Ordered a Faulty Megger BMM80 with intention to repair. - Page 1
Forum section: electronics / repair

author: challie2
author_rank: Contributor
timestamp: October 06, 2016, 10:01:02 pm
content: Ordered a MEGGER BMM80 off someone in hope to get it workingThe fault was described by the seller below"Hi, When turned on,the screen shows the display as shown in the picture,then the display occasionally goes blank then comes on.Its as if there is a loose connection somewhere.If I squeeze the meter I can make the display go on and off too. Regards."I would agree with the sellers statement loose connection it might be power supply or perhaps a loose connection,Now although I have been electrocuted countless times when using an Insulation Tester,Are they're any Highly Dangerous Risks evolved if i open it such as capacitors or coils and inductors etc? i always expect a residual shock of some kind when i open anything to repair, however given this is 1kV even at low amperage I am slightly questionable about it. especially large capacitorsAny Advice would be appreciated maybe you even know what might potentially be the cause.Thanks

author: Jeff_Birt
author_rank: Regular Contributor
timestamp: October 06, 2016, 10:20:54 pm
content: Electrocution is execution by electrical shock. Since you started this thread I will assume you are not dead, thus you have never been electrocuted. You have no doubt received an electric shock on more than one occasion. Sorry to be pedantic but the misuse of term 'electrocuted' is a pet peeve of mine.With any HV source you want to remove the power source and bleed off any caps that might be storing a high voltage or be used to generatea high voltage.

author: lowimpedance
author_rank: Super Contributor
timestamp: October 06, 2016, 10:53:38 pm
content: Why have you had countless shocks from insulation testers ??. Is this a 'proceedural' issue??. So why would you need another tester if you appear to have one 'fully functuional' one..As for the faulty unit there might be some mechanical damage inside causing the LCD 'zebra strip' to loose contact given the display can be made to come and go by squeezing the case. So pictures of the opened unit (when you get it!), would be helpful too.And follow the previous advice when playing with high voltage generation circuits.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: October 06, 2016, 11:03:00 pm
content: Hi,I did a quick search and found the Service Manual, which contains full schematics. This should make it easier and safer.Link:http://www.testitnow.co.uk/test_equipment_manuals/MEGGER/BMM2000%20Service%20Manual%20Issue%201.pdfI had a look at the High voltage supply. You can defeat the high voltage supply by shorting R132 like this:this will make it much safer to work on.It is probably a loose connection or bad zebra strips in the display.Regards,Jay_Diddy_B

author: challie2
author_rank: Contributor
timestamp: October 07, 2016, 07:16:43 am
content: Thank you for the correction we learn something new everyday

author: challie2
author_rank: Contributor
timestamp: October 07, 2016, 07:31:03 am
content: I dont have a megger myself yet, i just got made redundant and I am contracting, and i found this for £20 so if it is not repairable then i havent lost too much i get a kick out of fixing things, as for the shocks College tutors lessons and fellow student pranks, engineering initiation rituals, work place pranks, and sometimes being plain dumb, especially after testing 500m 10mm 2 core cables and getting a zap from the residuals when i put what we call a condom (rubber tube basically cut up bleed pipe) over the cores too keep then protected and dry, otherwise the cable will be failed, need at least 50k ohm for railway signalling cable. Tested too 1kv.

author: challie2
author_rank: Contributor
timestamp: October 07, 2016, 07:32:13 am
content: Thanks this is pure gold.