Hi deicide67,
I would listen to Miles and AJT if I were you. Safety should never be a cavalier topic, and that what some recent posts feel like.
Save the heater power and use diodes. If you must stick a tube in that hole, don't connect it. I would use the hole for an extra capacitor, but that's just me. I have seen heater-cathode insulation fail. It can and does happen. Why leave yourself open to a failure mode that isn't necessary? You also have alternative means of dropping voltage. One even gives you lower supply ripple.
-Chris
I would listen to Miles and AJT if I were you. Safety should never be a cavalier topic, and that what some recent posts feel like.
Save the heater power and use diodes. If you must stick a tube in that hole, don't connect it. I would use the hole for an extra capacitor, but that's just me. I have seen heater-cathode insulation fail. It can and does happen. Why leave yourself open to a failure mode that isn't necessary? You also have alternative means of dropping voltage. One even gives you lower supply ripple.
-Chris
I'm fine with SS. The main issue is space where series caps take up twice the space as a single. Maybe with the series resistance between the secondaries and the rectifiers, I can get away with a 500V cap. If not, I may just cut a new plate and add a transformer for the filament on the glass rectifier.
I was trying to achieve a smaller form factor preamp.
Oh, and Miles, I still have your notes on the 6CB5. I'm going to try for a PPP with four into 1.5K for 100W or so this spring. Thanks!
I was trying to achieve a smaller form factor preamp.
Oh, and Miles, I still have your notes on the 6CB5. I'm going to try for a PPP with four into 1.5K for 100W or so this spring. Thanks!
Hi deicide67,
Well, the issue is that you just ended up with a spare hole to use in case you need to add a capacitor. A series resistor will drop the supply quite a lot, and slow the charging cycle some. Since it is a preamp, you don't need ton's of filtering and the current draw is reasonably constant. Therefore, you don't have to worry about a relay across an inrush current limiting resistor. I should be so lucky when rebuilding a preamp!
It sounds like an interesting project. Please let us know how it comes together and what you do with the power supply on this one.
-Chris
Well, the issue is that you just ended up with a spare hole to use in case you need to add a capacitor. A series resistor will drop the supply quite a lot, and slow the charging cycle some. Since it is a preamp, you don't need ton's of filtering and the current draw is reasonably constant. Therefore, you don't have to worry about a relay across an inrush current limiting resistor. I should be so lucky when rebuilding a preamp!
It sounds like an interesting project. Please let us know how it comes together and what you do with the power supply on this one.
-Chris
Don't do it! The filament winding associated with a directly heated rectifier is at B+ potential.
SS rectify that B+ rail. Directly heated rectifiers turn on almost as fast as SS diodes do. Install a CL-130 inrush current limiter between the SS diodes and the PSU filter and you'll do fine.
Hi Eli,
I used a 6AX4 and it does the trick, but to yours and everyone else's point, it makes it hotter than it should be. You mentioned using a CL130 series with the rectifier between the bridge and the first filter cap. I have never used one like this. Can a CL tolerate that much voltage? How long does a CL130 take to warm up and "Drop out"?
Thanks!
the cl130 is rated to carry 1.6A, 10 ohms cold but as current passes, it heats ups and resistance drops like a stone, i usually leave them in circuit....
you can get those out of atx psu's, that is where i get them for my builds....
you can get those out of atx psu's, that is where i get them for my builds....
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