Hey Guys,
I've been using the CB34EX for quite some time now on over 50 vessels (2 per boat). I tried replacing a couple of these due to failures, but every time I plug in a new one, they burn up right away while powering them up. Interestingly, however, is that the other one (older version) is being powered up from the same power supply and it's still running and functioning properly. I can swap power and data around on the older version and it still works, so I don't believe it has anythign to do with the power or the data signal. Anybody have a clue what I should check? Is there something I'm missing with the newer model? Please see my attachment for a image of the board.
Thanks for any help.
Timmy Hoang
Fried PCB Board on power up
Fried PCB Board on power up
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Re: Fried PCB Board on power up
I would try the following to look for a ground fault:
1. Power up with only the power connection, nothing on the data ports. Does that work?
Put a scope (not a meter) on the input power. Is there ever a spike above 24V? Even a momentary spike could cause damage. Maybe the new model has less headroom than the old one if your above 24V? What peak voltage do you see?
3. If items 1 and 2 are ok, tie a ground line from the power supply to the ground of whatever the serial ports connect to. This way you have a good ground between the two and its not using the CB34EX as the ground conductor. Only then hook up the serial ports. Does the unit burn up?
1. Power up with only the power connection, nothing on the data ports. Does that work?
Put a scope (not a meter) on the input power. Is there ever a spike above 24V? Even a momentary spike could cause damage. Maybe the new model has less headroom than the old one if your above 24V? What peak voltage do you see?
3. If items 1 and 2 are ok, tie a ground line from the power supply to the ground of whatever the serial ports connect to. This way you have a good ground between the two and its not using the CB34EX as the ground conductor. Only then hook up the serial ports. Does the unit burn up?
Re: Fried PCB Board on power up
Any luck? Always interesting to see how these things turn out.
Re: Fried PCB Board on power up
Thank you for your help, but I have not had the time to revisit this yet. When you say tie a ground from the data ground to the power supply ground, do you mean the -24VDC of the power supply? So a wire from where I am picking up -24VDC to the data ground on the plug?
Re: Fried PCB Board on power up
I thought your configuration was like this:
24V Power <--> CB34EX <-- RS-232 --> Some Device
| |
|-------------- ground wire ---------------|
So if my formatting doesn't get messed up, the above picture should show a ground from the power source to your end device. Without that ground wire the ground flows through the CB34EX, and if there is a grounding problem somewhere it could generate a lot of current through the CB34EX, causing the burn up if the PCB or components can't handle that much current. This is just for testing purposes since you seem to have a repeatable event.
PS: after posting I see my formatting gets messed up. There should be one vertical line under the 24V power to the ground wire, and the second under "some device" to the ground wire.
24V Power <--> CB34EX <-- RS-232 --> Some Device
| |
|-------------- ground wire ---------------|
So if my formatting doesn't get messed up, the above picture should show a ground from the power source to your end device. Without that ground wire the ground flows through the CB34EX, and if there is a grounding problem somewhere it could generate a lot of current through the CB34EX, causing the burn up if the PCB or components can't handle that much current. This is just for testing purposes since you seem to have a repeatable event.
PS: after posting I see my formatting gets messed up. There should be one vertical line under the 24V power to the ground wire, and the second under "some device" to the ground wire.
Re: Fried PCB Board on power up
Soem backgroudn that might be useful...
The original CB34EX was not protected from reverse polarity connection.
As part of revising the unit to pass the Modbus spec we had to make sure that the system would not be damaged from incorrectly connected
CAN signals and backwards power supplies. (We also added a micro SD Card)
We did this by changing the CAN transceiver and adding a series diode to the power supply.
We still wanted to meet the published voltage spec of 7 to 24V with this diode in place,
the power supply now had to run from 6 to 24V to account for the diode drop.
The old CB34 supply would not do this.
So as part of the redesign we used the same supply we have used on the SB700EX and several module carrier boards.
This new supply would run from 6V to 25V or so, comfortably inside our 7 to 24V spec.
The old supply would only operate properly between 7 and just a tad more than 24V.
Above 24V the inductor would go discontinuous and makes lots of EMI.
All would seem well, the problem is that the max voltage before damage spec of the old supply was 40V,
with most units going to 60V or so before being damaged. The unit would not really regulate properly above 24V or so,
but it would not be damaged til one was well above 40V.
The new supply would run just fine at 24V, but it would be damaged by transients above about 30V, still meets spec,
but we have had one customer where the old CB34 worked fine and the new ones died.
So if you had or have a CB34 installation where you might see transient voltages above spec we recommend that you add
a transient voltage suppressor right at the device.
We have also addressed this issue by changing some of the parts in the new CB34EX to be more tolerant of over voltages.
The new parts should not be damaged by transients of up to 40V, but are still short of the typical 60V levels in the old CB34.
The original CB34EX was not protected from reverse polarity connection.
As part of revising the unit to pass the Modbus spec we had to make sure that the system would not be damaged from incorrectly connected
CAN signals and backwards power supplies. (We also added a micro SD Card)
We did this by changing the CAN transceiver and adding a series diode to the power supply.
We still wanted to meet the published voltage spec of 7 to 24V with this diode in place,
the power supply now had to run from 6 to 24V to account for the diode drop.
The old CB34 supply would not do this.
So as part of the redesign we used the same supply we have used on the SB700EX and several module carrier boards.
This new supply would run from 6V to 25V or so, comfortably inside our 7 to 24V spec.
The old supply would only operate properly between 7 and just a tad more than 24V.
Above 24V the inductor would go discontinuous and makes lots of EMI.
All would seem well, the problem is that the max voltage before damage spec of the old supply was 40V,
with most units going to 60V or so before being damaged. The unit would not really regulate properly above 24V or so,
but it would not be damaged til one was well above 40V.
The new supply would run just fine at 24V, but it would be damaged by transients above about 30V, still meets spec,
but we have had one customer where the old CB34 worked fine and the new ones died.
So if you had or have a CB34 installation where you might see transient voltages above spec we recommend that you add
a transient voltage suppressor right at the device.
We have also addressed this issue by changing some of the parts in the new CB34EX to be more tolerant of over voltages.
The new parts should not be damaged by transients of up to 40V, but are still short of the typical 60V levels in the old CB34.
Re: Fried PCB Board on power up
Hi pbreed,
Thank you for the additional information. We do use the 72ex as well without any problems. All devices get power from the same source. Not sure if I mentioned this in my initial post, but the unit powers up and stays on perfectly fine. It's not until we plug in the CAN data plug which then shorts something in the circuitry. I then removed the power and data connectors and plugged them into an older unit, which still worked as expected.
Thank you for the additional information. We do use the 72ex as well without any problems. All devices get power from the same source. Not sure if I mentioned this in my initial post, but the unit powers up and stays on perfectly fine. It's not until we plug in the CAN data plug which then shorts something in the circuitry. I then removed the power and data connectors and plugged them into an older unit, which still worked as expected.