1950s or '60s vintage Zenith TVs, Need some info

[dieseljeep]

Originally Posted by Kevin Kuehn

But as far as we know both of those boxes were made for the US market? Right now as I'm typing I'm watching my Bugeye through that same Magnavox converter with the RF output set to ch 4. The only issue I have is these Zeniths buzz with text on the picture, which seems pretty common.

Are you aware of the fine tuning control on the back side of the tuner, and also there's a local oscillator adjustment for each channel that's accessible though the little round hole in the upper back side of the tuner?
If you don't have channel 3 or 4 precisely tuned you could potentially pick up all sorts of noise.

I was trying to find a picture of the VHF tuner.
I remember my Zenith set had a tuner that was unusual in a Zenith.
Maybe, just trying another 5U8 would help.

[Kevin Kuehn]

Now that you mention it my chassis is a 16Z21 which has the alternate VHF tuner shown in Sams page 12, so what I told you about the fine tuning and osc adjustments may not apply to yours. Otherwise schematicly our two chassis are identical as far as I can tell. This tuner almost looks like a standard coil unit with interchangeable channel modules.

[Kevin Kuehn]

OK I'm very sorry for the mix up, but the Sams for your TV doesn't even show my tuner on page 12. I have 2 Sams folders and the Riders all sprawled out for these TV's and it's all gotten just a little disorganized. But I did just look at the Sams for your set and it appears you have a circle of holes in the front side of your tuner that should be your local oscillator adjustments. But I'm going to go study that some more right now.

[Kevin Kuehn]

Does this page 7 match your Sams? Clearly shows the front local oscillator adjustments along with the channel number designations. I would think as long as you've already twerkulated your IF slugs there would be very little harm in trying to fine tune the oscillator adj. associated with either channel 3 or 4. This drawing also explains why your channel positions don't match mine.

https://live.staticflickr.com/65535/...252c2ebc_o.jpg

[vortalexfan]

Originally Posted by Kevin Kuehn

OK I'm very sorry for the mix up, but the Sams for your TV doesn't even show my tuner on page 12. I have 2 Sams folders and the Riders all sprawled out for these TV's and it's all gotten just a little disorganized. But I did just look at the Sams for your set and it appears you have a circle of holes in the front side of your tuner that should be your local oscillator adjustments. But I'm going to go study that some more right now.

My TV is the one covered in Sam's 333-17.

Yes the tuner on my TV has 13 adjustment screws arranged in a circle in front of the tuner that are marked 2-13.

I was thinking I might just see if I can hook the 1076 up to the tuner on my TV via the VHF antenna terminals on the back and then tune in each respective channel on the 1076 and check the tuner adjustments.

I'm just curious but when got this TV and first started working on it the 5BK7 RF tube in the VHF tuner was subbed out years ago apparently with a 4BQ7 tube, and I'm just wondering but could it be possible that someone had to tweak the tuner adjustments when they installed the 4BQ7 tube into the tuner in place of the original 5BK7 tube to get the tuner to function properly with that tube?

[vortalexfan]

Originally Posted by Kevin Kuehn

Now that you mention it my chassis is a 16Z21 which has the alternate VHF tuner shown in Sams page 12, so what I told you about the fine tuning and osc adjustments may not apply to yours. Otherwise schematicly our two chassis are identical as far as I can tell. This tuner almost looks like a standard coil unit with interchangeable channel modules.

Yeah that's definitely a way different tuner than I have in mine, I think yours is a bit earlier than mine as yours appears to be a VHF Only model and mine is the VHF/UHF model.

[vortalexfan]

Originally Posted by vortalexfan

Yeah that's definitely a way different tuner than I have in mine, I think yours is a bit earlier than mine as yours appears to be a VHF Only model and mine is the VHF/UHF model.

A little update, I hooked up the 1076 to the antenna terminals on the TV and sure enough you were right the first time, Channel 3 pointing up to the 12:00 position was indeed the correct position because as soon as I tuned the tuner to that position the 1076 came in loud and clear, it was just a matter of me having the tuner in the wrong position the whole time.

[Kevin Kuehn]

Originally Posted by vortalexfan

A little update, I hooked up the 1076 to the antenna terminals on the TV and sure enough you were right the first time, Channel 3 pointing up to the 12:00 position was indeed the correct position because as soon as I tuned the tuner to that position the 1076 came in loud and clear, it was just a matter of me having the tuner in the wrong position the whole time.

Very interesting. While the 1076 is a great trouble shooting tool, don't go so far as to assume it's an ideal frequency standard. But once you've established what's what, you can fine tune any channels local oscillator to whatever signal source you're wanting to watch. Essentially you're shifting the tuners's mixer IF output to accommodate whatever state of alignment your IF is at. The local oscillator can tune over a broader range, while the IF is optimized for a relatively narrow response.

[jr_tech]

Originally Posted by vortalexfan

A little update, I hooked up the 1076 to the antenna terminals on the TV and sure enough you were right the first time, Channel 3 pointing up to the 12:00 position was indeed the correct position because as soon as I tuned the tuner to that position the 1076 came in loud and clear, it was just a matter of me having the tuner in the wrong position the whole time.

With ch 3 at the 6:00 position, I suspect that ch 9 was at the 12:00 position, so the tv was actually tuned to ch 9. Ch 9 (186-192 mHz) falls in the range of the third harmonic of ch 3 (60-66 mHz), so is likely that the NES has a much stronger third harmonic output than your other devices, (poorer quality modulater).

jr

[vortalexfan]

Originally Posted by jr_tech

With ch 3 at the 6:00 position, I suspect that ch 9 was at the 12:00 position, so the tv was actually tuned to ch 9. Ch 9 (186-192 mHz) falls in the range of the third harmonic of ch 3 (60-66 mHz), so is likely that the NES has a much stronger third harmonic output than your other devices, (poorer quality modulater).

jr

OK, so that exlains why I was able to get the NES to come in so well at the wrong channel (CH. 9 rather than CH. 3.)

It looks like what I need to do is set my converter box and RF Modulator to channel 3 hook them up to the TV antenna input and then fiddle with the local oscillator adjustments for channel 3 until it shows a proper image on the screen and then adjust the fine tuning knob (UHF Tuner Knob) and go from there.

I think other than the channel selector confusion I think we can call the Bugeye TV as good as fixed!

[vortalexfan]

Now onto trying to figure out the Big Zenith!