The Trio 9R4 series receivers

W9RAN Comment:  In this blog entry, Masa discusses the first Trio receiver, model 9R4 and its successors.   This is one of the few Japanese receivers that is familiar to US hams because a later version was imported and sold well in the US by Lafayette Radio Electronics as the HE-10 or KT-200 if it was sold in kit form.   

 
These receivers look like a Hallicrafters S-38 but as the saying goes, appearances can be deceiving.   The S-38 is basically an All-American Five AC/DC five-tube superhet with a bandswitch to cover shortwave bands that was the bottom of the line for Hallicrafters.   The 9R4 is a much better receiver, incorporating a transformer-isolated power supply and using 9 tubes.    It has a real BFO, and S-meter, and even a Q-multiplier built-in.   What I learned from information Masa provided is that the earliest models did not include a speaker or output transformer!    These had to be provided by the user and that meant that B+ was exposed on the transformer primary, somewhat offsetting the improved safety provided by the power transformer.   Later models including the one sold by Lafayette did include the transformer, requiring only an external 4-8 ohm speaker which was commonly the case.

Masa discusses one of the Lafayette-branded versions he found at the Peoria hamfest a few years ago and after replacing one burnt-out input coil has it on the air with his other vintage US and Japan-made vintage equipment.

The Trio 9R4 Series Receivers

9R-4 is one of the very first receivers that Trio manufactured.  In fact, the company Kasuga Musen (Kasuga Wireless) had just changed its name to TRIO at that time.  9R--4 was made in 1954 along its modified version of 9R-42, which had better band spread for amateur radio use, otherwise it was a good general coverage MW to SW receiver.     Notice that Trio closely duplicated the Hallicrafters dial:

Trio was good at making so called "Coil pack unit" that made it easy for band switching. A band covers 550kc to 1600kc, B band covers 1.6Mc to 4.8Mc, C band covers 4.8Mc to 14.5Mc, and D band covers 10.5Mc to 30Mc.  A.B.C.D each band switches all of RF, IF and OSC coils flawlessly. 

Once it is aligned, there is not much fiddling needed during the operation. It is noted that the development of these coil packs contributed to home brewer of receivers regardless of TRIO brand products. The company continued offering these coil packs till late 60s. 

9R-4 and 9R-42 are later modified and refined as 9R4J and 9R42J.  9R-4J is the one US ham radio operators and SWLers are familiar with under Lafayette brand.  It is interesting that its predecessor 6R-4S was complete unit with audio output transformer, but 9R-4 and 9R-42 did not have audio output transformer. Transformer was added only after 9R-4J and 9R-42J series.  These most recent models used MT tube except rectifier tube. Early version used all octal tubes.  BFO was added only after J series.    When working on Trio or other Japan-made radios, US hams will find some components that look differently:

Another Japanese manufacturer, Delica (Mita Musen), also copied the styling of the Hallicrafters S-38 with their CS-7 receiver which is shown (along with other JA-land gear) in an ad from CQ Ham Radio magazine from Dec. 1961.

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