[ARC5] GO-9 Project: Why the Resistor?

[howard holden]

I never paid much attention to that resistor, but I can tell you that for 10 years of heavy use my GO has used the same tube in the IPA, with no noticeable difference in performance. Maybe related to the 1K resistor in the filament CT R207? Dunno. BTW that's where I key my GO, between R207 and ground. You'd think that was a lousy place to key but it's not.


I've seen one or two places where a dropping resistor was used in an oscillator filament circuit, can't remember any off hand though, and no idea of why they'd do that.


Howie WB2AWQ

On 10/22/2019 12:28 PM, David Stinson wrote:

Dear Smart People:
Please take a look at the GO-9 transmitter schematic attached.  The 837 MO and 837 IA tubes are supplied filament voltage from the same buss.  However, the connection to the 837 IA tube goes through R-312, a 4.5 Ohm 20 Watt resistor (red arrow).  At the 0.7 Amp current of the 837, this is going to drop around 3 Volts, reducing the tubes filament voltage from 12.6 VAC 800Hz down to 9.6 V.  I haven't found a mention of this in the manual's circuit description.  Why would they do this?

TNX OM ES 73 DE Dave AB5S[cid:part1.811C0CF8.2C0E9A60 at msn.com]

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