Restoring a 1949 General Electric 806 Table Model Television
November 2018 Restoration
UPDATE November 2018
1. THE PROBLEM: The picture above shows how unstable the picture is. Adjusting the contrast affects the video gain so it was very hard to get a picture like the one above. Suspect DC restore and video gain problems causing sync loss.I really needed to find the correct schematic diagram for this set and stay with that one. When I first worked on this set, I had problems with the version and worse, the SAMS Photofact, John Rider and Supreme Most Often Needed all had different schematics for my version ( T version as stamped on the chassis). When I first restored, I kept going between the three and replace capacitor values based on different schematics (NOT GOOD!). Finally concluded that the Supreme (Beitman) Most Often Needed Television Service Diagrams was the ONLY correct version.
RIGHT: That 2.2 megohm rewire helped alot!
4. With the vertical and horizontal easier to adjust and lock in, I decided to touch up the video IF to make the sync stiffer. However the picture was never stable for any length of time. I started to check tubes. The tubes I originally had installed were good on my Hickok 600 Tube tester, but after swapping out some of the IF tubes there was a noticeable gain difference, so I put in a new set of tubes. There was some improvement. I then replaced the 6AU6 Limiter Amp tube, which suspected the least.. Put a new one in and everything locked in. Solid sync and excellent contrast.
Turned out that the low 1st Video Amp plate bias is on the same line (+145 VDC) as the Limiter Amp cathode. This may have affected the bias.
Decided to iron out picture instability problems that plague this set, from past restoration. The complex network of "tag" boards make this TV difficult to service. In addition the rubber bezel I reinstalled was crooked and needs to be realigned.
2. With an oscilloscope I found that the video detector to 1st Video Amplifier grid was low as well as the bias to the plate of the Ist Video Amp (12AT7) tube. Video signal well under 2 Vpp and plate bias was around 70 instead of 100 VDC
Word of Warning
Since the GE 806 is a transformerless TV set, beware of the possible hot chassis if the plug is inserted the wrong way. When I was using an oscilloscope the ground lead of the probe is connected to the power company ground or true ground. As I started to probe the set, the house breaker went out, indicating a short, when I reverse the plug everything is fine. When testing this set take an AC voltage check between true ground and the set's chassis or floating ground. If you get 117 VAC connect the plug the other way. On my set I will be installing a polarized plug and the AC interlock on the set I will only allow it to be in the ground safe position.
A problem I found while checking the drawings was that a 2.2 megohm grid bias resistor for the Sync and Clipper tube was incorrectly installed, possibly by me, when I unwisely changed capacitors due to schematic problems. Corrected that and installed capacitors to original values.
3. Fired up the set and got a more stable picture but still touchy on contrast. I tuned the oscillator and got no improvement, so there was still a problem. Definitely on the right track
4a. Solid picture showing Charlie's Angels. There is a white vertical line on the left side of the picture, indicating transient suppression failure problem.
FABRICATE A BACK COVER
As with most vintage TV's the back cover is missing. I was able to find a picture of one. Back in 2015 when I first restored the set, I made the back cover out of press board and since the TV was not working well I stopped until now.
I drilled the vent holes and the made the rear control, antenna and AC cutouts and painted the back with a flat walnut color.
The next challenge was the lettering, I bought a set of word and letter rub ons years ago and luckily saved them. I was able to transfer the correct words and letters to the back cover and it made it look pretty professional. I then sealed it with oil base polyurethane spray giving it a nice standout look.
Add polarized plug to minimize the HOT chassis
GE actually connected the source and return lines correctly. However the plug is not polarized so one can still get an high voltage electric shock. Without making a modification on the AC chassis connector, I decided to ID the AC return side of the connector.
I used a cord with a polarized plug (wide blade) and connected the wide blade wire to the return side of the marked connector.
White line on left side:
According to tv servicing books such as "Mandhl's Television Servicing" by Matthew Mandhl, this is caused by transient oscillations when the damper circuit fails to suppress the transient oscillation cause by the kickback of the horizontal sweep. I changed the 25W4GT with a new one and no affect. The resistor checks good but there are two very low value mica caps, that are rated a 1000 V and are difficult to find. I let it go until another time. At least I can watch the TV comfortably now.
Restoration Comments and Final Checkout
Restoration Comments and Final Checkout
I made a short video summarizing this restoration>>>
1949 GE 806 Table Top TV_xvid.aviGo Back to Restoring 1949 a GE 806 Television: Page 1 GE 806 RESTORE