Zenith A3720W1
 

How would I open up the back of this television because there are knobs on the side?

I am also interested in any pdf of the schematics, any brochure with it, and any other paperwork of it.

The side knobs just pry off. There may also be a white knob on the back marked "peak picture". Pry that off too.
The side knobs sometimes are captive so they will just hang off. Dont
forget to remove any wires from the antenna terminal board.
When opened you can get the chassis number. Its usually on a tag
pasted to the HV cage. Its what we go by as a rule.

73 Zeno:smoke:
LFOD !

From the 1970 catalog
A3720W ( walnut) the Raeburn. Also available A3720P in pecan finish.
A cheaper model A3710J in tan cabinet & no dial lights also offered.

The chassis was also used in 14" sets. Chassis built between 1969
& apx 1976, a long run.
16" sets phased out abt 1974 & replaced with 17" solid state sets.
14" models phased out 1976 & replaced with the 13" solid state set.
Later sets had AFC, high focus voltage CRT, Chromacolor CRT &
remote in better models.

73 Zeno:smoke:
LFOD !

I have removed the knobs on the side and now I am stuck on removing the plug.

The plug comes off with the back. It's a deliberate safety feature called a safety interlock - the intention is that you cannot use the TV without the back cover installed, so that you don't get a shock. Pull the back cover off as a whole, and the cord will disconnect itself. Don't try and defeat the interlock and operate the TV without the back cover until you learn what a "hot chassis" is, and how to work on such a set safely.

Nice Zenith btw, I have a very similar one which is the main TV in my house - I've had it for 25 years, it was my first vintage tv, first tv in general, and the reason I signed up for this website. It's capable of a very nice picture when it's working right.

Also don't forget the screws on the bottom of the TV, as well as all those on the back.

So I have cleaned the dust off the chassis and checked if any tubes were not fully in their places. I tries to test the television and this is the result.

Also, is any want the chassis model, it is 12A10C15.

Looks like a bad CRT or video problem. Be sure you didnt knock
any of the plug in transistors loose when dusting.
Also run it for 3-4 hours & see if it slowly gets better. If so
that points to the CRT.

73 Zeno:smoke:
LFOD !

You might be missing luminance.

clean and or check the service switch

Loss of luma can also be heater-cathode short in the CRT. Tapping on the neck will usually show it up.