Philco 118 AVC Levels - Printable Version
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Philco 118 AVC Levels - glwells - 09-28-2010
I have been chasing an AVC level issue on a 118 that I have completely recapped, resistors checked, tubes checked, and recalibrated. I find that the AVC level rarely gets above -3VDC and often will slip positive approx 1.5 VDC with no signal. I am looking for guidance as to whether a slight positive voltage is normal on the AVC bus with no signal and if not, suggestions as to where to begin my investigation. I thought AVC was always in the range of zero to negative values. Thanks for all of your help and guidance.
Gary
Re: Philco 118 AVC Levels - Chuck Schwark - 09-28-2010
Average AVC voltage is highly dependant on incomming signal level.
Weak signals will make the AVC hover near zero (max gain), like is should.
Since this set needs (and was designed for) an outdoor aerial of at least 30ft.,
I suggest trying that. Be sure to also use a lightning arrestor and install it properly.
Also very inportant is a good Ground on the set to a cold water pipe or ground rod.
This will also maximize your receiving signal strength.
Chuck
Re: Philco 118 AVC Levels - glwells - 09-28-2010
Thanks for the response. I do have a 100 ft long wire on it although no ground. The receiver sounds good on AM and SW bands so I tend not to tamper any further. The shadow meter functions good for the most part but really only narrows up on really strong signals. I measured the AVC on the left side of the 2 meg resistor R15. I just wasn't sure that AVC should swing slightly positive like it does when it is at max gain.
This radio was quite the challenge but I am very pleased with its performance so far.
Gary
Re: Philco 118 AVC Levels - exray - 09-28-2010
Makes a lot of difference with what type of meter you are using. Going positive goes against the 'book' but I don't have enough knowledge to address this specific model.