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Old 05-30-2014, 05:54 PM   #6
Per Hansson
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Default Re: Zyxel Prestige 660H Triple play ADSL Modem

This ADSL modem started acting up in January this year, it caused packet loss...
At first I thought it was the phone line that was bad, but after doing a thorough test I realized it was the modem.
---Before recap:---
Ping ISP's gateway, Zyxel connected directly to firewall:
Ping statistics:
    Packets: Sent = 58, Received = 48, Lost = 10 (17% loss),
Approximate round trip times in milli-seconds:
    Minimum = 18ms, Maximum = 246ms, Average = 26ms

---After recap:---
Ping ISP's gateway, Zyxel connected directly to firewall:

Ping statistics for:
    Packets: Sent = 58, Received = 58, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 19ms, Maximum = 176ms, Average = 23ms

In January I replaced all caps except the 2x large Hermei 2200F caps, I did not have them in stock but ordered them so I could do it "a little later".
That time finally came today, because there was a lightning strike that took out several lightning protection devices, but thankfully not the recapped ADSL modem
So due to the downtime I replaced the remaining two Jackcon caps, it looks like it was not necessary though because they measured 2150F & 0.1 ESR after I had taken them out...

The problem with the packet loss was actually not on the DSL side, but the Ethernet side. (Only the 1000F cap in the Ethernet side still measured good)
The two Hermei SH 22F 16v caps had an ESR of 50 & 37 respectively
And the two 220F 10v Hermei HT caps had 3.2 & 3.6 ESR respectively
Before the recap reducing the link speed from 100Mbps to 10Mbps "solved" the packet loss issue.
The issue can even be seen on the ethernet LED's on the modem, instead of blinking rapidly with traffic they would go dark, for seconds in a row.
At the same time a packet loss would be registered, and any download in progress would slow to zero...

The Jackcon caps around the DSL area had ESR ranging between 0.2 > 0.8 (They have no model marking, only the text "LOW E.S.R"
And as mentioned the Jackcon LHK 2200F 25v caps measured good, I still replaced all caps though...

This is how the link looked before the recap:

And this is after the recap, the link is slightly better, due to the improved capacitors:

What was interesting with last weekends lightning strike is that it improved the link, the phone line was cut in two places which the telco had to repair, after this it became much more stable:

I will also need to buy a new "whole house" protector for the incoming phone line because it got destroyed, as did an APC surge protector with built in phone line protection...
(This was a part of the reduced quality on the ADSL signal but the biggest reason was the line itself...)

Note the very cool "lightning strike pattern" on the underside of the PCB between the lines & ground! (It arcs over even before it reaches the Epcos surge arrester)

The name of this surge protector is OBO Blitzbarriere FLD 60T
Attached Images
File Type: jpg IMAG0465.jpg (632.5 KB, 84 views)
File Type: jpg PICT2727-Capacitors.jpg (1.59 MB, 81 views)
File Type: png Zyxel b4 recap.PNG (66.7 KB, 83 views)
File Type: png Zyxel after recap 1 month uptime.PNG (79.2 KB, 84 views)
File Type: png ZyXel After Lightning without protection.PNG (110.5 KB, 81 views)
File Type: jpg IMG_3796.jpg (276.5 KB, 83 views)
File Type: jpg IMG_3797.jpg (239.4 KB, 82 views)
"The one who says it cannot be done should never interrupt the one who is doing it."

Last edited by Per Hansson; 05-31-2014 at 01:24 AM.. Reason: spelling
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