HRO 60

[VK3JM]

Hi Guys,
Have just joined the forum, and it looks like a good one. I have just obtained a HRO 60, the first one I have ever seen. And I have some questions.There is only one coil box with it marked "B" Gen. coverage 7.0 - 14.4 Mc. BS 14.0 - 14.4 Mc. silk screened on the front. Is this a HRO 60 or a HRO 50 box?
The radio is a bit rough on the top of the chassis and the case is scratched a bit, but under the chassis it is almost untouched. I have replaced HV electro's
And fused the HV centre tap. Are coil boxes obtainable? All the caps underneath are red Sangamo 600v and will need to be replaced. High voltage caps are very hard to get here, are they hard to get in the US?
Fred VK3JM

[WQ9E]

Fred,

The HRO-60 is dual conversion on the frequency range from 7 Mhz. up and the HRO-60 coil sets for these ranges will have a third hole in the back of the coil "can" on the far right of the plug-in which activates the dual conversion circuitry.  This third hole is an easy identifier for HRO-60 higher range coils.

The C and below range coils from a HRO-50 will work fine in your HRO-60.  I believe (but have never tried) that HRO-50 coils for the higher frequencies will work OK in your HRO-60 because without the hole in the can your HRO-60 will operate in single conversion.  Of course you wouldn't have the benefit of better image rejection provided by the dual conversion feature if you installed HRO-50 coils.  HRO-60 coils for 7 mhz. up will definitely NOT work in a HRO-50.

I have used E and F coils from the HRO-5 series in my HRO-50 and HRO-60.

Coils do show up on ebay fairly often and the regular A,B,C,D coils are usually pretty reasonable.  The E and F (AM broadcast band) along with the 15 meter bandspread coil are quite a bit more when you find them.

Several National receivers of this era have a .1 cap from one of the rectifier plates to ground.  Either remove this cap or replace it with a modern HV unit designed for AC.  When this cap fails it will take out the power transformer.

HV caps are readily available here, I order everything from Mouser but there are a number of supply houses.  Ebay might be a place to look if availability/shipping are problematic.

[MikeKE0ZUinkcmo]

The HRO-50 coil packs (the upper pic) have their information stamped/filled on the front of each.   The  HRO60 coil packs (lower pic) have a name plate rivited on the front of each.  Kind of a classy addition I think.  

The main difference between the two models were mostly performance enhancements like better image rejection and narrower IF bandwidth, I presume to deal with ever more crowded AM bands, and possibly better SSB performance.   There also were a couple of detail changes in the dial plates, but there wasn't much that showed up on the front panel.

The HRO-60 is in the top ten percent of high performance tube type receivers and I enjoyed mine for many years.  

A bit of a detail about the "switch".   The single/double conversion switch in the HRO60 is actually "activated" when "C" and lower frequency coil packs are used, forcing the receiver into "single conversion" mode.   The switch IS NOT activated when "B" and higher frequency coil packs are used.   This made the HRO-60 backward compatible with earlier models on the lower frequencies.  

There were 13 coilpacks, aside from possibly some single customer specials, for the HRO-60 covering the frequency range from 50KC to 54 Megacycles.   I think thats a broader frequency range than any other receiver of its time.

Removal of the cap Rodger mentioned is VERY important as its a power transformer KILLER.