UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

Keith · 5th May 2019, 4:23 pm

David,
If you're getting Drive in transmit, it implies that the BFO is working in this mode. In TX the HT to the BFO is via the relay so maybe there is just a problem with the Net switch in receive. Check either side of the switch with a meter. I have had problems with these paxolin layer switches due to dirty contacts - they can be dismantled for cleaning by drilling out the rivets and replacing with 8BA bolts/nuts to re-assemble. Try switch cleaner first, of course. Other than that, just check all the components around V2B triode (R1D, R6A etc) - it's basically a simple tuned grid oscillator (L5A/C41A) with anode feedback via C19A/L5B. One other possibilty is that it has moved some way off frequency - on mine the small ferrite core fell out of it's plastic insert so had to be glued back in.
The lack of HT2 meter indication is quite common. R25A is a 1.2Mohm - these often go very high.

5th May 2019, 4:23 pm	#15
Keith Heptode Join Date: Jan 2003 Location: Tewkesbury, Gloucestershire, UK. Posts: 693	Re: Another 19 set rebuild David, If you're getting Drive in transmit, it implies that the BFO is working in this mode. In TX the HT to the BFO is via the relay so maybe there is just a problem with the Net switch in receive. Check either side of the switch with a meter. I have had problems with these paxolin layer switches due to dirty contacts - they can be dismantled for cleaning by drilling out the rivets and replacing with 8BA bolts/nuts to re-assemble. Try switch cleaner first, of course. Other than that, just check all the components around V2B triode (R1D, R6A etc) - it's basically a simple tuned grid oscillator (L5A/C41A) with anode feedback via C19A/L5B. One other possibilty is that it has moved some way off frequency - on mine the small ferrite core fell out of it's plastic insert so had to be glued back in. The lack of HT2 meter indication is quite common. R25A is a 1.2Mohm - these often go very high. __________________ Keith Yates - G3XGW VMARS & BVWS member http://www.tibblestone.com/oldradios/Old_Radios.htm Last edited by Keith; 5th May 2019 at 4:28 pm.