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

space_charged · 18th Jul 2018, 2:03 pm

I think the 770R was "deaf" by modern standards even with a fully working aligned IF strip. I'm sure mine will improve once I've replaced the caps.

I only found the fault when using a wobbulator/scope and working back from the last IF. I found one IFT that didn't have a resonant peak at all! I could screw the core from fully in to actually removing it and the peak didn't change at all! Then when poking round with a soldering iron (for dry joints) it started working again. Seemed to be the heat that provoked it to work - for a while.

Interesting Keith that you have a 770U. As a matter of fact, so do I. When I collected my 770R from the seller, he offered me the 770U for a small additional sum. Its a bit of a "basket case" and I haven't even started restoration. Its main problem is the biscuits. I'm not sure they are all there and any that are there are in poor/rubbish condition. Seems like they fall to bits. Added that, if you think valves are a bit "deaf" at VHF you should hear them (not) at UHF. Once had a valve UHF tuner that was part of a UHF converter for a TV. The tuner was seriously deaf. When I replaced it with a transistor tuner it all sprang to life.

From what others here have said, some versions of the 770R had IFTs with discrete capacitors fitted. The problem I'm seeing may not apply to all 770Rs.

18th Jul 2018, 2:03 pm	#49
space_charged Hexode Join Date: Dec 2014 Location: West Midlands, UK. Posts: 315	Re: IF fault on Eddystone 770R I think the 770R was "deaf" by modern standards even with a fully working aligned IF strip. I'm sure mine will improve once I've replaced the caps. I only found the fault when using a wobbulator/scope and working back from the last IF. I found one IFT that didn't have a resonant peak at all! I could screw the core from fully in to actually removing it and the peak didn't change at all! Then when poking round with a soldering iron (for dry joints) it started working again. Seemed to be the heat that provoked it to work - for a while. Interesting Keith that you have a 770U. As a matter of fact, so do I. When I collected my 770R from the seller, he offered me the 770U for a small additional sum. Its a bit of a "basket case" and I haven't even started restoration. Its main problem is the biscuits. I'm not sure they are all there and any that are there are in poor/rubbish condition. Seems like they fall to bits. Added that, if you think valves are a bit "deaf" at VHF you should hear them (not) at UHF. Once had a valve UHF tuner that was part of a UHF converter for a TV. The tuner was seriously deaf. When I replaced it with a transistor tuner it all sprang to life. From what others here have said, some versions of the 770R had IFTs with discrete capacitors fitted. The problem I'm seeing may not apply to all 770Rs. Last edited by space_charged; 18th Jul 2018 at 2:09 pm.