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Old 29th July 2009, 03:07 AM   #1
WimVL is offline WimVL  Belgium
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Question Crescendo troubleshoot

I builded my crescendo, the 1982 one from elektuur already two times, but always have the same problem. The crescendo works but after a couple minutes there exist a noisy sharp sound that rises up. and then after about 5 minutes collaps C14 or C15(the big Elco's on the PCB's) only one will explode.I checked the polarity for mor than 100 times, but still have this problem, can anyone help me. I think is't something stupid,

Is there maybe a fault in the chematic that i don't have? I think sombody told me ones there was a fault in the chematic, is it true am I the problem.

I hope somebody can axplain my problem, because I builded it complete and it looks very ok, only the sound don't works.

I'm from Belgium.
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Old 29th July 2009, 05:23 PM   #2
tiefbassuebertr is offline tiefbassuebertr  Germany
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Location: D-55629 Schwarzerden
I have this elektor magazine, this diy project starts at page 30 from German Elektor December 1982.
The reason for your damage cap is, that one of cap C14/C15 see more than 100 V - so I think.
Please choise voltage 200V or 250V instead 100V for this one.

Then remove the MOSFETs and make short wire between each gate and output and connect ballast resistor arround 5K to GND. Now you have only voltage amplifier and you can perform complete function test through measurements - both dc conditions so as ac conditions.

If there are any voltages with other values as in schematic (resp. unwanted MHz-ostillation), the faulty is by voltage amp.

If not, your MOSFETs or PCB wires are faulty.

At best you order the complete article so as schematic in your language by http://www.elektor.nl/
please read also the threads

If you haven't experience with troubleshooting, please go to an amp specialist

many success and greetings to Antwerben
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