Problems with Pioneer F-104 Tuner - diyAudio
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Old 18th September 2009, 12:23 AM   #1
pekinin is offline pekinin  Spain
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Join Date: Mar 2009
Default Problems with Pioneer F-104 Tuner


I have a AM/FM Stereo tuner from Pioneer. Exactly the F-104 model. The problem is as follows:

I tune a high-power local FM Station with freq: 87.7 Mhz. The sound is mono and the "tuned" LED light is off. If I move de freq to 87.8 Mhz, the STEREO and TUNED indicators lit. But the sound is worse (with a little interference). I measure the S-Meter pin, and I have more signal at 87.7 than I get in 87.8 (obviously)

(NOTE: In the AM Band, the reception are good)

I open the tuner and see in. Everything looks ok, but obviously not well.

The board have 3 ICs:

LM7001 (the PLL with 7.2 Mhz XTAL)
LA1265 (the FM/AM tuner)
and AN7470 (The STEREO demux)

I think that the problem is in the stereo demuxer. But I'm a bit lost in the matter.

Anyone have any idea about it? The AN7470 have a little trimmer to change their VCO. If I tune the 87.8 (100khz up of the freq) and I move the trimmer I get frequency move a little but not enough to move it 10 or 100 khz to the station frequency.

I think I've explained a bit wrong. But if anyone understands it and can help me. I'll be very grateful.

(Obviously, the problem exist in all frequencies 102.8 Mhz station, lit stereo light at 102.9. 88.3 -> 88.4... and so. Every station links stereo 100 Khz up!)
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Old 18th September 2009, 12:49 PM   #2
diyAudio Member
Join Date: Mar 2004
Location: Budapest, Hungary
I think the problem is around the FM demodulator and not in the stereo demultiplexer. The coils might be misaligned - any previous owner tampered it?
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Old 18th September 2009, 08:26 PM   #3
pekinin is offline pekinin  Spain
diyAudio Member
Join Date: Mar 2009
Hi oshifis!

You are in the right way! The 10.7 Mhz coil of FM Demodulator are the problem. I change the alignment a little and... the stereo locks at the right freq. And the "TUNED" light too.

Thanks! This tuner is a second hand product. And is possible that the last owner touch the value of coil.

Thanks! and another time thanks!
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Old 19th September 2009, 06:45 PM   #4
diyAudio Member
Join Date: Mar 2004
Location: Budapest, Hungary
Hi pekinin,
I am glad that I could help. It is unfortunate that FM stations nowadays do not broadcast test signals. Correct alignment can be done only with a test signal (broadcast or test generator). Good luck anyway!
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Old 3rd December 2009, 08:56 PM   #5
diyAudio Member
Join Date: Dec 2009
Unhappy pioneer fm tuner troubles

hi. i'm from romania and i have buyed pioneer deh p6800mp mp3 player from ebay from u.s.a.
i have received and mounted it but i have some troubles on fm radio.
it's tunning only 89.1 and 89.3 and 89.5. in romania i need it to tune 89.1-89.2-89.3 etc.
tell me please what can i do.
the best regards from romania.
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