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animateme
New Member
3 Posts |
 Posted - Jan 24 2013 : 4:08:04 PM
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Hello,
I have an old xenon strobe (disco light) that had been stored for a very long time and when I tried to turn it on recently, it no longer worked. I first assumed it was the xenon tube bulb so I replaced it but it still does not work.
I opened it up (circuit was inside wood box) to try and measure voltage at different points to see if I could determine any current interruptions but as soon as I plugged it in, there was a point on the back of the circuit that lighted up (burning) and even some smoke came out. I immediately unplugged it.
Searching information on this I found this topic: http://www.aaroncake.net/Circuits/strobe2.asp , and it seems like my circuit is very similar. The burning came from one of the terminals on what seems to be the 4KV Trigger Transformer (see red arrow on attached photos).
I am no electronics expert (I do own and can operate a multimeter), and that is where I would greatly appreciate any support on this forum, is there a way that I can troubleshoot this circuit to get it working again? Any suggestions or ideas?
Thanks on advance for any comments.
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pebe
Nobel Prize Winner
United Kingdom
1078 Posts |
Posted - Jan 25 2013 : 10:32:55 AM
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It looks like the unit was stored in a damp environment and had not been dried out before it was switched on. That caused the tracking across the PCB.
You might be able to salvage it, assuming there is no component damage. Re the PC track that is to the right of the damage. Cut sections of the track away near where it connects the soldered components to isolate it (take away all the track if you can), and then replace the track with a length of wire, routed away from burnt area.
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Edited by - pebe on Jan 25 2013 10:34:44 AM |
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animateme
New Member
3 Posts |
Posted - Jan 26 2013 : 1:48:40 PM
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Thank you for responding pebe. I am pretty sure there was no humidity at all where this was kept. The strange thing is that I first powered the circuit several times, with the xenon tube in place (although it did not light up), and no burning occurred. Then, not sure if this had anything to do with it, I removed the xenon tube and it was at this moment that the burning occurred when I powered up the circuit. Could this have had anything to do or it was just coincidence?
I will follow your advice on re-routing the track away from the burnt area. Now, as for the xenon tube not lighting up, even before the burning happened, is there anything else that I can check on the circuit to try and troubleshoot the issue?
Thanks, |
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Feb 03 2013 : 11:19:43 AM
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It's important to determine why it burned. Top of my list to check would be the rectifier diodes and main capacitors. Check that the diodes haven't become wires (they should only conduct in the direction of the bands) and just replace the capacitors.
As mentioned, the board will need to be repaired.
You'll need to check the SCR out of circuit in order to get a good measurement. Here's a quick link on how to do this:
http://www.circuitstoday.com/how-to-test-an-scr
Also check the trigger transformer to make sure it isn't a direct short. |
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animateme
New Member
3 Posts |
Posted - Feb 08 2013 : 6:45:40 PM
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Thanks for the response. I scraped away the carbon burnt area, placed the xenon bulb back into place, powered up, and the burning is no longer happening. Still, no strobe flash.
Can you please explain how I can check that the diodes haven't become wires? Also, how can I check the trigger transformer to make sure it isn't a direct short?
As for the Capacitors, is there a way to check these?
Thanks for the link on how to check the SCR.
Thank you. |
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Feb 09 2013 : 10:43:32 AM
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You'll need a meter with a diode check function. Unsolder one end of the diode from the board so that it's no longer part of the circuit, then use the meter to check the diode in both polarities. Should show very low resistance or continuity in one direction, VERY high resistance in another.
You can check the capacitors, but don't bother. Replace them if they are suspect.
As for the trigger transformer, there will commonly be three connections. A HV out, a ground, and a primary coil. The primary should show high resistance to the HV out (they are tied together at the ground). The HV out should show high resistance to ground, and higher resistance to the primary. The primary should have maybe 5 - 100 OHMs to ground. |
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Xenon Strobe repair
