Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of electronics-maker TTM Technologies (NASDAQ:TTMI) were getting shocked today, falling as much as 17% today after getting downgraded by Stifel Nicolaus.

So what: In addition to the downgrade, shares were falling as a result of the broad-based sell-off around Apple (NASDAQ:AAPL) and its suppliers, as TTM makes circuit boards for iPhones. Stifel Nicolaus, which dropped its rating from buy to hold, called out a number of issues with TTM, including "soft demand, excess industry capacity, and ongoing margin pressure."

Now what: Stifel Nicolaus' downgrade is just the latest in the past few months that has seen JPMorgan Chase and Longbow Research cut their estimates on the circuit-board maker as well. With the news yesterday that Apple cut its parts orders in half, this is probably a good time to stay away from its suppliers until further notice. TTM reports earnings on Feb. 4, with the consensus EPS at $0.18 a share. Given recent developments, it could easily miss those estimates.

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