I've found a Bruel & Kjaer 4230 Sound Level Calibrator which has quite suffered, being not used for many years with a linking battery and some components failed due to an error when connected to a lab bench supply.
I have changed some transistors and capacitors, and it now delivers a fine 1 Vrms sinus across the piezo driver.
However, I thought it would start to do that only for a couple of seconds when the switch is pressed and then goes off .
Instead of that, the sound is emitted as soon as the battery is connected and does not stopped until the battery is removed.
Pressing the switch appears to do nothing.
I do not have the schematics.
Can someone help me to recover the initial functionning state of this litte tool ?
Here some photos :
I have changed some transistors and capacitors, and it now delivers a fine 1 Vrms sinus across the piezo driver.
However, I thought it would start to do that only for a couple of seconds when the switch is pressed and then goes off .
Instead of that, the sound is emitted as soon as the battery is connected and does not stopped until the battery is removed.
Pressing the switch appears to do nothing.
I do not have the schematics.
Can someone help me to recover the initial functionning state of this litte tool ?
Here some photos :
Attachments
Thanks for the help.
The PCB is out of the box. When I press the switch, it makes the contact correctly.
Yes, seeing the PCB, quite hard to think that the manufacturer is the most known for acoustic measurement tools.
Mine stays on for a few minutes with a fresh battery. You might not be waiting long enough. However you will need to have your calibrator calibrated. Although it is supposed to be once a year, mine has yet to drift enough to bother. A psitonphone is a reference and does not need to be calibrated.
BTY your pictures are almost clear enough to allow drawing a schematic. It looks quite simple inside. The inductor is "Pot Core" for those not old enough to have seen one. It is a very high Q inductor. (Value really does't matter to fix them. If it is cracked you really can't find a modern replacement.)
Of course you probably have already fixed it as this thread is a year old.
BTY your pictures are almost clear enough to allow drawing a schematic. It looks quite simple inside. The inductor is "Pot Core" for those not old enough to have seen one. It is a very high Q inductor. (Value really does't matter to fix them. If it is cracked you really can't find a modern replacement.)
Of course you probably have already fixed it as this thread is a year old.
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Yes, you're rigth, the PCB isn't complex, but the mine is modified (some parts has been changed). Therefore I'll happy, if You could take some picture about the PCB, and if You could write down the type of the transistors!
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