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PCI MAX 3000+ v1 high pitch tone

 
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PCI MAX 3000+ v1 high pitch tone
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maxmaxxed
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Post PCI MAX 3000+ v1 high pitch tone Reply with quote
Hi,

I'm experiencing the same issue on my V1 PCI3K unit discussed in the thread "PCI MAX 3000+ v2 high pitch tone" http://www.pcs-electronics.com/phpBB2/viewtopic.php?t=2597

The tone is only apparent on certain frequencies, as detailed in the other thread - 92.50 is bad, 91.7 is OK.

I removed the RDS board with no effect. I have tried a 470uF capacitor across the GND and 5V lines on the RDS pin header, no change.

The tone is apparent when installed in a PC or running standalone on a bench PSU.

Is there a similar resolution for a V1 board to the one published for the V2 board?

If it helps trace board revision, my software is "PCI3K v1.1 02/10".

Thanks,

Max.
Wed May 15, 2013 6:08 pm View user's profile Send private message
pcs
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Go ahead and apply the same fix, I think the capacitor is in the same position.

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Marko - PCS Electronics
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Wed May 15, 2013 10:11 pm View user's profile Send private message Visit poster's website
maxmaxxed
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Post Reply with quote
Thanks Marco.

I'm think I'm being a bit slow but it's not clear to me which component to remove referencing your PDF.

Here's an annotated picture of the components I think your PDF refers to - which letter should I remove?
(I did try B but it had no effect).






Thanks
Wed May 15, 2013 11:49 pm View user's profile Send private message
pcs
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I have checked the schematic of the old V1 from 2009, the old v1 did not use PWM to set power so if you have a problem it is caused by something else.

I would disconnect audio input and if the problem dissapears than use USB audio instead.

It could also be a noisy power supply in your PC. If this is the case using external power supply would probably help.

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Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Thu May 16, 2013 12:08 am View user's profile Send private message Visit poster's website
maxmaxxed
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Post Reply with quote
Thanks for the info.

I'm running the unit on an external, linear bench PSU. The problem was also apparent when running on the PC PSU.

It is frequency dependent. 91.7 is clean, 92.5 has the tone.

I've checked the frequency and it's around 9 Khz (half 19 Khz?)

Any suggestions where I might check next?
Thu May 16, 2013 6:52 pm View user's profile Send private message
pcs
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Post Reply with quote
It is hard to say, probably coming from your PC and creating a beat tone with another signal, could even be coming from sound card or motherboard.

Probably a very unfortunate combination of several factors.

Experiment a bit, you can even take the card out, it does not need to be inside PC actually.

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Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Fri May 17, 2013 1:27 am View user's profile Send private message Visit poster's website
maxmaxxed
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Post Reply with quote
I've removed the card from the PC and it's running on a linear bench PSU.

Once the transmitter is running, I've even disconnected the USB feed, but the tone is still apparent.

Disabling stereo on the unit and feeding an external multiplexed signal in results in the same tone being present.

I've monitored the signal at a distance and the tone is there.

Is it possible to obtain a circuit diagram? Where is the best place to probe the audio input into the VCO?

Any other recommendations welcome.
Fri May 17, 2013 12:39 pm View user's profile Send private message
maxmaxxed
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Post Reply with quote
If it helps, there is a "bodge cap" on the back of the board (across earth and what seems to trace back to pin 7 of the atmel). If I lift this, the tone increases in volume. The primary frequency measured at this point is 48 Khz.
Fri May 17, 2013 7:48 pm View user's profile Send private message
pcs
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Post Reply with quote
Hi,

in that case the board could be broken, if its still under warranty we'll replace it for free.

If not you can still send it and we'll have a look at it.

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Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Fri May 17, 2013 10:26 pm View user's profile Send private message Visit poster's website
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