I obtained and 'polished up' a Fisher 1800 recently, described at RSSteve's "1800 Roll Call and Information" thread:
http://audiokarma.org/forums/index....iver-information-thread-and-roll-call.724824/
I'm quite happy with the overall condition of this receiver and it sounds very good. Still puzzling over the relay-controlled "Stereo Beacon" control, though. It didn't work at all in "FM Automatic" mode when I first got it. After an FM IF/Ratio Detector alignment, it started working again. I also cleaned the contacts on the relay while doing various work in the unit.
Now that the 1800 is playing in the listening room, I'm impressed with the sensitivity of the receiver with just a wire dipole antenna. I live about 35 miles from Philadelphia 'as the crow flies' and there are plenty of strong stereo stations, as well as a few even closer in Wilmington DE. These stations put the signal meter at or well past 4 out of 5 and come in with very little noise in "Stereo Filter" mode (full time FM multiplex).
However, the Beacon light only lights in Automatic mode on 3 or 4 of the very strongest stations. Looking at the schematic, there appears to be no way to adjust the circuit. The 6GK5 SB amp tube tests strong (mutual conductance). I performed Dave Gillespie's "800C Service Bulletin" to change out B+ supply resistors to the diode matrix that controls this circuit.
I did not try to align the multiplex decoder, as it showed good stereo operation and separation when driven with my Sencore SG-165 (if it ain't broke…..). There is good apparent separation when listening as well. No distortion in stereo on moderately strong to strong signals. The signal meter shows 4+ with strong signals, about 3 between signals and close to zero or 1 with no antenna connected.
So, the question: should the Beacon be operating on more stations? If so, what should I look at to achieve it? MPX decoder alignment? Other?
Thanks!
Dave
http://audiokarma.org/forums/index....iver-information-thread-and-roll-call.724824/
I'm quite happy with the overall condition of this receiver and it sounds very good. Still puzzling over the relay-controlled "Stereo Beacon" control, though. It didn't work at all in "FM Automatic" mode when I first got it. After an FM IF/Ratio Detector alignment, it started working again. I also cleaned the contacts on the relay while doing various work in the unit.
Now that the 1800 is playing in the listening room, I'm impressed with the sensitivity of the receiver with just a wire dipole antenna. I live about 35 miles from Philadelphia 'as the crow flies' and there are plenty of strong stereo stations, as well as a few even closer in Wilmington DE. These stations put the signal meter at or well past 4 out of 5 and come in with very little noise in "Stereo Filter" mode (full time FM multiplex).
However, the Beacon light only lights in Automatic mode on 3 or 4 of the very strongest stations. Looking at the schematic, there appears to be no way to adjust the circuit. The 6GK5 SB amp tube tests strong (mutual conductance). I performed Dave Gillespie's "800C Service Bulletin" to change out B+ supply resistors to the diode matrix that controls this circuit.
I did not try to align the multiplex decoder, as it showed good stereo operation and separation when driven with my Sencore SG-165 (if it ain't broke…..). There is good apparent separation when listening as well. No distortion in stereo on moderately strong to strong signals. The signal meter shows 4+ with strong signals, about 3 between signals and close to zero or 1 with no antenna connected.
So, the question: should the Beacon be operating on more stations? If so, what should I look at to achieve it? MPX decoder alignment? Other?
Thanks!
Dave