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Old 15th Feb 2024, 1:22 pm   #21
Philips210
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Default Re: PM 5519 pattern generator

Great news that you found the fault!

Re the transistor array, perhaps one of the transistors failed when the can of C533 shorted across to one of the feed resistors. You could do a junction check with your multimeter (diode test) referring to the circuit diagram for the relevant transistor bce connections.

Regards,
Symon
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Old 15th Feb 2024, 7:40 pm   #22
buggies
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Default Re: PM 5519 pattern generator

Quote:
Originally Posted by Malcolm G6ANZ View Post
I’m starting to think the only way forward now is to feed in a -12v from an external supply and see where the smoke comes from?.
Setting the external power supply to about 0.8 volts and its current limit to (say) 250mA should be fairly safe. Then measure around the various -12v points to find the lowest mV point?
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Old 15th Feb 2024, 8:07 pm   #23
Malcolm G6ANZ
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Default Re: PM 5519 pattern generator

I won’t need to do that now. As,with help, I found the fault. It there is still more to do as the output voltage is way too small
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Old 15th Feb 2024, 11:19 pm   #24
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Default Re: PM 5519 pattern generator

Duh! - sorry about that - Was looking at the cached web page without refreshing.
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Old 16th Feb 2024, 10:00 am   #25
Malcolm G6ANZ
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Default Re: PM 5519 pattern generator

No problem. All help and advice gratefully received.
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Old 18th Feb 2024, 1:23 pm   #26
Malcolm G6ANZ
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Default Re: PM 5519 pattern generator

It’s all back and working correctly. The lack of output was my stupid fault. There are a set of links to select the modulation polarity , I had them both selected and so killing the output from the IC. With one one selected it came to life.
Thanks again for the help and advice
Malcolm
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