Information
As the Stereo20 is nearly 60 years old I used Google to search for information relating to circuit diagrams, rebuild issues, testing, etc. I was surprised that there is quite a lot of good information out there. Below I have listed some of the sites I have found very useful....
This youtube video is for a TL12 rebuild but the mechanics and problems are the same. It also shows some techniques for testing.
During the video it highlights the fact that the resistor bodies used in the 50's/60's were significantly larger than those of today. Also the physical length has also changed and new resistors will not, in some parts, reach between the tags. To this end the video recommends modern 2/3 Watt resistors so that they fit but also match the original aesthetic layout of the tagboard. I duly noted this and ordered resistors checking the physical specification. The spec of resistor I chose was 2 Watt with a length of 66mm. When they arrived the overall length was too short by several millimetres. Fortunately resistors are as cheap as chips. I again searched high and low for suitable resistors. After much googling I found a site in America, Digi-Key, and they had what I was looking for with resistor lengths of 73mm. Ordering required a statement of use as per US regulations and delivery was fairly expensive, but they were delivered in 3 days by UPS!. And yes they are perfect both in length and the resistor body size. I will post a photo once the resistors are installed.
This is another rebuild video, this time a TL50.
Another link that has lots of information on Leak products and variants. It appears that Leak produced a Mark2 version. This had a few component changes and, more importantly, different mains and output transformers. I now realised that I had the Mark2 version
Finally this link takes you to a download site. It has a component list which is useful when ordering the components. It also contains lots of other information; in particular circuit diagrams and overlay drawings. NOTE : The circuit diagram relates to the Mark2 version. The previous site has both versions.
If you are looking to renovate a Stereo20 yourself then the above online reading/viewing is recommended.
For a more in depth history of the Stereo20 then Janine Elliots article on HiFiPig is worth a read.