Fluke 9100ft digital troubleshooter SMPS trips rid (RCD) - UK Vintage Radio Repair and Restoration Discussion Forum

backflipper · 31st Jan 2012, 12:39 am

Hello all,
I am Hopng someone can help me. I have the above bit of test gear and it has recently started tripping the red (RCD) in my workshop. I have disconnected all output rails from the SMPS and bypassed the input filter and after 3-5 minutes the red (RCD) trips. I was monitoring the output voltages and they are rock solid +5,-5,+12.

Any ideas? Unfortunately the service manual for the unit does not have the schematic for the SMPS so I am kimd of going by prior knowledge.

Any help would be greatly appreciated.

Cheers
Steve

DangerMan · 31st Jan 2012, 1:55 am

Hi Steve,
I don't know this piece of equipment, but I'm guessing its smps is fed from single phase (red-neutral).

I'm also guessing it's an RCD trip that is going out...?
When you say "bypassed", do you mean completely removed from circuit? As with a separate filter that you've taken out completely and fed the mains directly to the smps?

If so, perhaps the smps itself has an earth fault.. It is most likely it will have its own on-board AC filter, and the fault could be a Y capacitor although they are designed not to do it!
Alternatively, a duff X cap could be self-healing and taking out an MCB... (dunno which one is actually tripping, RID = RCD ?).

Pete

PS. If it really is an earth fault, despite HI-pot tests etc. of the smps transformer, the transformer can cause this if it develops an insulation fault. Unlikely, but the only cure then is a new smps.
It's VERY unusual these days (especially with something from Fluke, I think) and won't necessarily be shown up by off-load voltage checks. Pri-sec megger tests, might show it.

Station X · 31st Jan 2012, 9:34 am

I've edited references to "rid" and "red" to read "RCD". Perhaps rid and red are protective devices I'm unfamiliar with though?

backflipper · 31st Jan 2012, 8:05 pm

Thanks for the reply, by bypassing I mean I completely skipped the mains filter and fed 240vac directly into the switcher. I am chasing down a replacement as it maybe the easiest solution. It's not your common 12v,-5v,5v psu so hopefully I can source a second hand one from a faulty unit.
Cheers
Steve

backflipper · 31st Jan 2012, 8:08 pm

I should also add that I isolated the supply after the first bit of rectification ie. after the bridge rectifier and rectifier cap so any mains filter caps should have tripped it but alas they did not.

backflipper · 1st Feb 2015, 3:42 pm

Long time since I posted this but I thought I should update...

After replacing the main filter it sorted the problem. This was one of those IEC moulded mains filters..

31st Jan 2012, 12:39 am	#1
backflipper Tetrode Join Date: Mar 2010 Location: Haslemere, Surrey, UK Posts: 73	Fluke 9100ft digital troubleshooter SMPS trips rid (RCD) Hello all, I am Hopng someone can help me. I have the above bit of test gear and it has recently started tripping the red (RCD) in my workshop. I have disconnected all output rails from the SMPS and bypassed the input filter and after 3-5 minutes the red (RCD) trips. I was monitoring the output voltages and they are rock solid +5,-5,+12. Any ideas? Unfortunately the service manual for the unit does not have the schematic for the SMPS so I am kimd of going by prior knowledge. Any help would be greatly appreciated. Cheers Steve

31st Jan 2012, 1:55 am	#2
DangerMan Heptode Join Date: Jul 2009 Location: Stoke-on-Trent, Staffordshire, UK. Posts: 719	Re: Fluke 9100ft digital troubleshooter SMPS trips rid Hi Steve, I don't know this piece of equipment, but I'm guessing its smps is fed from single phase (red-neutral). I'm also guessing it's an RCD trip that is going out...? When you say "bypassed", do you mean completely removed from circuit? As with a separate filter that you've taken out completely and fed the mains directly to the smps? If so, perhaps the smps itself has an earth fault.. It is most likely it will have its own on-board AC filter, and the fault could be a Y capacitor although they are designed not to do it! Alternatively, a duff X cap could be self-healing and taking out an MCB... (dunno which one is actually tripping, RID = RCD ?). Pete PS. If it really is an earth fault, despite HI-pot tests etc. of the smps transformer, the transformer can cause this if it develops an insulation fault. Unlikely, but the only cure then is a new smps. It's VERY unusual these days (especially with something from Fluke, I think) and won't necessarily be shown up by off-load voltage checks. Pri-sec megger tests, might show it. Last edited by DangerMan; 31st Jan 2012 at 2:08 am.

31st Jan 2012, 9:34 am	#3
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Fluke 9100ft digital troubleshooter SMPS trips rid (RCD) I've edited references to "rid" and "red" to read "RCD". Perhaps rid and red are protective devices I'm unfamiliar with though? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

31st Jan 2012, 8:05 pm	#4
backflipper Tetrode Join Date: Mar 2010 Location: Haslemere, Surrey, UK Posts: 73	Re: Fluke 9100ft digital troubleshooter SMPS trips rid (RCD) Thanks for the reply, by bypassing I mean I completely skipped the mains filter and fed 240vac directly into the switcher. I am chasing down a replacement as it maybe the easiest solution. It's not your common 12v,-5v,5v psu so hopefully I can source a second hand one from a faulty unit. Cheers Steve

31st Jan 2012, 8:08 pm	#5
backflipper Tetrode Join Date: Mar 2010 Location: Haslemere, Surrey, UK Posts: 73	Re: Fluke 9100ft digital troubleshooter SMPS trips rid (RCD) I should also add that I isolated the supply after the first bit of rectification ie. after the bridge rectifier and rectifier cap so any mains filter caps should have tripped it but alas they did not.

1st Feb 2015, 3:42 pm	#6
backflipper Tetrode Join Date: Mar 2010 Location: Haslemere, Surrey, UK Posts: 73	Re: Fluke 9100ft digital troubleshooter SMPS trips rid (RCD) Long time since I posted this but I thought I should update... After replacing the main filter it sorted the problem. This was one of those IEC moulded mains filters..