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Old 10th March 2010, 11:26 PM   #121
nhuwar is offline nhuwar  United States
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You know you can use the chokes on the grounded side of the b+ supply.

Make your voltage requirement a lot easier to meet.


Nick
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Old 11th March 2010, 03:14 AM   #122
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I'll be using Lundahl 1638 chokes. Consulting with Kevin (US Lundal distributor), I should be ok with the voltages and the currents they'll be used with. No value will be exceeded.

http://www.lundahl.se/pdfs/datash/1638.pdf


JD

Quote:
Originally Posted by ron parola View Post
Jeffery, Whose chokes are you using for the HV power supply. So far I've found nothing commercially available at these voltages. I'm hoping NOT to have to special order any. Thanks Ron p
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Old 11th March 2010, 03:55 PM   #123
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Thanks! Ronp
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Old 18th March 2010, 04:21 PM   #124
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Methinks it's just about there. Added a delay and slow start circuit to the megabeast. Turn on sequence for upper supply:
1. turn on main power switch... Amperite 75 second delay to primary while 866a MV rectifier filaments heat.
2. Amperite trigers and secondary 6.3v sets the 25 second solid state 555 based timer (Sophia Electric). **In case of a power blip, the Solid State device will reset and give some time for the heaters to warm, as the Amperite will probably be too hot to give the 75 second delay**.
3. Sophia trigers and separate 6.3vct tranny heats the 6CG3 damper diode.
4. damper diode slowly heats then ground circuit in upper supply is made and full B+ is availible.

Note 1 .... The center tap of the damper diode filament transformer is biased to the cathode as to keep their potential at the same level. The Damper diode has a max rating of 900volts Cathode to heater w.r.t heater being negative (relative to cathode).

Note 2 ...I liberally use CL80's for turn on current surge for the big tranny as it's a toroid and to add just a bit of ramp up time. Redundant, maybe, but cheap and they only cost a couple of volts, not to much to worry about. The Damper Diode also costs about 20 volts or so.
The lower supply uses a 5852 Bendix, a Aerospace version of a 6X5GT. It has a 45 second heat up time, so it can be used as-is for the 20B.

JD
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Last edited by Jeffrey Davison; 18th March 2010 at 04:27 PM.
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Old 28th October 2010, 04:37 PM   #125
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Construction pics ???
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Old 1st November 2010, 07:52 PM   #126
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Hello. I am also curious to hear how this amp turned out. The switches were thrown, the anticipation was building, and....
Thanks for sharing. This has been a fun thread to follow.
CR
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Old 8th March 2016, 12:12 PM   #127
CV6045 is offline CV6045  United Kingdom
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Default 304TL circuit

hi Frank,

I am on the point of starting to build my 304TL SE amp. as all the other guys have said it is a mammoth task and is a different world than building with something like an EL34...but heck the enjoyment and sense of achievement when its up and running is a real blast. Anyway attached is my circuit diagram which I hope helps you out. Note the 13E1 can be replaced with 6C33...good luck and let us know how you get on...James


Quote:
Originally Posted by angelfj View Post
I am new to the forum but I have been reading about the 833A based SE amps. I have a supply of 304TL tubes. Would this tube be suitable for a class A SE? Any suggestions for a circuit? Would the driver and output transformer selection be similar to the 833A?

Thanks in advance.

Frank

Last edited by CV6045; 8th March 2016 at 12:22 PM.
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Old 8th March 2016, 12:18 PM   #128
CV6045 is offline CV6045  United Kingdom
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Default 304TL Circuit

Quote:
Originally Posted by CV6045 View Post
hi Frank,

I am on the point of starting to build my 304TL SE amp. as all the other guys have said it is a mammoth task and is a different world than building with something like an EL34...but heck the enjoyment and sense of achievement when its up and running is a real blast. Anyway attached is my circuit diagram which I hope helps you out. Note the 13E1 can be replaced with 6C33...good luck and let us know how you get on...James
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Old 9th March 2016, 04:13 PM   #129
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Default 304 amp

Well, I've built a pair of them based on a fellow's design called "bitches brew", you can search that on the web. It's a battery biased (on the el 20a ) driver, direct coupled parafeed design and does work well. Electroprint made the coupling choke and the output transformers, Lundahl input. Standard transformers for high voltage (1.5kv) and Russian oil caps for the hv power supply. Since I was worried about size and weight (97lbs!) I'm not using tubes for power supplies, I'm infact using a switching power supply for the 304 heaters, a 50 amp one, a 20a wouldn't handle the inrush current. And in addition I'm staging the two halves of the 304 heaters AND the two amps to start slowly. In the chassis is a cooling fan which exits at the base of the 304s within a glass chimney, you CAN heat the room with these. And if you are worried about noise with a switching supply; they cycle at 50kz, a bit above what I can hear with a resonance at 25 which a choke dampens. You DON'T breadboard these you Plywood them. good luck rp
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File Type: jpg DSCF0910.JPG (198.3 KB, 89 views)
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Old 9th March 2016, 08:15 PM   #130
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Hi Ron,
Nice work. What is the dissipation of the 304TLs when you are running them?
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