Marantz 2220B no left channel on FM stereo - Help please.
- Thread starter daveyh
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Yes! The FM multiplex board has an IC to process the composite signal into two channels. One channel originates at IC H301 at pin 5 and goes through some filtering and to transistors H304 and then H306. The other channel comes out at H310 pin 4 -> H305 -> H307. You might be able to measure these with a meter set to AC volts but a scope would be better. Good luck!
petehall347
the brandy coffee man
what happens when tuned to a mono station mono button out ?
daveyh
Super Member
Thanks I will check these.
daveyh
Super Member
With the Mono button in it works in both channels. With the Mono button out it only works the right channel. If I turn the volume all the way up and the balance control all the way to the left I can hear a very faint FM signal. Right channel works fine when the balance is centered or all the way to the right.
catrafter
Marantz Specialist
Here is some advise that helped another 2220B owner...
Tom
If the Stereo lamp works in aux, phono and tape, and goes off when you select Mono in those functions, then there are other things to look for other than the mono switch.
The path for the stereo lamp in FM Stereo operation is pin 6 of H301, through R311 to pin J305 then to S001-1 pin 6 then to S001-1 Pin 5 (because it in the 'FM' position), then over to JH11, through the Mono switch which is not pressed, out JH10 to one side of the 'stereo lamp. The other side is connected to plus 7VDC, the source.
If you don't have a frequency counter, set the selector to FM and tune in a strong station, that is, one that will send the signal meter up at least half way. Use an antenna of some sort if you need too, I can usually get away with a foot or two of wire. If the base of H303 is less than 0.6VDC, and the collector or Pin 8 of H301 is above 2VDC, then check H301, pin 14. If it is above 3VDC, then mark where R304 is now so you can set it back if things don't work out. Now try moving R304 a bit each way and see if the stereo lamp comes on.
Expanding on the operation a bit, the levels in parentheses () are what you should see on the P300 board for FM stereo operation. Look for less than 0.6Vdc on the base of H303, it monitors signal quality and shorts pin 8 of H301 to ground if it's too low, forcing H301 into mono operation. The VCO test point at R312 (TPB on the schematic) should be 19kHz. If there is nothing there, H302 could be on or shorted emitter to collector killing the VCO, It's base is driven positive when the selector is in AM to prevent interference.
Tom
If the Stereo lamp works in aux, phono and tape, and goes off when you select Mono in those functions, then there are other things to look for other than the mono switch.
The path for the stereo lamp in FM Stereo operation is pin 6 of H301, through R311 to pin J305 then to S001-1 pin 6 then to S001-1 Pin 5 (because it in the 'FM' position), then over to JH11, through the Mono switch which is not pressed, out JH10 to one side of the 'stereo lamp. The other side is connected to plus 7VDC, the source.
If you don't have a frequency counter, set the selector to FM and tune in a strong station, that is, one that will send the signal meter up at least half way. Use an antenna of some sort if you need too, I can usually get away with a foot or two of wire. If the base of H303 is less than 0.6VDC, and the collector or Pin 8 of H301 is above 2VDC, then check H301, pin 14. If it is above 3VDC, then mark where R304 is now so you can set it back if things don't work out. Now try moving R304 a bit each way and see if the stereo lamp comes on.
Expanding on the operation a bit, the levels in parentheses () are what you should see on the P300 board for FM stereo operation. Look for less than 0.6Vdc on the base of H303, it monitors signal quality and shorts pin 8 of H301 to ground if it's too low, forcing H301 into mono operation. The VCO test point at R312 (TPB on the schematic) should be 19kHz. If there is nothing there, H302 could be on or shorted emitter to collector killing the VCO, It's base is driven positive when the selector is in AM to prevent interference.
daveyh
Super Member
I checked H303 at the base and it reads 47.7mV
H301 pin # 8 = 2.32VDC
pin # 14 = 3.07VDC
The stereo lamp is on with the mono button out but it is just not strong in the left channel. Very strong and clear in the right channel. Both channels work fine in mono mode with the button pushed in. I checked all the transistors on the board and they read OK.
H301 pin # 8 = 2.32VDC
pin # 14 = 3.07VDC
The stereo lamp is on with the mono button out but it is just not strong in the left channel. Very strong and clear in the right channel. Both channels work fine in mono mode with the button pushed in. I checked all the transistors on the board and they read OK.
daveyh
Super Member
What am I looking for? Edit: There is no distortion on both of these H305 -> H307 it just has very low volume on that channel but only in FM mode. Also, when I touch the top of capacitor C322 with the tip of my finger while the unit is on there is a hum but no hum when I touch the top of C321.
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daveyh
Super Member
There is feet on the unit but the screws are not long enough to touch any jacks.
My methods were to troubleshoot exactly your problem. I never said anything about distortion.
The cap thing may point more towards transistors H304 and H306. You could also measure the three pins on these for the dc voltages printed on the schematic. If they are weird, post them and we'll take a shot at analysis / guesses.
Those all look reasonable. Next you'll have to be able to measure the AC levels with a meter or scope to see where the signal is not there.
Another alternative is to try a powered speaker to listen to the various stages. Couple the signal to the speaker through a capacitor, minus side toward the speaker if it's an electrolytic. Hopefully you have a cap of some kind in the 1uF or smaller range to use. Compare good channel to bad channel at the IC output and at the base and collector of each transistor H304-307.
Another alternative is to try a powered speaker to listen to the various stages. Couple the signal to the speaker through a capacitor, minus side toward the speaker if it's an electrolytic. Hopefully you have a cap of some kind in the 1uF or smaller range to use. Compare good channel to bad channel at the IC output and at the base and collector of each transistor H304-307.