Why does the Internet constantly disappear through the D-Link DSL-2500U?

Question

D-Link

Good afternoon!
There is Internet from Rostelecom and an ADSL modem D-Link DSL-2500U (BRU / D; H / W Ver.: D1), I recently updated the firmware to RU_1.52, before that there was an old original one.
The essence of the problem: on average, every 30 minutes (but it happens in different ways), the Internet falls off and appears only after the modem is turned off / on (it even happens that you have to do this 2 times). On the old firmware there was a similar problem, but it did not appear so often, maybe once a day.
What could be the problem, I do not know, so I ask for your help.

Answer 1

1. If Adsl, then the first thing to check is the telephone line. Just connect directly without phones and splitter.
2. The modem is already old and if it has been working for more than a year, then disassemble and look at the containers.
3. Notice the modem.