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slybunda
Senior Member
Last Activity: 02-24-2024, 02:23 AM
Joined: 02-18-2012
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  • From what i read if selecting a higher voltage cap and the cap never reaches its rated voltage then something happens to it where it cant be reformed and looses capacitance?
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  • That explains why i couldnt find it on the caps.

    Gemcon website says they are made in tiwan so guessing they are decent quality?...
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  • slybunda
    replied to Alarm Siren issue
    iv tried 2 of the largest scrapyards in my city and nothing available from them. 10 years ago this would have been very easy to nab but now not even ebay etc has any. dont think anyone needs and aftermarket alarm and immobiliser since all cars came standard with it after year 2000 or so.....
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  • slybunda
    replied to Alarm Siren issue
    i dont have a replacement siren for this one. someone is sending me a different type of siren which i may be able to use for parts.
    iv worked out the part of this siren thats used for charging the battery, looked like they used zener diodes for a constant voltage charging system, the big diode on the board is to prevent the battery in the siren back feeding to the alarm control box. this should be fixable once i get to look at another siren that uses a similar type of setup to get an idea of whats going where.
    no harm in posting in different places since people on different forums...
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  • slybunda
    replied to Alarm Siren issue
    fantastic. any ideas on how the read the code from this chip? can it be done with an arduino uno?
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  • slybunda
    replied to Alarm Siren issue
    removed the sticker of the small chip and its got some markings on it:

    12C508A
    04/P01V
    0113

    maybe if i can find a datasheet for this it may give schematic info of whats supposed to be connected to it and how?​...
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  • Ok cool, noticed that wurth brand caps seem to be rated way higher than other caps for lifetime
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  • Picking long life capacitor replacements?

    to pick some good quality capacitors for long lifetime do i just go to mouser, rs etc and select the capacitance and voltage then sort by the highest number of hours and pick the caps that have the highest number of lifetime hours?
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  • slybunda
    replied to Alarm Siren issue
    pic of the top added here. missing zener is marked Z1 on the board.
    my siren had a nickel cadmium battery, later revisions seems to have switched over to nimh battery.

    im sure the siren used to sound when battery was removed from car if alarm was armed i think. cant remember that far back and this battery seems to have been dead for a long time....
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  • slybunda
    replied to Alarm Siren issue
    thanks for that info above. iv got someone sending me a siren from a cobra alarm so will see how that is inside.
    the siren has a single cable which has 3 wires in it that go to it from the control box. the 3 wires are Ground, Trigger and Vbat, so im guessing its just 12v + and - along with a signal to trigger the siren.
    im wondering if the zener diode that broke off was for the battery, is it possible it is forward biased when it has above something like 9v and then reversed bias when the car battery voltage drops too low to power and trigger the siren?...
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    Last edited by slybunda; 02-06-2024, 03:57 PM.

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  • slybunda
    replied to Alarm Siren issue
    Spoke to someone from toad any they not taking any liability saying the alarm should be serviced every year at a cost of £100 which is stupid since over the 20 years iv had it that would be £2000 wasted on alarm service lol.
    they offered a siren replacement at a cost of £130 plus delivery which is a total ripoff.
    I need to work out what circuitry is for battery charging and what part is for the actual siren operation. May be able to then reverse engineer something onto a breadboard and if it works move it to a perf board or even have jlcpcb etc make a replica.
    If i had photos...
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  • Gemcon capacitor replacements?

    taken from my thread about car alarm siren here: [url]https://www.badcaps.net/forum/troubleshooting-hardware-devices-and-electronics-theory/troubleshooting-audio-equipment/3210373-alarm-siren-issue[/url]

    there are 2 caps which im looking to get replacements for.
    Branded as Gemcon
    single 100uf 16v 6.5mm x 11.5mm
    single 100uf 50v 8mm x 11.5mm
    lead spacing is around 3mm

    there is space for 16mm tall caps

    rs components is good place for me to go since its close by, what replacements do you suggest and do these need to be low esr?
    ...
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  • slybunda
    replied to Alarm Siren issue
    more pics after desoldering stuff, zener diode is toast its broke in half so not sure what to do there. the 2 burnt out resistors seem to both have the same resistance of 100ohm so maybe they are 100 ohm or they both got cooked to the same temp to give same wrong reading? not sure there. some trace damage too looks like a single layer board so not sure now....
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  • slybunda
    replied to Alarm Siren issue
    too hard to get a replacement item these were aftermarket alarm systems and production stopped many years ago. iv posted this on many other forums, car forums and electronics to get as much help as i can.
    the speaker in the alarm unit still works the car can make its alarm noise like normal when ultrasonics or door switch is triggered. but the harming and disarming of the alarm doesnt make any sounds from the siren like it used to do, it just makes that constant noise here: [url]https://www.youtube.com/watch?v=ZjsqndhionU[/url]
    thats why the siren gets warm and is draining the car...
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  • slybunda
    replied to Alarm Siren issue
    speaker plugs into the connector next to the transistors battery plugs in on the connector next to the aluminium capacitors, can see the wire had to be cut for the battery the connector is corroded. battery had red and black wire, speaker had black and black with white stripe wire....
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  • slybunda
    replied to Alarm Siren issue
    I see, so im guessing the 2 that are not burnt out handle the alarm sound when it is triggered (which still works) and the 2 burnt ones handle the chirp noise when arming and disarming which no longer makes sound any more.
    could this be it?
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  • slybunda
    replied to Alarm Siren issue
    would these be the same: [url]https://uk.rs-online.com/web/p/bipolar-transistors/4859777?gb=s[/url] ??

    also what would these be used for? could they be audio amplifiers in this circuit?https://would these be the same: [ur... this circuit?would these be the same: [url]https://uk.rs-online.com/web/p/bipolar-transistors/4859777?gb=s[/url] ??

    also what would these be used for? could they be audio amplifiers in this circuit?
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  • slybunda
    started a topic Alarm Siren issue

    Alarm Siren issue

    Apologies if this is in the wrong section but being a car alarm siren that makes noise i thought it be best to put it in the audio section.
    Had weird alarm issues where siren made a strange noise: [url]https://www.youtube.com/watch?v=ZjsqndhionU[/url]
    took siren out of the car and checked it out and pics attached seem to be the source of the issue.
    shockingly the alarm still makes its normal sound if i trigger it manually so speaker seems to be intact.
    getting a replacement is gonna be next to impossible, its a Toad Ai606 which is no longer in production and cant see to...
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  • Has quality dropped when they outsourcing?
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  • Whoa does this mean we need to add chemicon to the ban list? Or is the place you got them from just reusing packaging?
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