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Marantz 2226B--no FM stereo

M

morgan

morgan
Couldn't find any threads relating to this problem on the forum.
I have three 2226B with exactly the same problem. Won't receive FM in stereo.
I replaced the HA1196 IC, stereo indicator came on briefly indicating stereo, but went out after about 10 seconds.
FM signal is strong and shows stereo in other receivers.
The stereo indicator lamp is correct for this model---supply voltage to the lamp is 10vdc + or -.
Is it possible the replacement HA1196's are subpar quality?
The voltages on the IC pins are reasonably close, since the schematic seems to show voltages when receiving stereo.
 
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Sounds like you need to adjust the VCO for the MPX circuit. Correct way is to tune to a point with no signal strength and use a frequency counter to the correct frequency ( 38khz or 19 khz or 76 khz - check the manual) Quick and dirty method is mark the current setting of the VCO varialble resistor, then try adjusting it with a strong stereo station, find the center of the range which turns the stereo light on. There may be an issue with muting thresholds, but I'm not that familiar with this models. YMMZ - good luck. It is possible that the chips are bad, but I haven't seen anything other places about problems with supplies of this chip, but I haven't been looking that hard either. There also is a polyester or film type cap which can go bad, but 3 is very doubtful. Steve
 
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C302 360pF - description says film type, but is usually polystyrene. R301 is VCO adjust. Q301 conducting I believe (someone correct me if I'm wrong) turns off VCO and is controlled by muting circuitry. Good luck.
 
bump. Did some re-education on my part (similar problem in a Nikko tuner). Muting threshhold and mono stereo switch turn off mpx signal by apply small voltage to pin 12 of HA 1196 (difference is zero vs .6 volts at the pin). Grounding pin 12 should allow mpx to work. Muting problems can cause no stereo reception. Q301 kills the VCO when AM is selected as far as I can tell.
 
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