UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Hallicrafters SX-43 2nd I.F. won't peak

turretslug · 21st Oct 2020, 2:36 pm

I had just this scenario when aligning the IF of an Eddystone 670A a wee while back- all the cores were well recessed down and one in particular showed soggy and indeterminate change when rocked either side of existing setting, almost as far down as it could go. Starting from scratch and winding the cores right back out quickly gave definite peaks with all cores much further out than previously, on-air use confirmed good gain and satisfactory bandwidth. (The output valve's 220 ohm cathode resistor had also been changed to 100 ohms- presumably the previous owner was disappointed that UL41s weren't being consumed fast enough- and they'd managed to defeat the inner-chassis-to-outer-metal-case isolation in not one but two places.... Never be too surprised at what has been done to something that's been around for a few decades).

21st Oct 2020, 2:36 pm	#29
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,395	Re: Hallicrafters SX-43 2nd I.F. won't peak I had just this scenario when aligning the IF of an Eddystone 670A a wee while back- all the cores were well recessed down and one in particular showed soggy and indeterminate change when rocked either side of existing setting, almost as far down as it could go. Starting from scratch and winding the cores right back out quickly gave definite peaks with all cores much further out than previously, on-air use confirmed good gain and satisfactory bandwidth. (The output valve's 220 ohm cathode resistor had also been changed to 100 ohms- presumably the previous owner was disappointed that UL41s weren't being consumed fast enough- and they'd managed to defeat the inner-chassis-to-outer-metal-case isolation in not one but two places.... Never be too surprised at what has been done to something that's been around for a few decades).