Will this work? - Page 3

Merlinb · 5th May 2006, 03:12 PM

The choke bobbin should be mounted at 90 degrees to the power trans' bobbin or it may induce hum in the HT supply. Dunno if you've already done that!

jaymanaa · 5th May 2006, 03:20 PM

Thanks for the reply. That was one of the things I was unsure of. When you say bobbin, is that the core (laminations)?

Merlinb · 5th May 2006, 04:16 PM

Sort of, its the orientation of the internal bar that goes through the bobbin that matters. That forms the axis of the magnetic field.

jaymanaa · 5th May 2006, 05:02 PM

Gottcha

Thanks, Jay

jaymanaa · 20th May 2006, 04:04 AM

Well, I got the power supply hooked up. I used motor run oil caps and a big old choke that I don't have specs on. I learned alot, but have one small problem. Instead of 430v I ended up with 570

This is without the .13 load, but I'm not expecting much sag out of this monster tranny. I'm going to put together a load (any suggestions on how) and see what I get. I've got it all built on a chassis so I may be looking for some other tube (schematic) that can handle this voltage and will like the 10kohm primary OPT's. Maybe 807's? I don't know if it is feasable to try and drop B+ 120 to 140 volts. I do have another choke.

lndm · 20th May 2006, 04:15 AM

You could look at a choke input filter. This will drop your voltage. It may be a little less predictable to design, sim if possible to check for ringing.

If you want to produce a dummy load, divide your desired B+ by your desired current draw for a stage and this gives you a resistance value to use. Apply it to your supply to see whether it drags it down to where you wanted it to be.

Also, multiply the voltage by the current to see what power the resistor will be dissipating.

jaymanaa · 20th May 2006, 12:14 PM

By my handy ohms wheel it looks like I need a resistor 4385ohms*74 watts. Heres a picture.

lndm · 20th May 2006, 12:41 PM

Umm <lndm picks up jaw from floor>, thats a large resistor.

Options:
1. Put a couple of 10W resistors in series and only turn on long enough to take measurements.

2. Use a circuit simulator, I like this method.

3. Make use of the fact that valves are resilient. Make best estimates on values, build your circuit, double check it, and switch on. I mean, if you have a large supply voltage, using that to calculate a dropping resistance for the supply (voltage to drop / current), and using the factory spec cathode resistance, you'll probably end up with less than the expected voltage on your devices anyway. Set your multimeter on a critical point in your circuit before turn on and watch it. You might chose the cathode resistor, so you can watch the current, or measure the anode voltage. If for some reason the voltage gets too high, just switch off.

Killing voltage with series resistance can work for a single ended circuit, but class AB draws a range of current and makes the choke input look like a better idea.

I also have 130V to kill. I use some series resistance to protect my rectifier from excess capacitance, I use some series resistance to reduce ripple, I use a choke that has series resistance. I have enough capacitance at the end to make it all good.

BTW, those are nice looking caps

jaymanaa · 20th May 2006, 12:51 PM

They do seem to be nice caps. I have a supplier at work who sells to me at cost if stuff is for my use. I got them for 6 bucks each. I'm going to do a little experimenting with some dummy loads and see if I have any sag at all on this contraption. The down side to all this is I have to do all the laundry now as my wife refuses to come down into the basement. Oh well. Thanks for the ideas, Jay

jaymanaa · 20th May 2006, 08:29 PM

Quote:

Originally posted by lndm
You could look at a choke input filter. This will drop your voltage. It may be a little less predictable to design, sim if possible to check for ringing.

If you want to produce a dummy load, divide your desired B+ by your desired current draw for a stage and this gives you a resistance value to use. Apply it to your supply to see whether it drags it down to where you wanted it to be.

Also, multiply the voltage by the current to see what power the resistor will be dissipating.

I misunderstood. The circuit I'm using wants 430v@.13A. I built this light bulb thing to simulate that load. Five 15 watt bulbs. It brought the vdc down to 515 from 582. Now I will try to figure out a resistor value (to put in series with the load?). Thanks, Jay

5th May 2006, 03:20 PM	#22
jaymanaa diyAudio Member Join Date: Jan 2006 Location: Kansas	Thanks for the reply. That was one of the things I was unsure of. When you say bobbin, is that the core (laminations)? __________________ "Make everything as simple as possible, but no simpler" Einstein

5th May 2006, 05:02 PM	#24
jaymanaa diyAudio Member Join Date: Jan 2006 Location: Kansas	Gottcha Thanks, Jay __________________ "Make everything as simple as possible, but no simpler" Einstein

20th May 2006, 04:04 AM	#25
jaymanaa diyAudio Member Join Date: Jan 2006 Location: Kansas	Well, I got the power supply hooked up. I used motor run oil caps and a big old choke that I don't have specs on. I learned alot, but have one small problem. Instead of 430v I ended up with 570 This is without the .13 load, but I'm not expecting much sag out of this monster tranny. I'm going to put together a load (any suggestions on how) and see what I get. I've got it all built on a chassis so I may be looking for some other tube (schematic) that can handle this voltage and will like the 10kohm primary OPT's. Maybe 807's? I don't know if it is feasable to try and drop B+ 120 to 140 volts. I do have another choke. __________________ "Make everything as simple as possible, but no simpler" Einstein

20th May 2006, 12:51 PM	#29
jaymanaa diyAudio Member Join Date: Jan 2006 Location: Kansas	They do seem to be nice caps. I have a supplier at work who sells to me at cost if stuff is for my use. I got them for 6 bucks each. I'm going to do a little experimenting with some dummy loads and see if I have any sag at all on this contraption. The down side to all this is I have to do all the laundry now as my wife refuses to come down into the basement. Oh well. Thanks for the ideas, Jay __________________ "Make everything as simple as possible, but no simpler" Einstein

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5th May 2006, 03:12 PM	#21
Merlinb diyAudio Member Join Date: May 2006 Location: York	The choke bobbin should be mounted at 90 degrees to the power trans' bobbin or it may induce hum in the HT supply. Dunno if you've already done that!

5th May 2006, 04:16 PM	#23
Merlinb diyAudio Member Join Date: May 2006 Location: York	Sort of, its the orientation of the internal bar that goes through the bobbin that matters. That forms the axis of the magnetic field.

20th May 2006, 04:15 AM	#26
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	You could look at a choke input filter. This will drop your voltage. It may be a little less predictable to design, sim if possible to check for ringing. If you want to produce a dummy load, divide your desired B+ by your desired current draw for a stage and this gives you a resistance value to use. Apply it to your supply to see whether it drags it down to where you wanted it to be. Also, multiply the voltage by the current to see what power the resistor will be dissipating.

20th May 2006, 12:41 PM	#28
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	Umm <lndm picks up jaw from floor>, thats a large resistor. Options: 1. Put a couple of 10W resistors in series and only turn on long enough to take measurements. 2. Use a circuit simulator, I like this method. 3. Make use of the fact that valves are resilient. Make best estimates on values, build your circuit, double check it, and switch on. I mean, if you have a large supply voltage, using that to calculate a dropping resistance for the supply (voltage to drop / current), and using the factory spec cathode resistance, you'll probably end up with less than the expected voltage on your devices anyway. Set your multimeter on a critical point in your circuit before turn on and watch it. You might chose the cathode resistor, so you can watch the current, or measure the anode voltage. If for some reason the voltage gets too high, just switch off. Killing voltage with series resistance can work for a single ended circuit, but class AB draws a range of current and makes the choke input look like a better idea. I also have 130V to kill. I use some series resistance to protect my rectifier from excess capacitance, I use some series resistance to reduce ripple, I use a choke that has series resistance. I have enough capacitance at the end to make it all good. BTW, those are nice looking caps

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