VG224 low idle voltage: RMA needed?

Unanswered Question
Dec 14th, 2006

Hi,

I'm having a funny issue with my VG224:

Port0 delivers something like -38VDC, same is true for other pairs (Measuring directly on Pins 1/26 that are on opposite sides of the RJ-21 connector).

However, Port 3 (Pins 3/28) delivers only -19VDC, same is true for other pairs. This is not enough for my end devices!

All Ports have the default setting of "idle-voltage high".

There seemed to be a couple bugs related to power on an IAD/VG224, but really nothing like my problem..

What are your suggestions? Ever seen something like this? RMA?

Thank you very much for your feedback

/David

PS:

The IOS is 12.4(9)T2 and my FXS chipset is as follows: "1 On-Board Twenty-Four FXS Analog Voice Module V2.1".

I have this problem too.
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Rob Huffman Thu, 12/14/2006 - 16:44

Hi David,

My vote is for RMA time. This low voltage will cause device issues as you have seen. Here is a Cisco doc that indicates what the "idle line voltage" should be. Have a look;

Ringing and Idle Voltages on Cisco FXS Interfaces

Idle Battery Voltage

Cisco voice gateways were designed for ONS connections and by default the FXS interface supplies either -24Vdc or -36dvc idle battery, whereas Off Premise Services (OPS), such as a CO, would require voltages of -48v because it may have to interconnect over much greater cable lengths.

VG224 should supply -24 Volts (low) -48 Volts (high)

From this doc;

http://www.cisco.com/en/US/tech/tk652/tk653/technologies_tech_note09186a008011c7f3.shtml

Hope this helps!

Rob

MICHAEL WHALEY Tue, 06/12/2007 - 10:36

Looks like this is a pretty common problem. We are having the same issue on some brand new VG224s. TAC is doing some additional research, but a few things to try:

Depending on the code version you may not have idle voltage set to high by default:

vg(config-voiceport)#idle-voltage high

You can also try manually bumping the voltage:

vg(config-voiceport)#alt-battery-feed feed2

The alt-battery-feed command in our VG bumped the idle voltage to -43VDC but still was not quite enough vs a PSTN POTS line which was giving us -45VDC.

http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCse92359

Mike

d.haeni Wed, 06/13/2007 - 05:40

I completely forgot to let you folks know that the RMA didn't solve the problem.

Believe it or not: the -19V Problem persisted until I downgraded the code to 12.4(4)T7 -Ouch! :)

MICHAEL WHALEY Wed, 06/13/2007 - 05:47

Our unconfigured ports show -18 to -19VDC but once they are configured as a POTS port they went to -38VDC. (We are running 12.4(13A) Mainline.

If you apply the alt-battery-feed feed2 to the voice-port you will get about -43VDC, however, TAC told us that they can not get -48VDC due to a hardware/firmware limitation. They are in the process of revising the docs on CCO.

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Posted December 14, 2006 at 3:48 PM
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