Clock sync issues on "classic style" Axia Nodes
This article applies to the "classic style" Axia nodes. These are the silver-face, full rack width nodes for Analog, AES, and Microphone inputs/outputs. The classic Axia GPIO node does not require a clock, and so does not apply to this document.
Here is a picture of the classic nodes.
The customer complaint often starts with hearing "clicking" on some inputs or outputs. To have reliable audio in or out of a Node, you need to have a stable Livewire clock. A solid SYNC light on the front of these nodes indicates a stable clock.
The SYNC light should be on solid all of the time unless;
- It is the MASTER Node, in which case the MASTER light illuminates on the front.
- It is in the process of syncing to a master. Sync happens after a reboot of the node but should become stable after a short time.
There is a single capacitor in the PLL circuit that is responsible for the stability of that circuit. Over time the capacitor can no longer do its job reliably and needs to be replaced.
The capacitor to replace is labeled C2 on the PC board. This capacitor is in different locations on each type of node (Analog, AES, and Microphone); however, it is labeled as C2 on all three types.
The capacitor is a Panasonic, 6.3 Volt, 220uF, SMT style, aluminum electrolytic capacitor. The Panasonic (RoHS compliant) part number is EEEHA0J221WP. These are Telos part number 1111-00209 and are available as a parts order from us; however, they can also be obtained from many online electronics parts distributors like Mouser or Digikey.
Here is a picture of the capacitor. Note there are two small tabs on either side of the capacitor which need to be de-soldered in order to remove it. One of the solder tabs is shown in this image.
The following picture shows a bird's-eye view of the capacitor on an Analog node. This capacitor is in similar positions on the AES and Microphone node.
This capacitor can affect the master as well as any synced nodes. That is to say that the reason why the SYNC light is blinking could be that the master is not sending a stable signal. Generally, if you have multiple nodes with blinking sync lights, the problem is likely the master. If it's only a single node, then the possible problem is that node. Chances are if one node is having an issue, all of them could be. Replacing the C2 cap in all nodes when one needs it is a good idea.
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