Wima 'Tropyfol F' caps - any experience? - UK Vintage Radio Repair and Restoration Discussion Forum

Lucien Nunes · 5th Aug 2013, 5:49 pm

Unusually, I'm tempted to leave original coupling capacitors in an audio amplifier. The chassis is part of a rather unusual British-made electric organ in which many different types of non-electrolytic cap are used throughout the circuitry. Some sections feature Wima 'toffees' which I plan to replace outright without further consideration. Others, such as the amplifier, use the 'Tropyfol F' polyester film/foil type of conventional wrap and fill construction. These are the gold-coloured 0.1/400 parts in the pic below, all eight of which test to over 1GΩ at 250V. One was subjected to 500V for 15 seconds with the same result. The epoxy seals all look excellent with no sign of discolouration, shrinkage or cracking. I am inclined to think they are Wima's equivalent of the Mustard cap, well made from long-lasting materials. They seem to have survived well in guitar amps etc, although I have seen failures of the metallised version 'Tropyfol M'.

It might sound a trivial issue, whether to replace 8 capacitors. However this is an electric organ, where things often come not in eights but in 48's or 61's. For each suspect cap in a frequency divider, changing all its stablemates as a precaution runs to 96 capacitors, leading to a general reluctance to replace things just for the sake of it, quite apart from wanting to conserve originality. It just happens that the first section in which these have been put to the test is the amplifier, where there are output bottles at stake.

Has anyone had experience of these, good or bad?

Lucien

G6Tanuki · 5th Aug 2013, 6:05 pm

I hope they're OK, as I'm in the process of replacing all the 1950s-era waxies in a modulator with a batch of new Wimas (0.1uF 400V) acquired at a good price recently.

Restoration73 · 5th Aug 2013, 6:08 pm

These capacitors are excellent and failure is rare in my experience. They were widely
used in some of the Marconi Marine gear in preference to UK items. If I remember the
early Wima "lozenge" type caps used in 50's valve gear were unreliable, and the maker
made a special effort to clear this problem. Pity Hunts didn't do likewise !

Tony

bobbyball · 5th Aug 2013, 6:25 pm

I have some of these capacitors NOS which came from the component stock of a now defunct company that had contracts with the government and military. That they were specified for this type of work says much for the anticipated quality and I will probably use some as replacements in some of my own projects. I have never yet seen one of these to have failed.

jjl · 5th Aug 2013, 7:18 pm

They were also used in large numbers in '60s era UK and European mainframe computers and associated peripherals. In about 1980 I salvaged thousands of this type of cap from defunct computer PCBs and not one was found to be faulty.

John

MotorBikeLes · 5th Aug 2013, 8:37 pm

Grundig colour TVs from around 1970-73 used many of them. I don't particularly remember ever changing any. (Unlike the little black ceramic types they spread around their Tuner-IF and self seek boards in the late '70s and on. I used to replace them almost on sight. An Avo on the 15v backed high ohms range would smell them out. I think they adsorbed moisture and then were leaky).
Les.

HamishBoxer · 5th Aug 2013, 9:13 pm

Top flight cap!

Lucien Nunes · 5th Aug 2013, 9:31 pm

These positive reviews all agree with my own findings, so I will leave them in circuit unless found to be faulty. Apart from the 'toffees' there are other caps automatically under suspicion e.g. Dubilier 470s and other rubber-sealed metal-can papers. If the polystyrenes, the good Wimas and the best of the paper caps in non-critical positions can be retained, this will leave about half the caps to be replaced.

Lucien

Leon Crampin · 5th Aug 2013, 9:35 pm

I tested these for my employer - a major UK automotive electronics organisation - in the '70s.

The dielectric and connections to the metallising are of good quality and unlikely to give trouble unless subjected to high peak currents. The epoxy encapsulent has a fairly high coefficient of linear expansion and will stress the capacitor element at the extremes of its temperature capability. Cycling between the limits as can occur in an automotive application gave rise to a few failures. As the encapsulent is unconstrained (eg. by a metal can), minor temperature excursions generally do not cause problems.

I would be perfectly happy to use these devices in a "domestic" application, but I didn't approve them for use over their stated temperature range.

I clearly remember testing some Rifa devices as part of the same job - "inappropriate for our applications" was my comment at the end of the report...

Leon.

Lucien Nunes · 5th Aug 2013, 9:50 pm

If they withstood your thermal stress tests, they will have fared well in the relatively comfortable conditions in the organ. Although all-valve electronic organs were widely known as 'toasters' on account of the supposed large heat output from the many valves (this one has about 85) in fact most of the circuitry is built around ordinary double triodes and it takes a lot of ECC82s to heat a box the size of an organ console. Life in the deflection area of a typical TV would be much more challenging electrically and thermally for a component.

Lucien

Leon Crampin · 5th Aug 2013, 10:00 pm

It is the number of cycles and the extent of the temperature excursion which partly determines the stress on the element. A good capacitor in the '70s would take 500 cycles limit to limit - sometimes I would simultaneously subject the leads to their rated axial pull if I had any doubts as to their mechanical integrity. Some designs such as those using metal cans filled with epoxy, were a complete liability.

No British components, with or without military approval would ever pass these tests - the best were Philips and some Japanese.

The TFMs are fine for domestic use.

One reason why our domestic electronics industry folded - UK components were rubbish.

Leon.

ronbryan · 6th Aug 2013, 8:36 am

Quote:

Originally Posted by Leon Crampin

The TFMs are fine for domestic use.
Leon.

Leon

Did you mean TFF? The Wima TFM is a different capacitor - as far as I recall these were physically smaller than the TFF for a given capacitance and voltage rating.

Ron

Leon Crampin · 6th Aug 2013, 9:59 am

Ron, as I recall, I tested the TFM and TFFs together with similar results. If the physical materials used in the encapsulation and the method of construction are the same, the performance in my thermal cycling tests was nearly always similar.

I could never understand why critical users (eg the military) were incapable of understanding the failure mechanisms relevant to these and other components, and devising tests to weed out the rubbish. That was part of my job in a commercial organisation.

Have a look at a Racal RA 17 or a late Solartron 'scope now and see how the components are holding up. A cheap Philips or Sony radio made at the same time will run rings round it...

Leon.

5th Aug 2013, 5:49 pm	#1
Lucien Nunes Rest in Peace Join Date: Apr 2008 Location: London, UK. Posts: 2,508	Wima 'Tropyfol F' caps - any experience? Unusually, I'm tempted to leave original coupling capacitors in an audio amplifier. The chassis is part of a rather unusual British-made electric organ in which many different types of non-electrolytic cap are used throughout the circuitry. Some sections feature Wima 'toffees' which I plan to replace outright without further consideration. Others, such as the amplifier, use the 'Tropyfol F' polyester film/foil type of conventional wrap and fill construction. These are the gold-coloured 0.1/400 parts in the pic below, all eight of which test to over 1GΩ at 250V. One was subjected to 500V for 15 seconds with the same result. The epoxy seals all look excellent with no sign of discolouration, shrinkage or cracking. I am inclined to think they are Wima's equivalent of the Mustard cap, well made from long-lasting materials. They seem to have survived well in guitar amps etc, although I have seen failures of the metallised version 'Tropyfol M'. It might sound a trivial issue, whether to replace 8 capacitors. However this is an electric organ, where things often come not in eights but in 48's or 61's. For each suspect cap in a frequency divider, changing all its stablemates as a precaution runs to 96 capacitors, leading to a general reluctance to replace things just for the sake of it, quite apart from wanting to conserve originality. It just happens that the first section in which these have been put to the test is the amplifier, where there are output bottles at stake. Has anyone had experience of these, good or bad? Lucien Attached Thumbnails Last edited by Lucien Nunes; 5th Aug 2013 at 5:58 pm. Reason: Addition

5th Aug 2013, 6:05 pm	#2
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,007	Re: Wima 'Tropyfol F' caps - any experience? I hope they're OK, as I'm in the process of replacing all the 1950s-era waxies in a modulator with a batch of new Wimas (0.1uF 400V) acquired at a good price recently.

5th Aug 2013, 6:08 pm	#3
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: Wima 'Tropyfol F' caps - any experience? These capacitors are excellent and failure is rare in my experience. They were widely used in some of the Marconi Marine gear in preference to UK items. If I remember the early Wima "lozenge" type caps used in 50's valve gear were unreliable, and the maker made a special effort to clear this problem. Pity Hunts didn't do likewise ! Tony

5th Aug 2013, 6:25 pm	#4
bobbyball Octode Join Date: Jul 2011 Location: Stockport, Greater Manchester Posts: 1,215	Re: Wima 'Tropyfol F' caps - any experience? I have some of these capacitors NOS which came from the component stock of a now defunct company that had contracts with the government and military. That they were specified for this type of work says much for the anticipated quality and I will probably use some as replacements in some of my own projects. I have never yet seen one of these to have failed. __________________ Robert

5th Aug 2013, 7:18 pm	#5
jjl Octode Join Date: Jan 2003 Location: Ware, Herts. UK. Posts: 1,082	Re: Wima 'Tropyfol F' caps - any experience? They were also used in large numbers in '60s era UK and European mainframe computers and associated peripherals. In about 1980 I salvaged thousands of this type of cap from defunct computer PCBs and not one was found to be faulty. John

5th Aug 2013, 8:37 pm	#6
MotorBikeLes Nonode Join Date: Dec 2012 Location: Kirk Michael, Isle of Man Posts: 2,350	Re: Wima 'Tropyfol F' caps - any experience? Grundig colour TVs from around 1970-73 used many of them. I don't particularly remember ever changing any. (Unlike the little black ceramic types they spread around their Tuner-IF and self seek boards in the late '70s and on. I used to replace them almost on sight. An Avo on the 15v backed high ohms range would smell them out. I think they adsorbed moisture and then were leaky). Les.

5th Aug 2013, 9:13 pm	#7
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: Wima 'Tropyfol F' caps - any experience? Top flight cap! __________________ G8JET BVWS Archivist and Member V.M.A.R.S

5th Aug 2013, 9:31 pm	#8
Lucien Nunes Rest in Peace Join Date: Apr 2008 Location: London, UK. Posts: 2,508	Re: Wima 'Tropyfol F' caps - any experience? These positive reviews all agree with my own findings, so I will leave them in circuit unless found to be faulty. Apart from the 'toffees' there are other caps automatically under suspicion e.g. Dubilier 470s and other rubber-sealed metal-can papers. If the polystyrenes, the good Wimas and the best of the paper caps in non-critical positions can be retained, this will leave about half the caps to be replaced. Lucien

5th Aug 2013, 9:35 pm	#9
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Wima 'Tropyfol F' caps - any experience? I tested these for my employer - a major UK automotive electronics organisation - in the '70s. The dielectric and connections to the metallising are of good quality and unlikely to give trouble unless subjected to high peak currents. The epoxy encapsulent has a fairly high coefficient of linear expansion and will stress the capacitor element at the extremes of its temperature capability. Cycling between the limits as can occur in an automotive application gave rise to a few failures. As the encapsulent is unconstrained (eg. by a metal can), minor temperature excursions generally do not cause problems. I would be perfectly happy to use these devices in a "domestic" application, but I didn't approve them for use over their stated temperature range. I clearly remember testing some Rifa devices as part of the same job - "inappropriate for our applications" was my comment at the end of the report... Leon.

5th Aug 2013, 9:50 pm	#10
Lucien Nunes Rest in Peace Join Date: Apr 2008 Location: London, UK. Posts: 2,508	Re: Wima 'Tropyfol F' caps - any experience? If they withstood your thermal stress tests, they will have fared well in the relatively comfortable conditions in the organ. Although all-valve electronic organs were widely known as 'toasters' on account of the supposed large heat output from the many valves (this one has about 85) in fact most of the circuitry is built around ordinary double triodes and it takes a lot of ECC82s to heat a box the size of an organ console. Life in the deflection area of a typical TV would be much more challenging electrically and thermally for a component. Lucien Attached Thumbnails

5th Aug 2013, 10:00 pm	#11
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Wima 'Tropyfol F' caps - any experience? It is the number of cycles and the extent of the temperature excursion which partly determines the stress on the element. A good capacitor in the '70s would take 500 cycles limit to limit - sometimes I would simultaneously subject the leads to their rated axial pull if I had any doubts as to their mechanical integrity. Some designs such as those using metal cans filled with epoxy, were a complete liability. No British components, with or without military approval would ever pass these tests - the best were Philips and some Japanese. The TFMs are fine for domestic use. One reason why our domestic electronics industry folded - UK components were rubbish. Leon.

6th Aug 2013, 9:59 am	#13
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Wima 'Tropyfol F' caps - any experience? Ron, as I recall, I tested the TFM and TFFs together with similar results. If the physical materials used in the encapsulation and the method of construction are the same, the performance in my thermal cycling tests was nearly always similar. I could never understand why critical users (eg the military) were incapable of understanding the failure mechanisms relevant to these and other components, and devising tests to weed out the rubbish. That was part of my job in a commercial organisation. Have a look at a Racal RA 17 or a late Solartron 'scope now and see how the components are holding up. A cheap Philips or Sony radio made at the same time will run rings round it... Leon.