Power supplies for HG612 modems

There has been a lot of debate about whether or not they should be changed out and whether the additional 300mA is required.

I have both 2B and 3B modems here along with a black and a white power supply. Both are 12V DC and the older black a 700mA unit whereas the white is rated at 1.0 A

The two modems look identical inside, and there appear to be no component changes - there is some extra silicon "glue" to hold some components stable and the heatsink square but nothing else.

The quiescent current - no network or DSL connection. 490 - 500mA

Connected the network and DSL, there is a small peak before settling back to 490 - 500 mA

During a full download of a 200MB file (40 seconds) the current increase to around 520 mA

With an upload there is a similar increase and if the upload and download are running at the same time the current peak at 550 mA

The 2B took a few mA less than the 3B but that could be due to tolerances. The current from the black power supply was also marginally less.

So, a 700 mA supply should be capable of supplying a modem running 17c profile and a 40/10 connection.

However, when 80/20 Mbps is introduced, I would expect there to be an increase in power to 600mA (or thereabouts) and if BT ever bring in 30MHz profiles then potentially another 50-100 mA which will be on the limit of the supply. The extra power will be required for the processing in the software modem and driving the upstream.

Also, at turn on teh peak current was in excess of 600mA (meter limit for fine measurments) and around 0.8A (higher rated range) which should not be a problem for even the black power supply for s short burst.


I also measured the DC voltages:

Black: offload 13.3v loaded 13.1v and was not wonderfully stable.
White: offload 12.2v loaded 12.15v

Not too much of an issue but there will be a need to dissipate an additional 600mW of heat.


Overall conclusion from a short 2 unit test is that the black PSU will cope but will towards its limit where as the white is well within design parameters.

Do I think they should be replaced? Yes, to improve long term reliability of the PSU and potentially modem.

Nothing to do with your post but I just translated your Sig It gave a me a good laugh. Nice one my friend.

Steve

In reply to a post by MHC:

I would expect there to be an increase in power to 600mA

You mean an increase in current

Apparently the new 1A PSUs are black.

DrT

In reply to a post by DrTeeth:

In reply to a post by MHC:

I would expect there to be an increase in power to 600mA

You mean an increase in current

Apparently the new 1A PSUs are black.

DrT

What it should say is ... "an increase in power requiring 600 mA"

Kelly are doing it right, they are instructed to not replace the PSU i.e. there is no need to

Later batches of swap outs will be modems supplied without a PSU at all, i.e. only option is to use the existing one.

So if damage is caused due to a power supply catching fire, and the insurance company refuses to pay out because the PSU was under-rated...?

It's OPENREACH's problem as the power supply and VDSL2 modem are their property...

Yeah, that's what I thought.

That'll make it much easier to get any recompense

In reply to a post by MrSaffron:

Kelly are doing it right, they are instructed to not replace the PSU i.e. there is no need to

Later batches of swap outs will be modems supplied without a PSU at all, i.e. only option is to use the existing one.

All I had to do was ask. The engineer said he was going to get a box of 10 from stores - why if new PSU not needed? They should not be available.

DrT

I was told that the original batches came with the modem, later batches do not.

Thus it is feasible that Kelly may have boxes of spare PSU's now in their own stores.