Any photos of your work, Don? I just ordered some parts and will gradually catch up with you and the videos.
I'm sorta confused. Heil's power supply has 1 transformer and 1 tube. Yours has 2 of each, will you explain?
I used a bridge rectifier because I happened to have one. I built the PSU my way. Not that it is better in any way. It just reflects what is in my junk box. A low value 5 watt resistor stands in for what would be normally a choke. The caps are 20uf 450volt. The bleeder resistor is a little hi in value but in the ball park and much better then none. The second transformer is really a audio transformer but only the secondary is used (as the audio choke. because that is what I have in stock. ) The bare wire is Ground bus for those who like to worry. The second tube is there because there will be one. The mod section it says is driven by a audio pre amp or speech amp. 12ax7 s are often used there so I mounted it in right now. I still have to mount the crystal socket and Pi network . I left room for a pair of 12BH7 s for a quad four PA if it works well. (GG of course!) donVe3LYX
I wondered if he was just working ahead... I don't have enough experience to recognize the solid-state bridge rectifier but I am working to rectify that situation. Thanks!
Thanks, Don, for the details. I figured you were working ahead, and using what you've got is totally understandable. Am I correct that with your way you get full-wave rectification and with Heil's circuit we only get half-wave?
No Ur good with his circuit. Still full wave. Doesn't matter. No hum is the only goal that matters. The rest is just bragging rights. I don't usually use a bridge but happened to have this one and it was for the proper voltage. That is the only reason I used it. Not better just in stock. I normally spend nothing when building or maybe a dollar or so at the end to finish. My Schwaben heritage. (Dulmage is Canadian for Dolmetsch). I only had a 12 volt transformer and not centre tapped so I had to wire the tubes 12 volt. I don't have a 12 volt rectifier tube but I did have this bridge so the decision was easy. I am really into his build. Doing this kind of thing is very productive for us. One always learns something no matter what. I am hoping lots will do the build so we can have a coasts to coasts (urs and mine) group all on the same freq with these little Ham Nation AM sets. Equipment like this that is relatively easy to build brings understanding at a level that would not be otherwise. Power levels both input and output are relatively safe if you use your head. I made the field Strength meter and really enjoy it.I set it up in my shack with a old collapsible ariel from a old radio I scrapped and watch it when tuning my rigs up. The Power supply can be used for many HB projects just by adding a plug outlet. (I often use flat car trailer connectors (4 wire) and wire everything the same way so nothing will ever get plugged in wrong. AM is a lot of fun. This modulation method is most interesting so lots to be gleaned there too. And FUN. Nothing beats wiring up a bunch of parts plugging it in a making a contact. Oh, you will meet lots of critics but I have learned over my years that no one who actually builds criticizes. Because? You'll know soon as you get urs done and make a contact. Or maybe you do already. So in my heart I say "Sori, can't hear U, I'm having too much fun ;>) Anyway I am into this but you could probably tell. donVE3LYX
Full wave, I see. I only had to look again (not to mention look at the tube data sheet). Yeah, I can tell you have fun at this! And it's interesting to read the reasons for your decisions and design choices regarding your PSU. This'll be my first vacuum tube anything to build so I'm looking forward to learning a lot and already having fun looking up parts. I haven't yet accumulated a junk box nor the experience to know what will substitute for what anyway. I think that's right most of the time. I'm going to keep looking over your shoulder as this project progresses.
When you reach a point when you are unsure or nervous ask yourself "What is the worst that could happen." Usually the answer is "a fuse might blow or a resistor" but usually nothing happens except it works. Tubes are just cold hearted transistors that need to keep warm. FET and a triode are the same thing. U'll be fine. Don't overcomplicate it and don't let anyone else either. I am no expert. Just curious. The more I build the more fun I have. I am looking forward to Ur build. This is a really good project. We will be talking about it when we are in "the home!" donVe3LYX
I wish either Twit or Ham Nation had a discussion forum where people (like me) could ask questions about the build. Twit used to have a forum, but closed it down.
Here is mine . Note lucite hand guard preventing any touching. Pair of 811As at 1250 volts. Built on wood. However a pair of 12BH7s would be about right for this rig we are building. For those of us who don't live near anyone. Otherwise it should be fine as is. donVe3LYX
Even though I have been building ahead, I am not sure the circuit we have been looking at is the one Bob is doing. So if that is so I may have to build both. There is an extra 12ax7 in his parts list and I dont know what it is for. However a 12ax7 regen rx is a real decent piece of gear . I have built several , the first being about 1965. I have given them away over the years. So if all works out, time for a new one. I powered up and measured PSU voltages and got the required 130v under load. (131.6 v 17.4 ma)
