When there's a down side to having one major customer, claim you've got a new one.

That appears to be how Supertex ( SUPX) hopes to avoid looking vulnerable to cost-cutting at Motorola ( MOT).

Supertex -- a Sunnyvale, Calif., maker of LED chips -- has an enviable sweet spot as a keypad-light supplier for the Razr, Motorola's hottest phone. In the most recent quarter, sales to Motorola accounted for 22% of Supertex revenue.

But Motorola has been shaking up its supply chain and shifting to lower-cost or less lucrative parts. This has been crushing news to other Motorola suppliers like Multi-Fineline Electronix ( MFLX), a contract manufacturer that buys Supertex's keypad lights.

Earlier this year M-Flex, as it is called, cut third-quarter guidance because its 80% customer -- Motorola -- was moving to lower-margin parts. M-Flex shares are down 72% from their late-March peak.

Worries about a similar fate have since hung over Supertex. Its stock is down 29% since its high in April, though it rose 6% to $33.69 Tuesday.

A comment by Supertex chief Henry Pao on last month's second-quarter earnings call seemed intended to tamp down worries about Supertex's dependence on its biggest customer.

"We have two over 10% customers ... well, we'll list those in the 10-Q, but we had two greater than 10% customers, GE ( GE) and Motorola," Pao said in response to an analyst's question, according to the July 25 Fair Disclosure Wire transcript.

Motorola's certainly no surprise, but listeners were a bit shocked to hear GE's name. Supertex had discussed growth opportunities in medical electronics, such as ultrasound gear. But GE hasn't been mentioned as a 10% customer in any recent filing.

Pao explains in an interview that when it came to writing up the first-quarter filing, a mere technicality kept GE's name out.

"The reason," says Pao, "is that 9.9% is the actual number. Our attorney reviewed it and said it wasn't 10%, so we couldn't put it in."

Curiously, Supertex has raised the prospect of GE as a big customer before. In a May 2005 earnings conference call, an executive said, "Actually, at the top of our list of customers are people like GE, in the medical world." But two years of filings show no mention of GE as a 10% customer.

To be sure, medical electronics represented about 35% of Supertex's total sales in the fiscal first quarter, and GE may in fact be a big buyer.

But Supertex's filings seem to contradict the rosy conference-call story about an exciting new 10% customer.