Vista 20p problems: siren buzzing, low batt


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Old 04-06-21, 10:14 AM
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Vista 20p problems: siren buzzing, low batt

Dear all, thanks in advance for your help. I have two issues with my Vista 20p, but first some context:

I've been using a Vista 21iP for the past 5 years with no problems. Not leaving the house for many months, we have now started to venture out (hooray for vaccines!) and realized our TC Connect 2.0 app doesn't work. Long story short, we realized the in-built comms function in the 21iP was not working.

As such, I migrated from the 21iP to a 20p with a standalone communicator, which allows both cell and internet access. I did the migration and it works well for the most part. Communicator works well and is now synced with TC Connect 2.0. Here's my problems now:
1. The sirens emit a low level, high frequency buzz. Sounds like white noise. This seems to be caused by a 2.5V DC potential between the two siren output terminals 3 and 4. This is not a true alarm - that works fine - but this occurs 24/7 constantly even when disarmed. I've confirmed all the connections are correct... I've confirmed this is not due to the communicator, since disconnecting the communicator and/or switching it off does not affect the buzzing.
2. There is a Low System Batt warning that won't go away. I've waited the 4+ hours and it is still present. The battery measures fine - it's at 12.9V unloaded and 13.5V under charge. Looks healthy to me...

Anyway, would love your advice and help. Thanks in advance.

Robert
 
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Old 04-06-21, 11:58 AM
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1) When you measure the 2.5 VDC between T3 & T4,, is that with the siren wires connected or disconnected? In other words, is the 2.5 VDC originating from the Panel or from the siren wires? Sometimes long wire runs can pick up inducted voltages.

2) A weak Panel battery disconnected from the Panel might still read in the 12.9 VDC range if it's not powering a load. That's called "Open Circuit Voltage," and can be deceptive. As long as you're going to take off the siren wires (from T3 & T4), put those across the disconnected battery (observe polarity) and see what the battery reads while it's powering the siren directly. A strong battery will drop its voltage some, but not down below 11.5 VDC.

If that's the original battery from 5 years ago, I recommend you change it whatever the reading.
 
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Old 04-06-21, 04:24 PM
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Welcome to the forums.


it's at 12.9V unloaded and 13.5V under charge.
You can also disconnect the AC or unplug the transformer and measure the voltage again.
The panel will also supply load.

Battery quality today is poor. A five year old battery is definitely due for a replacement.
 
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Old 04-07-21, 07:27 AM
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Thanks for the response, guys.

The 2.5V is measured in-circuit WITH the sirens connected measured at the panelt. It is the cause of the hum. As such, I highly doubt it is the result of induced voltages and that also wouldn't make sense since it's DC. There's no significant AC component.

I am buying a new battery but I don't think that's the case - we'll find out tomorrow when it arrives. I'm saying this because the battery is less than 1 year old, and I deliberately replaced it with a 7Ah (standard is 4Ah).

Still stumped!
 
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Old 04-07-21, 02:37 PM
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For the siren circuit, there is a small supervision voltage that is supposed to be present. _Most_ 12v sirens have enough built in impedance, and/or a polarizing diode, that this doesn't produce the kind of leakage sound you are experiencing. Sometimes less expensive or older sirens will make a sound with this. The solution is normally to install a resistor across the siren output. 1000 ohms is usually enough.
 
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Old 04-08-21, 10:27 AM
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Wow, MrRonFL, you are a genius. The system was installed 6 years ago so it's not that dated, but your solution totally did the trick. 1k across the siren output now it's completely silent!!!

I'm still getting the low battery warning (now with a brand new battery), but you totally fixed this issue. Thank you!
 
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Old 04-08-21, 02:36 PM
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Usually, it's the polarizing diode in the siren that starts to "leak" a small amount of current. The reaper of the 2nd law of thermodynamics eventually comes for even devices that simple...

Not sure why you are getting the low battery. It's not accompanied by a zone number, is it?
 
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Old 04-08-21, 04:15 PM
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Thanks very much.

For the low battery warning, it's a "System Low Batt", not specified to a zone. The battery I'm using now measures at 12.9V under load (i.e., AC supply disconnected, battery connected) and 13.6V charging (AC supply connected, battery connected). I've tried triggering the walk test to force a battery test, and no love. Anyway, the battery should be automatically tested every 4 hours anyway, right? Weird.

I'm now trying an external battery charger to really juice up the battery before I hook it up. Hopefully that will do the trick.
 
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Old 04-09-21, 02:53 PM
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If tweaking the battery doesn't resolve it, I'm going to have to conclude that you may have gotten a V20p board with a bad power supply section.
 
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Old 04-09-21, 06:32 PM
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If you're metering the battery immediately after taking off AC, and if the Panel isn't powering very much beyond the V-20P Panel itself and Keypad, (e.g., not also powering RF Receiver, expansion modules, additional KPs, several wired motion & glassbreak sensors, etc), then a weak battery might still read as high as 12.9 VDC until it has a little time to drain.

Before you go buying a new V-20P panel, I'd take one last check and meter the battery after the AC has been disconnected awhile, maybe half an hour or so.
 
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Old 04-10-21, 05:55 AM
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New sealed lead-acid batteries leave the factory with a surface charge. The surface charge causes "false" voltage readings (reading higher than the actual voltage). Once the battery has charged, voltage readings should be accurate.
 
 

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