UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Trio 9R-59D receiver problems.

David G4EBT · 20th Jan 2019, 10:05 pm

There are only two components connected to pin 2 (cathode) of V8, namely, C37 and R35, which are in parallel with each other, with one end going to pin 2, the other, to chassis ('ground'). R35 should be 330 Ohms +/- 10%, so if it's between 297 Ohms and 363 Ohms it will be in spec. To check it, with the power off and the set unplugged from the mains, with your multi-meter on the Ohms range if you connect your meter prods as shown in the attached diagram, between pin 2 of V8 and the chassis, if it reads between 297 and 363 Ohms, it's OK. If not, change it with the one that Graham gave you.

There needs to be 6.5V or close to it from pin 2 and chassis. With your meter on the low DC Volts range and set switched on, (and V8 plugged into the socket), and the test prods at the same points as when you checked R35, there should be 6.5V DC. If so, all's fine.

It shouldn't be hard to find which R35 is - there are only two components (C37 & R35)connected to pin 2 of V8. If you're struggling with that, look at the PCB track from pin 2 of V8 and see where it goes. You've already changed C37, both ends of which go to R35. (As R35 is rated at 2 Watts, it might be a small wirewound resistor, looking a bit different from most others).

Incidentally, this is all about ensuring that V8 is working as it should be - it has no bearing on the excessive hum of course, which has yet to be resolved. (Likely culprits: C40/41/42?).

Hope that might rekindle your interest.

20th Jan 2019, 10:05 pm	#106
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,766	Re: Trio 9R-59D receiver problems. There are only two components connected to pin 2 (cathode) of V8, namely, C37 and R35, which are in parallel with each other, with one end going to pin 2, the other, to chassis ('ground'). R35 should be 330 Ohms +/- 10%, so if it's between 297 Ohms and 363 Ohms it will be in spec. To check it, with the power off and the set unplugged from the mains, with your multi-meter on the Ohms range if you connect your meter prods as shown in the attached diagram, between pin 2 of V8 and the chassis, if it reads between 297 and 363 Ohms, it's OK. If not, change it with the one that Graham gave you. There needs to be 6.5V or close to it from pin 2 and chassis. With your meter on the low DC Volts range and set switched on, (and V8 plugged into the socket), and the test prods at the same points as when you checked R35, there should be 6.5V DC. If so, all's fine. It shouldn't be hard to find which R35 is - there are only two components (C37 & R35)connected to pin 2 of V8. If you're struggling with that, look at the PCB track from pin 2 of V8 and see where it goes. You've already changed C37, both ends of which go to R35. (As R35 is rated at 2 Watts, it might be a small wirewound resistor, looking a bit different from most others). Incidentally, this is all about ensuring that V8 is working as it should be - it has no bearing on the excessive hum of course, which has yet to be resolved. (Likely culprits: C40/41/42?). Hope that might rekindle your interest. Attached Thumbnails __________________ David. BVWS Member. G-QRP Club member 1339.