Zenith System 3.

[Rod Beauvex]

Were they good? Were they bad? I seem to have heard both here.

[radiotvnut]

Depends on which version. The "System 3" name was applied to Zenith TV's made between 1978 and the early 1990's. The first ones still retained a power transformer and were the best ones. The main problems these gave were issues with the 9-153 HV module and the plastic edge connectors. The second generation sets used the infamous 9-160 series power supply/sweep module and there was no longer a power transformer. These sets were OK; but, had a lot of problems with the 9-160 module and the crappy plastic edge connectors making intermittent contact. The third generation, introduced around 1982, used the 9-181 main board and the 9-186 sweep module. These are not very high on my good list and they can be a pain to troubleshoot. I own a 13" set that uses the 9-181 chassis and even though it has a good picture, I'm not going to invest much time or money in it when it takes a dump. By the mid '80's, there was the "Advanced System 3" that had stereo sound and other features. In the late '80's, there was the "digital system 3" that was a high priced set; but, was a total dog. A have a friend who bought a 31" digital system 3 in the late '80's and he paid around $1600 for it. It gave trouble from day one and he finally got tired of it and gave it to me a few years ago after it had been dead for years and serving as a stand for another TV. I patched it up good enough to give to the starvation army and haven't missed seeing it one bit. By the '90's, the quality had really gone down with bad CRT's and major chassis issues. If a Zenith system 3 was the only TV I could own, I'd stick with either the first version from '78-'79 that uses a power transformer or a 9-160 based one. All system 3's used inline gun CRT's that did not hold up as well as the old delta gun CRT's. The early inline CRT's were the best and it seems like the smaller screen tubes held up better than the 23" and 25" tubes. As time went on, the quality of Zenith CRT's continued to decline.

The best Zenith's were the chromacolor sets of the '70's that used either the horizontal "tube look-alike" chassis and the vertical chassis and used delta gun CRT's. The last chromacolor II portables from '78-'79 used the same inline tube as the first system 3's.

[Rod Beauvex]

Can always count on you for a thourough answer.

My local thrift store in fact has one of those '79 era units you describe.

[radiotvnut]

Is it a console or a portable? From '79, it could either be the one with a power transformer or the one with a 9-160 module.

[Rod Beauvex]

Console, actually. Don't know the model number. Has the varactor tuner with the little push buttons, and the indicators are orange. Has that color sentry button that turnd yellow when pushed down.

[radiotvnut]

Here's what the first ones looked like:





The chassis was laid out differently in the consoles; but, still used the same boards. Actually, the "chassis" was more like a plastic frame that held the boards and the whole thing was connected with interconnecting cables.

[Rod Beauvex]

Yeah, I was looking around on You Tube, and ones like that were the ones I found.

This one has (I think?) the channel buttons that are not behind a door. I plan on taking pictures and taking down model numbers when I go back Monday, to add to my thread in Curbside.

Not to derail my own thread, but they have another set, one I've actually been considering, or at least I was until I plugged it in. It is a Zenith as well, rebadged as a Montgomery Ward. It was made in 1988, and has stereo A/V inputs, but it has this problem where only about 9/10ths of the screen fills up until the set warms up. Is this worth fixing? My Dad had another Zenith from ap revious generation that did this as well.

[radiotvnut]

That sounds like bad electrolytic capacitors in the vertical circuit, is a common TV fault, and is worth fixing (provided the TV otherwise has a decent picture).

I've seen some Zenith's with a non-remote pushbutton varactor tuner. A friend had one that I replaced the 9-153 module in back in the mid '90's. His was a 25" console with two speakers below the CRT.

[zeno]

My post didnt make it so I will do it again.
RTVNUT is 100% that the first system 3 was the best. Check
the model #. If it starts SK25?? or K25?? its the good one.
They only made them one year, the K line. Very robust
chassis & great pix. Only common problem was cold joints on
the hoz drive transformer, a few PS boards (24V reg) & 9-155-01
CRT boards.

9-160 sets were WAY over engineered in the PS & hoz.
They did introduce a comb filter on better models that made
a huge improvement in pix. Also you could get a real RATS.
Also the first Zenith monitor a 19" cube set with 2 seperate speakers
called "video high tech". Dont remember model # or year.

73 Zeno

[Rod Beauvex]

*nods* I'll take down the model numbers.

[radiotvnut]

I've ran into a lot of 9-160 TV's and 9-181 TV's that would have failures of multiple modules at the same time and it's highly possible to damage a new module because of a defect on one of the remaining modules. This was especially true on the 9-181/9-186 style chassis. I remember one 9-181/186 chassis that caused me to lose some hair. The set acted like it was trying to start; but, all it would do is make a roaring noise from the speaker and all power supply voltages were low. This set used a standard power/volume knob with an electronic tuner. When I unplugged the power cable going to the tuner, the rest of the chassis came to life full blast. The problem was a dead shorted electrolytic capacitor inside the tuner. I don't remember the value; but, I think it was something close to 1000uf, 25V.

One thing I forgot to mention was that the 9-160 sets were known for bad solder connections all over the sweep module. These connections usually cause intermittent power up, a set that would shut down and make a roaring sound, and a set that would blow horizontal output transistors.

I remember one 9-160 set that was given to me that had a shorted HOT and blown fuse. I resoldered any suspect connections and replaced the HOT and fuse, only to have the set make a roaring sound. I don't remember what all I replaced next; but, I seem to remember one of the horizontal driver transistors, a diode, and an 8-pin IC in the power supply being bad. After that, I turned it on and the flyback violently arced. I've seen those 9-160 flyback transformers go up many times and they will get your attention. Zenith wouldn't sell just the flyback; instead, you had to buy the whole board. I ended up taking a flyback off another board and the set worked and I feel like it was the arcing flyback that took out the other parts that I had to change. I don't know exactly what years the 9-160 sets were in production; but, the earliest ones I've seen were from mid-late '79 and the newest was a console from '83. The earliest 9-181 set that I've seen was from '82 and the most recent was from around '86. The earliest 9-181 sets used the same tri-focus CRT that the earlier system 3's used. Then, they dropped the tri-focus tube and went to using a standard inline CRT like what everybody else was using and continued to use up until the end of the CRT era. IMO, the older tri-focus tubes had the best picture.

From what I've read, Zenith really didn't want you to repair those 9-160 boards to component level. As for me, I tried to fix them to component level whenever possible because I liked the idea of only spending a few dollars vs. spending $80+ on a new 9-160 module (the last ones I priced were over $80). When I first started working on them, they were around $54 exchange.

[zeno]

If it was slow we did some 9-160 repairs. NEVER with a shorted HOT.
As with you I learned a few painful lessons so we just swapped them out.
Lots of PC cons, filters & 32 V source transistors. We kept abt
6 of both flavors in the truck & shop.
Never liked 9-181 sets, to awkward to work on. And the start circuit
was dumb ass. Funny thing is a lot of them ran 20+ years without
a repair.
One thing Zenith must be given credit for from the 9-160 era.
The spark gaps. I never had a Zenith destroyed by lightning but
saw tons of those spark gaps toasted. The sets survived usually
with a blown fuse at worse. Often the customer never knew, I
noticed it when repairing something else later on.

Thanks for the memories

73 Zeno

[Rod Beauvex]

Wait, what? So the sets still worked with the spark bulbs fried?

[Electronic M]

Not all spark gaps were bulbs...On tube era Zeniths they consisted to two strands of enameled copper wire in parallel lashed together with cloth shrink tubing.

[radiotvnut]

I don't remember the board numbers; but, there was a chassis used in 13"/19" sets, right after the 9-181 chassis, that consisted of a main module that was mounted horizontally in the bottom of the cabinet. To the right of the main board, there was a stand-up sweep module. To the left of the main board, was a stand up power supply module.

The next chassis was the 9-470 chassis, that was in production from roughly '87 to around '91. This TV contained most circuitry on a single module, with the video output, tuner, and stand-by power supply being on seperate modules. There was a knob-tuned version of this set that did not contain a stand-by power supply module or an electronic tuner module. This chassis also marked the end of Zenith knob tuned sets.

After this chassis was when Zenith went to a series of single board chassis "modules" and this is the era when bad CRT's started showing up a lot.

As far as larger screen sets, there was a model after the 9-181 series that contained a 9-517 main moudle, a switching power supply module, the video output module, the stand-by module, electronic tuner module, and stereo audio moudles (in sets with stereo sound). There was also the 9-516 module that was more of a single board chassis, except for the video output module and space command power supply & tuner. On the 9-516 sets, there was an electrolytic cap mounted under a metal shield in the power supply and when this cap started failing, the TV would take a long time to start up. I think this chassis was around until '90-'91, when single board modules took over.

The digital system 3 dog from the late '80's used, IIRC, a 9-700 main module that was totally shielded in a metal can.

Some of the higher end sets of the early to mid '90's used what was called a "dual module monster" chassis (power supply/sweep module, main signal module with smaller modules attached to enable certain features of the TV).

AFAIK, Zenith stuck with the modular concept on most of their color TV's until the end. Most other companies went to a single board non-modular chassis where the technician was expected to fix the set to the component level by the late '70's-early '80's.

The whole idea behind modular construction was to enable the technician to make a quick repair in the customer's home and it was also a good concept for older technicians who were more familiar with tube sets and not as familiar with troubleshooting a solid state set to component level. The main problems with modules is that they are generally costly and some modules become unavailable as the set gets older. Another problem was faulty module socket contacts that caused intermittent operation.

As far as Zenith's from the mid-to-late '80's, I find that bad electrolytic capacitors in the deflection/power supply and bad solder connections are the most common problems.