Zenith model R-70 portable radio - chassis number?; three-volt Sony portable

[Jeffhs]

I have a Zenith model R-70 AM/FM transistor portable radio, 1980 vintage, with 11 transistors. I have the service manual, but it doesn't show the chassis number. Did Zenith still use these numbers by 1980 or were they just using a model number by then? I know the earlier Zenith transistor radios all had chassis ID numbers in the format xZTxxxx..., with the first number usually being the transistor count. Going by this, I would guess the chassis number for my R-70 would begin with 11, as in 11ZTxxxx. I'm wondering what the actual chassis number (if indeed there is one) would be. Any information will be appreciated. Thanks in advance.

BTW, my R70 works and sounds great, even with a 4.5-inch speaker; typical Zenith.This portable was built for good sound and RF sensitivity, as it has a push-pull audio output, four IF stages and a ceramic filter on FM, and two IFs plus a ceramic filter on AM. (I wish, however, Zenith had included a switch to defeat the AFC while tuning; as sensitive as this radio is, it can often pull in stations closely spaced on the dial, some of which [the weaker signals] will not be heard because the AFC pulls the tuning towards the stronger signal, locking the radio onto the latter at the expense of the former.)

I was knocked for a loss, however, when I found out shortly after getting the radio (it was an eBay score a couple years ago) that it uses only three C-size batteries; most radios I've seen of this type, including all the transistor portables in my collection except this Zenith and another set I will mention shortly), use either four or six C- or D-cells. Why was the R-70 designed to operate on 4.5 volts, rather than six, nine or twelve volts (the last being the voltage requirement of the Royal 1000 and other older solid-state Zenith Transoceanic portables)? I also have a Sony TFM-7200W AM/FM portable that runs on two D-cells for three volts; I'm wondering how this radio can operate as well as it does on such low voltage. Haven't used it in some time, but the last time I fired it up it sounded great; the only problem was a scratchy volume control. This was also, IMO, a prime example of how transistor radios used to be built before everything went overseas, was outsourced, and now is assembled in a slap-dash manner on an assembly line. My Sony TFM-7200 was built 35 years ago and still works very well, probably almost as well as when it was new; ditto for my Sony MR9700W 17-transistor stereo FM portable of the same vintage. As with Zeniths, they don't make them like that anymore.

[KentTeffeteller]

Hi Jeff,

Your R 70 was likely last of the US made sets or early Korean import. It was made when Zenith was going to PC boards and lower voltage circuitry. It's likely a very fine performer. The last Zenith radios were Korean built. They were still better than average. 73 de K4KT

[Jeffhs]

Originally Posted by KentTeffeteller

Hi Jeff,

Your R 70 was likely last of the US made sets or early Korean import. It was made when Zenith was going to PC boards and lower voltage circuitry. It's likely a very fine performer. The last Zenith radios were Korean built. They were still better than average. 73 de K4KT

Thank you for the information.

My R70 was in fact manufactured in Korea in 1980, as stated in an embossed label on the back cover. The receiver is very solidly constructed and works much better than most AM/FM portables of that era, as I would expect from a radio with four FM intermediate-frequency amplifier stages and a ceramic filter (two IFs and a ceramic filter on AM as well, so the AM performance is also above par even without an AM RF stage ahead of the antenna). It sounds very good as well, even with a 4-inch speaker, but again this is exactly what I would expect from the R70 as it has a push-pull audio output stage.

This radio is, IMHO, truly one of the last (if not in fact the last) high-performance portables from Zenith before the company went out of the radio business for good in the early 1980s. However, I recently learned from Bill Cohn, N9MHT, a former Zenith design engineer (in a reply to one of my posts to the AntiqueRadios.com message board) that Zenith-branded radios were actually manufactured by Lucky Goldstar (LG) beginning in 1974, so the LG era actually began some thirty years before the entire Zenith Radio Corporation (including its television plant) moved their operations to Korea.

73,