Hello All,
I'll start off by saying that I am a newbie here, and although I am a student of electrical engineering, I will readily admit that I have relatively little knowledge about what I am working with here.

I recently came across an old 16" Zenith Chromacolor at a local tech dump, and I figured it would be a good idea to run it past some folks with a bit of knowledge on the subject of vintage televisions before something potentially worth saving got trashed. If it is a set of any value, my eventual goal is to test the set to see if it is still working and then work to find a home for it.

In terms of initial impressions, I would be tempted to say that the condition was decent, were it not for some strong indications that it came from a smoking environment. That said, looking in back, all the parts and original tubes seem to be there, so I would give it a reasonable chance that there is still some life left in it. I plan on putting it up on a variac and giving it a slow start up over the weekend. Assuming I can get it to at least turn on, though, how would you folks recommend I test the picture/reception? Are there any analog stations that I might be able to pick up these days?

Furthermore, regardless of whether I can get it working, is it even worth saving at all, even for parts? Basically speaking, what should I do with this now that I have it? Sadly, although the history and design of old tech fascinates me, I really don't have the room to hold onto something like this, so unless I can find a suitable home for it, I will be forced to take it back to the dump.

Any information or advice you might be able to give me, no matter how basic it might seem, would be greatly appreciated. Especially with regards to testing, any advice you might be able to give so that I can minimize the risk of damaging the set would be invaluable.

http://i1084.photobucket.com/albums/j410/jlny1/IMG_7366_zps006490ad.jpg

http://i1084.photobucket.com/albums/j410/jlny1/IMG_7370_zps4efdb6f4.jpg

http://i1084.photobucket.com/albums/j410/jlny1/IMG_7371_zps9bc0a9c1.jpg

Hello and welcome to VK!

That is a very cool find, color portables from this era are hard to find in good condition.
What size screen is it? can't tell perspective from the Photo but I'm guessing 14"-15"?
It's new enough that I would probably just plug it in and see if it works, watching closely for smoke.

Since you have a Variac available to you then that would be a wiser choice but you don't need to spend the whole weekend bringing it up, 30 minutes would be more than enough. I monitor the amperage as I ramp up the voltage and as long as it stays below an amp or two I just keep cranking it up until I hit 115.

Being a Zenith from the 60's I would guess it'll at least turn on and give a raster.

Please don't return it to the dump, if you decide you don't want it I have no doubt someone here would be happy to take it off your hands!

Eric,
Thanks for the quick reply. It is a 16" screen. I wasn't actually planning on taking the entire weekend to bring it up so much as I was stating that the weekend was when I would have time to do it. I'll probably ramp it up over an hour or two, just to be safe.

If this is something that people might want, though, I will definitely consider passing it along to one of the members here at some future date. The entire reason I pulled it out was on the hope that someone might want it.

Nice find and I think this one is from around '73-'74. If it were mine, I'd fire it up at full line voltage. Being a Zenith, it could very well still work just fine.

Welcome from a fellow EE student.

I've got one of the CCI consoles running right now, and it has been a daily driver set for around 5 years. They are great sets, well worth saving from the dump. There is not a whole lot of collector value for them though. You can probably get 10-50$ for it depending on condition, who wants it and who is close.

As for signals there are options. There may be analog LP stations near you, but if not DTV converter boxes, cable/sat boxes with RF outputs, VCRs, DVD players and older video game consoles all are potential signal sources for your set.

If no body else steps up to the plate I might just give that set a home(I have a big soft spot for Zenith products).

BTW what is the set next to it?

Be a shame to dump it, portables seem to be rare probably
cause there easy to get rid of. Also this one is a chromacolor CRT
& has high focus voltage like large sets. Probably a C or D
line set, apx 72-73. Replaced by a 17" solid state in '74.

73 Zeno:smoke:

its a zenith so its plug and play!those were some fine sets and the picture was always the best in class.great find

being a zenith portable from the 1960's makes it rare, I have not seen one locally in years. You should have no problem finding a home for it from someone here.

...

Welcome from a fellow EE student.

I've got one of the CCI consoles running right now, and it has been a daily driver set for around 5 years. They are great sets, well worth saving from the dump. There is not a whole lot of collector value for them though. You can probably get 10-50$ for it depending on condition, who wants it and who is close.

As for signals there are options. There may be analog LP stations near you, but if not DTV converter boxes, cable/sat boxes with RF outputs, VCRs, DVD players and older video game consoles all are potential signal sources for your set.

If no body else steps up to the plate I might just give that set a home(I have a big soft spot for Zenith products).

BTW what is the set next to it?

That's the back cover from the set! :yes:
I have one like it in my stash. IIRC, it originally came from Doug. :thmbsp:

Not being an EE but a broadcaster for 44 years it might be educational to see what came before current EE thinking in this small plastic box full of lead solder, glass enclosed amplifiers just above the diode level, RF signals that magically become analog voltage signals, the division of those signals to sound and picture, a brute force voltage via capicitance to make an electron beam, the ratios of time and frequency to make a scanned picture in a particular ratio, color suddenly worms it's way in to the signal, and a view of it's little place in American design. A great well-rounded education on television...then, not now.

Please keep it and learn from it. It ain't that big. We all have worse problems with our wooden box console sets. You are already most of the way there with the screen name of Diode which is already friendly to us and we are in your corner. And we are looking for an EE to make our miserable flat-screens better. Back to the basics?

An update on the set: I cranked it up on a variac over the course of a couple hours and it seems to be working great.

Sadly, unable to pick up any analog stations, and lacking anything that outputs analog video at RF, all I was able to display was snow. (it doesn't have an F-connector, so I am not exactly sure how I would input it anyway, except to maybe strap an antenna to the video source somehow). I am considering making some kind of frequency modulated transmitter and using an RCA output as the modulation signal so as to get a video signal to the antenna, but perhaps there is some easier solution I am missing here?

http://i1084.photobucket.com/albums/j410/jlny1/IMG_7374_zpsd6c91ee2.jpg

wally world and radio shack both sell cheap RF modulators that can take a composite video signal and output to channel 3 or 4. Then you need an composite video source, most DVD player still have that (video, audio L and R).

Or if you can find an older DVD player they had the RF out again to 3 and 4, thrift stores often have them for 5-10$

Or you can use one of the digital boxes sold during the change to digital (think it was 2009). Ebay/cragslist and may even still find them at places like radio shack, but not cheap (50$+ IIRC). These were often poorly made so I would not spend a lot of money on one. with these you need some kind of antenna, a cheap rabbit ears will work if you are near a large city.

you need a balun to convert from 300ohm to 75ohm (I am presuming the set has a 300ohm antenna connection) and some coax to hook up from what ever the device used to the set.

Baluns of the type needed to connect the set to coax can be had at radio shack for ~5$.

I have one of these, but mine is the remote control version. I got it in about 1994 and have used it ever since... Mine was made in 1973. I love the TV, it makes an excellent picture, and if I had to get rid of all of my televisions except for one, this would be the one I would keep! It responds well to a decent RF modulator and a signal from a DVD. The tubes in the tuner can be replaced if the picture is a bit fuzzy. Once you get a signal to it the condition can be evaluated. I am also an EE, I picked up my Zenith as a young teen and it taught me a lot about how TV works. I watch it daily.

Don't bother to make an RF modulator - too hard considering you can buy one at radio shack

http://www.radioshack.com/product/index.jsp?productId=2103095

The "balun" you need to put a signal to the input is this

http://www.radioshack.com/product/index.jsp?productId=2062049

Get a short length of coax as a jumper between the modulator and the balun, connect the balun to the "VHF" terminals, set the TV to channel 3 or 4, and feed a composite video and line level audio signal into your RF modulator.

For now don't put a lot of effort into cleaning the chassis beside using a vacuum with a soft brush to get the dust out. I have had good luck cleaning plastic with aerosol microwave oven cleaner, and the screen of course can be cleaned with windex.

GOOD LUCK and hope you keep it, someone needs to hold the torch for the old TV hobby heading into the future. also this is a "hot chassis" TV, so be sure to read up on what that means and how to deal with it before attempting to operate it without the back cover!

This is a great TV. It's a 14DC15 chassis, introduced in 1973 and last offered in 1975. The '75 models I've seen were all produced sometime in 1974 however, I've yet to find a 14DC15 built in '75. That being said, this would be the last of the "mostly tube" hybrid chassis, while the legendary 4 tube hybrid would remain as Zenith's very last tube chassis in production until mid 1975. The model# of your set is either D3721 (1973), E3721 (1974) or F3721 (1975), all being identical in every way except for the model number prefix which designated the model year. The marketing name for this set was called the "Hals" and it was Zenith's lower end "economy" model TV. A step up would be a 14DC16 chassis which would have had AFC or in some cases, Space Command 100 remote control. I have this exact same set in my collection that I've had for years. I used to find so many of these back in the early to mid 90's and they are almost impossible to find now. You are fortunate to have found this for it's a great example of a quality tube type zenith TV in a small package.

It looks like it has much potential here. Looks like you need to adjust the color killer control so the colored snow *just* disappears. The color killer is on the back of the chassis. It's also a hot chassis. A cost cutting move which also resulted in the added benefit of weight reduction by removing the power transformer. As a result, the chassis can either be hot or neutral depending on which way you plug the set into the mains voltage. If you work on the set with the back removed and plugged in, be sure that the chassis is on the neutral leg of the 120v mains, otherwise you could be in for a surprise if you touch something and you are grounded.

You can buy an HLLY 50 mw TV transmitter on ebay, just input a composite video source from the output of a DVD to DTV converter and transmit on essentially any TV channel between 2-83. A great accessory so you can enjoy the old TV's without the mess of wires and cables hooked up to the set.

All,
After a long delay, I finally got around to ordering an RF modulator and a 75-to-300 ohm balun. I fired it up with a video source, and the sound and picture are pretty good! I haven't messed with too many of the settings yet, but for the moment it seems to have a bit of a greenish tint, even after I adjusted the front tint adjustment. Also, for some reason, the picture does not seem to be as sharp as other televisions I compared it with (including other CRTs-- see below).

I can probably fiddle with the rear color balance adjusts to get rid of the green, but the sharpness adjustment did not seem to affect the fuzziness in the picture. Would the "focus" adjustment help with this? If I understand Maxhifi's comment, changing out the tubes in the tuner may be required, or was the "fuzziness" he was referring to was more with regards to static and snow? I have played around quite a bit with the adjustments for oscilloscope CRTs, so I get the general theory here, but a television picture is quite a bit more complex than an O-scope trace, so I'm not entirely sure.

http://i1084.photobucket.com/albums/j410/jlny1/IMG_7503_zps8c01023c.jpg

http://i1084.photobucket.com/albums/j410/jlny1/IMG_7494_zpse460a11f.jpg

I apologize for the abysmal lighting in this room as well as my poor photography. For anyone curious, the television in back is an 18" Hitachi, circa 1980's-- not even old by your standards, but even so, I am happy to report that after about 30 years it remains in near-daily use. More to the point, you can see that the picture on both of these sets is quite a bit sharper than the Zenith (compare the news logos in the bottom right corners).

Also, to follow up on drh4683's comment, I found some faded numbers labeling it as "F3721L", so I would assume that it is a '75 model.

Thanks for all the info you guys have given me on this. It is amazing how knowledgeable you folks are about this! On an unrelated note, do any of you know where/if I might be able to find schematics for this? I have a basic knowledge about the general principles behind CRT's, NTSC scanning and all that, but it would be interesting to learn more precisely what makes something like this tick, preferably without having to tear apart and reverse-engineer a perfectly working set like this one. With tube circuits especially, it is fascinating to see how much designers are able to do with such a small number of active components.

if you turn the color control fully CCW so you have a B&W pic, is the green still there? if you get a good B&W and the issue is not enough tint range (but it is working just not enough range) then you likely need a a slight tweak of the burst detector transformer. I just went thru this on a CTC-12 (had some issues with color in general, replaced the burst amp tube and suddenly the tint was too green. I could have tried another tube but instead I opted t tweak the that transformer.

So you could try some tube swaps 1st (burst amp, or other tube that is in the color circuit that controls the 3.58 mhz osc) or tweak the correct coil. The tweaking should not be done unless you know which coil to tweak which would require a schematic to make sence of it. Never just start tweaking with out knowledge of the circuit and are sure what should be done.

If the black and white image is tinted it means that you need to balance the drive and G2 adjustments for proper monochrome.

Google Sam's schematic. Their sits will allow you to search your sets model and or chassis number. Don't buy the print from sam's if a local library has them it will be much cheaper to photocopy. I also have some Zenith factory manuals coming in the mail so I may be able to give you a copy if your chassis is in the manuals I'm getting.

What a great find you have. I thought these were gone after 1973! I have a 1972 13" Zenith with a very similar Chassis #14CC15 and it looks about the same using a DTV converter box. I'm interested in what you find gets the color improved.

All,
Turning down the color does not leave any noticeable tint. the problem does seem to be that the tint does not have enough range (it is turned all the way CCW, and it is still a bit green). So what exactly is this burst detector transformer? what would it look like? If it is something that can be easily adjusted, I would hazard an attempt at it, although I agree that I wouldn't feel comfortable doing anything more involved without a schematic.

I looked at that Sam's website you mentioned, although I don't know how I feel about paying $22 for a manual for a TV that I got for free... I also don't have much in the way of spare tubes on hand (a single 12AU7), so that is also not an option for the immediate future. If drh4683 is correct in stating that it is a 14DC15 chassis, would anyone here have schematics which could be scanned? Where is the chassis model marked?

looks like you need to adjust the burst amplifier output coil. Looking to see if I can find something for you. if can post a pick of the chassis from the back would help to point it out.

looks like the coil to the right of the 3EJ7 tube. starting from the back it should be the second row of tubes (thinner tubes), the second tube from the left (looking from the rear of the set. To the right of that 3EJ7 should be a coil (from the top of the chassis it is just a hole with pins around it, from the bottom you should see the coil).

That is the burst amp output coil. You need the correct tool (don't improvise here) commonly referred to as a "diddle stick" or TV alignment tool, its a hex shaped plastic tool. You may still find them at rat shack, if not easy to find on ebay.

The idea is to put s piece of masking tape on it to make a flag, so you can see how much you turn. then adj one way and see if the tint shift is correct if not simply reverse. You should not need more than a 1/4 turn so if nothing happens put it back to the starting position. Either that is not the correct coil or something else is wrong. Just don't turn in more than 1/4 and keep track of where you started.

if you want to wait I will make a video showing what I am talking about, prob sometime tomorrow.

https://www.youtube.com/watch?v=OPO9H787vbE&feature=youtu.be

uploading now, should be ready in about 30 min.

If you do adjust it whatever you do don't use a metal hex tool. If you do you'll crack the adjustable core(don't ask me how I know).

https://www.youtube.com/watch?v=OPO9H787vbE&feature=youtu.be

uploading now, should be ready in about 30 min.

Thanks, This is exactly what I was looking for. I should have no trouble finding it now. Fair point about the plastic hex tool, though. I was tempted to try it with a metal Allen key, but I'll definitely order the proper one before I do this.

I'm going to be gone for a few days for the holidays, so you may not hear back from me on this until after New Year's.

Wish me luck, and I wish you all happy holidays.
-Diode

good luck happy holidays :thmbsp:

oh you may find that just putting in a new 3EJ7 could fix it too, tubes are not like solid state, they can very quite a bit and in some circuits this can have fairly drastic effects. I dealt with this just recently when working on the CTC-12 that had the tint issue. In my case the tint or hue was not being consistent on a fixed image (part would be red part would be purple, and it was not a purity issue).

I had a tube that had some shorts in it that when replaced not only cured the changing hue but also shifted the entire hue toward the green. I could have tried a few other new tubes to see if I could correct the tint shift but chose to just adj a coil and fix it that way.

Is a 3EJ7 used as burst amp?:saywhat:
Normally it's an IF tube. I was just curious as to how an IF tube would affect tint range.

In this chassis zenith a new burst amp tube solved a quite similar problem as well as tweaking the coil with color bars displayed. Be very very careful adjusting coils in the colour section though, you can easily throw it so far out of alignment you'll never get it back without proper test equipment.

The colour IC sitting on a tube socket is sure a weird sight in this hybrid chassis, I never really understood why Zenith stayed away from circuit boards for so long and advertised it as a feature

Older PCBs can be a nightmare to service. I have a '64 Silvertone color roundy That has needed PCB solder joint touch-ups on multiple occasions, and that I define to be relatively tolerable...Imagine what techs who had to deal with it daily started to think about PCBs.

All,
After another long delay, I was able to adjust the burst detector transformer, and now the tint issue has been fixed. The adjust was a bit finer than expected-- I had to turn it a good 180-270 degrees or so to get it within a good range, but now the picture looks excellent. Your advice on which can to adjust was dead on. I might fiddle a bit more with the focus, but honestly the picture makes it look worse than it is. Thanks for everyone's help on getting this all looking good again.

http://i1084.photobucket.com/albums/j410/jlny1/IMG_7603_zps889e6a12.jpg

Can't wait to come get it on Friday! Thanks again, Diode:thmbsp:

Glad you got it worked out. :thmbsp:

I've decided not to take the set..surely someone else on the board wants it worse than I do!

If it could be shipped I would be on it in a heart beat.

I like it. And I'm 20 minutes away from both the GWB and Lincoln tunnel...