ZTE ZXDSL 831 Firmware Update for Auth Bypass & Req Forgery?

[Guest]

I had the same issue too. The modem would periodically lose sync for 5 minutes at a time for about a week, before it completely crapped out.

There are test points on the bottom of the PCB with clearly labeled supply levels. It turns out one of the electrolytic capacitors used in a voltage regulator was dead/dried up (I think it was on the 1.2V rail). I switched it out, and now it's running fine again.

Which cap on the PCB is this? I think it would help others who have had their ZTE crap out.

[moogra]

I had the same issue too. The modem would periodically lose sync for 5 minutes at a time for about a week, before it completely crapped out.

There are test points on the bottom of the PCB with clearly labeled supply levels. It turns out one of the electrolytic capacitors used in a voltage regulator was dead/dried up (I think it was on the 1.2V rail). I switched it out, and now it's running fine again.

Which cap on the PCB is this? I think it would help others who have had their ZTE crap out.

I don't remember off the top of my head, and it's likely that other modems may have different failed caps, given that the same model capacitor is used in multiple places on the board.
The best way to check is to look for bulging capacitors (dead giveaway), measure the capacitance and check if it's in spec, and check if there is ripple on the supply line (10-20mV is fine, but the 1/2 volt shown is not normal). It may be best to just replace them all, but I was just lazy, and didn't have enough extra capacitors laying around

Also, the board is leadfree, so you'll need a higher temp iron compared to the leaded ones.

[Guest]

I don't remember off the top of my head, and it's likely that other modems may have different failed caps, given that the same model capacitor is used in multiple places on the board.

Maybe so but consumer products tend to fail the same way for many people. These caps are probably under-speced in the first place.

[dane]

The ZTE gear is pretty old, and was basic and inexpensive to start with. Our experience with it, and with Motorola equipment are some of the factors that led us to a carrier solution and Sonic taking responsibility for the end-to-end life cycle of the service. The Pace equipment is better, but more importantly it is part of our network and our responsibility.

If you don't have one of our Sonic Pace modem/router/firewall units, you can opt in and get one here:
https://newsignup.sonic.net/equipment

[Guest]

The ZTE gear is pretty old, and was basic and inexpensive to start with. Our experience with it, and with Motorola equipment are some of the factors that led us to a carrier solution and Sonic taking responsibility for the end-to-end life cycle of the service. The Pace equipment is better, but more importantly it is part of our network and our responsibility.

It's true for those who want to have something that's centrally managed, Sonic's rental is attractive. On the other hand, there are some disadvantages to the option:

• In our ever more disposable way of thinking, I don't like the idea of throwing away something that is working/fixable. I much prefer to repair things within reason until there is no recourse, say some VLSI chip burning out. A capacitor or even SMD component is easily fixable by those who are technically savvy.
• The Pace modem does not have a true bridge mode and I would like to minimize overhead, opting to use my own firewall.
• Individuals who take the time to maintain their own network will have no trouble configuring QoS, IPv6, and updating their router's firmware.

The real issue with going your own for a modem is the firmware may not be supported/available to end-users. This is probably due to some contract the manufacturer has with the ISP. And with a modem that does not have a true bridge mode, one has to rely on more of the CPE's firmware, potentially enlarging its attack surface. A good compromise is if people could purchase the CPE that it be crippled so that it only works as a modem and only the modem component is flashable via firmware--admittedly a not very likely outcome. This suggestion isn't the only way to handle it, of course.

[adame]

The Pace modem does not have a true bridge mode and I would like to minimize overhead, opting to use my own firewall.

The Pace modem does have a true bridged mode. Support can walk you through enabling it.

[Guest]

The Pace modem does have a true bridged mode. Support can walk you through enabling it.

Thanks for correcting--that's encouraging. I must have been thinking about AT&T's version of the Pace. It will be interesting how things play out in "a couple of months." Please let there be "good news" for those behind an RT.

[khawar]

Note that the ZTE modem I had for a couple years starting getting dropouts and needing rebooting, and it was just because the modem was crapping out (this was several years ago), so it is entirely possible that us the problem you are having.