[App_rpt-users] CM108 modification

Doug Bade kd8b at thebades.net
Wed Jul 8 09:10:46 EDT 2009


The schematic looks logically correct...

C2 and C3 are in the usbfob.pdf picture..

C1 does not appear to be.. It seems C1 is on the schematic but not 
the construction picture.... I would think it should be there... as 
to avoid DC coupling between the stages...

I just recently got some CM109 based adapters from China that are 
currently available and will be making some notes on them as I 
perfect a mod..electrically they are the same.... the chip is really tiny :-)

Doug


At 08:24 PM 7/7/2009, you wrote:
>Ok, I'm modifying a CM108 USB adapter, and though I've done it 
>before I can't remember if whether the picture or the schematics are 
>correct in the pdf file.  In the picture, I see that for the mic 
>input (RX Audio) has the twisted (or just soldered) end of the 68K 
>and 470K attached to the 9 pin connector.  In the schematic, the 
>twisted end is attached to a capacitor (which isn't in the picture 
>and directions) and then to the mic input on the USB adapter.
>
>Can anybody tell me which way is the correct way to hook this up?
>
>Thanks,
>Jeff
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