18-03-2017, 01:55 PM
I'd just go with the weight/dimensions. Half a kilo suggests 30VA or 50VA. If one winding gives 15VA, then at 6V, that's 2.5A. Both in parallel should be plenty...
If the weight suggested a smaller transformer, then we might need to get more precise. Just keep an eye on the temperature when it's running...
Antrim aren't going any more, sadly. They did a lot of custom stuff, so that part number could be specific to a particular customer/product. YK08 looks a bit like a Maplin part number, and I think Antrim did supply Maplin at one stage.
Will the sets in question be happy with AC? Saves a whole load of hassle and heat sinking if so. Guess you've already considered that...
Have you tested it at 2A though? I'd expect the output voltage to drop a bit. The regulation of a typical 30VA transformer is around 18-20%, and perhaps 15% for 50VA. You're only taking 12VA, so it won't drop as much as that, but even so...
I'd say that 6.7 volts off-load is not enough for a regulated supply. Let's assume the output drops by 10% to 6.1V. You'll lose nearly a volt in each diode in the bridge, so 2V in total (rounding up). So I think you'd struggle to get 6V after the rectifier. And the regulator will need 3V or thereabouts of "headroom". You need 9V at the bottom of the "troughs", so the average - as measured by a voltmeter - needs to be more like 10 or 11V.
You can half your rectifier losses by putting the windings in series to give 6-0-6, and use 2 diodes (or half your existing rectifier). And you can get that down to around 0.3V by using Schottky diodes (rob them from a dead PC PSU or similar). But you'd still need to find a LDO (low dropout) regulator IMHO.
470uF is far too small for 2A. Add another "0"
If only you had a 9V transformer...
If the weight suggested a smaller transformer, then we might need to get more precise. Just keep an eye on the temperature when it's running...
Antrim aren't going any more, sadly. They did a lot of custom stuff, so that part number could be specific to a particular customer/product. YK08 looks a bit like a Maplin part number, and I think Antrim did supply Maplin at one stage.
Will the sets in question be happy with AC? Saves a whole load of hassle and heat sinking if so. Guess you've already considered that...
Have you tested it at 2A though? I'd expect the output voltage to drop a bit. The regulation of a typical 30VA transformer is around 18-20%, and perhaps 15% for 50VA. You're only taking 12VA, so it won't drop as much as that, but even so...
I'd say that 6.7 volts off-load is not enough for a regulated supply. Let's assume the output drops by 10% to 6.1V. You'll lose nearly a volt in each diode in the bridge, so 2V in total (rounding up). So I think you'd struggle to get 6V after the rectifier. And the regulator will need 3V or thereabouts of "headroom". You need 9V at the bottom of the "troughs", so the average - as measured by a voltmeter - needs to be more like 10 or 11V.
You can half your rectifier losses by putting the windings in series to give 6-0-6, and use 2 diodes (or half your existing rectifier). And you can get that down to around 0.3V by using Schottky diodes (rob them from a dead PC PSU or similar). But you'd still need to find a LDO (low dropout) regulator IMHO.
470uF is far too small for 2A. Add another "0"
If only you had a 9V transformer...
