Marantz 2215 FM Decoder troubleshooting...

The adjustment of L103 is critical for stereo operation.
If the incoming station, the tuner front end or the IF gain is weak then the circuit mostly composed of H109/L103/H118/H119 won't be able to turn H302 off to enable the multiplex decoder, H301 to decode stereo (If H301 pin 8 is at or near zero volts, then the decoder is forced to mono operation).
In the last 2215B I rebuilt, L103 was bad and I had to get one by buying a donor board from the auction site.
To adjust L103, tune in a strong stereo station and monitor J114 with a voltmeter. Use the proper alignment tool to adjust L103 for maximum positive voltage, which should turn H302 off.

Tom
Want to get this right, L103 is the local oscillator, is that correct? Or do you mean adjust L107?
 
The adjustment of L107 is critical for stereo operation.
If the incoming station, the tuner front end or the IF gain is weak then the circuit mostly composed of H109/L103/H118/H119 won't be able to turn H302 off to enable the multiplex decoder, H301 to decode stereo (If H301 pin 8 is at or near zero volts, then the decoder is forced to mono operation).
In the last 2215B I rebuilt, L107 was bad and I had to get one by buying a donor board from the auction site.
To adjust L107, tune in a strong stereo station and monitor J114 with a voltmeter. Use the proper alignment tool to adjust L107 for maximum positive voltage, which should turn H302 off.

Tom

Hi Tom / Everyone, I'm new here but just tried pulling H302 out & I finally have STEREO! I bought my unit used over 10 yrs ago for $75 & just noticed (after upgrading all the lights to LEDs / kit) that my STEREO Light wasn't the only problem... I wasn't even hearing things in Stereo... EVER! Now I'd like to make things right. I mainly use it in my shop with speakers so I never really noticed... but after installing the new lights & trying to find out why they still wouldn't light after replacement, I found many people had the same issue.

Is there any problem/issues with just leaving H302 out???

Tom,
You say to "tune in a strong stereo station and monitor J114 with a voltmeter"... what voltage are we looking for here? Mine never seemed to get higher than 100mV DC, a little higher (maybe 150mV) when turning L107.

Anyone else with how to resolve this would be cool... I like these old units but don't want to kill myself with weeks of tech or parts I don't need.

Thanks for your help!!!
 
If you can only get +100mVdc at J114, then I suspect the problem is caused by something ahead of the stereo decoder.
Perhaps in the area of H109, L107 , H118 or H119.
Leaving H302 out will cause the decoder to try to 'decode' stereo when the signal is too weak for good stereo reception, this may be better for you than no stereo at all.

Tom
 
Thanks Tom,
I'm going to check the diodes & other parts/areas you suggested. I forgot to note that when I press the "FM muting" there is NO SIGNAL at all... not sure if this helps shine a light on things?

Also, what avg voltage "should" I be reading at J114/J115, with a strong FM channel tuned in?

& you'd said you had a bad L107... any advise on what to look for or how to test that?

BTW, I am a tech but mostly tube amps & recording studio gear... not much experience with radios. So I have a scope & meters & a cheap hand-held Frequency Gen (goes from 20Hz to 150k.

I should also note that I haven't replaced any parts or IC's yet.
Does pulling H302 rule out the IC's being bad???

My unit uses (STOCK PARTS):
H201 = HA1151
H301 = MC1310P (same pinout as HA1156)
 
Last edited:
Thanks Tom,
I'm going to check the diodes & other parts/areas you suggested. I forgot to note that when I press the "FM muting" there is NO SIGNAL at all... not sure if this helps shine a light on things?

Also, what avg voltage "should" I be reading at J114/J115, with a strong FM channel tuned in?

& you'd said you had a bad L107... any advise on what to look for or how to test that?

BTW, I am a tech but mostly tube amps & recording studio gear... not much experience with radios. So I have a scope & meters & a cheap hand-held Frequency Gen (goes from 20Hz to 150k.

I should also note that I haven't replaced any parts or IC's yet.
Does pulling H302 rule out the IC's being bad???

YES!


My unit uses (STOCK PARTS):
H201 = HA1151
H301 = MC1310P (same pinout as HA1156)

The fact that the muting sdeosn't work right indicated a problem with the IF signal strength detector circuit including L107.

Tom
 
Since it decodes stereo with H302 out, the HA1156 circuits are working.
You could ohm the windings on L107 to look for an open, but substitution is what I did.

I checked for 10.7Mhz on the collector of H109 with my scope. There was some there, and some DC voltage was present. There was nothing on the secondary of L107 feeding the rectifiers H118 and H119. Both rectifiers checked good.
The DC voltage representing the IF signal strength is also used to drive the muting circuit, H110 and H111.
On a working system there should be enough positive voltage at J114/115 to turn H302 OFF.

Tom
 
Since it decodes stereo with H302 out, the HA1156 circuits are working.
You could ohm the windings on L107 to look for an open, but substitution is what I did.

I checked for 10.7Mhz on the collector of H109 with my scope. There was some there, and some DC voltage was present. There was nothing on the secondary of L107 feeding the rectifiers H118 and H119. Both rectifiers checked good.
The DC voltage representing the IF signal strength is also used to drive the muting circuit, H110 and H111.
On a working system there should be enough positive voltage at J114/115 to turn H302 OFF.

Tom
I have been down that road many many times. Never was a bad multiplex chip, but always a bad capacitor around the chip. Check the caps, electrolytics, mylars, and ceramics can fail even when we do not expect them to fail.
 
I have exactly the same problem, just with a Rotel 1025. Many tuners use the same topology sharing both the 1137 and 1156 IC's. Mine also won't go into stereo and removing the transistor will get it into stereo.
But then the muting function will be down, for me that is not a repair but a crude workaround.

I do think that the primary issue involves the transistor that forces the 1156 into ground (thus forcing mono). In my case it never gets the voltage from the 1137 IC that it needs. All components around it check out fine.
Thus there should be something in another part of the circuit that creates this rather common behaviour.
What I can think of is that the signal strength isn't actually reflected correctly by the signal meter. So we may think it is a clear and strong signal when in reality the system thinks it is not.
Or that there is too much noise / distortion in the signal that triggers the behaviour.

Regards,

Bert
 
Back
Top Bottom