You've got me thinking about adding a little more flexibility to the mount. I may slip a Teflon washer between the aluminum connector and the flanged insert to allow a little bit more side to side motion in case of expansion. Of course I have to strike a balance between firmly holding the tube upright and allowing enough flexibility to compensate for thermal expansion.
I've made progress over the last week, with the fan power supply and 6E5P power supply installed, as well as most of the input/driver circuit and the shunt regulator for the 833 cathode. See picture. It's getting crowded in there. The cans of the two big can caps (33uF GE oil and 430uF Clarity TC PP) are grounded to the chassis, so they should provide some shielding from the power supply for the input circuit. I also made a shield for the fan using TI-Shield, as can be seen.
Still need to add the mu-follower board in the right hand corner, then it's over to the 833 PS, then the power and OPT will be added. It's already getting heavy...
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Still need to add the mu-follower board in the right hand corner, then it's over to the 833 PS, then the power and OPT will be added. It's already getting heavy...
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833 Progress
Magz, you do seem to be making progress now and Chassis Real Estate will diminish rapidly.Its amazing just how much different elements you need on a project of this size. As I said before you have spurred me on to take another look at building a BEAST. I have made a start already and include here some initial design concepts. This will probably be the last Amp that I ever build so I want it to be a statement and one that may encourage others and get there creative juices flowing....... I envisage making a start in about 2 months time with completion in 6 months. Like you I will photograph every step along the way.
Magz, you do seem to be making progress now and Chassis Real Estate will diminish rapidly.Its amazing just how much different elements you need on a project of this size. As I said before you have spurred me on to take another look at building a BEAST. I have made a start already and include here some initial design concepts. This will probably be the last Amp that I ever build so I want it to be a statement and one that may encourage others and get there creative juices flowing....... I envisage making a start in about 2 months time with completion in 6 months. Like you I will photograph every step along the way.
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WOW, that WILL be a monster amp!
Guess I need to get both of mine done in the next two months, so I can sit back and watch yours evolve!
833
Yes you are right....I will need 10 volts @ 25 amps just for the Filament (that's 2.5 times what the 833 needs)....on its own (250 watts) I will have to get rid of a great deal of heat....so it going to be a number of Fans strategically placed in and around the cabinet....its thanks to Magz and his researching that he has come up with a quiet Fan...so my thanks to him for that
Yes you are right....I will need 10 volts @ 25 amps just for the Filament (that's 2.5 times what the 833 needs)....on its own (250 watts) I will have to get rid of a great deal of heat....so it going to be a number of Fans strategically placed in and around the cabinet....its thanks to Magz and his researching that he has come up with a quiet Fan...so my thanks to him for that
8239/3cx3000f1 µ=5 A1 goodness
welder grade filament supply
Finished up the input/driver stage installation today (picture 1).
Picture 2 is a 2k square wave fed to the input jack and measured at the 833 grid connection.
Picture 3 is a 10k square wave.
Noise is barely one minor division on my scope at the most sensitive setting. Of course, the 833 HV or filament supplies weren't running at the same time, but at least I know the noise from the 6E5P supply is negligible.
Voltage at C2 of the supply is 408V from 120V input. Current through the 6E5P is 29.4mA.
Whoopee! About 2/3 of the way there!
Picture 2 is a 2k square wave fed to the input jack and measured at the 833 grid connection.
Picture 3 is a 10k square wave.
Noise is barely one minor division on my scope at the most sensitive setting. Of course, the 833 HV or filament supplies weren't running at the same time, but at least I know the noise from the 6E5P supply is negligible.
Voltage at C2 of the supply is 408V from 120V input. Current through the 6E5P is 29.4mA.
Whoopee! About 2/3 of the way there!
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Mounted the Hammond 369KX PT on top of the chassis and wired it up with the soft start for the input/driver/filament stages (green board toward the back of the unit); a second soft start for the output stage HV with front-mounted pushbutton will mount stacked above the one in the picture. Also finished up the wire dress for the input/driver stage and mounted the fan failure detection circuit (stacked above the DC heater supply for the 6E5P in the pictures). The input/driver and filament circuits are now complete; next up is the output stage.
The 369KX is a universal voltage PT, so there are a few leftover wires. I coated the cut ends with "liquid electrical tape" (cool stuff, available at Home Depot) and while the "tape" was still wet, screwed on wire nuts. Tight, secure and even if the wire nuts fall off (unlikely), still insulated.
The 369KX is a universal voltage PT, so there are a few leftover wires. I coated the cut ends with "liquid electrical tape" (cool stuff, available at Home Depot) and while the "tape" was still wet, screwed on wire nuts. Tight, secure and even if the wire nuts fall off (unlikely), still insulated.
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Finished up the 833 B+ supply today. It's a pretty full chassis now. See picture.
In the upper left corner you can see the soft start board for the 833 stacked on top of the soft start for the 6E5P and filament supply. The 733A PT wires aren't screwed into the soft start output terminals yet since I want to bring the 833 B+ up on a variac for it's "maiden voyage"...
In the lower right corner you can see the Gas Discharge Tube across the OT primary. It's a nominal 6000V +/- 20% GDT, so the lowest it could fire if it was at the bottom of the spec would be at 4800V. According to LTSpice, my OT should see a max of ~4200V at full power, so that GDT should be just about right for overvoltage protection. If it's at the other end of the spec it wouldn't fire until 7200V, so I hesitate to go higher in nominal voltage for fear of not having protection when it's needed.
The wiring in the 833 B+ circuit is 18ga test lead rated for 5kV WV. All solder joints have been smoothed to remove any sharp points and coated with corona dope.
Next step is to shape the outer edges of the teflon mounts I made for the 833 so that they fit inside the pyrex glass cylinder that will surround the tube. Then I'll drill holes in the ends of the mounts for the threaded inserts that will secure the cylinder in place. Then it's final assembly and testing.
In the upper left corner you can see the soft start board for the 833 stacked on top of the soft start for the 6E5P and filament supply. The 733A PT wires aren't screwed into the soft start output terminals yet since I want to bring the 833 B+ up on a variac for it's "maiden voyage"...
In the lower right corner you can see the Gas Discharge Tube across the OT primary. It's a nominal 6000V +/- 20% GDT, so the lowest it could fire if it was at the bottom of the spec would be at 4800V. According to LTSpice, my OT should see a max of ~4200V at full power, so that GDT should be just about right for overvoltage protection. If it's at the other end of the spec it wouldn't fire until 7200V, so I hesitate to go higher in nominal voltage for fear of not having protection when it's needed.
The wiring in the 833 B+ circuit is 18ga test lead rated for 5kV WV. All solder joints have been smoothed to remove any sharp points and coated with corona dope.
Next step is to shape the outer edges of the teflon mounts I made for the 833 so that they fit inside the pyrex glass cylinder that will surround the tube. Then I'll drill holes in the ends of the mounts for the threaded inserts that will secure the cylinder in place. Then it's final assembly and testing.
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833 amp
Nice job Magz...the chassis is getting crowded....you do seem to be paying a great deal of detail to the 833 possibility of corona discharge......I especially like the mention of smoothing down the solder joints....that is something I never thought about but will take on board with my own 2000T amp......I am dying for you to fire it up and give us an appraisal of its performance....from what I see you must be close to doing that in the next couple of weeks....it would be good if you could post it up on YouTube.
Nice job Magz...the chassis is getting crowded....you do seem to be paying a great deal of detail to the 833 possibility of corona discharge......I especially like the mention of smoothing down the solder joints....that is something I never thought about but will take on board with my own 2000T amp......I am dying for you to fire it up and give us an appraisal of its performance....from what I see you must be close to doing that in the next couple of weeks....it would be good if you could post it up on YouTube.
Next couple of weeks for sure. Of course, it's only one channel so the appraisal will be limited to mono...then I need to start all over again on the left channel.
This thing weighs a TON, I can barely lift it to move it around for assembly, mostly I just slide it around on the beach towel I have under it. For sure I want to get it right before it leaves the workbench - this is not the amp to be making continual tweaks on, unless you're a powerlifter!