more on ACT CR230 repeater failure

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- Dan Lanciani
  
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posted
18 years ago

Tue, Oct 11, 2005 2:56 AM

On closer examination it turns out that both pads of the zener had separated from the board (a good trick considering that one of them is part of a little ground plane). The trace that supplies power to the drivers is routed through the zener's pad, so it's difficult to determine what happened. Depending on the order of pad failure the drivers could have seen no voltage, high voltage, or anything in between. There is a 50V electrolytic across the output which might break down and limit the voltage a bit. Based on my initial measurements (but after I had probably disturbed the board) I'm leaning towards no voltage.

Dan Lanciani ddl@danlan.*com

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- Marc F Hult
  
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posted
18 years ago

Tue, Oct 11, 2005 4:43 AM

Is this a 1 watt 1n47xx ? I have an ACT CR225 also and considering preemptively replacing with a higher wattage zener.

Ironically, the Leviton 6201 that the ACT CR230 replaces in my system (via a detour with the factory-supplied Leviton HCA02-10E when the 6201 failed ) also had darkening around the zener.

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Leviton didn't bother to specify positioning the zener away from the board so as to increase dissipation and reduce heating of the board although numerous _other_ discrete components were sloppily inserted and not snug against the board.

.... Marc Marc_F_Hult

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- Dan Lanciani
  
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posted
18 years ago

Tue, Oct 11, 2005 10:14 AM

| | Is this a 1 watt 1n47xx ?

No, it's a 5W 1N5366. I actually complained about the excessive heat about 5-6 years ago (the board was starting to discolor even then) but they said in effect that it was just a cosmetic issue since the zener was rated for enough power. And I suspect the zener itself is fine, it's just the board that is destroyed...

| I have an ACT CR225 also and considering | preemptively replacing with a higher wattage zener.

Couldn't hurt. If I decide to repair the repeater I'll probably mount a fresh zener away from the board, possibly with a heat sink. The question of exactly how the failure was causing the effect it was causing remains.

Dan Lanciani ddl@danlan.*com

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- BruceR
  
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posted
18 years ago

Tue, Oct 11, 2005 12:04 PM

In talking to Phil Kingery about this issue a couple of years ago, he advised me to use high heat solder in doing repairs in this area, as the heat will melt standard solder. He also mentioned that the more signals that pass through the unit, the lower the heat will be. Not sure I understand why though. The newer units (last couple of years or so) have heat sinks added.

From:Dan Lanciani ddl@danlan.*com

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- Dan Lanciani
  
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posted
18 years ago

Wed, Oct 12, 2005 2:32 AM

| In talking to Phil Kingery about this issue a couple of years ago,

Interesting. He wouldn't admit to me that there _was_ an issue. :(

| he | advised me to use high heat solder in doing repairs in this area, as the | heat will melt standard solder.

Yikes. It's a pretty bad design that requires hard solder for temperature reasons, and they stuck an 85C capacitor right next to the zener. In any case, it wasn't the solder but the board material that failed.

| He also mentioned that the more signals | that pass through the unit, the lower the heat will be. Not sure I | understand why though.

The zener is being used more-or-less as a shunt regulator. The more power used by the output drivers the less the zener has to dissipate as waste heat, at least to a first approximation. However, I assume the zener is also conducting in the forward direction to charge the dropping capacitor on the positive half of the cycle and it may end up passing more current then when the load is higher. Regardless, one would hope that they designed the device to run for long periods with no signals...

| The newer units (last couple of years or so) | have heat sinks added.

Yet still no UL sticker. :(

Dan Lanciani ddl@danlan.*com

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- Tickerguy
  
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posted
7 years ago

Wed, Jun 1, 2016 1:24 AM

replying to Marc F Hult, Tickerguy wrote: Anyone happen have the zener specs on the 6201? I happen to have one here with a nicely-burnt board, it appears the solder job and traces held but I'll lay odds that the zener is open considering that it is not only no longer amplifying it also occasionally likes to spam the original signal back on the incoming phase forever!