Advent 300 tuner woes.

thetube0a3 · 5th August 2010, 01:05 PM

Had a hard time deciding which section to post this in, hope this is the right one.

Working on an Advent 300 receiver and am having minor issues with the tuner. All aluminum electrolytic caps are new as of yesterday. When aligning the tuner I noticed L501 which is the 2nd coil (out of 2) as well as the second tunable trimmer cap have absolutely no effect. The tuner also has poor sensitivity although does pick up a few stations.

by second tunable trimmer cap I mean the trimmer on the third "final" section of the tuning capacitor.

I am assuming Q501 which is the fet in that section is probably bad. I'm planning on ordering a few replacements as they are available cheap as well as a replacing a few of the ceramic caps in the stage as well.

Sorry for my poor descriptions as i'm not that familiar with tuners, just know the basic alignment procedure and am learning as I go.

I'm using the Schematic from the website below.

http://www.davidreaton.com/PDFs/Adve..._schematic.pdf

Any opinions? things I should look for?

thetube0a3 · 6th August 2010, 02:46 AM

Oh cmon, no responses?

i'm trying to get this rapped up.

thetube0a3 · 6th August 2010, 05:25 PM

got it figured out with the help of an RF engineer at work.

I was looking at the circuit backwords. The coil and trimmer which are linked to the FET on the input are what does not work. The FET is not drawing any current ergo no sensitivity.

MPF280 is impossible to find but it appears J310G is extremely close. If anything it has to be better then nothing atall

5th August 2010, 01:05 PM	#1
thetube0a3 diyAudio Member Join Date: May 2008	Advent 300 tuner woes. Had a hard time deciding which section to post this in, hope this is the right one. Working on an Advent 300 receiver and am having minor issues with the tuner. All aluminum electrolytic caps are new as of yesterday. When aligning the tuner I noticed L501 which is the 2nd coil (out of 2) as well as the second tunable trimmer cap have absolutely no effect. The tuner also has poor sensitivity although does pick up a few stations. by second tunable trimmer cap I mean the trimmer on the third "final" section of the tuning capacitor. I am assuming Q501 which is the fet in that section is probably bad. I'm planning on ordering a few replacements as they are available cheap as well as a replacing a few of the ceramic caps in the stage as well. Sorry for my poor descriptions as i'm not that familiar with tuners, just know the basic alignment procedure and am learning as I go. I'm using the Schematic from the website below. http://www.davidreaton.com/PDFs/Adve..._schematic.pdf Any opinions? things I should look for?

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6th August 2010, 02:46 AM	#2
thetube0a3 diyAudio Member Join Date: May 2008	Oh cmon, no responses? i'm trying to get this rapped up.

6th August 2010, 05:25 PM	#3
thetube0a3 diyAudio Member Join Date: May 2008	got it figured out with the help of an RF engineer at work. I was looking at the circuit backwords. The coil and trimmer which are linked to the FET on the input are what does not work. The FET is not drawing any current ergo no sensitivity. MPF280 is impossible to find but it appears J310G is extremely close. If anything it has to be better then nothing atall

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