In this case, I replaced the selenium rectifier with a silicon bridge rectifier, since it is always a good idea to do so. I also replaced the two paper electrolytic capacitors on the 7199 tubes with new Nichicons.
Controls and switches were cleaned with Caig DeOxit D5 cleaner. Importantly, I did the following modification, per the well known advice of Jim McShane. There have been some cases where the new production 7591A (and 7868) tubes have had trouble in circuits using a very high value grid resistor - as vintage Scotts, Fishers, and others sometimes do. The best solution is changing. All the grid resistors to 200K-220K from the original value, since often the factory spec resistors exceeded the maximum recommendations.
For instance, Fisher routinely used 330K carbon resistors that would often drift up to 360K over time! To prevent loss of deep bass energy a change of the output coupling cap value to. 1 uf (preferred) is needed. The faceplate looks very good and just has some minor blemishes here and there.
The transformers show no rust. All original knobs are present. Brand new Matched Quad JJ Electronic 7591 output tubes.
(4) 12AX7 front end tubes = all vintage, original GE tubes, testing strong. (2) 7199 = two original HH Scott labeled. (1) 5AR4 = one vintage Russian. From HIFI Engine web site.
Unlike conventional amplifiers that supply their rated power output only in the midrange frequencies, the LK-72 provides a full 40 watt per channel down to 20 cps. Distortion is below 0.8% throughout. The LK-72, like all Scott amplifiers, is completely stable with any type of load or even with no load. The use of an electrolytic aluminum chassis, DC heated preamp tubes, copper shielded power transformers, and carefully filtered power supply insure total hum and noise below 25mV even on phono inputs. A true self-balancing phase splitter eliminates all other adjustments and insures that your LK-72 will exceed its conservative specifications.
The LK-72 is an ideal choice for the finest stereo music systems. Power output: 40 watts per channel into 8? Frequency response: 20Hz to 20kHz.
Total harmonic distortion: 0.8%. Input sensitivity: 3mV (MM), 500mV (line). Tube complement: 4 x 12AX7, 4 x 7591, 2 x 7199, 1 x GZ34. Dimensions: 15.5 x 5.25 x 13.25 inches. Weight: 25 lbs (before packing).This item is in the category "Consumer Electronics\Vintage Electronics\Vintage Audio & Video\Vintage Amplifiers & Tube Amps". The seller is "mesh50" and is located in this country: US. This item can be shipped to United States.