Possible Phenomenon - UK Vintage Radio Repair and Restoration Discussion Forum

Bookman · 10th Mar 2018, 8:09 pm

Within my private enclave I use a Harman Kardon 560 as my main amp.
The other day I noticed that it was playing through one channel and my thoughts immediately were more associated with "Horror of Horrors". Could it be a loose connection or faulty component or just a wire that had come off somewhere or had the output protection device functioned?
I then remembered that the better half had been polishing in and around the area so I checked all connections which were all sound. I decided to leave it until this morning after I had been for the paper and lottery tickets.

Here is where the problem starts. The item is a USA model and as such I use a 110V supply and the original 2 pin USA plug on the amp lead. My first thought was to remove the txfr so that I could power the item in my work area (kitchen at this time). It was then that I noticed that the amp plug was half hanging out of the socket. Clearly, I pushed it fully in whereupon the other channel picked up immediately - strange or what?

twinturbo · 10th Mar 2018, 11:44 pm

clutching at straws, suggests half wave AC.

2 pin or 3 pin plug?

Any other source of a possible earth/ground

mike_newcomb · 11th Mar 2018, 2:02 pm

Hi Bookman,
I would start by checking the plug for signs of heating on its exterior Terminals.

If present, it could signify lower power was getting through.

Regards - Mike

dseymo1 · 11th Mar 2018, 2:51 pm

Clearly, if you're interested in investigating further, you could run the amp with something like a lamp limiter in what was the partially-disconnected leg and make some measurements and observations.
I do think things like this are worth following up; we too easily assume that current theory explains all that is worth knowing, and dismiss anything which seems not to fit, thereby perhaps missing some important discoveries.

Boater Sam · 11th Mar 2018, 3:00 pm

One side only getting its neutral connection via a short to earth?

Dave Moll · 11th Mar 2018, 3:08 pm

... unless the supply is served by an RCD - in which case it would surely trip.

mole42uk · 11th Mar 2018, 3:34 pm

Phantom power?

Boater Sam · 11th Mar 2018, 3:41 pm

30mA at mains voltage is a what? 'Leccy leaking from the plug, laa.

Bookman · 11th Mar 2018, 3:54 pm

I can confirm that this is a 2 pin unearthed supply with no direct or indirect earth connected. The attached diagram does however show items bonded to the chassis with an earth symbol?

ms660 · 11th Mar 2018, 4:14 pm

Quote:

Originally Posted by Bookman

I can confirm that this is a 2 pin unearthed supply with no direct or indirect earth connected. The attached diagram does however show items bonded to the chassis with an earth symbol?

That's not an earth symbol, it's a chassis symbol.

Lawrence.

Radio Wrangler · 11th Mar 2018, 4:21 pm

Does it have an anti-thump relay or other shutdown system?

I was just wondering if an arcing/resistive mains connection could have reduced the rail voltages and just hit the point where one channel shut off and the other one wasn't quite at shutoff due to tolerances?

David

hannahs radios · 12th Mar 2018, 5:58 pm

I was thinking maybe it shut down due to a sharp thump due to a poor connection. I had a radio cassette that did similar, one day the mains lead came loose causing a loud thump in the speakers then silence, so I reconnected the lead properly and switched on and all was well, similar to your experience yes? Not important my radio was Sanyo brand run from 240 volt mains

stevedee · 13th Mar 2018, 3:57 pm

It sounds like a dry joint. Is the mains socket mounted on the main PCB, or does it touch the PCB?

Pushing the connector fully-in has disturbed something completely unrelated to the mains (maybe by flexing the chassis...if it has one).

10th Mar 2018, 8:09 pm	#1
Bookman Hexode Join Date: Aug 2017 Location: Taunton, Somerset, UK. Posts: 318	Possible Phenomenon Within my private enclave I use a Harman Kardon 560 as my main amp. The other day I noticed that it was playing through one channel and my thoughts immediately were more associated with "Horror of Horrors". Could it be a loose connection or faulty component or just a wire that had come off somewhere or had the output protection device functioned? I then remembered that the better half had been polishing in and around the area so I checked all connections which were all sound. I decided to leave it until this morning after I had been for the paper and lottery tickets. Here is where the problem starts. The item is a USA model and as such I use a 110V supply and the original 2 pin USA plug on the amp lead. My first thought was to remove the txfr so that I could power the item in my work area (kitchen at this time). It was then that I noticed that the amp plug was half hanging out of the socket. Clearly, I pushed it fully in whereupon the other channel picked up immediately - strange or what?

10th Mar 2018, 11:44 pm	#2
twinturbo Retired Dormant Member Join Date: Mar 2018 Location: Carlisle, Cumbria, UK. Posts: 10	Re: Possible Phenomenon clutching at straws, suggests half wave AC. 2 pin or 3 pin plug? Any other source of a possible earth/ground

11th Mar 2018, 2:02 pm	#3
mike_newcomb Rest in Peace Join Date: Apr 2012 Location: West London, UK. Posts: 665	Re: Possible Phenomenon Hi Bookman, I would start by checking the plug for signs of heating on its exterior Terminals. If present, it could signify lower power was getting through. Regards - Mike

11th Mar 2018, 2:51 pm	#4
dseymo1 Retired Dormant Member Join Date: Dec 2007 Location: Shropshire, UK. Posts: 3,051	Re: Possible Phenomenon Clearly, if you're interested in investigating further, you could run the amp with something like a lamp limiter in what was the partially-disconnected leg and make some measurements and observations. I do think things like this are worth following up; we too easily assume that current theory explains all that is worth knowing, and dismiss anything which seems not to fit, thereby perhaps missing some important discoveries.

11th Mar 2018, 3:00 pm	#5
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Possible Phenomenon One side only getting its neutral connection via a short to earth?

11th Mar 2018, 3:08 pm	#6
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,127	Re: Possible Phenomenon ... unless the supply is served by an RCD - in which case it would surely trip. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

11th Mar 2018, 3:34 pm	#7
mole42uk Nonode Join Date: Aug 2010 Location: Resolven, Wales; and Bristol, England Posts: 2,608	Re: Possible Phenomenon Phantom power? __________________ Richard Index: recursive loop: see recursive loop

11th Mar 2018, 3:41 pm	#8
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Possible Phenomenon 30mA at mains voltage is a what? 'Leccy leaking from the plug, laa.

11th Mar 2018, 3:54 pm	#9
Bookman Hexode Join Date: Aug 2017 Location: Taunton, Somerset, UK. Posts: 318	Re: Possible Phenomenon I can confirm that this is a 2 pin unearthed supply with no direct or indirect earth connected. The attached diagram does however show items bonded to the chassis with an earth symbol? Attached Thumbnails

11th Mar 2018, 4:21 pm	#11
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,868	Re: Possible Phenomenon Does it have an anti-thump relay or other shutdown system? I was just wondering if an arcing/resistive mains connection could have reduced the rail voltages and just hit the point where one channel shut off and the other one wasn't quite at shutoff due to tolerances? David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

12th Mar 2018, 5:58 pm	#12
hannahs radios Hexode Join Date: Jan 2012 Location: Weymouth, Dorset, UK. Posts: 422	Re: Possible Phenomenon I was thinking maybe it shut down due to a sharp thump due to a poor connection. I had a radio cassette that did similar, one day the mains lead came loose causing a loud thump in the speakers then silence, so I reconnected the lead properly and switched on and all was well, similar to your experience yes? Not important my radio was Sanyo brand run from 240 volt mains

13th Mar 2018, 3:57 pm	#13
stevedee Retired Dormant Member Join Date: Feb 2018 Location: Horsham, West Sussex, UK. Posts: 19	Re: Possible Phenomenon It sounds like a dry joint. Is the mains socket mounted on the main PCB, or does it touch the PCB? Pushing the connector fully-in has disturbed something completely unrelated to the mains (maybe by flexing the chassis...if it has one).