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Re: DC Filament voltage low
 9/16/1999 2:11 PM |
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Scott | Re: DC Filament voltage low You would still have the proper voltage across the filaments IF the "-" on the bridge and filter cap were "ungrounded" and connected to pin 9 and one lead of the .047 cap(through the filament wire, of course). In this hookup, all filament negative is at the potential of one lead of the .047 cap and the other lead of the .047 cap connects to ground. ONLY the second lead of the .047 cap can connect to ground. If you hook it up like this and measure between pins 4,5 and 9, you should still measure 6.1 VDC. If you measure between pins 4,5 and ground, you will get some other value because the DC potential of the filament with respect to ground is "floating" on the .047 cap. You may get the 5 VDC that started all this. The floating hookup works fine, but I have found that the grounded filament is quieter. One other point - The 1.5 ohm resistor is at least a 5 Watt, right? If you calculate the dissipation, it is probably around 1-2 watts, and a 2 watter will run very hot. |
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