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Transformers for Chinese TDA1541 DAC board

Johan64

Member
Hello
I have a Chinese TDA1541 DAC board. It has three voltage inputs (AC).
15V AC for DAC + OP etc. (+-15V, +-5V DC)
Capacitors 6800uF

7V AC for SAA7720P/A (+ 5V DC)
7V AC for CS8412-CP (+ 5V DC)
Capacitors 2200 uF

What I'm thinking about is how big the transformers should be (VA/W/A).
Thinking of using toroidal.
Anyone that can help me?

Sincerely
Johan
 
This is the one.
Don't know how (just get a error message about spam)
Search for TDA1541 DAC Kit Board Support coaxial fiber (not included TDA1541 IC & 4pcs OP)
(Green board)
/Johan
 
Found it on google which referenced picclick. Clicked that link, but shown as not available on eBay.
Were there no instructions with it?
 
Board.jpg
 
The OP will likely need a custom made transformer if going for just one as separate 15V and two 7V windings are not an off the shelf item. Two 7.5V windings to give either 15V, or two separate 7.5V windings or one 7.5V winding at twice the current, depending on how they are used, should be easy enough to obtain and two of these could give 15V from one transformer and 2 x 7.5V (near enough) from the other. I would expect 30VA units to be more than adequate but 50VA would be the next common size up if in doubt.
 
Unfortunately the image is of too poor a quality to be able to read anything off it, but as Jez said, you will need a 2x15v ac transformer for your 15/0/15 input and a 2x7.5v ac transformer so you can use each winding separately for the SAA7220P and the CS8412-CP. Moderate sized frame transformers would be fine. The SAA uses quite a lot of current (0.2A) so as long as you have the 2x7.5 with at least 15VA, that will give you 1A from each winding and similarly 15VA for for the 2x15 as a minimum.
 
..added to which, be sure to buy some decent-sized / but convenient to fit, heatsinks for the 3pin regs.

e.g if you go , for convenience sake - and that might make good sense for a chunky, convenient, off-the-shelf transformer as well described by @a.palfreyman - for a 9vAC winding for the 5vDC supplies, you will then need to dissipate about 1.5W min on the 5vdc regs. Not a problem - if you plan for it : )

In fact, I suggest plan on that basis regardless - keeping such parts cool, makes for reliability. I'd want to look for clip or push-on heatsinks for To220 parts that could fit, and are perhaps 12 to 10degC per watt range. Even smaller parts (higher c/w value) would still be useful. HTH.
 
All depends what it actually needs! If 1 x 15V and 2 X 7V as OP says then my suggestion of a pair of TX's each with twin 7.5V windings, one wired to give 15V seems the way to go but if the TX in the link above is OK then it suggests that 2 x 7V are not required and that a 15 - 0 - 15 is required... rather different from the OP!
 
I've modified CD players with a dedicated power supply for the SAA7220 on a few occasions and have found a 7vac transformer to be the ticket. As Martin and A.P warn, the SAA7220 draws a fair bit of current and if the voltage reg is asked to drop too much voltage drop it'll get pretty toasty with the small sized heatsinks you typically get with such kits.

Did you buy a kit of just the bare board?

A 7805 only needs a few volts of headroom and a 7v transformer will give you a rectified voltage of about 9.8v, so plenty of headroom for the reg without asking it to dissipate too much heat.
 
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