Rifas again - UK Vintage Radio Repair and Restoration Discussion Forum

Studio263 · 18th Jul 2014, 12:46 pm

I've had two Rifa capacitors fail this week, both in the usual way (smoke, burning smell that hangs around for ages, equipment keeps on working) in seperate and unrelated pieces of equipment. Could it be the heat that brings this on? Its been really warm down here. Strange; I always thought that it was dampness that caused them to let go.

Herald1360 · 18th Jul 2014, 12:49 pm

Humidity has also been quite high, which wouldn't help.

Are the unrelated bits of equipment of a similar age?

18th Jul 2014, 5:28 pm

Probably a butterfly flapping it's wings in the Amazon, these things go all the time.

G6Tanuki · 18th Jul 2014, 6:39 pm

Or maybe... the current warm-and-humid spell being accompanied by a high barometric air-pressure. Could this have helped to push damp air in through the cracks in the cap's encapsulation?

[ Don't dismiss this: pressure cycling is a big issue in avionics that spend their lives outside the benign environment of the pressurised passenger/crew-compartment ]

Silicon · 19th Jul 2014, 5:55 pm

Could it be voltage spikes from the lightning we had recently?

mark pirate · 19th Jul 2014, 6:09 pm

It could be any of the above, these things don't need much of an excuse to go up in smoke

If I find these in any equipment I work on, they get replaced as a matter of course. I have experienced the foul smell and smoke first hand, it is only a matter of time until they cause a fire!

Mark

bobbyball · 19th Jul 2014, 8:46 pm

I recently had cause to "refurbish" the same mains panel in a similar B&O set and out went the "Rifa" mains filter capacitor - as a matter of course. There are some other filter/isolation capacitors on that board, between the "isolated" and "non isolated" sides of the chopper/EHT transformer. I replaced these too but the repacements, ironically, were Rifa branded, the only make I could find at the time without paying silly money. These are however, of recent production/current stock. As these sets came out around 1980 I guess the original caps have lasted longer than the set maker would have expected the set to be in use for!

Studio263 · 24th Jul 2014, 7:33 am

Make that 3, all in the space of a week! I don't think the smell will ever go away, but I may get used to it in time... The eqiupment that failed was:

1) Old Philips oscillocsope (late 70s I think)
2) B&O 77XX TV chassis (early 80s)
3) BBC Micro model B Issue 7 (1984)

Strange business this, assuming that I am not alone I wonder how much old stuff got thrown away last week because it "caught fire"?

Refugee · 24th Jul 2014, 8:56 pm

I had one go in the vacuum cleaner about a month ago.

Okto1984 · 24th Jul 2014, 10:27 pm

I think that they develop cracks in their plastic cases as they age, but keep working with the cracks until damp gets in and shorts them out. Long periods of not using an appliance could allow damp to migrate in and get trapped in the paper (explaining why they often like to pop just after switching on when something hasn't been used for a while), or simply high pressure and humid air could do it.

Top Cap · 24th Jul 2014, 11:39 pm

My first day in a repair centre and I was asked to look at a switched mode power pack.
Looking through the vent slots in the case I saw a blackened Rifa that had blown the supply fuse and told the Supervisor I could fix it for less than a couple of quid. Being the new boy I don't think he took me seriously and sent it out for repair. It came back repaired all right but with a repair ticket of £350! We could have bought a new one for less but I didn't care as it taught the idiot a lesson and surprisingly, he accepted every decision I made after that

8 Tracker · 26th Jul 2014, 4:48 pm

They are everywhere. I bought a couple of Grasslin digital, two-channel, panel mount timers last weekend. I opened them up to check the memory-retention batteries and there sat a very cracked Rifa, directly across the mains input to the transformer. I took them out on each timer, both looked the same. Didn't bother replacing them.

Just for fun, I connected a mains lead to them, stuck them out of the window and switched on. The first one instantly went bang and released the usual foul-smelling smoke. The second lasted about three seconds before exploding. As normal, no flames, which is good news. Kept me amused for a few minutes.

18th Jul 2014, 12:46 pm	#1
Studio263 Octode Join Date: Apr 2007 Location: Hampshire, UK. Posts: 1,577	Rifas again I've had two Rifa capacitors fail this week, both in the usual way (smoke, burning smell that hangs around for ages, equipment keeps on working) in seperate and unrelated pieces of equipment. Could it be the heat that brings this on? Its been really warm down here. Strange; I always thought that it was dampness that caused them to let go.

18th Jul 2014, 12:49 pm	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Rifas again Humidity has also been quite high, which wouldn't help. Are the unrelated bits of equipment of a similar age? __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

18th Jul 2014, 5:28 pm	#3
Guest Guest Posts: n/a	Re: Rifas again Probably a butterfly flapping it's wings in the Amazon, these things go all the time.

18th Jul 2014, 6:39 pm	#4
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: Rifas again Or maybe... the current warm-and-humid spell being accompanied by a high barometric air-pressure. Could this have helped to push damp air in through the cracks in the cap's encapsulation? [ Don't dismiss this: pressure cycling is a big issue in avionics that spend their lives outside the benign environment of the pressurised passenger/crew-compartment ]

19th Jul 2014, 5:55 pm	#5
Silicon Nonode Join Date: Jun 2007 Location: Coulsdon, London, UK. Posts: 2,163	Re: Rifas again Could it be voltage spikes from the lightning we had recently?

19th Jul 2014, 6:09 pm	#6
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: Rifas again It could be any of the above, these things don't need much of an excuse to go up in smoke If I find these in any equipment I work on, they get replaced as a matter of course. I have experienced the foul smell and smoke first hand, it is only a matter of time until they cause a fire! Mark

19th Jul 2014, 8:46 pm	#7
bobbyball Octode Join Date: Jul 2011 Location: Stockport, Greater Manchester Posts: 1,214	Re: Rifas again I recently had cause to "refurbish" the same mains panel in a similar B&O set and out went the "Rifa" mains filter capacitor - as a matter of course. There are some other filter/isolation capacitors on that board, between the "isolated" and "non isolated" sides of the chopper/EHT transformer. I replaced these too but the repacements, ironically, were Rifa branded, the only make I could find at the time without paying silly money. These are however, of recent production/current stock. As these sets came out around 1980 I guess the original caps have lasted longer than the set maker would have expected the set to be in use for! __________________ Robert

24th Jul 2014, 7:33 am	#8
Studio263 Octode Join Date: Apr 2007 Location: Hampshire, UK. Posts: 1,577	Re: Rifas again Make that 3, all in the space of a week! I don't think the smell will ever go away, but I may get used to it in time... The eqiupment that failed was: 1) Old Philips oscillocsope (late 70s I think) 2) B&O 77XX TV chassis (early 80s) 3) BBC Micro model B Issue 7 (1984) Strange business this, assuming that I am not alone I wonder how much old stuff got thrown away last week because it "caught fire"?

24th Jul 2014, 8:56 pm	#9
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Rifas again I had one go in the vacuum cleaner about a month ago.

24th Jul 2014, 10:27 pm	#10
Okto1984 Retired Dormant Member Join Date: Dec 2013 Location: Winchester, Hampshire, UK Posts: 288	Re: Rifas again I think that they develop cracks in their plastic cases as they age, but keep working with the cracks until damp gets in and shorts them out. Long periods of not using an appliance could allow damp to migrate in and get trapped in the paper (explaining why they often like to pop just after switching on when something hasn't been used for a while), or simply high pressure and humid air could do it.

24th Jul 2014, 11:39 pm	#11
Top Cap Octode Join Date: Mar 2006 Location: Watford, Hertfordshire, UK. Posts: 1,270	Re: Rifas again My first day in a repair centre and I was asked to look at a switched mode power pack. Looking through the vent slots in the case I saw a blackened Rifa that had blown the supply fuse and told the Supervisor I could fix it for less than a couple of quid. Being the new boy I don't think he took me seriously and sent it out for repair. It came back repaired all right but with a repair ticket of £350! We could have bought a new one for less but I didn't care as it taught the idiot a lesson and surprisingly, he accepted every decision I made after that __________________ Whether the Top Cap is Grid or Anode - touching it will give you a buzz either way!

26th Jul 2014, 4:48 pm	#12
8 Tracker Hexode Join Date: Jul 2009 Location: Mablethorpe, Lincolnshire, UK. Posts: 286	Re: Rifas again They are everywhere. I bought a couple of Grasslin digital, two-channel, panel mount timers last weekend. I opened them up to check the memory-retention batteries and there sat a very cracked Rifa, directly across the mains input to the transformer. I took them out on each timer, both looked the same. Didn't bother replacing them. Just for fun, I connected a mains lead to them, stuck them out of the window and switched on. The first one instantly went bang and released the usual foul-smelling smoke. The second lasted about three seconds before exploding. As normal, no flames, which is good news. Kept me amused for a few minutes.