Wolf Saphire drill rectifier blown - UK Vintage Radio Repair and Restoration Discussion Forum

TowerRadio · 26th Apr 2018, 10:34 pm

I have two of these drills ,the one I bought in 1975 blew the dual speed rectifier and shortly after the switch packed up. This one I use at fixed high speed with a foot switch and a Wolf drill column. The other one has also blown its speed rectifier with a loud crack. I know from the first drill that this rectifier is a very small thing, about the size of a 1N4001. Any ideas what I could replace it with? (The Rifa 0.1 250volt PMX 2003 had blown up before I obtained this drill so that needs to be changed also)

Refugee · 26th Apr 2018, 11:56 pm

The capacitor fails first and due to the spikes the diode fails later.
I would use another 800V diode of any make and a new mains rated capacitor.
You can go bigger with the diode such as 1N5407.
http://uk.farnell.com/c/semiconducto...ctifier-diodes
A pulse capacitor of the type found doing flyback duty in an old CRT screen can be used.
The value is not too critical but make it more than about 0.01uf.
We will need to know the package type for the capacitor.

barrymagrec · 27th Apr 2018, 8:19 am

Not quite on topic but I have a 35 year old Wolf Saphire 4 inch angle grinder and a couple of weeks ago while using it the supressor cap exploded and sent a lump of molten innards out of the vent and burnt the side of my face - the grinder carried on unperturbed.

Boater Sam · 27th Apr 2018, 10:45 am

I was going to offer free Rifa caps to replace these, I had 40+ of them, new, but thought better of it as I would not be popular when they blew.
Some of them were already cracked!
1N4007 would do but 1N5407 is better, as has been said.

TowerRadio · 27th Apr 2018, 11:27 am

Thanks for the replies, I have a 33nF 1100v cap I shall use(courtesy of whiskas) and somewhere I have a 1000 volt 3 amp rectifier which will probably fit outside the switch.Les

26th Apr 2018, 10:34 pm	#1
TowerRadio Hexode Join Date: Mar 2008 Location: Bristol, UK. Posts: 388	Wolf Saphire drill rectifier blown I have two of these drills ,the one I bought in 1975 blew the dual speed rectifier and shortly after the switch packed up. This one I use at fixed high speed with a foot switch and a Wolf drill column. The other one has also blown its speed rectifier with a loud crack. I know from the first drill that this rectifier is a very small thing, about the size of a 1N4001. Any ideas what I could replace it with? (The Rifa 0.1 250volt PMX 2003 had blown up before I obtained this drill so that needs to be changed also)

26th Apr 2018, 11:56 pm	#2
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Wolf Saphire drill rectifier blown The capacitor fails first and due to the spikes the diode fails later. I would use another 800V diode of any make and a new mains rated capacitor. You can go bigger with the diode such as 1N5407. http://uk.farnell.com/c/semiconducto...ctifier-diodes A pulse capacitor of the type found doing flyback duty in an old CRT screen can be used. The value is not too critical but make it more than about 0.01uf. We will need to know the package type for the capacitor.

27th Apr 2018, 8:19 am	#3
barrymagrec Octode Join Date: Dec 2017 Location: Morden, Surrey, UK. Posts: 1,557	Re: Wolf Saphire drill rectifier blown Not quite on topic but I have a 35 year old Wolf Saphire 4 inch angle grinder and a couple of weeks ago while using it the supressor cap exploded and sent a lump of molten innards out of the vent and burnt the side of my face - the grinder carried on unperturbed.

27th Apr 2018, 10:45 am	#4
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Wolf Saphire drill rectifier blown I was going to offer free Rifa caps to replace these, I had 40+ of them, new, but thought better of it as I would not be popular when they blew. Some of them were already cracked! 1N4007 would do but 1N5407 is better, as has been said.

27th Apr 2018, 11:27 am	#5
TowerRadio Hexode Join Date: Mar 2008 Location: Bristol, UK. Posts: 388	Re: Wolf Saphire drill rectifier blown Thanks for the replies, I have a 33nF 1100v cap I shall use(courtesy of whiskas) and somewhere I have a 1000 volt 3 amp rectifier which will probably fit outside the switch.Les