Fixing a blown fuse

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crisscross

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Sep 3, 2009
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Hyderabad
I have the Swan M200 speakers. Link below and these are the US 110 Volt version inadvertently I hooked it up directly to the plug without using the step down and ended up blowing up the transformer. Can this be fixed? Do i get it rewound or replace the transformer? I am in Hyderabad so any recommendations for support in this city would be appreciated.

Thanks!

Product information:Swans M200MKII
 
crisscross said:
I have the Swan M200 speakers. Link below and these are the US 110 Volt version inadvertently I hooked it up directly to the plug without using the step down and ended up blowing up the transformer. Can this be fixed? Do i get it rewound or replace the transformer? I am in Hyderabad so any recommendations for support in this city would be appreciated.

Thanks!

Product information:Swans M200MKII
Click to expand...

From this forum and pictures, it looks like 17.5V-0-17.5V, 2A secondary centre tapped transformer. (If your transformer is also 3 wires at secondary, connecting to PCB). Nearest you can put 15-0-15, 3A. Because 18-0-18 would need those big power caps rated 35V. The chip amps based on LM1875 has wide supply range.

Buy new transformer as you can get it easily. Repairing old one would be costly.
 
Last edited:
Thank you omishra. I checked with a couple of stores and it doesn't look like 17.5-0-17.5 are available. 18-0-18 however are more readily available. Is it possible to replace the caps?
 
crisscross said:
Thank you omishra. I checked with a couple of stores and it doesn't look like 17.5-0-17.5 are available. 18-0-18 however are more readily available. Is it possible to replace the caps?
Click to expand...
First look inside if it has indeed 3 wires connecting to PCB - 2 X orange, 1 black.
18-0-18, 2A will do provided you upgrade big caps to any voltage rating above 25V. For that value 35V or 50 or 63V. But keep in mind diameter of same should be fit to PCB.
 
Last edited:
Dear crisscross, did you check the trafo thoroughly? is there a thermal fuse inside it? or it is burnt out? if burnt, better get it rewound. the core material in replacement trafos are not anywhere near OEM trafos. rewinding such stuff is not a big deal (if not a toroid!). pour some paint thinner in a container, place the trafo in it such that it is immersed up to 1 inch. after 24 hors, you can remove the E I laminations easily. carefully unwind the secondary and find out the number of turns. there you can calculate primari number of turns.
 
No need of counting primary secondary. Just wind it for 240V primary and 16-0-16V, 3A secondary over same core material and bobbin. On no load condition it would be 17.5V. It would retain the OEM cover over it. But I am not sure about rebuild winding cost and quality. Also the used Amp does have Desktop speakers as application. It may not do better job by rebuild. YMMV

That is why buying new EI/toroidal/rcore transformer will be easy. Find out Electro Magnetic Devices (EMD) in Hyderabad.
 
I have one troidal taken from AV Receiver.

Input is 220V

Let me check the output voltage

Tell me the size of your trasformer. If size and voltages are maching, I will send you without charging.

Cheers!

In Delhi, we can find some rewinders in RajpathRoi Market.
 
Last edited by a moderator:
Thank you omishra and tiger. I took it to emag today and when we opened it up we noticed that the speaker had a fuse :) so I was able to replace it and get it working again!

Mr. Hebbar said that while he could make a matching transformer in 220v it would not come with a EM shield and he was concerned that since the heatsink was very close it might be a problem.
 
So that means without opening the box you made assumption that transformer is failed and put all of us to work? :p

Anyway that worked then its okay, congrats and enjoy! :)
 
:D sorry I did open it but could not find the fuse and the transformer was shielded so no way of telling if it failed or not unless i opened it up.

Yesterday at emag they removed the PCB and only then found the fuse.
 
omishra said:
No need of counting primary secondary. Just wind it for 240V primary and 16-0-16V, 3A secondary over same core material and bobbin. On no load condition it would be 17.5V. It would retain the OEM cover over it. But I am not sure about rebuild winding cost and quality. Also the used Amp does have Desktop speakers as application. It may not do better job by rebuild. YMMV

That is why buying new EI/toroidal/rcore transformer will be easy. Find out Electro Magnetic Devices (EMD) in Hyderabad.
Click to expand...

But every trafo core has a turns per volt ratio depending on its core area. blindly winding without taking this into consideration will lead to lack of power delivery. so counting the turns will give you an iedea about turns/volt ratio and will help rewinding at optimum performance.
and one more thing I wold like say; during era of VCR I hand wound some VCR power trafos without using a winding machine and them trafos worked ffor years without any trouble.
only thing to care about is make the winding tight and tidy, impregnate the core and windings with hot warnish.
 
Yes, me too hand wound many transformers including toroidal s. Never failed a single.
I have one for my BUSH radio which has blown output transformer of its push pull output stage.
 
Offtopic: I sat on on the live 2 pin plug outlet wire while replacing the power brick casing for the T-754 pre-amp I bought. It was real fun :p
I saw a small fireball from the extension cord outlet..I was a bit worried but it turned out that the extension cord's fuse (10A) blew and nothing majour happened except the tripped LCB.
I replaced the fuse with a single strand of very thin (0.25 mm) copper wire. Wondering its enough to handle 250+400W of peak power !
 
marX said:
I replaced the fuse with a single strand of very thin (0.25 mm) copper wire. Wondering its enough to handle 250+400W of peak power !
Click to expand...
Refrain yourself from doing that :indifferent14:. Replace proper fuse in place.
Otherwise next time you sit on the live wire it will burn important part leaving behind only copper wire. ;) :D
 
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