Another Hameg HM 605 - Page 1
Forum section: electronics / repair

author: Apofview
author_rank: Contributor
timestamp: August 27, 2019, 07:45:45 am
content: Hi,Following Dave's suggestion bought HM605 scope of eBay. ( I already have siglent SDS 1104X-E and I'm happy with it)On eBay description says item is in good working condition, but when received item i just showed dot on display.First thing downloaded manual and I checked power supply and voltages on Chp connector.On connector there was no 140VDC rail, next step replaced electrolytic capacitors and got 100VDC and working scope. On 68V rail got 50V...Manual says 140V and 68V, so I replaced greatz on 140 and 68 rail but no change it is still 100 and 50VDC but scope for now is working.What do You think is this correct working voltage?And device was so dirty... dismantled all buttons and dish washing detergent to bright and shiny :-)

author: Apofview
author_rank: Contributor
timestamp: August 27, 2019, 07:50:43 am
content: Did not managed to upload manual here, but i uploaded on scribid.https://www.scribd.com/document/423344654/Hameg-Hm605-Oscilloscope-Service-Manual-Deutsch

author: Apofview
author_rank: Contributor
timestamp: August 27, 2019, 07:59:05 am
content: Here are some images:

author: Apofview
author_rank: Contributor
timestamp: August 27, 2019, 08:02:52 am
content: Also did a little cleanup of switches, and re-flow solder on CRT and on all dials.

author: tautech
author_rank: Super Contributor
timestamp: August 27, 2019, 08:25:54 am
content: Start by placing all the red knobs in the Cal position. (OFF)Then check the sweep circuitry for a sawtooth output. There should be example waveforms in the Service manual.The rising amplitude of the sawtooth is what drives the raster across the display by proportionally changing the voltages on the horizontal plates.

author: Apofview
author_rank: Contributor
timestamp: August 27, 2019, 08:41:36 am
content: There is adjustment plan in service manual.Z board of the CRT - Chp connector pin 5 1250V, with probe 10X thru 10nF 2kV capacitor, VR604 intensity control.what do You think I will achieve with this?

author: tautech
author_rank: Super Contributor
timestamp: August 27, 2019, 08:52:34 am
content: Worry about that later after you can at least get a sweep.After the scope is running properly you can do the fine adjustments.If the LV power rails are within spec don’t adjust anything else yet.When I get time I’ll downlo the manual.

author: Apofview
author_rank: Contributor
timestamp: August 27, 2019, 11:02:30 am
content: Quote from: tautech on August 27, 2019, 08:25:54 amIm sorry I dont understand, where to look for a sweep signal?What is sweep signal :-)

author: tautech
author_rank: Super Contributor
timestamp: August 27, 2019, 09:54:28 pm
content: Quote from: Apofview on August 27, 2019, 11:02:30 amIs this earlier picture you posted of your scope ?If so it's working properly so disregard any sweep comments.FYI, sweep is the left to right travel of the trace across the display at slow timebase settings.Some basic explanation here:https://www.explainthatstuff.com/howoscilloscopeswork.htmlStudy paragraphsHow an oscilloscope worksandElectronic graphs

author: shakalnokturn
author_rank: Super Contributor
timestamp: August 27, 2019, 10:21:38 pm
content: Quote from: Apofview on August 27, 2019, 07:45:45 amYou mean working as in sweeping?If you've been through all the larger electrolytics that could account for seeing low power rails (usually goes with excessive ripple) and nothing is obviously getting too hot, have a look at the back of your scope there is usually a line voltage selector. Depending on your country and present settings you may want to attempt the 90° flip from 125V to 110V or from 240V to 220V.The unregulated voltages are not that important as long as the PS has enough headroom to maintain regulation where required. You may even choose to let it run a little low, less heat, longer life.

author: Apofview
author_rank: Contributor
timestamp: August 28, 2019, 08:52:09 am
content: Quote from: shakalnokturn on August 27, 2019, 10:21:38 pmThank you for sweep explanationAs of the voltage selector, it did crossed my mind... Scope has settings 110/125/220/240 VAC, currently is set to 220VAC. Europe outlet voltage is 220 but my outlet is around 235 volts.Also ordered some little-bit better quality caps and will replace this cheep off the shelf ones.