Here’s another classic all-analog AM only portable from the 60’s…this one was recommended to me by a reader who said it was a sleeper among super sensitive receivers. I really appreciate it when readers bring new (and old) radios to my attention. Even if the radio is not a Five Star performer, I have acquired and learned a lot about many models I would have never otherwise known about and many have become favorites of mine. I have long been a fan of Sony’s popular line of Super Sensitive portables and have several of them…now I see Hitachi described the TH-812 as “Super Sensitivity” … I had to see that. The writer thought it was a worthy top-performing radio that I should review and he went a step beyond…he offered me a spare set he had gotten for very cheap price and that was an offer I couldn’t refuse. Plus, this is the first Hitachi radio I’ve had so I was very interested to learn all I could about it. There is almost no information about it on the internet other than from Radiomuseum.org and Beitman’s…I guess it really is a sleeper. I ordered the SAMS Photofact as well.

Description: The Hitachi TH-812 was evidently first available in 1964 although I don’t know how long it was available or how many were sold. It is old school all the way…a 9-transistor design with a tuned RF stage and three gang air variable tuning condenser…the 9^th transistor is a bias regulator in the output stage. It features a 5” ferrite rod of large cross-section, a big slide rule dial, 3 1/2” x 5 ½” (approx.) oval speaker, leather case and gives very long battery life from its 6 D cells. It also has a Battery Saver switch which we’ll discuss later…this was a popular feature in many radios of the era.

Checking It Out: The seller had accurately described one issue with this sample…the leather snaps which hold the back closed were broken off…I eventually used a magnetic latch to keep it closed. I also found a metal piece loose inside which turned out to be a PCB support bracket that had broken loose in shipping…both of its screws were present but its mounting stud which is one of the speaker mounting studs was broken. Luckily the radio can be used just fine without it but when all repairs were done, I glued that broken stud back in place as much for appearance as anything. I also noted some sort of washer stuck behind the dial glass and was curious to see where that came from.

Above: Washer Stuck Behind Dial Glass

After getting further into the radio it seemed it may have previously been worked on and that means you don’t know what you might find. The service manual specifies AM coverage as 530 – 1605 KHz but mine measured 528 – 1685 and that discrepancy, in addition to ruining the dial calibration at the top of the band, is more than I would expect to see as a result of component drift over the years…it seems likely a previous owner may have attempted to increase coverage into the Expanded Band. The first thing I needed to do was to get the radio apart and it was a bit finicky in that regard. To explain, on some of the better radios (including the Zenith I will be comparing it with later) the entire chassis comes out in one piece making disassembly and re-assembly easy. The Hitachi requires either desoldering several connections or risking breaking the several wires connecting the battery box, battery saver switch, speaker and earphone jack with the circuit board. After getting the radio out of the cabinet I ended up lengthening those wires so I didn’t have to desolder them again…even the battery box wires were so short they had to be strained just to change the batteries…now there is enough slack to make this less cumbersome.

Above: Loose Bracket Found Inside Radio & Damaged Speaker Cone

I discovered that the loose washer stuck behind the dial glass was half of a deteriorated rubber grommet. Three of these are used to mount the tuning gang while insulating it electrically from the chassis. Two were crumbling and the third had broken away completely so the tuning gang was dangling loosely…amazingly the radio still seemed to tune pretty normally. I found some rubber grommets and although the ones I got are a bit larger than the originals I was able to squeeze them into position so the tuning gang was now properly mounted and insulated. (Some radios do not insulate the tuning gang this way and I’m not sure what the purpose is…the radio seemed to work either way. I suspect it may affect some stray capacitances near the tuning condenser).

Left: Deteriorated Insulating Grommets – Right: Replacement Grommets

I also discovered a small hole in the speaker cone. It’s likely that the loose mounting bracket did the damage during shipping. Luckily the hole is too small to be a problem…the speaker sounds fine, but to be extra cautious I patched it with some tissue soaked in Aleen’s Tacky Glue.

There was good news too…the electrolytic caps all measured strong and the radio sounded loud and clean so all I needed to do was to align it to specs.

The IF’s were all spot on which was reassuring but the RF adjustments were somewhat off. I had mentioned that as received the AM band topped out at 1685 KHz which was clearly incorrect and the dial calibration was off over the top third of the band as a result. SAMS specifies 1605 KHz as the top end which is lower than the usual 1610-1620 KHz we usually see, and I ended up getting the best overall results using 1620 as the top limit…setting it up this way the dial calibration was virtually perfect across the whole band. Also, since the dial scale is not present with the radio disassembled, I made up a template to be sure dial tracking was good during alignment…a trick I have used with many radios. After alignment reception was reassuringly strong and clean.

Above: Template Used To Check Dial Calibration During Alignment

It was a bit tricky getting the radio back together…it’s tiny non-ferrous screws could not be held using a magnetized screwdriver and the mounting studs didn’t line up with the chassis mounting holes…I risked damaging them but finally managed to bend them a bit closer to where they should be and eventually got it all buttoned up. My best guess is that the case may have slightly warped or changed shape over the years.

Above: Magnetic Latch To Hold Back Closed

Battery Saver Switch: Many radios of that era featured a Battery Saver switch to conserve battery power. I found that the Hitachi circuit was a simple yet clever design which changes a tap on the amplifier’s output transformer to reduce the output power. Using tones to make steady measurements easier I found that the current consumption at a fairly low volume was reduced from 11.7 ma to 10.5 ma…roughly a 10% power reduction. I cranked the volume up until the current draw was 20 ma – that came down to 14.9 ma with the battery saver on…a 25% reduction so it appears that the power savings increases with increasing volume. (I didn’t go higher for fears that the very loud tone might damage the speaker). Yet listening to normal program material the effect was subtle until I cranked the volume quite high…then the switch reduced the output more noticeably…not so much a volume reduction as a difference in clarity. It seems you could leave the switch on and not notice much degradation of performance unless you were playing it quite loudly. Also, note that the earphone jack gets the full speaker output with no attenuation and so can be used to drive an external speaker if desired.

Performance: The Hitachi is a very nice radio and competes well with other radios in its class. I decided to put it against two of my favorites…the Zenith Royal 755M and the less well-known RCA RZG133E Globetrotter, both of which I have reviewed and used for years. These three have a lot in common. All are AM-only, lunchbox-sized, all-analog 8 or 9 transistor designs with tuned RF stages and three gang air variable tuning condensers with vernier tuning. All were made in the 1960’s and feature all discreet transistor designs…no IC’s. As a reality check I also used two reference radios for these comparisons…the venerable Panasonic RF-2200 and a C. Crane CC-3.

Scanning dozens of receivable frequencies on the AM band at midday in a very low noise environment the results were very consistent up and down the band…the TH-812 placed right in the middle between the Zenith, which rates ****1/2 on the AM Mega Shootout and the RCA which rates **** so the Hitachi has to be rated ****1/4 (a new category) which is great performance. Although many stations were received similarly, there were some weaker signals which were obviously clearer and less noisy on the Panasonic and C. Crane which are both ***** radios…no surprise there. And although none of these has the super selectivity of some modern multi-band DSP radios with multiple bandwidths which are needed for hard-core DXers, all are selective enough for the typical AM listening and DXing.  

Above Left: Zenith Royal 755M – Center Hitachi TH-812 – Right RCA RZG133E

For another reality check I next moved the radios to a spot with slightly higher background RFI noise levels typical of many homes today and in that location, it was somewhat harder to discern the differences in the radios. When external noise becomes the limiting factor comparisons are much less revealing. Also, at night with many stronger signals the differences in sensitivity were much less obvious…all of these are great at night bringing in all the skip I would expect.

The Hitachi has pleasing sound quality and fairly powerful audio although a bit more crispness would be nice, perhaps with a tone control – it is the only radio in this group without one.

Conclusion: Any nits aside the TH-812 is a very nice radio and is near the top in this category of lunchbox radios. It easily beat the RCA but was slightly edged out by the Zenith so it ranks ****1/4 on the AM Mega Shootout which is strong performance. It is solid and attractive with a large dial scale and very long battery life. Its earphone/speaker output jack will drive an external speaker directly and being all-analog it has that smooth, natural tuning behavior that makes a radio-lovers’ eyes light up. Holy Grail? No. Very nice radio? Definitely yes.

If you love analog radios find one if you can.

Jay Allen