So, I needed a schematic or at least an IC pinout to fix a problem with my junky $10 iRock FM Stereo transmitter. (Yes, instead of throwing it away and buying a newer, bigger, better one I spent 10 minutes and fixed it.) Well, the designers sanded off the part numbers of the components to "prevent" repairs. This is common practice with cheap electronics to get you to buy a new one. I've dealt with more than a few devices whose engineers thought they would be clever: satellite receivers, VCRs, etc.

So, I checked the FCC database. The iRock device itself (FCC ID: O5U FMLINK) is actually a rebranded Kima Link-It made by Akoo. No shock there... I bought mine as a factory refurb from Tiger Direct. Only thing in the FCC EAS are a couple of photos, some vague test information, and a botched confidentiality request. I was hoping they slipped and let the part number through in their internal photos. They usually do and it looks like they did at first... Well, until someone caught the mistake and tried to get their photos made confidential which isn't allowed. So they replaced the photos with altered (read blurry) versions.

As a last ditch effort, I counted the number of pins on the IC... 22 pins... A somewhat unusual number of pins for an IC. So I entered "FM IC 22 pin" into Google and sure enough the second hit was a Rohm BH1415f Wireless Audio Link IC (first hit being an AM/FM dual band version) which matched the iRock FM IC pinout perfectly. And, as usual in cheap electronics, the entire device itself is taken largely from the application notes supplied with the IC itself. Also, they cleverly use a Maxim MAX619 charge pump to increase the 2.5-3VDC from the two AAA cells up to the 5VDC required to power the FM transmitter component. Have I ever mentioned that I really like charge pumps?

So, once again, thanks go to Google.

Labels: technology