tag:blogger.com,1999:blog-2554001380039969960.post4358843835950461926..comments2024-03-26T01:18:16.882+01:00Comments on LA3ZA Radio & Electronics: Transformerless tube power supplySverre Holmhttp://www.blogger.com/profile/08306221557326542499noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-2554001380039969960.post-14500479898347507952012-08-29T00:17:17.385+02:002012-08-29T00:17:17.385+02:00I may have been a little unclear on the step-up tr...I may have been a little unclear on the step-up transformer, therefore I revised the text a bit above also. This transformer is exactly like the step-down transformer. It was taken from the first burned out PCB. Since I had been experimenting with the transformer I had to rebuild it to the original state. <br /><br />I would guess you can just connect the minus to ground like with other power supplies.Sverre Holmhttps://www.blogger.com/profile/08306221557326542499noreply@blogger.comtag:blogger.com,1999:blog-2554001380039969960.post-3887523300246583362012-08-28T21:20:16.821+02:002012-08-28T21:20:16.821+02:00OK, I see. Thank you for the further details on th...OK, I see. Thank you for the further details on the circuit. I look forward reading your results.<br /><br />I will try and see regarding the step-up transformer. Did you do any calculations or did you just try?<br /><br />Maybe protective ground is more correct to say. I want to connect the amp's metal case to ground, so if any high voltage cable in the amp get lose it will trigger/burn the fuse. Otherwise there is a risk that one touches the amp case and something that is grounded, creating a closed circuit.<br /> <br /><br /><br /><br /><br />Robin Liljanoreply@blogger.comtag:blogger.com,1999:blog-2554001380039969960.post-80667907080566116862012-08-28T18:34:51.059+02:002012-08-28T18:34:51.059+02:00Hi Robin. I planned to wait with publishing of the...Hi Robin. I planned to wait with publishing of the schematics until I had tested the power supply in a real application. <br /><br />But it is very straightforward. The high voltage part is a bridge (Delon) circuit as in the <a href="http://en.wikipedia.org/wiki/Voltage_doubler" rel="nofollow">Wikipedia article</a> with 220 uF/400 V capacitors (from an old switch mode power supply) and 1N4937 diodes. I haven't tested it yet with respect to how much the voltage varies with load.<br /><br />In your case, I would guess that a straightforward rectifier might give too little voltage and a doubler too much, so a doubler with a changed winding ratio could perhaps be the way to go?<br /><br />Safety ground, what's that? I haven't really thought much about that.Sverre Holmhttps://www.blogger.com/profile/08306221557326542499noreply@blogger.comtag:blogger.com,1999:blog-2554001380039969960.post-74578407940000337472012-08-28T15:47:11.410+02:002012-08-28T15:47:11.410+02:00Hi! Interesting approach indeed. However, do you h...Hi! Interesting approach indeed. However, do you have any schematics?<br /><br />I need to provide 220VDC 60 mA to my OTL head amp (Cavalli Jones). Should I wind the step-up transformer to match that requirement, or should I use fewer windings together with a multiplier? What do you reckon?<br /><br />How do you ground (safety ground) a thing like this?Robin Liljanoreply@blogger.com