Zenith Space Command 600 - manual channel adjustment?

[AdamAnt316]

Hello everyone. At my grandparents' house, there sits a vintage Zenith "Space Command Six Hundred" solid-state console TV, chassis 25CC55. I'm guessing it's from the early-mid '70s, though the remote is of the earlier oval button type. Amazingly, it still powers up, though there is little to be received on it due to the digital TV switchover, so I'd like to feed it with a VCR which outputs channel 3 (no channel 3/4 switch on the back). Unfortunately, there is no channel 3 preset in the motorized tuning mechanism, and there seems to be no method of manual tuning on this set. I've tried using the Fine Tuning knob on the presets for channels 2 and 4, but can't get nearly close enough to channel 3 for a clear picture. Is there a way to alter one of the presets to tune channel 3? I looked in the back of the set, and spotted a number of what look like small knobs arranged in a circle on the back of the tuning mechanism. Are these for altering the presets, and if so, how would I use them to alter the selected preset? Thanks in advance!
-Adam

[sampson159]

should be a tab you can turn to eliminate or stop at that channel

[radiotvnut]

That's a '72 model and is one of Zenith's best solid state sets.

[AdamAnt316]

Originally Posted by radiotvnut

That's a '72 model and is one of Zenith's best solid state sets.

Good to know, thanks. I figured it was fairly high-end, but wasn't sure where it sat in their lineup. Has quite a nice cabinet, with hinged double doors to cover the front panel when not in use.

Originally Posted by sampson159

should be a tab you can turn to eliminate or stop at that channel

It's not a matter of where the tuner (which is a horizontal rotating drum with channel number cards in it for the presets) stops, but re-adjusting one of the existing presets for a different channel. There is a neat little meter behind the front panel door to show what channel the selected preset is tuned for. Just need to figure out how to make that meter move.
-Adam

[radiotvnut]

I'm trying to visualize what tuner you have. From what you describe, it sounds like an early version of the single knob varactor tuners that Zenith used from the mid '70's until the mid '80's. The non-remote versions had a single silver channel selector knob and the remote versions had a motorized tuner without the channel selector knob.

Both versions used an 18 position tuner. Channels 2-13 were VHF and positions U1-U6 could be set to whatever UHF channel was needed and the Ux tab could be replaced with the correct channel number. In order to set the channels on those models, you first need to set the channel selector to the desired channel position. Then, set the AFC switch to "off". Then, there is a white knob on the control assembly. Push this knob in and slowly turn the knob until you get the best picture. You might have to turn the knob clockwise or counterclockwise in order to obtain the best picture. Once you have a good picture, turn the AFC switch back on.

If you can show a picture of the control panel of your TV, we can probably more easily help you on this.

[dieseljeep]

Originally Posted by AdamAnt316

Hello everyone. At my grandparents' house, there sits a vintage Zenith "Space Command Six Hundred" solid-state console TV, chassis 25CC55. I'm guessing it's from the early-mid '70s, though the remote is of the earlier oval button type. Amazingly, it still powers up, though there is little to be received on it due to the digital TV switchover, so I'd like to feed it with a VCR which outputs channel 3 (no channel 3/4 switch on the back). Unfortunately, there is no channel 3 preset in the motorized tuning mechanism, and there seems to be no method of manual tuning on this set. I've tried using the Fine Tuning knob on the presets for channels 2 and 4, but can't get nearly close enough to channel 3 for a clear picture. Is there a way to alter one of the presets to tune channel 3? I looked in the back of the set, and spotted a number of what look like small knobs arranged in a circle on the back of the tuning mechanism. Are these for altering the presets, and if so, how would I use them to alter the selected preset? Thanks in advance!
-Adam

The VCR might have a setting in the menu for changing the 3/4 output.

[kx250rider]

If it's an electronic tuner (has a row of channel numbers along the right edge of the mask), it has actually 12 or 14 separate tuners; each one can be set to any channel. There is either a thumb wheel or a small adjustment stem for each channel. Some thumb wheel models had a slide switch to tell it whether you want to set that channel for VHF-lo,VHF-hi, or UHF, and the turn-stem models had an outer ring on each stem to switch bands.

Charles

[andy]

....

[AdamAnt316]

Sorry for the delay in responding; was having issues logging into VK.

Originally Posted by radiotvnut

I'm trying to visualize what tuner you have. From what you describe, it sounds like an early version of the single knob varactor tuners that Zenith used from the mid '70's until the mid '80's. The non-remote versions had a single silver channel selector knob and the remote versions had a motorized tuner without the channel selector knob.

Both versions used an 18 position tuner. Channels 2-13 were VHF and positions U1-U6 could be set to whatever UHF channel was needed and the Ux tab could be replaced with the correct channel number. In order to set the channels on those models, you first need to set the channel selector to the desired channel position. Then, set the AFC switch to "off". Then, there is a white knob on the control assembly. Push this knob in and slowly turn the knob until you get the best picture. You might have to turn the knob clockwise or counterclockwise in order to obtain the best picture. Once you have a good picture, turn the AFC switch back on.

If you can show a picture of the control panel of your TV, we can probably more easily help you on this.

There is a channel select knob, but it just cycles through the presets on the drum without engaging the motor. The tuner in this set appears to allow any preset to carry a VHF or UHF station, as evidenced by the "band select" knob (which isn't marked with positions) and the 2-44-4 channel sequence on the drum. The light for the channel meter turns on or off depending on the setting of said knob (guessing there's a burnt-out bulb or two).

Unfortunately, I was unable to take pictures of this set last time I was there, and it is currently 40 miles away. I'll try and take some photos next time I'm there.

Originally Posted by kx250rider

If it's an electronic tuner (has a row of channel numbers along the right edge of the mask), it has actually 12 or 14 separate tuners; each one can be set to any channel. There is either a thumb wheel or a small adjustment stem for each channel. Some thumb wheel models had a slide switch to tell it whether you want to set that channel for VHF-lo,VHF-hi, or UHF, and the turn-stem models had an outer ring on each stem to switch bands.

This is definitely one of their electromechanical tuners, with the motorized drum holding the presets, and the number cards showing through a little window. There are no thumb wheels, just a single fine tuning knob, and a rotating band select knob which controls the selected preset, so no markings.

Originally Posted by andy

As others have said, set it to channel number 3, and use the fine tuning knob to adjust it to channel 3. If it won't adjust, then there's something wrong with the tuner. The gears that drive the fine tuning pots tended to crack in those, so you might try a different channel slot if #3 doesn't work. Any slot from 2-6 should be able to tune channel 3 with adjustment. I forget if 7-13 cold be tuned low enough.

Hopefully, the fine tuning control is intact. As stated before, any preset seems to be able to be tuned to any channel, so being in the low end probably doesn't matter, though it might help, who knows. I'll give it another shot next time I'm there, and take some photos.
-Adam