hameg hm1005 broken y amplifier - Page 1
Forum section: electronics / repair

author: WirelessESD
author_rank: Newbie
timestamp: April 20, 2020, 04:46:04 pm
content: Hey everyone,I own a Hameg hm1005 that worked every now and again if you tilted the case right. It never worked with the cover off but recently its been on the frits more and more. Now it basically does not work anymore expect for a very brief moment were you impact the y amplifier board with a large amount of force. Obviously such a nice scope is of little use if you can only use it in single shot capture mode :p When not being impacted with sudden force the trace never gets above the bottom half of the crt and you have to crank the y position to max to see anything.I have found the relevant service manuals and can link them in if anyone wants. The problem is they don't correspond to the boards in my scope at all. Its like someone stuck another front panel on this scope and pretended it was an hm1005. Luckily if you squeeze your eyes hard enough you can manage to identify each boards purpose. This allowed me to identify the y amplifier and its two drive signals coming in called y1 and y2. This whole board is basically mirrored along the middle one side for each drive signal. So I figured one side is clearly working just trace down the signals across all transistors until I see a difference.So I found that at the output of the '1fks4b3t' is much lower than its brother. Unfortunately, I can't find any datasheet on this part if I would use the service manual it would be SL3127ssl but my board only has one 2n3866 stage and instead has four BF959ssl's instead of two.Naturally, the tapping made me suspect it was a bad solder joint at first but I measured all resistors and diodes and they have the same values on both sides so I really think '1fks4b3t' is giving up. I measured the diodes and resistors in the remaining amplifier after '1fks4b3t' as well in case it was pulling it low but that one measures the same as well.I hope someone can help me out as I don't know what to do if I can't find the actual part to replace it with. I was also really surprised how badly the circuit diagram and board layouts match the actual scope.Kind regards,Corne

author: WirelessESD
author_rank: Newbie
timestamp: April 23, 2020, 08:53:06 am
content: I now believe the marks on the transistor to say TFK s483t which seems to return a lot more results. The sl3127 seems to be a drop in replacement for ca3127. I have found plenty of 'ca3127' on ebay but I presume they are all fake. Bought a couple of the supposed ca3127's none the less, at least they have a decent change of being reasonably matched coming from a transistor array.

author: WirelessESD
author_rank: Newbie
timestamp: November 13, 2022, 12:01:04 pm
content: Hello everyone, I have managed to repair the board.Turns out one of the traces had burned of the PCB, some bridges later and we are good to go. I have added the before and after as attachments.Still plenty of things to do, most pentiometers are clearly flaky and the triggering does not seem to be very stable (could also just be the scope but would expect better results at 1 khz square wave).

author: WirelessESD
author_rank: Newbie
timestamp: October 04, 2023, 07:34:41 am
content: I have written a blog post summarizing my repair and how I approached the problem maybe its interesting to someone:-https://dantalion.nl/2023/06/02/hameg-hm1005-oscilloscope-repair.html

author: Zenith
author_rank: Frequent Contributor
timestamp: October 04, 2023, 03:15:56 pm
content: It's interesting to me because I have a Hameg HM1005 in the queue of things to fix properly. Your experience sounds quite similar to what I've seen.When acquired it it powered up and some of the front panel lights worked but no display, as I was told when I bought it. I took the cover off to look for anything burnt, damaged, badly repaired, loose connections or anything else obviously wrong. I checked the power supply voltage levels, which were correct. I fed in a signal from the calibrator and the scope displayed a square wave. I put the cover back. It's powered up and worked on the several times I've tried it since. I suspect a bad soldered joint or an unreliable cable connection.It works fairly well but the square wave at low frequency is not right. On this the Y pre-amplifier shields have no holes to access the presets. I haven't looked at it properly yet, and there may be no need to do that, but I find it irritating.Hameg are nice scopes, but the technical documentation is lacking. No parts lists, which are useful, and just a few hints on set up, no factory set up procedure, at least that I've seen. I've occasionally heard of people having Hameg scopes of a certain model, with some circuit boards that are quite different to the manuals they can find for that model.

author: EvgenyG
author_rank: Regular Contributor
timestamp: February 14, 2024, 04:12:30 am
content: Probably better late than never. Not many people know, but these guys are the remnants of what used to be Hameg.https://www.sky-messtechnik.de/I was able to source parts and service/calibration/adjustment manuals. You just need to ask politely in an email.They also may answer your specific question and point you in the right direction if something is broken.