What sort of PSU is this?

[FNQ]

Hi all...
I recently bought a TCC-TC750 phono preamp which came with a nasty quality wallwart power supply rated at 12vdc 200mA output.
Many friends on hifi forums have suggested replace the wallwart with a decent 12vdc regulated PSU.
To save on costs I realised I had an old unused Dgetc dh2000a digital set top box and wondering what its psu was like I opened the dgtec today and saw the psu is clearly quite separate from the main pcb in the housing.
I looked closely and the psu board has outputs clearly labelled as +35v, +12v, -8v, "AG" (ground?) then +6.3v and +3.8v.
I found a schematic of this psu circuit which I have below.
I need to know if this psu board would be suitable to power my preamp with 12vdc, friends tell me that a supply of at least 2amps would be great for the purpose.
So I ask my mates on here (you are included!! ) if this board's 12v out is DC?
Can you tell from the schematic what amperage it would give?
I guess the terminal marked "AG" would be the ground?
I can solder etc and would safely mount the board in a suitable box with plenty of vent openings.
The mains lead is already attached.(It's in Australia and mains is 240v with this psu board also 240v input.
You would gather my knowledge of componentry/electronics is basic so I ask maybe semi-mundane questions as I don't want to endanger my hardware or my life
Your advice is welcome and many replies will be appreciated to ensure nothing is missed or overlooked.
Thanks heaps guys..

[Elvee]

My advice is: don't tie a switch-mode device to sensitive audio equipement, unless you have no other choice.
Put together a 15V/5VA transformer, a rectifier bridge, a filter cap and a 7812, it won't cost you a fortune and it will be much quieter (and more reliable) than your switcher.

[Zoran]

Classic PS with full rect with CT transformer, with good core laminates,
and calculated primarry turns for lower induction
(not high as 1.2 to 1.6 Tesla for refrigerators...)
but less than 1T (0.7, 0.5)
will run up until the end of the time without overheating, hum and vibrations.

[sreten]

Hi,

You cannot tell from the schematic what current level it will support. Your
simplest option is a decent regulated 12V wall wart, 2 amps is plenty enough.

rgds, sreten.

[RJM1]

The 12V DC out is rectified by a UF203 diode which is rated at 2A continuous so your output current would generally be half that or less. The feedback for the supply is taken from the 6.3V output so you would need to put a load on the 6.3V rail to get it to regulate at all. Go with the wall wart.

[FNQ]

Thanks guys for your replies.
Now I have learned the schematic I put up on here is for a switched PSU.
NEXT: I already have a walwart transformer which steps my 240v mains down to 15vAC.
I'd like to utilise this with the few bits needed to make a regulated PSU and ELVEE advises I need an IC type 7812, a rectifier bridge(is that just one diode?) and a filter capacitor. Elvee, if u r still there..any chance of a hand-drawn note showing what gets joined to what????? It wld be very appreciated.
Sreten the off the shelf version of what I need sells in Australia about $40.00 so if I can make it up using my 15vAC walwart that gives me a few days of petrol
RJM & ZORAN-thank you also-asking seemingly dumb questions like I have today allows me to learn from your replies. If I can put this together it will be my 1st achievement with basic electronics!! At least I'm not this dumb when it comes to other aspects of audio and visual gear operation etc lol

[sreten]

Hi,

FWIW what matters is what happens after the DC enters your phono stage.
If its then fully regulated down to say 9V a regulated DC supply is moot.
(Just stick some more capacitance inside the original wall wart.)

15V AC will rectify to ~ 20V DC (load dependent), use a full wave bridge.
Also depends if 15V AC is the no load voltage, (turns ratio) or the loaded.

Rectifier circuits : DIODES AND RECTIFIERS

rgds, Sreten.