Fixing an old HM203-4 CRT Oscilloscope (video) - Page 1
Forum section: electronics / repair

author: TmaxElectronics
author_rank: Regular Contributor
timestamp: August 28, 2022, 10:24:44 am
content: I just fixed my old Hameg HM203-4 analog oscilloscope and made a video of it because I was bored. I'd love to get some feedback on the videohttps://youtu.be/2uUBCTRTBJs

author: agent_power
author_rank: Regular Contributor
timestamp: August 28, 2022, 05:46:10 pm
content: Good job on showing the troubleshooting steps including mistakes, I always hope they're included in videos as they're as educational as the rest of the diagnostics.Any reason you attached the ground lead on that particular capacitor? I try to avoid areas where it could fall down / into something and potentially cause a short... most of the time I clip it to the chassis (if it's referenced to ground).PS: awesome tesla coil videos

author: TmaxElectronics
author_rank: Regular Contributor
timestamp: August 28, 2022, 08:55:04 pm
content: Thank'sThat mistake was so dumb I just couldn't cut it from the video, I did spare you from watching me probe stuff wondering why there was no riplle anywhere for 10minutes thoughI chose that ground as the reference pretty much just because it was the first place I found with ground on it and it could easily take a croc clip from my meter. Usually I'd be worried about it falling down too, but because there was so much space around it I could get a good grip on the leg.

author: TaylorD93
author_rank: Regular Contributor
timestamp: August 30, 2022, 08:47:10 pm
content: genuinely LOL'd when you realised it wasn't on, been there before. Fair play to you for keeping it in the video.One thing i have done before when fixing my Hameg scopes, is make the signal as big as possible on the display (to aid the trigger cct), and set it to "line trigger" then set it to a timebase to around 20/10/5mS/div. if you see it "lock" on the trigger, you can then measure the period between the ripple/spikes and quite easily find 100Hz (bad rectifier cap) or 50Hz (bad rectifier diode).In your case it wouldnt have helped, but is still another really useful quick test to do when you suggest having a "play around with the settings"I had a HM605 with a bad PSU, knackered bulk caps and a dead (previously replaced) bridge rectifier, helps narrow down where the PSU fault could be etc before even opening the scope.Ps. just got another YT subscriber

author: TmaxElectronics
author_rank: Regular Contributor
timestamp: September 01, 2022, 09:38:11 am
content: Didn't actually think of the line triggering thing. Definetely seems like a good ideaGlad you liked the video.I think I was just quite lucky with my scope. When I got it (like 7 years ago now) there was no way I would have been able to fix it. I barely knew the word capacitor back then... not even jokingWhen I got the scope I was sent the video dave made about not blowing up your scope by one of my chemistry nerd friends and got started watching electronics content. Up until that point it was really just arduinos and shields which had gotten kinda boring to me (hence me getting more into the chem side of things). The videos I watched (Bigclive, dave, mikeselectricstuff etc.) really got me back into electronics again. Fast forward to today where I'm doing electronics projects way beyond anything I ever thought one could do at home and just finished my first EE degreeCertainly quite a strech to put it down to just one coincidence 7 years ago, but it certainly helped a lot lol

author: TaylorD93
author_rank: Regular Contributor
timestamp: September 02, 2022, 10:14:05 pm
content: growing up playing around with electronics in my teens, money was quite short so owning an Oscilloscope seemed to be a far off dream, in recent years however ive been playing around fixing them and to an extent, hoarding them (much to my landlords annoyance) i now own almost 20 in may different states of "Broken-ness"plenty to get my teeth stuck into an tinker with however

author: TmaxElectronics
author_rank: Regular Contributor
timestamp: September 02, 2022, 11:56:15 pm
content: Yeah the transition from measuring with a multimeter and owning a scope is really the most drastic one in terms of tinkering capability I think (apart from maybe a soldering iron). At least from a standpoint of what sort of projects you can get intoIf you have trouble storing old oscilloscopes just wait until you see the space power electronics takes up after you've been amassing a collection of stuff for a whileThat's not only big but notoriously heavy too (like hundreds of kg per item).My 2m tesla coil has almost become a meme because it's in the way of something 90% of the time just being pushed around my workshop. It's awesome enough that the 10% of time it's not just wasted space is worth it once you find some space to use it though