TOKYO-- Sony Corp. investors have suffered through years of losses, but the latest massive one, reported Friday, contained a bit of good news for the Japanese electronics and entertainment giant.

Booming sales of its PlayStation 4 videogame console and of camera sensors for smartphones offset weakness in the company's own mobile division, resulting in a less-than-expected net loss of Yen136 billion ($1.22 billion) for the summer quarter.

Without a previously announced Yen176 billion write-down of the value of its struggling mobile business, Sony would have posted a profit, the company said. As a result, even some Sony executives were broaching the possibility that Sony might have finally hit bottom.

"Excluding one-time effects, we have gradually started to make profits," said Kenichiro Yoshida, Sony's chief financial officer, at a press conference in Tokyo.

Sales in the videogame business surged 83%, and the division recorded an operating profit of Yen21.8 billion, reversing a year-earlier loss. Sony's "devices" unit, which supplies Apple Inc. and other smartphone makers with image sensors, posted an operating profit of Yen29.6 billion, about two-and-a-half times the year-earlier level. Both units raised their full-year revenue forecasts.

Even Sony's TV unit, which has been losing money for much of the last decade, logged an operating profit--marking its first back-to-back quarters in the black since fiscal 2003. Sony has said it expects the unit to be profitable for the full financial year ending in March. Sony's overall sales rose 7%, to Yen1.9 trillion yen, in the quarter.

To be sure, no one is celebrating yet. Over the last decade, Sony has repeatedly offered hints of a possible turnaround, only to dash hopes with a renewed slump. The latest worry is the weakness of the Japanese currency, which plunged against the dollar Friday after the Bank of Japan surprised the markets with monetary-easing measures. Mr. Yoshida said every decline of one yen against the dollar costs Sony Yen3 billion in losses.

Sony also needs to fix the smartphone business, which the company only a year ago said was a pillar of its turnaround strategy. Since then the business has been hit by severe competition from inexpensive Chinese handset markets. The segment showed an operating loss of Yen172.0 billion in the July-September quarter, largely due to the charge to write down the business.

On Thursday, Sony named a new head of its mobile division, Hiroki Totoki, who is seen as a close ally of Mr. Yoshida. The chief financial officer has stepped up restructuring and cost-cutting efforts since being named to that post earlier this year.

Mr. Yoshida said Friday that Sony would scale back its smartphone business in China, the world's biggest mobile market, by giving up on sales of low-end handsets that compete with domestic makers. Mr. Yoshida said the board was considering shrinking in other emerging countries, but declined to specify.

The decision to reduce its handset offerings in China led Sony to revise downward its sales target for Xperia smartphones for the full year ending in March, to 41 million units from 43 million. That was the second cut to Sony's smartphone forecast this year; initially the company predicted sales of 50 million smartphones, up from 39.1 million in the previous fiscal year. Most analysts said at the time that the projection was unrealistic.

"We had debated whether it would be right to shrink our presence in the world's largest smartphone market, but have judged what we need to do right now is to rebuild the business structure," Mr. Yoshida said.

Analysts say the fortunes of Sony's smartphones now depend on the U.S. market. They are hopeful that Mr. Totoki, who was a start-up member of Sony's banking unit, would be able to build stronger relationships with U.S. mobile carriers, which have sometimes been reluctant to carry Sony smartphones, and to make the business more efficient.

"With his experience of setting up and running a bank, I'm confident Mr. Totoki can establish a relationship of trust with carriers," said Atsushi Osanai, a former Sony product strategist who now teaches at Tokyo-based Waseda Business School.

Mr. Totoki said he is proud of the company's smartphones and wants to turn the mobile division into a star performer once again. But some Sony watchers are wary, saying more radical measures than the 15% personnel reduction that Sony has announced for the division may be necessary.

"We could be told it will cost more and take longer for Sony to finish the mobile unit restructuring," said Yasuo Nakane, an analyst for Deutsche Securities.

Write to Takashi Mochizuki at takashi.mochizuki@wsj.com

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