Splitdorf R-500 Receiver

 

  I bought this early American receiver on the spur of the moment. It was very old, very large and very cheap. When it arrived it turned out to be a huge restoration project, if I ever attempted it, that is. It was made in 1925 and someone seems to have started its restoration but didn't get very far.

It's so big at about 30 inches wide, I had to stand on a stepladder to take pictures.

 

 

 
 The chassis is a large piece of ebonite. There are two very solid interstage transformers and these were loose inside. The chassis has been broken and then glued back together. I suspect the set was perhaps shipped from the USA and suffered a bump. The g-forces from the bump caused the left hand transformer to break the chassis and probably a number of thinner ebonite pieces, such as the coil mountings.

 

 
 Another view shows the three tuning condensers, and a pair of rheostats. The American designs usually didn't employ reaction (positive feedback to increase the overall gain) but used more valves to produce the desired output volume. Mr Marconi wasn't able to extract his stealth tax on US manufacturers so to get more gain they just added an extra valve or two. In the UK every valve attracted the Marconi tax but not so in the US where valves were very cheap anyway. This receiver was originally equipped with a set of five triodes on UX4 bases, probably the UX199.

 
 

 

 On the right is a picture of one of the two identical transformers that came with the set looking more modern than its UK cousins of the same date. Both these SM220 transformers have windings measuring 3Kohm & 9Kohm so will be servicable

Below, the label fixed to the chassis with model name and serial number, and the maker's nameplate on the front panel.

 

 

 

Now some close-ups of the Chinese style decoration on the doors and sides of the set. Presumably sunlight has caused the paint damage and makes restoration of the case as difficult as restoration of the contents.

 

 

 

 

 Below is the circuit diagram of the Splitdorf R-200 which is probably identical to that of my R-500.

This has the same number of valves, transformers, rheostats, tuning condensers and coils.

My receiver has a small collection of loose parts which includes a pair of fixed condensers.
 

 Because this old receiver has no reaction circuitry and caters for only medium waves, the restoration should be relatively straightforward.

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