help identifying transformer - Page 1
Forum section: electronics / repair

author: valleyken
author_rank: Contributor
timestamp: July 08, 2025, 05:10:29 pm
content: Hello,- I am trying to repair a set of Auditek pc speakers. The problem seems to be with the transformer because the output of the transformer measures nothing but a few milliVolts. But there doesn't seem to be any information printed about what the output voltage should be?It has El-28 / 220V printed on the top of the transformer. 220V is the input voltage (mains here in Europe). That seems to be an L in El, not an i. I added some pictures . Anybody knows what kind of transformer I need to replace it ?Valleyken

author: tunk
author_rank: Super Contributor
timestamp: July 08, 2025, 05:27:36 pm
content: Look at the datasheets for the chips and see what voltages they can run at.Also see the voltage ratings of the capacitors.Does it have two or three low voltage pins?

author: valleyken
author_rank: Contributor
timestamp: July 08, 2025, 08:07:26 pm
content: - The highest voltage capacitor is 50V (0.1uF). So I guess the transformer output must be less than 50V? The lowest cap is 10V (220uF).- There is only 1 chip which has EX 2822 (C09) printed on it. I think it is this chip, as the ST logo seems to match the logo on the chip too. It's an audio amplifier chip with 8 legs. It runs on 1.8V apparently.https://www.st.com/resource/en/datasheet/tda2822d.pdf- The transformer has 2 output legs.

author: inse
author_rank: Super Contributor
timestamp: July 08, 2025, 08:27:57 pm
content: Hook it up to a lab power supply and crank up the voltage until you can achieve the desired volume.That should give you a direction what transformer to look for.Remember, DC voltage is roughly 1.4 times the AC voltage.

author: fzabkar
author_rank: Super Contributor
timestamp: July 08, 2025, 09:56:01 pm
content: What is the rating of the capacitor on pin #2 of the IC? The absolute maximum rating for the IC is 15V.What is the rating of the speaker (on the speaker itself, not the whole unit)?I think that EI-28 refers to the construction of the core.https://centersky.en.made-in-china.com/product/OyxmJSKCCphU/China-Hot-Sale-Ei-28-Silicon-Steel-Lamination-for-Transformer.html

author: valleyken
author_rank: Contributor
timestamp: July 08, 2025, 11:37:57 pm
content: - The speaker itself says 4 Ohm, 1 Watt. There are 2 of them, as it's a set of 2 little pc speakers.- On the label of the outside of the speakers, it says 180W (P.M.P.O). PMPO = Peak Music Power Output, which the speakers should be able to handle for a very short time. It's usually much higher than the real output of the speakers. Mostly a marketing trick to make speakers seem more powerful than they really are.- Indeed the Ei seems to refer to the shape of the core. 28 I guess is the size. They seem to have some different models on that made-in-china site, but I would still need to figure out the output voltage. And they sell in big volumes, but I might be able to order a sample.- The capacitor on pin #2, I will have to check tomorrow.- Powering it with a lab power supply is something I will try, when I get my hands on a working power supply. There is a chance that the output of the transformer is 5V, in which case I might maybe be able to power it with a usb charger maybe which would cut out the whole transformer mess. That would be nice, but I should first confirm the voltage (and possibly amperage too I guess?).