Marantz 2240B: FM tuning meter problems

flambart

New Member
Since some months, I own a beautiful 2240B Marantz receiver: I bought it from US, in superb conditions, inside and outside.

I love it a lot, but... I've only one problem, not too serious, nor affecting the sound quality, but annoying me a bit.

The FM tuning meter gauge is perfectly centered when FM is not in use, and even in FM mode, with no signal applied. Instead, in order to correctly tune all the stereo stations (i.e. stereo indicator on), I have to place the gauge about 10°-15° right respect to the meter center. Otherwise, there is no way to obtain a stereo reception.

I've carefully followed the service manual instructions, but with no results.

Does anyone have an idea about a possible solution ?

Thank you very much in advance to everyone

Ciao, Paolo
 
Paolo: I have a 2252B that had a non-working tuning meter. I sprayed the adjustment pots on the tuner board and worked them making sure to re-set them to where they were before. The tuning meter came back to life, perfectly centered. I don't know if that helps but sometimes cleaning the adjustment pots cures problems. Yours might be a centering problem and one of the pots should adjust but I don't know which. Welcome and good luck.
 
I also have a non working tuning meter. What pot did you spray? I'm looking at 3 metal covered pots, red, black and yellow plus several plastic ones. I'm assuming one of those are what you are talking about. Better still if you could give me the corresponding number of the pot I could look on the board. What did you use to spray it with? Are we talking about the same board?? James
 
You say you followed the instructions in the service manual. The symptom you describe is usually caused by misalignment of the IF filters and discriminator. What equipment did you use?
 
I also have a non working tuning meter. What pot did you spray? I'm looking at 3 metal covered pots, red, black and yellow plus several plastic ones. I'm assuming one of those are what you are talking about. Better still if you could give me the corresponding number of the pot I could look on the board. What did you use to spray it with? Are we talking about the same board?? James

I sprayed with deoxit all of the white (plastic) trim pots on the tuner board, worked them and then returned them to the original positions. A couple of them were stiff indicating possible oxidation and loss of contact. Stay away from the metal covered ones.

It worked for me, please be careful!
 
That's just the FM discriminator being off a little bit.

Usually, it just takes a slight turn of the coil's core to fix it.

DH
 
Wow !
First of all, thanks to you all for your kind answers.

Coming back to the matter, I read the point 8 of chapter 4 (FM Alignment Procedure) of service manual:

"Adjust the secondary core (upper) of discriminator transformer L201 so that the center tuning meter pointer indicates its center at no signal applied"

I did it

"Set the FM SG to 98MHz and increase its output level 1 KµV and tune the receiver to the same frequency so that the center tuning meter pointer indicates its center. Adjust the primary core (lower) of L201 for minimum distortion"

About this step, as I do not have a real FM signal generator, I did nothing.

If I've understood well your replies, this could be the point: am I right ?

Can I replace somehow the FM SG ? Any trick available ?

Many thanks in advance, Paolo

P.S. : I forgot to mention that I have a Visual Analyzer (v. 8.30.21) available on my desktop. This tool includes even a distortion meter, but no FM generator. Could it be useful somehow ?
 
In your case, I would just adjust the upper core. It should turn quite freely and only need a little tweek. Just tune your FM to a strong station around 98 MHz and then adjust the discriminator for center indication at maximum signal strength deflection. That will likely be very close to what you'd get if you had a FM signal generator to work with.

DH

Wow !
First of all, thanks to you all for your kind answers.

Coming back to the matter, I read the point 8 of chapter 4 (FM Alignment Procedure) of service manual:

"Adjust the secondary core (upper) of discriminator transformer L201 so that the center tuning meter pointer indicates its center at no signal applied"

I did it

"Set the FM SG to 98MHz and increase its output level 1 KµV and tune the receiver to the same frequency so that the center tuning meter pointer indicates its center. Adjust the primary core (lower) of L201 for minimum distortion"

About this step, as I do not have a real FM signal generator, I did nothing.

If I've understood well your replies, this could be the point: am I right ?

Can I replace somehow the FM SG ? Any trick available ?

Many thanks in advance, Paolo

P.S. : I forgot to mention that I have a Visual Analyzer (v. 8.30.21) available on my desktop. This tool includes even a distortion meter, but no FM generator. Could it be useful somehow ?
 
Sorry, but the above method will not work. You need to tune to some known signal so that the center tuning meter is centered, then adjust the discriminator coil for minimum distortion. But all that is useless if you haven't adjusted the IF first (assuming the IF filters are adjustable and not ceramic, I don't have the service manual.)
What you can do is make a poor man's RF generator.
1. Buy a FM stereo modulator, the kind you use to play an Ipod through your car radio. You will also need a low distortion 1KHz tone. You can buy a test CD with test tones on it. www.mcmelectronics.com sells one.
2. Connect your CD player to the FM modulator and play the 1KHz test tone.
3. Tune the receiver to the modulator, so the tuning meter is centered.
4. Connect the Tape Out of the receiver to your soundcard input, and start up the distortion analyzer.
5. Adjust the lower coil of the discriminator for minimum distortion.
6. If there are any adjustable IF filters, adjust them slightly for minimum distortion.

That should fix it, unless your soundcard is noisey and you can't read very low distortion. I had that problem with mine. If that is the case, invest in an HP 333 or 334 distortion analyzer.
 
Thanks again for your prompt replies.

I will follow your suggestions: where can I find a cheap FM generator ?

Another thing, please let me know if someone needs the service manual. I have a .pdf version, so I can easily make it available

See you soon, Paolo
 
There isn't such a thing as a cheap FM Stereo generator. I use a Sound Technology ST-1000A. I purchased it off E-Bay and I think I paid $250 for it. You can find an old Eico mono generator for less, but you need one with low distortion, that is stereo, so a cheapie won't do the job. I used to have one, and, trust me it's frustrating.
 
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