Zenith Space Command fine tuner - Videokarma.org TV - Video

Carmine · #1 01-01-2010, 06:35 AM

Happy New Year all!

I spent a little time last year (yesterday) working on the Zenith emperor that Doug gave me. As he mentioned, the set is full of hack repairs (capacitors soldered to chassis test points, wires cut and twisted together, etc.).

One of the first problems I need to address is the inability to use the fine tuner. It appears that you are supposed to push-in and turn a small knob. Pushing in the knob moves a lever which engages a gearshaft to turn the tuning coil.

However after removing the tuner, I can only see a how the lever engages, but there is no way to turn the actual gearshaft (coil).

I find no evidence of a missing part (i.e. a witness mark on a shaft where another gear might have been) and see no obviously broken parts.

So what's wrong here? Never had a Space Command 600, so I'm not familiar with the tuning set-up.

Adam · #2 01-01-2010, 10:42 AM

If this is like the tuner on my color Zenith, it's missing a small rubber belt, see pic here: http://www.videokarma.org/attachment...1&d=1256920009

Carmine · #3 01-01-2010, 03:05 PM

Thank you Adam! I'd never seen a belt used for fine tune before, so i assumed I was missing a gear. I'll go down to my local Zenith store and I'm sure they'll have a replacement belt.

Barring that, I'll try to find a rubber band that will do the job.

Carmine · #4 01-02-2010, 09:56 AM

Huh... I went down to the local Zenith shop to purchase the fine-tuner belt, which I assumed they'd have behind the counter with their boxes of 6DJ6s and NOS metal-cone CRTs, and found the shop had been replaced with a Korean Nail salon. (They could not help me, but suggested I junk the set and replace it with a Samsung flatscreen)

Thus necessity is the mother of invention...

and we are back in the fine-tuning business...

almost ready for Star-Trek, as long as you can live without luxuries like the color "blue"...

drh4683 · #5 01-02-2010, 10:47 AM

Chris,

The belt that zenith originally used is nothing more than an o-ring. For anyone curious, the original zenith fine tuner o-ring is p/n is 32-46. I'm sure the original belt is on the bottom of the cabinet under the tuner area. The aged belt develops a crack and just falls off when someone attempts to fine tune the set. It probably broke when you were adjusting it, as I doubt that TV was touched in the last 20 years! I just buy a few from the local ACE hardware, you'll need a #20, which is 1-3/16 x 1 x3/32". If you want to get some strange looks at the hardware store, you can always bring the tuner assembly in with you so you can make sure it works OK. The employees will ask if you need help and they'll see you carrying this "thing" around with you and they'll wonder what you're doing. That might be a good opportunity for someone to advise you that we made the switch to digital television and that you should just get rid of the old TV you're trying to fix....

Zenith used the o-ring as its essentially eliminates any backlash in the fine tuning. Also, be sure to check the actual gear that engages on the channel strip. The nylon gear is pressed over a serrated shaft, 9 times out of 10, the gear develops a hairline crack down one of the splines and the gear slips on the shaft making fine tuning either impossible or intermittent. Just turn the fine tuner and watch to see if if you can spot the crack. I remove the entire assembly, which is very simple, pull the gear off, add a little drop of super glue to the shaft and push the gear on and give it a quick turn so it sets up. Problem solved. In the pics, this is a different zenith actuator, but the nylon gear Im pointing to is exactly the same on belt drive types.