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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Re: Watching 2A3 burn , Help! posted by Les Hudson on March 3, 2007 at 10:04:37:
Les,
If this is exactly how you set up your 2A3 filaments I expect burning 100ohm resistors are the least of your problems. I don’t think that amp will work as drawn. I would not turn the amp on again until a few things are changed and you use a variac. You risk killing your power supply transformer as well as your output transformers and your 2A3s.Since a 2A3 has a filamentary cathode your high-tension supply (B+) can goes to ground through the 2A3 heater if you let it. In your case it’s about 300V through the 2A3 plate to cathode to 100ohm resistor to ground, which is enough to light those 100 ohm resistors up.
In addition I don’t see how you are biasing the grid on the 2A3? If you are attempting to bias the 2A3 with the pair resistors coming off your filament you will need to use much higher values. Or just hook up an 800 ohm resistor to ground from their junction.
Try looking at five or so other 2A3 schematics and see if you can figure out how they are dealing with DHT issues, mostly how they are setting Vbias and completing high-tension DC and AC circuits. Good luck, variacs really help.
Matt
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Follow Ups
- Re: Watching 2A3 burn , Help! - mwiebe 11:05:13 03/03/07 (2)
- Re: Watching 2A3 burn , Help! - Les Hudson 14:48:50 03/03/07 (1)
- Re: Watching 2A3 burn , Help! - mwiebe 16:18:08 03/03/07 (0)
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