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

snowman_al · 29th Jun 2022, 1:36 pm

Some of you may have seen this on Pinkfish already.

I always fancied an American Scott amplifier.
The HH Scott LK48 is the kit version of the Scott 222D. Circuit here: http://hhscott.com/pdf/fs/LK48B_C1.JPG

This one came in very good condition physically with the correct knobs and decent case etc.. Who ever constructed it originally did an excellent job to.
But one output transformer was open primary... Off to Ed for a rewind.

I read all the US sites with 'do this', 'change that' etc. most of it unnecessary in this case. I've replaced most of the coupling caps, but the originals were fine in value and leakage. I very carefully monitored the electrolytics for days, all good. A few resistors had drifted high so the got replaced and the bias rectifier (selenium) was poorly so that got repacked with 4 silicon diodes.

The valves were all original apart from a couple of odd ECF82s replaced with US 6U8s, but the four 7189 outputs needed replacement to set and balance the bias properly.

And it is huge and weighs 17 kilo grams!

Alan

Album here; ****************/album/vZdP16

29th Jun 2022, 1:36 pm	#1
snowman_al Octode Join Date: Dec 2018 Location: Llandeilo, West Wales, UK. Posts: 1,092	HH Scott LK48 restoration Some of you may have seen this on Pinkfish already. I always fancied an American Scott amplifier. The HH Scott LK48 is the kit version of the Scott 222D. Circuit here: http://hhscott.com/pdf/fs/LK48B_C1.JPG This one came in very good condition physically with the correct knobs and decent case etc.. Who ever constructed it originally did an excellent job to. But one output transformer was open primary... Off to Ed for a rewind. I read all the US sites with 'do this', 'change that' etc. most of it unnecessary in this case. I've replaced most of the coupling caps, but the originals were fine in value and leakage. I very carefully monitored the electrolytics for days, all good. A few resistors had drifted high so the got replaced and the bias rectifier (selenium) was poorly so that got repacked with 4 silicon diodes. The valves were all original apart from a couple of odd ECF82s replaced with US 6U8s, but the four 7189 outputs needed replacement to set and balance the bias properly. And it is huge and weighs 17 kilo grams! Alan Album here; ****************/album/vZdP16 Attached Thumbnails __________________ Never Leave Well Enough Alone...