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 Post subject: 6888 transmitter and FM MP3 Player
PostPosted: Jan Mon 15, 2018 9:21 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2224
Location: Warkworth, Ontario, Canada.
Some years ago I picked up a couple of the FM MP3 players that were popular in this forum.

Attachment:
sku_94814_3.jpg
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Sorry, rear view only but those familiar with the thread will recognize it.

Problem is when I connect either one to my 6888 transmitters the frequency of the FM station being received changes.

For example when I set the FM receiver at 96.7 it shows that frequency on the screen but the actual FM frequency received is 98.6mc.

How can I get around this.

Thanks.

Ed.


Last edited by Ed Kraushar on Jan Tue 16, 2018 5:08 pm, edited 1 time in total.

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 Post subject: Re: 6888 transmitter and FM MP3 Player
PostPosted: Jan Mon 15, 2018 11:55 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Beautiful Downtown Burbank CA
Could it be the FM receiver is being thrown off with the closeby AM transmit?


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 Post subject: Re: 6888 transmitter and FM MP3 Player
PostPosted: Jan Tue 16, 2018 6:45 pm 
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Location: Warkworth, Ontario, Canada.
Mike Toon wrote:
Could it be the FM receiver is being thrown off with the closeby AM transmit?


Thanks for the reply mike. I tried a separation of 8 feet and then 20 feet and I still get the same frequency shift. I wonder if the audio cable connecting them could be contributing.

The output from the FM MP3 is fed into a LM3900 amp and then into the transmitter.

The setup works great if a pre-recorded SD card is used as the sound source in the MP3 unit.

Ed.


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 Post subject: Re: 6888 transmitter and FM MP3 Player
PostPosted: Feb Sat 03, 2018 9:22 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Beautiful Downtown Burbank CA
Can't help with your FM problem, but this might help others using these players.

On my MP3/FM players like yours, when the power is turned on the volume defaults to "30" which is max and overloads the separate LM386 amp. I have to use the remote to lower it to about 26-27 for a cleaner sound.

The mini mp3 player in my other transmitter stays at the last level you set. With no visual way to see the volume you have to guess at the level using the remote. It claims it has no amp but it does and was set really low. I tried the remote volume button and it really came to life!

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 Post subject: Re: 6888 transmitter and FM MP3 Player
PostPosted: Feb Sat 03, 2018 10:06 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2224
Location: Warkworth, Ontario, Canada.
I believe I have solved the problem.

Both 6888's were early versions using an antenna coil on one and a toroid on the other.

Took a while till I had the time to rewire them to the latest schematic I could find. They now transmit the signal indicated on the receiver display.

Ed.


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