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 Rola Transformer Help
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 Return to top of page · Post #: 1 · Written at 1:17:58 PM on 24 August 2020.
Destino's Gravatar
 Location: Bells Beach, VIC
 Member since 20 July 2020
 Member #: 2428
 Postcount: 39

Hi there.

Further to the repair of my Calstan 529 valve radio.

The 12" Rola loudspeaker transformer has one of its output leads broken off very close to the point where it enters what appears to be a bitumen type material. It is one of those totally enclosed transformers in a bell like structure. I've sent a image off to Brad for publication.

It has three printed sets of numbers 5000 , C11 , Rola 2 INS.

I will try and connect up the tiny stub of a wire. However if I an unsuccessful is it possible to remove this bitumen type material from the casing and potentially get closer to the source of the terminal.

Other than this issue the transformer appears to measure OK.

Alternatively is there a source for this component?




 Return to top of page · Post #: 2 · Written at 1:52:59 PM on 24 August 2020.
Jimb's Gravatar
 Location: Kanahooka, NSW
 Member since 18 November 2016
 Member #: 2012
 Postcount: 712

You should be able to melt out the bitumen with a heat gun and tap it out of the housing.
Regards Jim

 Return to top of page · Post #: 3 · Written at 2:39:52 PM on 24 August 2020.
Johnny's avatar
 Location: Hobart, TAS
 Member since 31 July 2016
 Member #: 1959
 Postcount: 513

Just dig into the black stuff.
You only need a couple of millimeters to be able to get a good solder joint.
Then support the joint with a little of melted bitumen(use an old soldering iron for this, or mini heat gun).

 Return to top of page · Post #: 4 · Written at 2:43:02 PM on 24 August 2020.
MonochromeTV's avatar
 Location: Melbourne, VIC
 Member since 20 September 2011
 Member #: 1009
 Postcount: 1155

According to the Rola transformer data output transformer type C11 is for 7000 ohms primary to 2 ohms secondary. Type C1 is for 5000 ohms primary to 2 ohms secondary.

Is the Rola 12" speaker a type 12-K, 12-M or 12-O?

 Return to top of page · Post #: 5 · Written at 2:45:36 PM on 24 August 2020.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4749

Those are commonly referred to as ISO transformers. Often the frame inside is alive. With some dodgy mounting they also cut wires with the cap. Heat gun will help. With no one to complain here, kitchen oven often finds another use with suitable containment in place. Don't use a gas one


 Return to top of page · Post #: 6 · Written at 4:44:49 PM on 24 August 2020.
Brad's avatar
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6854

Photo uploaded.

A valve a day keeps the transistor away...

 Return to top of page · Post #: 7 · Written at 5:27:17 PM on 24 August 2020.
Trobbins's avatar
 Location: Melbourne, VIC
 Member since 11 July 2012
 Member #: 1179
 Postcount: 56

It will smell - be prepared.

 Return to top of page · Post #: 8 · Written at 6:42:11 PM on 24 August 2020.
Destino's Gravatar
 Location: Bells Beach, VIC
 Member since 20 July 2020
 Member #: 2428
 Postcount: 39

Thanks all for your help.

Marcc : Having recently rebuilt my kitchen I'm pretty sure using the new oven is a big no no.

MonochromeTV: Pretty sure it says 5000 on the top of the transformer. The most significant figure is a bit rusty but i'd say its a 5. The circuit schematic that I have says 5000 ohms.

The DC resistances of the windings are about 500 ohms for the secondary and 2 ohms for the primary. Are these typical or am I wasting my time.

There are no markings other than a 3 on the speaker so I don't know what type of speaker it is other than a 12" Rola.



 Return to top of page · Post #: 9 · Written at 7:18:29 PM on 24 August 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 2109

I assume you mean 500 ohms for the primary and 2 ohms for the secondary. If so, that sounds about right.

 Return to top of page · Post #: 10 · Written at 10:46:20 PM on 24 August 2020.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4749

My kitchen & house are 2012. Chemical knowledge leads to all sorts of goings on. Oven yields great cakes when I am in the mood. Do it right unlike the C-19 experts, no contamination.

If its a secondary copper wire and you can get at it by melting around it with a soldering iron clean & tin it. Then there really is not a major issue.

Tin a bit of winding wire, bend it into a "J" shape such that there is enough to crimp around the stub. Bend it 90 degrees, crimp it around the stub & solder.

Similar will work on primary.

 Return to top of page · Post #: 11 · Written at 8:28:42 AM on 25 August 2020.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1817

Destino I have two spares of these transformers if you want one my email is open on my profile. Either that or go to jaycar and get a 100 volt line transformer for 11 bucks and that will work.

 Return to top of page · Post #: 12 · Written at 1:20:53 PM on 25 August 2020.
Robbbert's avatar
 Location: Hill Top, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1737

I know what I'd do - I'd get a hammer and punch and break away a bit of that bitumen for about 5mm. Then clean up the broken wire and solder a new one to it. Shouldn't take long.

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