Murphy V200a - UK Vintage Radio Repair and Restoration Discussion Forum

peter10tv · 11th May 2011, 6:19 pm

Hello All

Further to my request for a LOPT for the Murphy V200a that I am restoring, I have further information to report on.

The transformer fizzled and spouted smoke at the exact time as I was turning the set to get to the IFs for retuning after an 'engineer' had twiddled them. Not getting any response to my request for a replacement I decided to remove the trans for rewinding. After emptying out the oil I removed the top of the can by spinning it in a lathe. When I removed the transformer I could see no sign of damage, and considering the amount of smoke I expected the burn to be obvious. So I connected it up again without its can and low and behold it worked fine without any sign of burning. Back into the can it went along with new oil and it worked for a few minutes then fizzle and smoke again. This time when under closer examination I could see the the oil soaked paxolin around the overwind coil fixing stud was blacker than the rest and carbonised. So I cut out around the stud and moved the coil end to another, unused stud. Once again into the can and again filling with oil and then back into the set. Turned on it has now been swithed on for four hours without a blip.
When I initially emptied out the oil from the dry unleaking transformer I was amazed to see only enough to fill a quarter of the can. I can only sumise that moving the set just gave it enough of a jolt to set the overwind stud to arc to the metal can.. The moral of this story to those with oil filled transformers is to check that they are indeed full. There is an unfixed wire protruding from the top of the rubber cover, this is the filling spout and the transformer is easily filled from there. Check yours now and avoid a Kaput transformer.
Next line... Has anyone got any ferrite slugs to replace those butchered by the previous 'engineer.. They are M8 size.
All the best
Peter.

murphyv310 · 11th May 2011, 6:31 pm

Murphy oil filled transformers can actually absorb moisture, this was documented in the late fifties in "Murphy News".
They said that under certain circumstances the transformer can get saturated with moisture and Murphy advised the TV set should be run for at least 2 hours continuously every 2 weeks. The problem was in damp houses and those people who would only watch a short program.
I have drained out the oil in all my Murphy's and allowed the transformers to properly dry out then refilled them with vegetable oil, I had no further troubles with mine, and I do run them regularly for a good few hours!

peter10tv · 11th May 2011, 7:43 pm

Thanks Trevor,

This Murphy must have been running for an agregate of at least 20 hours over the last few weeks before any trouble occured, and it happened just as I turned the set over to attend to correct alignment. Of course there could have been residual dampness, but lack of oil could not have helped. Although it must have been over 40 years since I repaired these sets full time, we live and learn. That's what this hobby is all about.

Regards Peter.

11th May 2011, 6:19 pm	#1
peter10tv Pentode Join Date: Oct 2008 Location: Essex, UK. Posts: 108	Murphy V200a Hello All Further to my request for a LOPT for the Murphy V200a that I am restoring, I have further information to report on. The transformer fizzled and spouted smoke at the exact time as I was turning the set to get to the IFs for retuning after an 'engineer' had twiddled them. Not getting any response to my request for a replacement I decided to remove the trans for rewinding. After emptying out the oil I removed the top of the can by spinning it in a lathe. When I removed the transformer I could see no sign of damage, and considering the amount of smoke I expected the burn to be obvious. So I connected it up again without its can and low and behold it worked fine without any sign of burning. Back into the can it went along with new oil and it worked for a few minutes then fizzle and smoke again. This time when under closer examination I could see the the oil soaked paxolin around the overwind coil fixing stud was blacker than the rest and carbonised. So I cut out around the stud and moved the coil end to another, unused stud. Once again into the can and again filling with oil and then back into the set. Turned on it has now been swithed on for four hours without a blip. When I initially emptied out the oil from the dry unleaking transformer I was amazed to see only enough to fill a quarter of the can. I can only sumise that moving the set just gave it enough of a jolt to set the overwind stud to arc to the metal can.. The moral of this story to those with oil filled transformers is to check that they are indeed full. There is an unfixed wire protruding from the top of the rubber cover, this is the filling spout and the transformer is easily filled from there. Check yours now and avoid a Kaput transformer. Next line... Has anyone got any ferrite slugs to replace those butchered by the previous 'engineer.. They are M8 size. All the best Peter.

11th May 2011, 6:31 pm	#2
murphyv310 Dekatron Join Date: Sep 2006 Location: Kilmarnock, Ayrshire, UK. Posts: 5,422	Re: Murphy V200a Murphy oil filled transformers can actually absorb moisture, this was documented in the late fifties in "Murphy News". They said that under certain circumstances the transformer can get saturated with moisture and Murphy advised the TV set should be run for at least 2 hours continuously every 2 weeks. The problem was in damp houses and those people who would only watch a short program. I have drained out the oil in all my Murphy's and allowed the transformers to properly dry out then refilled them with vegetable oil, I had no further troubles with mine, and I do run them regularly for a good few hours! __________________ Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member

11th May 2011, 7:43 pm	#3
peter10tv Pentode Join Date: Oct 2008 Location: Essex, UK. Posts: 108	Re: Murphy V200a Thanks Trevor, This Murphy must have been running for an agregate of at least 20 hours over the last few weeks before any trouble occured, and it happened just as I turned the set over to attend to correct alignment. Of course there could have been residual dampness, but lack of oil could not have helped. Although it must have been over 40 years since I repaired these sets full time, we live and learn. That's what this hobby is all about. Regards Peter.