Make that +650V on the high voltage side and it needs to supply up to 500ma maximum or 325W. That's a lot more power than your transformer can supply. For high voltage I would suggest a 1:2 line step up transformer capable of supplying up to 1A of current. When used in a voltage doubler circuit it should provide somewhere near the voltage and current you need under load. I see those transformers occasionally from various sources. The 207V/200ma winding likewise doesn't have enough "poop". You need 50 watts, in other words [EMAIL PROTECTED] Your winding can only supply 41.4W. Again, you might be able to find another transformer to meet your needs or go up on the current rating of the HV side and supply it from that half of the doubler, as Drake does in their AC-4. The big problem in my opinion will be finding a 12.6VAC at 5.5A transformer. Those (or reasonably close substitute) used to be plentiful at one time but are scarce now. In a pinch I have used a DC supply for the heaters. Most modern DC supplies have current limiting and that may be a problem on power up. If you can adjust the current limit to something over what the tubes need, you may be able to get away with it. At worst you may have to wait a lot longer for the tubes to warm up as the supply slowly comes out of current limit. That may be a good thing at least for the tubes if not for the supply since they won't be subject to a big slug of current when the filaments are cold. Another benefit would be a significant reduction in AC hum since the only AC in the rig will be at the PWR switch. It used to be easy in the old days. Just find a junked TV somewhere and rip out the transformer but alas, those have gone the way of the dinosaurs.
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of JJ HO Sent: Sunday, April 04, 2004 5:07 PM To: [EMAIL PROTECTED] Subject: [drakelist] Home brew PS question for TR4. Dear drake lovers, I am in the process of building a simple PS for TR4. Judging from the circuit of AC4, I need a transformer that can supply HV (~ 750V) and MV (~250V) and LV(~ -70V). I got a transformer with the following 2nd AC terminals: - 289V/200mA: this can supply around 750V with voltage doubling rectifying scheme. - 207V/200mA: this can make a 250V. The transformer had a 120/230V selection. I wondered if I could use one of the 120V primary as a AC source for providing this voltage. Also, for a 110V operation, do I need to connect the two primary coils in parallel or I can leave one as is. Thanks for you answers and helps. 73, Jonathan ---------------------------------------------------------------------- Submissions: [EMAIL PROTECTED] Subscribe: [EMAIL PROTECTED] - subscribe drakelist in body Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Brought to you courtesy of TLCHost.net http://www.tlchost.net/ ---------------------------------------------------------------------- ---------------------------------------------------------------------- Submissions: [EMAIL PROTECTED] Subscribe: [EMAIL PROTECTED] - subscribe drakelist in body Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Brought to you courtesy of TLCHost.net http://www.tlchost.net/ ----------------------------------------------------------------------
