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Marantz 2245 stereo issue

Traverso

Traverso

Active Member
Hello,

The stereo is no longer working on my Marantz 2245.

The stereo is not working on tuner side.
The bulbs are OK as they light when switched to Aux for example.
The two amplifiers are working fine.
The mono switch has no effect.
The radio is sounding on but like mono.

Is the problem coming from the P500 FM or P300 MPX PCB?
How to fix ?
I have been looking at the service manual, not very helpful.

Where to start from? Where is the Stereo signal coming from is it from the FM or MPX?

Thanks a lot for help.

Alain
 
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Mute switch OFF?

The FM tuner probably needs adjustment and without the right tools, its a wild shot.

I have managed to get lucky tweaking some. Hopefully someone with better info drops in here.
 
OK thank you for the attempt in helping.

I believed there was something straightforward, or some guide lines.

Cheers


Alain
 
I'm thinking its a minor tweak to a trimmer on the FM board.
You need the right plastic tool and know which hole its in.
Without all the test gear hooked up, its just a trial and error thing and its possible to really screw things up so I don't recommend hacking around wildly.
 
There is a good description in the service manuals for the 2245 and 2270, but it's kind of hard to follow.
The 2230 is slightly different.

IF signal strength is monitored by H306. If IF signal strength is above muting level, H306 is ON, H307 is OFF.
If there is excessive noise, then H552 is ON which is wire-ORed to H307 Collector, keeping H308 (FET) OFF.
If the discriminator is outputting DC due to the tuning being off station, either H560 or H561 is ON which are wire-ORed to H307 as well.

If the station is properly tuned, not noisy and the signal strength is high enough,
H306 is ON, SS OK
H307 is OFF, SS OK AND
H552 is OFF, Noise is OK AND
H560 is OFF Tuning centered AND
H561 is OFF Tuning centered
If SS, Noise and center tuning OK then:
H308 is ON allowing audio signal to pass to the center tap of the 38kHz transformer.
H302, 19kHz amplifier is enabled by H303.
If the 19kHz pilot is present from the broadcast station, then it is doubled to 38kHz by H304 and if of sufficient amplitude to decode stereo, H305 turns on causing the stereo lamp to illuminate.
The left and right matrixed audio signals are recovered by H317-H320, de-emphasis is applied, then they are amplified, filtered of high frequency noise and sent along through the selector switch to the preamp.

Tom
 
Tom, thanks for the very clear explanation - one of the most straight-forward that I've seen. I assume you're discussing the 2245/2270?
 
Thks a lot for this detailed explanation regarding this FM stereo adjustment.

It can be followed and checked without too many special tooling.

Alain
 
hirscwi said:
Tom, thanks for the very clear explanation - one of the most straight-forward that I've seen. I assume you're discussing the 2245/2270?
Click to expand...
Yes. The 2230 is almost the same, you can sus out the differences by looking at the description and schematic that is in the service manual.

Tom
 
I had poor fm on a 2330 and was surprised to fix it by manipulating the shielded (Black) antenna wire away from the P100 fm board and repositioning it .

It did not take more than 1/2 inch of movement to make a big difference.

Thanks Tom for the Info!, John
 
Traverso said:
This is correct, and consequently I brought my "beloved" 2245 to a fix and repair shop.

Alain
Click to expand...
Hello everybody,

I found the culprit, the stereo is back.

My fix and repair shop gave up and I took back my 2245 yesterday and spent my sunday (some hours only) to fix by myself.

The culprit is the H502 on FM detector P500 PCB.
Vbe out and consequently he was unable to send the info to other PCB's that there was an FM signal.

I replaced by a BC550 and it's perfect now, I can listen (stereo sound) my favourite jazz radio on the singing 2245

Thank you everybody for the help

Cheers

Alain
 
Yes transistor blown.

Good luck fo your case, hopefully you will find quickly!
4400 the one with the scope? and 4x50W? Nice on the pics.

It's my time to go asleep now quite late

Cheers


Alain
 
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