Synology RT1900ac: Power Amplifier Failure

My recent bought Synology RT1900ac on 7th July 2017 been having low 2.4GHz signal coverage recently, to the point that not usable by devices located at first floor. Tried out many methods that found from webs but none can solve the problem. As advised from Synology website livechat operator, details, screenshot and Logs were sent to Synology technical support.

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Router: Synology RT1900ac, firmware: SRM 1.1.4-6509 Update 3. Bought on 7th July 2017 at C-zone Computer, Petaling Jaya.

What’s the Issue: Router working fine from the day bought, but problem occured after last update SRM 1.1.4-6509 Update 3. 5GHz working fine as usual, but 2.4GHz not usable once distance away from 5GHz, when iPhone 7 Plus connected, it only shows 1 bar instead of 3-4 bars as previously. Connection will be dropped once loading apps that needed internet, such as YouTube, Facebook and Browser. Same happaned to all wireless devices stated below.

Wireless devices: iPhone 7 Plus, iPhone 6 Plus, iPad mini, Honor 6 Plus (Android phone), Huawei M2 (Android Tablet), Lenovo Thinkpad

Wired devices: Synology DS115j (LAN Cable port 3), Lenovo Ideapad 700 (LAN Cable port 2)

Application: Wifi Analyzer (Android), help to indicate signal strength, networks avaiable nearby and channels usage. From the graph, it shows the signal strength is strong, but connected device showed 1 bar although the router placed just right in front.

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Wifi Analyzer (Android), a very helpful app.

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5GHz and it’s channel

Below are some way in sequence, tried but can’t resolve the problem,

22/07/2017, while connected to Modem with Internet

2.4GHz/5GHz auto selection ON, Security level High – WPA2-Personal, Channel Auto – 5 GHz working fine, 2.4GHz displayed in WiFi list, signal strength on device dopped once connected and become not usable, device auto connect to 4G network if Simcard available.
Rebooted multiple times for test – no different
2.4GHz/5GHz auto selection Off, 5GHz signal band Off, Security level WEP – no different
2.4GHz/5GHz auto selection Off, 5GHz signal band Off, Security level WPA2 – no different
WPS Off – no different
SSID name change – no different

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frequently pop out such message on iPhone 7 Plus

23/07/2017, While disconnected from Modem and placed it on 1st floor, no cordless phone nearby, unplugged DS115j, with laptop plugged into Lan cable port

Rebooted multiple times for test – no different
2.4GHz/5GHz auto selection ON, Security level High – no different
2.4GHz/5GHz auto selection Off, 5GHz signal band Off, Security level WEP – no different
2.4GHz/5GHz auto selection Off, 5GHz signal band Off, Security level WPA2 – no different
WPS Off – no different
SSID name change for both 5GHz, 2.4GHz and Auto selection – no different
Trafiic Control removed for all devices – no different
AP isolation checked – no different
Switch Channel – tested 1,6,7,8 for 2.4GHz to avoid interfere from neighbor’s router, no different
Wireless mode n only – no different
Checked and uncheck “Downgrade USB 3.0 device to reduce interference to 2.4GHz signal” – no different

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my default setting

Restore to Factory default setting, but the firmware still remain SRM 1.1.4. However, it shows update available, and did the update after the test above.

24/07/2017, The method that works, with limited WiFi coverage
2.4GHz/5GHz auto selection Off, 5GHz signal band Off, Transmit power to “Middle” – every devices can connect but the range is limited, can’t reach devices located at 1st floor
2.4GHz/5GHz auto selection ON, Transmit power to “Middle” – 5GHz works as usual, 2.4GHz works but weaker signal can’t cover rooms at 1st floor.
Connect to Modem, turn-on cordless phone, plugged-in DS115j, internet works well, as above with limited coverage range

Channel width set to 20MHz for 2.4GHz, Transmit power High – unable to connect WiFi
Channel width set to 20MHz for 2.4GHz, Transmit power Middle – able to connect WiFi
Switch 5GHz Channel – tested 48, no different
Security set to none – unable to connect WiFi

In conclusion: Transmit power set to “Middle“, everything will works perfectly.

Feedback from Synology Technical Support:

Since reducing the transmit power immediately fixes the issue, that indicates you are facing a hardware issue with the power amplifier…There is nothing you could have done. A small number of units in the past ended up with this defective part.

Solution: Returned router to C-Zone and get a new replacement, one-to-one exchange since it is still within a month. It is now working perfectly as before, hopefully it will continue works well for years to come.

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