolve it. However, I read on this forum that I can only install firmware up to version 2.502, as versions beyond that require a hardware upgrade. Unfortunately, I can’t find this firmware version anywhere and the Rohde und Schwarz site wants me to create a account with a valid company Email and company details.If anyone has the firmware or a link to it, I would greatly appreciate it if you could share it with me.This is also my first post on this forum, so if I’ve done anything wrong or missed anything, please let me know, and I’ll do my best to correct it.

author: Swake
author_rank: Frequent Contributor
timestamp: January 04, 2025, 11:03:20 am
content: This one sounds challenging, as if the 'oscillo' part is ok but not the 'scope' part.If it was an old analog scope one could think that the time base knob is misaligned with the real settings. Or that the annuntiator (50ms) is out of wack somehow.It does make sense to have 2 different paths in the DSP. One for showing the signal itself and the other calculating the trigger.Is there some way to perform a complete reset or back to factory settings of some sort?I guess you already checked with signals of other frequencies and shapes and have found the same issue?

author: paulscout550
author_rank: Newbie
timestamp: January 04, 2025, 04:18:04 pm
content: I just tried resetting it to factory settings, but it seems to only revert the parameters to their default values without performing a deeper reset.I've also tested it with signals of different frequencies and shapes, but the issue persists.My best idea right now is to find an older firmware version somewhere, though that seems quite difficult since older posts suggest that R&S isn’t very interested in supporting the old Hameg oscilloscopes anymore. Even getting in touch with someone there without being part of a company seems like a nightmare.

author: Swake
author_rank: Frequent Contributor
timestamp: January 04, 2025, 05:01:40 pm
content: Questions/remarks in the category of 'nothing to loose'- Some Zoom function active?- What is generating the source signal?- Is the amplitude in line with the output of the source?- Do you have another source to scope, even the secondary of an old fashioned transformer is better than nothing?- Did you try the internal calibration output (if there is one it frequently is 1kHz)- Is there an 'auto' button and does it work as expected?- your first picture; trigger frequency seems in line with signal frequency (14Hz)

author: paulscout550
author_rank: Newbie
timestamp: January 04, 2025, 05:58:28 pm
content: I just went through your list with the oscilloscope:- No zoom function seems to be active, at least not the one controlled by the large button on the front panel. I guess through the reset to factory settings, it would also be turned off.- I am using a UNI-T UTG932E as a signal source.- I checked the frequency and amplitude of the UTG932E with my analog oscilloscope, and everything seems to be in line.- The first picture shows the automatic frequency measurement, while picture 4 shows the trigger frequency.- The Auto button just sets the time base to 50ns. My guess is that the Auto button uses the trigger frequency to determine the appropriate TIME/DIV setting. Since the trigger frequency seems to be correctly measured at 5MHz, it sets the time base to 50ns.I have also sent an email to CustomerSupport@rohde-schwarz.com to see if they have an older version of their firmware they might be willing to provide.