What transformer is this?

[zeebit]

Hey guys,

I have a TDK 2.1 speaker system that I use for my PC and it died. I took it apart and found out that the thermal fuse on the transformer blew out.

I am having trouble figuring out the ratings of this transformer. I tested the amp with a small 12-0-12 transformer I have and it works so I think its somewhere in this range.

 

[zeebit]

Bump.

The main smoothing caps are rated at 35V. An LM1875T drives the sub and an LM4752T drives the two sattelites.

Any guess?

Here are the datasheets:
LM4752T datasheet(1/18 Pages) NSC | Stereo 11W Audio Power Amplifier
LM1875T datasheet(1/11 Pages) NSC | 20W Audio Power Amplifier

 

[TonyTecson]

Hey guys,

I have a TDK 2.1 speaker system that I use for my PC and it died. I took it apart and found out that the thermal fuse on the transformer blew out.

I am having trouble figuring out the ratings of this transformer. I tested the amp with a small 12-0-12 transformer I have and it works so I think its somewhere in this range.

roughly 20VA for that size....if you bypassed the thermal fuse, you should install a 0.4 amp fuse instead to be able to use that traffo...

make sure that nothing is overheating before you put it back in service...

 

[zeebit]

I bypassed the fuse and hooked it up. I ran it for nearly half an hour and nothing is hot.

I will just get a new fuse.

Thanks!

 

[TonyTecson]

that's good to know..... 😀

 

[zeebit]

Okay I'm gonna bump this thread.
---------------------

I have a couple of UPS with dead batteries so I took the step up transformer. I dont have a multimeter so I am gonna need some help guesstimating the specs.

What I do know is that the secondary side is 220V or 240V. I need a guess on the primary side voltage ratings and the VA of the traffos. I am gonna use these as a step down traffo for my projects.

I will just link a couple of ImageShack album because I did not resize the pics.

First one is from a Sunstar brand 625VA UPS. I dont know if the rating is accurate but I assume its lower since its China made. I had this back in 2003.
ImageShack Album - 8 images

This one is from an APC Back-UPS ES 500VA. The rating should be accurate since APC is a top notch company. The battery had failed and its casing has cracked.
ImageShack Album - 2 images

 

[TonyTecson]

be careful, i once harvested the traffos from a Tripplet UPS with dead batteries, it turns out that the 220 volt windings are auto-transformer connected to the 12volt winding...

so check that the high voltage winding are truly isolated from the low voltage winding..

500VA/625VA are optimistic since these UPS's are often used intermittently(short working time), i'd reckon that less than half of that for continuous duty is available to you...

 

[zeebit]

Would the continuity test on a multimeter work?

 

[AndrewT]

........... I do know is that the secondary side is 220V or 240V. I need a guess on the primary side voltage ratings and the VA of the traffos. I am gonna use these as a step down traffo

Have you mixed up the words secondary and primary?

 

[TonyTecson]

Would the continuity test on a multimeter work?

yes...

 

[TonyTecson]

Have you mixed up the words secondary and primary?

in a UPS, the 12 volt winding is the PRIMARY when working as an inverter, Secondary when working as a battery charger...so depends on the function it is performing...