UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Rogers Ravensbrook series2 amp. Before attempting a capacitor replacement.

bikerhifinut · 3rd Jul 2020, 2:49 pm

Phew!
Think I may have got to the instability on disc.
The only electrolytics I hadnt replaced were the emitter bypass on the second stage of the disc preamp. All other capacitors were sound looking ceramics or polyester "tropical fish" or the tubular 5% jobs in the RIAA EQ.
So I swapped the electrolytics out, they didn't look to be leaky or even swollen but as they have a very low voltage on them I doubt I would anyway.
A quick hook up to the turntable and speakers and all seems good. A trifle noisy on the 50Hz hum but its still a bare PCB with no path to mains earth until the steel cabinet is back in place. Its also slightly noisy in terms of hiss etc but probably as good as it got in 1970 (No metal film resistors). Anyway I cranked the volume up and the motorboating and hf "Birdies" Had gone. I never realised that a bypass capacitor would have so much effect. Expert explanations will be very gratefully read.
So its concentrated my mind now to replace the lot as if ones gone then its a fair bet there are others about to or already failing.
I'm actually chuffed to bits that the old amp is doing such a good job in a modern audio set up. Father and I always liked the way the Rogers made music, no dramas, no flashing lights, but always pleasant. And a nice reminder at times that New or "Modern" isnt always that much of an advance in terms of grin factor!
These amps are a lot nicer to work on than their Armstrong and Leak contemporaries in my inexpert view, that nice Glassfibre board with well spaced and neat component layout makes it easy to follow and work on. Just don't use too hot an iron desoldering as the tracks will lift if not careful!

Back to the bench.

Andy.

3rd Jul 2020, 2:49 pm	#10
bikerhifinut Octode Join Date: Nov 2013 Location: Penrith, Cumbria, UK Posts: 1,993	Re: Rogers Ravensbrook series2 amp. Before attempting a capacitor replacement. Phew! Think I may have got to the instability on disc. The only electrolytics I hadnt replaced were the emitter bypass on the second stage of the disc preamp. All other capacitors were sound looking ceramics or polyester "tropical fish" or the tubular 5% jobs in the RIAA EQ. So I swapped the electrolytics out, they didn't look to be leaky or even swollen but as they have a very low voltage on them I doubt I would anyway. A quick hook up to the turntable and speakers and all seems good. A trifle noisy on the 50Hz hum but its still a bare PCB with no path to mains earth until the steel cabinet is back in place. Its also slightly noisy in terms of hiss etc but probably as good as it got in 1970 (No metal film resistors). Anyway I cranked the volume up and the motorboating and hf "Birdies" Had gone. I never realised that a bypass capacitor would have so much effect. Expert explanations will be very gratefully read. So its concentrated my mind now to replace the lot as if ones gone then its a fair bet there are others about to or already failing. I'm actually chuffed to bits that the old amp is doing such a good job in a modern audio set up. Father and I always liked the way the Rogers made music, no dramas, no flashing lights, but always pleasant. And a nice reminder at times that New or "Modern" isnt always that much of an advance in terms of grin factor! These amps are a lot nicer to work on than their Armstrong and Leak contemporaries in my inexpert view, that nice Glassfibre board with well spaced and neat component layout makes it easy to follow and work on. Just don't use too hot an iron desoldering as the tracks will lift if not careful! Back to the bench. Andy.