Hi guys,
How are you supplying the B+ voltage to Paul’s Power Antenna circuit? My plan was to use his switching HV Stand Alone Boost Supply in Video 75, but he says the switching noise would be difficult to filter out. I don’t disagree with that, but it begs the question of just how one does power a high voltage circuit without using a commercial HV Supply, a surplus radio transformer or another working radio, none of which I have. I like the Stand Alone Supply because it is variable and has 6.3V built into it. What are you guys using for your Power Antenna circuits?
Thanks,
Bruce
No one on here has shared or discussed that project yet. Personally if I was to build the project, I would build it all into a self contained enclosure. Spec out a transformer that would do the job, use diodes as rectifiers and add filtering (unless a tube rectifier would fit the theme). It would supply everything needed without the extra high frequency noise of the boost circuit.
A stand alone supply would absolutely do the job, but fitting it into an enclosure/hiding it would be fun. Not to mention they are not cost effective these days unless you find one cheap/local (just to power an antenna booster).
Radios + Tubes + Scopes + Cars= Nothing better!
@Kmpress: I plan to build the P. antenna myself but currently waiting for the tube to arrive. And yes this is a real issue (generally speaking) when it comes to small projects based on tubes since you almost always have to deal with providing various voltages at once and the aim here is to keep everything as small form factor as possible. And same here I do not have a small PSU (HV) readily available for the project. Now. since I own a little vintage (DIY) winding machine and already have tons of various sizes low voltage transformers ranging from 4V up to 2x36V I.m going to do some calculations to see what would be the smallest “form factor” transformer that has a separate secondary low voltage winding that is separate from the primary, rip that out and rewind it with a thinner magnet wire so it would supply the HV for the tube and as for the filament I could either make another winding (IF it fits) but if not would just use a separate tiny 6V transformer that I already have plenty of. However the original plan was to use some 18650 cells and multiply the voltage as needed but…it seem that the idea is…not suitable for this particular project. Damn…. 😖 😖 😖
Thanks for your inputs, guys. I, too, would prefer to use 18650s, but after a bit of digging it looks like I can get a tube preamp transformer with separate 6.3V and 220V windings from AliExpress for under $25 with shipping. I’ll have to run it on 100V 50 Hz but I don’t think the drop in output voltage will be significant.
@kmpres I have a few hundred recycled 18650s, you do have me thinking about the 1PC 35W Sec Voltage 220V x2 + 6.3V x2 R-Core Transformer for TUBE preamp DAC amp diy.
Thank you for sharing
Larry – N7LUF
I picked up a RCA WO-33a scope to make a curve tracer out of but it was in such bad condition I’m going to make a HV P/S for the power antenna. Think I’m going to keep the 6X4 for rectification and make a nice encloser with meters.
Don – N9SQS
@utumven11 Well….as long as the CRT works and the enclosure is still in one piece, all other parts can be restored with not too much of an effort (in my opinion). Perhaps you might actually want to reconsider. I know I would and It surely worth a try… Making a very useful piece of testing equipment out of it adds far more value to your lab then just cannibalizing it to make a simple power antenna out of it. But again…at the end of the day is entirely up to you. Just a thought… 😉
@ovi4 I agree with you and hate to cannibalize stuff that’s the reason I got it. The CRT is broken. it looks like it sat in a very humid place for a very long time and was dropped at some point. All the pots are seized, I tried to free one up but was unable to. I will find another one in better shape to convert but for now there is some good stuff to use the transformer and 6X4 are in good shape plus i get a pilot light. I think it will make a neat little HV power supply. I will share pics after I build it. Thanks for your advice and keep it commin 😀
@utumven11 Ah, the worst in a scope is to discover that the most important piece (the CRT) is gone. Hmmm…yes if that’s the case well…you do what you’ve got to do and, fingers crossed you’ll find another that is in a “better shape” next time👍… 😎
Likewise. I bought one a while back for a hefty price as it was all original, nice shape, and had all the original stuff with it. I couldn’t bring myself to modify it for the curve tracer so I got another cheaper/worse shape one. Well it has a super dim CRT with possible burn spots. I haven’t ruled out low HV or anything yet but I more or less need another hard to find CRT for it. Still undecided what I will do but now they sit side by side.
Radios + Tubes + Scopes + Cars= Nothing better!
I have a power transformer I salvaged from a Philco 45. I’m new to this world of electronics. The power to plates is 680 volts 1 leg of that to ground is 248vac. Plus it has the required 6.3 filament voltage. My question is I’m assuming I would need to build a bridge rectifier with a filter. How would I spec out the components? And is using one leg of the plate power to ground acceptable or should I use the center tap and resistors to reduce voltage ?
Any guidance on a path forward would be greatly appreciated.
First you need to know what you want to build with the transformer and make sure the transformer can handle the load. So with that try and find the specifications of the transformer then you can figure out if you want to use a tube like a 5Y3,5U4 or 5AR4. If you are building an tube amplifier I would use a tube rectifier rather than diodes. Using diodes you will have have a high current in rush where if you use a tube rectifier you won’t. There are a lot of books on the subject. I found some information years ago at removed link this is a good place to start.
Also, keep in mind when searching for an appropriate transformer, that the eventual rectified DC voltage will be considerably higher than the measured RMS AC voltage from the transformer, assuming you’re measuring with an RMS volt meter. The DC will be closer to what the actual P-P (peak to peak) voltage of the AC output. You would want to multiply your AC (RMS) voltage by 1.414 to get the peak voltage, which is what will be present after rectification and DC filtering. So for example, a transformer with a 200 volt secondary will be closer to 282.8 DC volts after rectification. There is a little loss due to the drop across the rectifier diodes, but it would be less than a volt or so, depending on the rectifier used.