PM 5519 pattern generator - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Philips210 · 15th Feb 2024, 1:22 pm

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

buggies · 15th Feb 2024, 7:40 pm

Quote:

Originally Posted by Malcolm G6ANZ

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?

Malcolm G6ANZ · 15th Feb 2024, 8:07 pm

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

buggies · 15th Feb 2024, 11:19 pm

Duh! - sorry about that - Was looking at the cached web page without refreshing.

Malcolm G6ANZ · 16th Feb 2024, 10:00 am

No problem. All help and advice gratefully received.

Malcolm G6ANZ · 18th Feb 2024, 1:23 pm

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

15th Feb 2024, 1:22 pm	#21
Philips210 Nonode Join Date: May 2007 Location: Redruth, Cornwall, UK. Posts: 2,672	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

15th Feb 2024, 8:07 pm	#23
Malcolm G6ANZ Octode Join Date: Feb 2006 Location: Bristol, UK. Posts: 1,056	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

15th Feb 2024, 11:19 pm	#24
buggies Heptode Join Date: Jan 2009 Location: West Lothian, UK. Posts: 785	Re: PM 5519 pattern generator Duh! - sorry about that - Was looking at the cached web page without refreshing. __________________ George

16th Feb 2024, 10:00 am	#25
Malcolm G6ANZ Octode Join Date: Feb 2006 Location: Bristol, UK. Posts: 1,056	Re: PM 5519 pattern generator No problem. All help and advice gratefully received.

18th Feb 2024, 1:23 pm	#26
Malcolm G6ANZ Octode Join Date: Feb 2006 Location: Bristol, UK. Posts: 1,056	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