Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Solid State => Topic started by: talsmag on April 18, 2011, 02:38:16 pm
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I've been working on a TOS build and I fired it up without tubes to test the heater circuits, etc. As soon as I switched power on, the bridge retifier starting smoking and melting. I'm using the relay plan that Doug suggested and have it wired from the 6.3 volt heater wires. I'm also using the PT from Doug (Super Reverb) and using the heater center tap. Should I not use the center tap and create the artifical tap with the two 100 watt resistors? Any help would be appreciated.
thanks,
Gary
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Talsmag, that happened to me recently when I was adding an LED to a footswitch; turned out to be what it is 99.99% of the time—a wiring error. Doug's relay plans are right on. The dreaded instant smoking rectifier phenom usually happens if you somehow manage a connection sending your relay B+ directly to ground—rather through the relay coil or through the resistor/LED. You might track the wiring as it meanders through jacks or switches. Good luck on it. Regards
dennis
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Yup,you miswired it for sure.Do you have a 5v tap on the transformer?It's easier by far to use a separate winging or even a small filament transformer to get your relay power from.
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I figured I probably wired it wrong. I've got another rectifier coming, so I'll rewire everything, double or triple-check it, and report back.
thanks,
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I've been working on a TOS build and I fired it up without tubes to test the heater circuits, etc. As soon as I switched power on, the bridge retifier starting smoking and melting. I'm using the relay plan that Doug suggested and have it wired from the 6.3 volt heater wires. I'm also using the PT from Doug (Super Reverb) and using the heater center tap. Should I not use the center tap and create the artifical tap with the two 100 watt resistors? Any help would be appreciated.
thanks,
Gary
Using the center tap with the full wave bridge is where you went wrong. Don't use the center tap and use the 100ohm resistors on the heater windings and you should be as good as gold.
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and test it using a lamp limiter. This will prevent smoke if it's still erroneous.
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You can also use the Center Tap but the bridge must be floating
Kagliostro
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You can also use the Center Tap but the bridge must be floating
Kagliostro
That's another way. Just requires one more wire. Probably a better and noise free way if the extra wire or connectors are not an issue.
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I replaced the bridge rectifier, pulled the center tap and created the artificial tap. Everything looks right, but I can't get the relay to switch. I'm reading 6.5v AC on the heater supply and only 2.5v DC at the relay coil. It should be about 5v Dc, right? The diode lights up fine when switched on though. Could the relay be fried? The amp only plays through the clean channel, and the volume is weak and distorted. Not usable at all. I've gone through the wiring and can't seem to find anything wrong. Shouldn't the amp work fine on the clean channel only, regardless of whether the overdrive channel was working or not? I'm running out of brilliant ideas.
Gary
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How can we possibly help you unless we can see what you have done?A picture and a achematic of what you are doing would help immensely.
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The schematic is the standard one posted here under the TOS thread. No mods. I can post pics or voltages, or both. Not sure what would be more helpful.
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Wiring, wiring, wiring. Headache, headache, headache. Odd as it may seem, the relays that I have have been polarity sensitive. You might try swapping the lead on the relay. Regards
dennis