Author Topic: Wanted 0.25ufd 500 volt axial capacitors  (Read 578 times)

Offline kubusi

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Wanted 0.25ufd 500 volt axial capacitors
« on: December 28, 2016, 10:45:23 AM »
Can anyone give me a lead to locate a source of 0.25 ufd 500 volt axial capacitors, I am in need of 12 of them. I realise no longer a standard value so 0.22 ufd or 0.27 ufd will suffice with a voltage rating of 500 volts or higher. These are needed for a restoration project I am currently busy with.
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Offline Family_Dog

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #1 on: December 28, 2016, 12:38:17 PM »
Have you tried RS? Couldn't find anything on Mantech's website. You could possibly also contact Mongoose on the forum.


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Offline kubusi

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #2 on: December 28, 2016, 01:01:14 PM »
Thanks Eric, for those leads I will be following them up, I had already downloaded the Maplin catalogue and they dont have anything even close to what I am looking for.
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Offline kenneths

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Offline Family_Dog

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #4 on: December 29, 2016, 07:27:43 AM »
Kenneth, your product searching capabilities on Mantech's site are far superior to mine! ;) I knew they should have them because I had previously bought 0.47uI Hi-voltahe caps from them, but after 20 minutes search on their website I just gave up. Normally I send them a RTQ list of what I need and let their staff do the picking.

Neil, email Catherine at Mantech in JHB, she is very helpful and her general pricing is better than the prices on their website.


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Offline afroaudio

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #5 on: December 29, 2016, 03:23:09 PM »
Assuming for coupling caps in valve amp..? I have had great results with the Polyprops from RS

Vishay MKP1839 mostly rated at 800V

I used 22nF in place of 25nF in my Leak Stereo 20 and the amp sounds very good. Recommended by others as well which is how I found them. Worth paying a bit more for Polyprops I think, more linear dialectric apparently (over Polyester)

Offline kubusi

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #6 on: December 29, 2016, 11:06:46 PM »
Many many thanks to Kenneths, Eric and Jonathan for the digging to find me a source to get these capacitors for me, I had a search at Mantech but did not find them. I also had a look at A1 in Durban, result nothing. I will most certainly contact Mantech in the new year for them and any other bits I may be in need of for the restoration project presently underway.
Johathan I think you can guess what I am busy restoring, coming on slowly, not rushing it at all.
Thanks again to all of you for your help.
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Offline Family_Dog

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #7 on: December 30, 2016, 07:34:55 AM »
>> Johathan I think you can guess what I am busy restoring, coming on slowly, not rushing it at all.

Now this is simply not right! Details, please. A valve amp seems obvious, but which one? You know pics are obligatory.


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Offline kubusi

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #8 on: December 30, 2016, 08:56:32 AM »
OK, Eric the main present project is getting three Leak TL 12.1 amplifiers back to as original as I can get them.  Two of them are the BBC versions and the third one is the standard version. One very interesting thing with the 2 BBC types, the capacitor blocks of 4 X  4 ufd paper caps. In the filter/smoothing circuits are perfect. In each case with all 4 connected in parallel at 500 volts across them the leakage current is less than 2 microamp.
Yes I have taken a few photos of them as I am going along.
Another project at present is a complete rebuild of a Mullard 5 - 10, starting from a bare stripped and repainted chassis, I have mentioned this one previously on the forum.
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Hot glass looks exactly the same as cold glass.

Offline Family_Dog

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #9 on: December 30, 2016, 11:57:57 AM »
The only Leak equipment I own are the Troughline FM tuner and Stereo 30+30 amp, with Sandwich speakers. I have never yet got my grubby paws on any of their valve amplifiers although I have given this some pretty serious thought, there have been a few for sale on and off on the forum. Guess one of these days I might still do so but the problem is where does one display all this equipment? I am already at the shameful state of storing much of my gear in cupboards (Hi, my name is Eric and I am a HOARDER!) but my original idea was to put them all on display in perfect working condition.

And yet I keep adding to my collection...   :thinking:  :help:


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Offline kubusi

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #10 on: December 30, 2016, 12:32:18 PM »
Eric I have a few other Leak bits, a Troughline tuner, solid state Stereo 70,  a Stereo 20 and a single Sandwich speaker that needs some TLC, got it in a slightly buggered condition originally. The tuner and Stereo 70 are still packed in their original boxes. I need to look at the Stereo 70 there is an intermittent problem with it, the odd crackle at times when I last used it.
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Hot glass looks exactly the same as cold glass.

Offline charles

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #11 on: January 01, 2017, 03:12:55 PM »
"OK, Eric the main present project is getting three Leak TL 12.1 amplifiers back to as original as I can get them.  Two of them are the BBC versions and the third one is the standard version. One very interesting thing with the 2 BBC types, the capacitor blocks of 4 X  4 ufd paper caps. In the filter/smoothing circuits are perfect. In each case with all 4 connected in parallel at 500 volts across them the leakage current is less than 2 microamp.
Yes I have taken a few photos of them as I am going along."

All the best with the restoration of the TL12 point one’s.

I have restored mine and found some interesting differences
between them: 

There are different wiring looms regarding the color-coding of the wires.

Two different types of Output Transformers in the Broadcast models.

The commercial Tl 12 has a 3rd different type of Output Transformer.

Are yours vintage SABC or real BBC TL12 point ones. Some call our
broadcast ones BBC types but there are differences between the two.

Offline kubusi

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #12 on: January 02, 2017, 12:21:53 AM »
Yes Charles there are a number of variations of these amplifiers, I have come across a few of them myself in my digging and I am sure there are more of them.

To answer your question my "BBC" types are both ex SABC and externally they look identical to most of the types which come up on  the Internet described as BBC versions. The output transformers on both are reference number TL/12/T2/1B  and the transformer on the third one has output transformer number TL/12/T2/2.

Of the BBC types I have identified the following variations in no particular order:-
Factory fitted heat shield between the valves and the inductors and paper capacitor block , there is  no change over switch from the 600 ohm input transformer to high impedance input, no volume control and no Jones plug input or octal input socket. The input transformer is mounted where the octal socket would normally be.

No heat shield but has a volume control only with transformer mounted as above. No switch or Jones Plug adjacent to volume control.

Has octal socket as per commercial version and 600 ohm input transformer moved back close to capacitor block has Jones Plug input, change over switch and volume control all in close proximity, this is the version my two examples are.

Another version I am aware of has a high impedance output transformer and was used to drive the modulators of AM transmitters. Have not come across any photos of this particular model

Adverts in Wireless World in the 1950's indicated that the special BBC version was also supplied to the SABC and the number mentioned was 600 amplifiers, so I had always assumed the locally used versions were in fact the same as the similar looking models used in the UK

The very early production models used an EF36 input stage, later changed to EF37 and  finally to the EF37A, all basically the same valve with improvements

Have not taken note of any variations in colours of the wires which you mention, I was not aware of the other variations in output transformers used, thanks for that information.


?
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Offline charles

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #13 on: January 02, 2017, 10:59:57 AM »
Dear kubusi regarding the BBC leaks:

I have a photograph of a pair BBC Leaks from the front side that shows the BBC lettering and the heat shield.

Another source is from the book firsts in High Fidelity
The Products and History of H.J.Leak & Co.Ltd. by Stephen Spicer
A picture with description indicates that the BBC incorporated the TL12 into the base of its studio
monitor loudspeakers with a 600 ohm input transformer, heat shield and an attenuator.

These two could be the same. I am also not sure because I have not seen enough photographs/descriptions of the BBC ones.

"Has octal socket as per commercial version and 600 ohm input transformer moved back close to capacitor
block has Jones Plug input, change over switch and volume control all in close proximity, this is the version
my two examples are."

The Broadcast ones (construction/looks) I have are the same as yours:
Four have the output transformers: TL/12/T2/1B
Two have the output transformers: TL/12/T2/1

The Commercial ones (construction/looks) I have are the same as yours:
Two have the output transformers: Tl/12/T2/2

According to Spicer's book there is another output transformer: Tl/12/T2/40, that was a high impedance output one. 

I also have not seen a picture of one used in an modulator role.
 
I have some Leak service sheets dated 1954 and 1951. The 1951 one indicated the Tl/12/T2/2 as standard and the
TL/12/T2/1 as non-standard.

Could not get any information on the TL/12/T2/1B one.

Thank you for your interesting information.

All the best regarding the restoration of the Leak 12 point ones.

 

Offline kubusi

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Re: Wanted 0.25ufd 500 volt axial capacitors
« Reply #14 on: January 02, 2017, 01:40:04 PM »
Charles, thank you for the additional information on the TL12.1,  I have not come across the book by Stephan Spicer so I must keep a lookout for it.
Have you ever read the article in the Australian magazine Radiotronics of September 1955 an interesting article by Fritz Langford-Smith and A R Chesterman about the Leak TL12.1 and covers correspondence between the authors and H J Leak as well as a lot of other  information pertaining to it.
I have the magazine in a pdf file and should you like a copy, PM your email address to me. The file size is about 20MB
Strangely Langford-Smith only made one brief mention of the Leak amplifier in the Radio Designers Handbook whereas  the Williamson is covered in depth
FIRST LAW OF VALVE AMPLIFIERS
Hot glass looks exactly the same as cold glass.