DHT Heater using VCCS - PCB or Kit (Possible Group buy)
#1111 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
I can also highly recommend Andrews boards. I run the standard boards (as opposed to the large) with 300B no issue. Make sure you size the transformer with plenty to spare - I had a buzz which eventually tracked back to toroidal overload.
#1112 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
Thanks RhythMick, what is the least voltage input for normal operation on Andrews board for 300B ?
#1113 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
Allow 4v for regulation. So for a 300B
(5v + 4v) is 9v peak, over 1.414 is 6.36v RMS
6.3v tx should be ok. 6v might be if your primary is 5% high. I went for a dual 7v toroidal with 4.4A secondaries to give plenty of headroom.
I also used the 63mm heatsinks for the 300B. These are onboard the smaller boards. I'm not using any forced air circulation and I regularly measure the temperature of both the heatsink and the transistor casings, usually about 60 degrees.
(5v + 4v) is 9v peak, over 1.414 is 6.36v RMS
6.3v tx should be ok. 6v might be if your primary is 5% high. I went for a dual 7v toroidal with 4.4A secondaries to give plenty of headroom.
I also used the 63mm heatsinks for the 300B. These are onboard the smaller boards. I'm not using any forced air circulation and I regularly measure the temperature of both the heatsink and the transistor casings, usually about 60 degrees.
#1114 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
Thanks !RhythMick wrote: ↑Mon Mar 09, 2020 7:08 am Allow 4v for regulation. So for a 300B
(5v + 4v) is 9v peak, over 1.414 is 6.36v RMS
6.3v tx should be ok. 6v might be if your primary is 5% high. I went for a dual 7v toroidal with 4.4A secondaries to give plenty of headroom.
I also used the 63mm heatsinks for the 300B. These are onboard the smaller boards. I'm not using any forced air circulation and I regularly measure the temperature of both the heatsink and the transistor casings, usually about 60 degrees.
#1115 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
Got more PCB on the way, had run out.
Analogue, the lost world that lies between 0 and 1.
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#1116 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
Andrew, did you ever get the higher power versions up and running ?
10V @ 10A would be nice.
10V @ 10A would be nice.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#1117 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
Not yet, I never got a round tuit, sorry.
It's on my list, but life keeps getting in the way.
It's on my list, but life keeps getting in the way.
Analogue, the lost world that lies between 0 and 1.
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#1118 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
Que Sera, Sera.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
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#1119 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
You got Doris Day's Greatest Hits too G-Popz?
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#1120 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
Perhaps, perhaps, perhaps Simon, who wouldn't ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
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#1121 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
I'll take that as a rhetorical question
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#1122 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
Whatever. (will be, will be)
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
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#1123 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
Another question for Andrew.
I've no experience of your small boards, but I'm thinking of filament bias on a 12A (112A) which would require 256.2 mA @ 14v. Will they cope with this ?
If so, when will you have kits available ?
I've no experience of your small boards, but I'm thinking of filament bias on a 12A (112A) which would require 256.2 mA @ 14v. Will they cope with this ?
If so, when will you have kits available ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#1124 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
Or 0.25A as the rest of the world would describe it. Some may argue you would need to adjust the current until you get 5v across the filament.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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#1125 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)
I don't think I've done filament bias before so I'd been looking at how Rod Coleman did things. I printed off his fact sheet so I can understand the details. What you say about the filament voltage sounds right, although I have read that slightly starving filaments may be an improvement.
My plan, if this idea comes to fruition, was to test things out with a 20R resistor in lieu of the filament to see how close to 5V it gets.
Rod recommends a 20-23v transformer to power his modules and I have a pair of 22v toroids.
*
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)