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

[Kevin Kuehn]

Originally Posted by vortalexfan

They are both set to channel 3 as far as I know. The reason I asked about the frequencies of channel 3 and 4 on my NES vs my converter boxes is because I know that in Japan even though they used NTSC just like we did, their channel frequencies were slightly different than ours were especially on the lower VHF channels like 2-6, the reason I know about this is because I saw the video Shango did on a late 1960s Hitachi Console TV that was originally meant for the Japanese market and when he worked on it he had to use different channel settings to get stuff to come in correctly on it.

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.

[vortalexfan]

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.

Ok, well I wasn't aware of those extra adjustments as my Sam's folder didn't mention those settings (at least not that I was aware of.) Also when I hooked up my NES to the TV which was set to channel 3 the only setting on the tuner that the NES came in at half way decently was when the tuner was set with channel 3 at the 6 o'clock position (3 is facing up) and nowhere else (so my TV has channel 3 at the 6 o'clock position and not at the 12 o'clock position like yours is).

[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

[Electronic M]

The NES, DTV boxes and TV are all US market. The Japanese marker version of the NES (called the Famicom) looks wildly different from the US market version to the point that side by side you wouldn't think in your wildest dreams that they were the same device. Japan also uses an incompatible DTV standard so a Japanese DTV converter wouldn't reciever anything in the USA.

Also Japanese low band VHF channels are off a country mile from US channels. The North American VHF band goes CH2-6(54-88MHz), 88-108MHz FM radio, some public service 2-way stuff, CH7-13(174-216MHz).
The Japanese VHF band went FM radio 76-90MHz (IIRC), CH1-3(90-108MHz), other things, CH4-12 (170-222MHz)...So the lowest frequency overlap would be US ch7 which mostly overlaps Japanese cut and a bit of the top of CH4.

Having seen Japanese VCRs (and owning a recently imported used Japanese domestic market ED-BETAMAX) I can tell you that most Japanese market VCRs and games use Japanese CH1 or 2...Which are both squarely in the US FM band....US CH6 fine tuning MIGHT be able to get japanese CH1 in some cases.

[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!

[vortalexfan]

A little Update: I hooked my B & K 1076 up to the IF Input on the 23" Zenith and I was able to get a weak intermittent IF Signal on the TV and so I twerkulated the IF tubes in their sockets just to see if maybe there was a loose or intermittent connection in the tube sockets and sure enough I wiggled the 6EJ7 3rd IF tube and the IF signal would go in and out intermittently and so I removed the tube (it was the original Zenith badged Telefunken tube) and so I replaced it with a NOS GE 6EJ7 tube and sure enough the IF circuitry woke right up and was producing a nearly perfect picture (except for a little weird issue at the top of the screen, which is I think a vertical issue, but maybe you guys can tell what it is when you look at the pictue I took of the screen on the TV.)

This TV has a really nice bright raster yet which tells me that for sure this was definitely a low hours TV (possibly just used as furniture, or only used on special occasions.)

one thing can't figure out is that the backlight circuitry on this TV for the tuner is kind of intermittent for some reason.

When you first turn on the TV the tuner backlight is dead (isn't glowing) and then after the TV warms up a bit then the backlight comes on and when you "scan" through the channels the pilot light for the UHF tuner won't come on right away when you hit the "UHF" position, I have to smack the side of the TV a little bit and then it comes on.

Any ideas as to what's going on here?

See picture below for a view of what the screen currently looks like on the 23" Zenith.

P.S. I never touched the IF cans in this TV, the picture that this TV is producing right now (as seen in the picture below) is how the IF cans were set when I got the TV.