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In Reply to: Re: Looking for a GOOD 211 / VT4-C Schematic posted by Gary Kaufman on July 18, 2003 at 08:14:38:
The power supply for your 211 looks incredibly complicated. Making a PCB for that cathode supply module will be a task on it's own. Actually, where would I find such a module? It would seem that to build a 1.3KV power supply with simple C-L-C would be much easier.Another point I should bring up is i've seen most are running DC on the 211 filament heaters. This is a big concern for such a DHT. or is it not in the case of the 211?? - how long will the tube last? And does running 10V AC cause that much noise that one would only think to use DC and live with replacing 211 tubes more often?
Follow Ups:
Acutally my power supply is very different than the one on PAE's site. I use individual AC transformers for each 211 filament, the 866jr and the 6C45 filament. The large Acro TP-550 provides 825-290-0-100-290-825 as well as additional 5 and 6.3v filament taps.At turn-on the individual filament transformers for the 211, 6C45 and 866jr's are started. There is a 2 minute delay to allow the 866jr's to come to full temperature before the TP-550 is started. This is done with a digital delay board.
When the TP-550 comes on it feeds the 825-0-825 to a pair of 866jr's, which go thru a damper diode for slow turn-on. This is choke loaded with a swinging choke --> 15uf/1000v oil ---> smoothing choke ---> 30uf/1000v oil with a small bleeder resistor for the B+
The power supply for the 6C45 is a 6106 (bendix indirect 5Y3GT with a very slow turn-on) into 12H, then 100uf for the driver stage.
The 100V tap provides bias voltage thru a 1N4007 and simple filter/divider network.
All said, it's pretty simple. First pre-heat 866jr's and filaments on 6C45/211's and bring up the bias. 2 minutes later start B+ which has a slow turn on because of the damper diode. Lastly the B+ for the driver stage comes up.
Even with AC on the 211's I get very reasonable hum levels. The power supply actually has a bridge rectifier and cap to filter the 10V supplies installed, but I never wired them up. AC was plenty quiet - even on Altec speakers.
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