Hallicrafters Model T-67 Television (1948)

           

           

This lovely 10-inch set was my second Hallicrafters television project. Although it's the same age as my Hallicrafters 505, it represents a definite step up in quality. The T-67 also was easier to restore.

Description

The Hallicrafters T-67 is typical of "doghouse" shaped 10-inch televisions of the late 1940s and early 1950s. Designed for a tabletop or low stand, it measures about 18 by 16 by 20 inches deep. It's heavy for its size, thanks to the transformer type power supply and dual chassis.

The first photo shows the restored television.

Priced at $279.50, this TV cost $80 more than the inexpensive model 505. The wooden cabinet has mahogany veneer. Lettered in gold script over the screen are the words Carnegie Hall Edition.

Like the model 505, this set uses a row of pushbuttons for tuning. Unlike the early 505s and T-54s, however, it does not feature the obsolete channel 1. The rightmost "button" in the bottom row is a rotary fine tuning control.

From left to right, the three large knobs above the tuning buttons control horizontal/vertical, power/contrast, and brightness/volume. It's unusual to have a power knob that also controls contrast, rather than volume, which has become the modern standard. In this respect, the T-67 is a little like my Sparton 1271 and Dominion Electrohome console radios, which pair the power switch with a tone control rather than volume.

Cosmetic Restoration

I bought this set at a local shop for $125 and the price included a spare unused picture tube. It was a one-owner set purchased from a local estate. Here's the TV sitting in my study on the day I brought it home. The cabinet was in fine shape except for a few little scratches and normal wear around the knobs.

The gold-colored bezel surrounding the screen is made of plastic. The thick safety cover is made like an auto window with plastic laminated between glass layers.

The next photo shows the cabinet after I touched up the finish. I gave it a light wipe with mahogany stain to darken the scratches and then briskly rubbed off the excess. Oil-based stain can take days to dry in our humid climate, so I added a little lacquer thinner to promote drying.

Here's an indoor shot of the finished cabinet with chassis installed.

T-67 Electronic Design

The Hallicrafters T-67 is well designed, with intercarrier audio, DC restoration, and automatic gain control (AGC). These features provide improved audio and video, as well as easier tuning, and they were not present in all 1940s TVs. Hallicrafters didn't enjoy great commercial success as a TV maker, but the T-67 compares well to my best 10-inch performers, the DuMont RA-103 and RCA 630TS.

Hallicrafters used this chassis in four different models from 1947-1949. The T-61 had a black bakelite tabletop cabinet with the same profile. Model T-64 came in a tabletop or console wooden cabinet and gave you a choice of 10-inch or 12-inch screen, while model T-69 offered a 15-inch screen in a console wooden cabinet.

The T-67 uses 23 tubes, including the 10BP4 picture tube:

Tube Type Function
V1 6AG5 RF amplifier
V2 6AG5 Mixer
V3 6C4 Oscillator
V4 6AU6 1st video IF amp
V5 6AU6 2nd video IF amp
V6 6AU6 3rd video IF amp
V7 6AU6 4th video IF amp
V8 6AL5 Video detector
V9 6AU6 1st video amplifier
V10 6AQ5 2nd video amplifier
V11 12AU7 Sync sep./DC rest.
V12 6AL5 Sync. discriminator
V13 6SN7GT Horizontal oscillator
V14 6SN7GT Vertical oscillator/amp.
V15 6AU6 Audio IF amplifier
V16 6AL5 FM detector
V17 6AU6 Audio amplifier
V18 6K6GT Audio output
V19 10BP4 Kinescope
V20 6BG6G Horizontal amplifier
V21 1B3GT High-voltage rectifier
V22 5V4G Rectifier scanning
V23 5U4G Low-voltage Rectifier

You can download the complete Sams service manual (set 65, folder 7) from the Early Television Foundation archive.

If I had to fault any part of the T-67 design, it would be the pushbutton channel switches. They have lots of contacts, which may get corroded or dirty, and lots of moving parts, which may wear out, need lubrication, or get bent out of alignment. Mine are in good shape, fortunately, but I wonder how well these held up under heavy use.

Here's a close view of the switch assembly. Channel 4 (third from the end) is selected—pushed in and locked. A vertical rail with notches catches the selected switch slide and locks it. Pushing in any other button releases the previous button and then locks the selected one.

The mechanism is ingenious, but most of the contacts are inaccessible for cleaning unless you use the sloppy method of spraying cleaner over the whole switch and working it repeatedly.

Another weak point is the little tan rubber cushion that keeps each slide from slamming the frame too hard when released. This cushion is clearly visible on the depressed Channel 4 slide. Looking down a little farther, you can see that the cushion is missing from Channel 6. Like many sixty-year old rubber parts, it dried up and fell to pieces.

Pushbutton tuning never became very popular. By the mid-1950s, many better-quality TVs like my RCA CT-100 used turret tuners, which are robust and easier to maintain. Turret types are also more expensive, of course.

Electronic Restoration

This television has two chassis. The smaller rear chassis holds the power supplies and sweep circuitry and the larger front chassis holds the tuner and audio sections.

The two chassis are removed in steps. First, you disconnect four inter-chassis cables and the picture tube anode lead, remove the mounting screws, and slide the rear chassis back.

Before removing the front chassis, you must unscrew the speaker from the top of the cabinet and unplug its cable from the chassis. Be careful not to spear the speaker cone on the mounting screws! Then you can slide the chassis partway out and unplug the speaker cable from its front.

Once the speaker is free, it's easier to remove the chassis completely.

After cleaning the switches and controls and tube pins with DeOxit, I replaced the capacitors in the power/sweep chassis. Here it is before and after recapping.

  

I left one of the old electrolytics in place under the power chassis (disconnected, of course). The new caps fit the space easily and the old case made a convenient anchor for a plastic tie. Elsewhere, I used the original metal clamps from the old caps to secure the new ones. Power-supply capacitors carry high voltage, so it's important to anchor them well and insulate their leads.

I normally replace power-supply electrolytic capacitors before trying out an old television. Sixty-year old electrolytics are invariably bad and turning on the TV before replacing them might ruin the power transformer or other parts.

I then replaced a couple of weak tubes, reconnected the chassis on the workbench, and slowly brought up the power using a variac. To my delight, the TV had a bright picture and great sound. Here's how it looked like at this stage.

The picture had some distortion as well as vertical and horizontal sync problems, but that's expected for a mostly-unrestored TV of this vintage. On the whole, things looked very encouraging!

Next, I replaced the remaining paper and electrolytic capacitors in the tuner chassis. The following photo shows both chassis with new caps in place.

When recapping was finished, I adjusted the picture controls and was pleased with the picture quality. One defect remained, however: a vertical line running down the left half of the screen. In the next photo, it's visible near the news lady's nose.

I queried the rec.antiques.radio+phono newsgroup and learned from TV veterans that this is "Barkhausen interference," caused by unwanted oscillation from the horizontal output tube (in this case, a 6BG6GT). The name refers to similarities in a Barkhausen-Kurtz ultra-high frequency oscillator.

One hallmark of this interference is that it's more prominent with weak stations than strong ones. In reading up on the topic, I learned about other, similar types of interference with amusing names such as "snivets" and "spooks."

The simplest cure for Barkhausen's is to substitute other output tubes until you find one that doesn't oscillate. The 6BG6GT tube is not expensive, so I ordered a new one from Antique Electronic Supply. In the meantime, I happened to attend a swap meet and picked up a used 6BG6GT for a couple of bucks. The used tube didn't cure the problem, but the new one eliminated it completely. Here's the picture minus Barkhausen's.

Another solution is to place a small circular magnet around the output tube and adjust it until the line disappears. Old-timers used spare ion trap magnets for this purpose. My DuMont RA-103 has a small magnet mounted in the back of the high voltage cage for Barkhausen suppression.

Once the interference was cured, several adjustments remained. I adjusted the yoke to make the picture horizontal and touched up the oscillators for each channel to avoid having to fuss with fine tuning every time you change stations. Then I fired up my pattern generator to adjust the picture geometry (height, linearity, and so on).

Now we have a crisp, bright picture.

With a new picture tube, here's a set that you can enjoy even in a brightly lit room. The audio is strong and clear. This is as good as any 62-year old TV gets. The spare 10BP4 will come in handy if I run across another 10-inch TV with a dud picture tube.

Final Thoughts

If only every TV restoration could be this easy! I was lucky to find a well preserved one-owner set that needed little attention other than cleaning the controls and replacing capacitors.

The T-67 is straightforward to work on. The small size makes it easier to manage than a big console. Each of the chassis can be laid on its side for recapping and you won't find any impossible-to-reach components underneath. If you're experienced in restoring other tube devices and you want to try a television, this wouldn't be a bad starter set.

©1995-2017 Philip I. Nelson, all rights reserved