Marconi 2019A Intermittent RF Output Fault - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Ti Pwun · 31st Mar 2016, 7:46 pm

Well, so much for that - started out OK but at 600KHz, I get a fluctuating frequency between 114 and 116KHz. Oh well, back to the drawing board...

G0HZU_JMR · 1st Apr 2016, 3:13 pm

Have you checked the DC tuning voltage for VCO 2 to make sure it is still well inside the normal range? If it has reached the edges of the tuning range it will become erratic in terms of lock reliability.

Also, I had several VCO failures on the VCOs in both of my 2019s over the first few years I owned them. I had failures due to poor connections, a failed transistor and also a failed ceramic capacitor that went intermittently short circuit.

It took me quite a few attempts to get my 2019s reliable over those early years but both generators have since entered a long period (well over 10 years now) when they have been very reliable apart from a sticky step attenuator on one of them if it doesn't get used often. So I think it is worth persevering and you may find a few more niggles along the way.

Ti Pwun · 2nd Apr 2016, 8:24 am

I think it's the BB809 varicap diode itself but I don't have a replacement I can drop in. I have some on order and I also ordered some BFR91A transistors. I think if I replace both it should be OK. Even though the transistor tested OK on my Atlas tester, I'll change it anyway..

As you say, I have been finding a few dry joint issues along the way and I'm repairing those as I find them so its improving all the time. Hopefully now that annoying, hard to find intermittent connection problem is out of the way, I'll get somewhere.

31st Mar 2016, 7:46 pm	#21
Ti Pwun Heptode Join Date: Aug 2013 Location: Bradford, West Yorkshire, UK. Posts: 888	Re: Marconi 2019A Intermittent RF Output Fault Well, so much for that - started out OK but at 600KHz, I get a fluctuating frequency between 114 and 116KHz. Oh well, back to the drawing board...

1st Apr 2016, 3:13 pm	#22
G0HZU_JMR Dekatron Join Date: Sep 2010 Location: Cheltenham, Gloucestershire, UK. Posts: 3,077	Re: Marconi 2019A Intermittent RF Output Fault Have you checked the DC tuning voltage for VCO 2 to make sure it is still well inside the normal range? If it has reached the edges of the tuning range it will become erratic in terms of lock reliability. Also, I had several VCO failures on the VCOs in both of my 2019s over the first few years I owned them. I had failures due to poor connections, a failed transistor and also a failed ceramic capacitor that went intermittently short circuit. It took me quite a few attempts to get my 2019s reliable over those early years but both generators have since entered a long period (well over 10 years now) when they have been very reliable apart from a sticky step attenuator on one of them if it doesn't get used often. So I think it is worth persevering and you may find a few more niggles along the way. __________________ Regards, Jeremy G0HZU

2nd Apr 2016, 8:24 am	#23
Ti Pwun Heptode Join Date: Aug 2013 Location: Bradford, West Yorkshire, UK. Posts: 888	Re: Marconi 2019A Intermittent RF Output Fault I think it's the BB809 varicap diode itself but I don't have a replacement I can drop in. I have some on order and I also ordered some BFR91A transistors. I think if I replace both it should be OK. Even though the transistor tested OK on my Atlas tester, I'll change it anyway.. As you say, I have been finding a few dry joint issues along the way and I'm repairing those as I find them so its improving all the time. Hopefully now that annoying, hard to find intermittent connection problem is out of the way, I'll get somewhere.