Amplifier input voltage

Thread Starter

bergaliv

Joined Apr 11, 2019
7
Hello. I (by mistake) bought an assembled amplifier from amazon. Note to self, read the full listing before clicking buy;-) Well, i got it assembled with some elbow grease and a hot iron.
The kit came without any instructions what so ever, so I'm a bit at loss at to what imput voltage i'm supposed to hook up. Looking at the pcb(picture in here) there is a marking AC and N on the input screws. So, to my complete lack of knowledge in these matters interprets this as it will take mains(220v) as input. From what i can tell(and again, i'm completely new to this) there is a rectifier with four diodes, and some huge caps. Will this work as a step down to the required voltage/current? amp_pcb.jpg
 

Yaakov

Joined Jan 27, 2019
1,611
It appears to want 12VAC, from a transformer. But that's a guess. Can you provide the link to the amazon listing?
 

Thread Starter

bergaliv

Joined Apr 11, 2019
7
Zerone Circuit Board 2.1 Mini Digital Amplifier Board 3 Channel Speaker DIY Auto Audio Stereo Subwoofer Amplifier Module on amazon.co.uk seems like i can't post the direkt link
 

dendad

Joined Feb 20, 2016
3,176
NO! NOT 220VAC.

What are the ratings on the big caps? The voltage there may give you a clue.
Try half the cap's voltage as the AC volts in.
But a link to the purchase site may help.
 

Thread Starter

bergaliv

Joined Apr 11, 2019
7
Big caps are 4700Uf 25v. For some reason i wasn't allowed to post the full link. Btw, thanks for the very prompt responses; I'm impressed:)
 

Thread Starter

bergaliv

Joined Apr 11, 2019
7
I have no powersupplyes that are AC, only dc ones. Looking at the cost of a transformer, i'd say this one goes into the parts bin. Lesson learned, read listings first, click second:) Can't thank you guys enough for the help. Thanks heaven i didn't hook it up to the mains!
 

Yaakov

Joined Jan 27, 2019
1,611
I have no powersupplyes that are AC, only dc ones. Looking at the cost of a transformer, i'd say this one goes into the parts bin. Lesson learned, read listings first, click second:) Can't thank you guys enough for the help. Thanks heaven i didn't hook it up to the mains!
Do you have a variable DC supply that can do 12V at a couple of amps?
 

Yaakov

Joined Jan 27, 2019
1,611
Not a variable one. I do have a bunch of fixed 12v ones though. Powerbricks , Pc power supplies and so on
If you are going to bin the board anyway, it’s worth trying one of those 12V supplies on it. Polarity won’t matter, the bridge rectifier will make it right whichever way you hook it up. I am guessing you will need at least a couple of amps, but you can test it with less.
 

Thread Starter

bergaliv

Joined Apr 11, 2019
7
Oh, awesome! Yeah, i won't cry if it blows up. Would be nice to get it working though. I'll test it tonight and let you know if the magic smoke leaves.
 

Yaakov

Joined Jan 27, 2019
1,611
I think it will need a center tapped transformer, like 12-0-12, or maybe 15-0-15.
This will give the amp a + and - supply.
I think you are right. There are three terminals and the amp is a TDA203DA which uses a dual supply. It seems to want a 12V supply, per the datasheet.

@bergaliv This looks like it would work. If you decide to try it the 0V terminals each go to the CT input, probably the middle terminal, and one each to the outside,s doesn’t;t matter which. I found it hard to locate a simple 24V CT transformer.

https://uk.rs-online.com/web/p/chassis-mounting-transformers/0504571/
 
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