Vox amplifier dating

The HRO-5TA1 shown in the photo above is a very late example with a production run code of 184.In late-1946, an HRO-6 was produced in a very small production run that used the same numerical designation as the HRO-5A1 production run, 184.When the receiver was in a table top cabinet it was designated as the HRO-5TA1 (rack mounts were HRO-5RA1.) The HRO-5A1 used 12 tubes - two additional tubes were necessary for the noise limiter circuit.Early versions of the HRO-5A1 may be found with the round S-meters, earlier surplus front panels which will have the National HRO-5A1 tag mounted just above the Noise Limiter control and many other minor variations that show that National was still trying to clear out old stock.National offered the WWII version HRO-5 in late-1945 as their new table model receiver.The HRO Senior had evolved through WWII but by the end of the war, it still didn't look very different than the old pre-war receiver.

For 1947, the HRO-7 was introduced and this receiver totally changed the appearance of the black wrinkle finish HRO.The last of the HRO-5A1 receivers will have a square S-meter, cadmium-plated chassis, a stepped-switch Crystal Filter Selectivity control and rubber insulated wire under the chassis in the wiring harness.The late versions of the HRO-5A1 receivers seem to be consistent in construction and use of new parts and components.Internally, a voltage regulator was added and the LO changed to a 6C4 miniature tube.Coil sets were changed to not employ handles for removal and levers were utilized.It appears identical to the HRO-5A1 externally and the only difference between the two receivers is a slight change to the Noise Limiter circuit.It's likely that the actual change in the Noise Limiter is that it was built directly onto the chassis instead of being built on a small chassis that was mounted on top of the receiver chassis.The major changes during the war involved the crystal filter design, the changeover to metal octal tubes, a new non-ventilated cabinet and the use of mostly JAN parts.These late-WWII receivers were designated as the HRO-5 and the HRO-W.Additionally, the graphs and charts were replaced with a linear calibration scale.Although the physical appearance of the HRO-7 changed dramatically, internally most of the updates to the HRO-7 were rather conservative.

Leave a Reply

  1. Live free sexy chat no join 17-Oct-2019 18:07

    The chatline provides live African American phone chat that can be used to connect, converse, and/or date.