The National HRO

HRO power supply

HRO 5T with coil packs before restoration

The HRO receiver started in production at the end of 1934 and appears in various guises and until a few weeks ago I knew nothing about them but having recently repaired my brother in law's set, for which exercise I read the handbook and examined the circuit diagram, I discovered a bit of information and a quick look around the Internet gave me some background. In 50 years I've probably only laid my hands on two. It was very odd then, that before the re-invigorated model left my workbench, a second should join it out of the blue when a customer offered me one for sale. After examining the first model (an ex-military R106 version) I found my purchase to be marked in tiny letters "5T". This must be a later model than the basic version because it has a range of octal valves rather than the older "UX" based set. I need to do some research.
The picture shows a few problems for the restorer. A slow motion dial connected to an Eddystone 40pF tuning condenser (in series with a 30pf beehive trimmer) has been fitted to provide a measure of fine tuning. That will need a hole filling up. The original crackle finish has been thickly repainted with a soft crackle paint and this is in poor condition. The main problem though is the case. I haven't had a good look yet to see why, but the receiver has been fitted with a wrap-round enclosure having a coarse aluminium mesh let into the top. This doesn't look original and was probably fitted because the original case was lost or for some reason was never fitted. A cursory look at the front panel doesn't indicate it to be a rack mount version. The power supply has a "matching" outer case and may conceal an original box underneath (I haven't looked yet). Oh and the original S-meter's been swapped.
I read the other day that an original HRO cost as much as the van it was delivered in ie. between 350 and 400 dollars.
All nine of the standard coils seem to be present with my new acquisition although I heard once that a set of amateur band coils were once supplied. I quite fancy trying the thing out but restoration will have to wait for a lot of inspiration.

See more communications receivers>>