Originally Posted by Findm-Keepm (Post 3074718)

Those flat chassis sets were workhorses - they'd eat a few caps, a diode or two, but they kept on plugging.

Here's some service gouge for your set - hope it helps.

Cheers,

Originally Posted by andy (Post 3074766)

You always want to do gray scale with the color off, or with a pure B/W signal. The G2 controls adjust the brightness of each color, and the taps adjust the contrast of each color. You adjust the G2 for neutral balance of dark gray (almost black), and the (drive) taps are used to balance high brightness areas of the picture.

My one complaint about Zenith TVs from the 70's is that to save money they replaced the drive controls with those three position jumpers. It makes it impossible to get perfect gray scale unless you get really lucky with the CRT.

Having said all that, the first thing I would do is measure the G2 voltage to all 3 guns to make sure that the G2 controls are working properly. Normally, you should be able to adjust the service line from black to fairly bright on all 3 guns. If the G2 supply is low, or there's a problem with one of the controls, you won't be able to adjust it properly.

Originally Posted by TinCanAlley (Post 3074768)

Where would I measure the G2 voltages? From the CRT socket? If so, do I just pull the socket off while it's operating, put the black probe to chassis ground and stick the red one in each socket and note the voltage? Do I move the G2 control back and forth while measuring?

I have the service manual, but it's the electronic version and it's not clear enough to note all the voltages on the socket. These are the ones I can read okay, but the 13 and 4 are blurry:

Pin:

2- 143V
11 - 142V
6 - 142V
7 - 36.4V
12 - 36.4V
3 - 36.4V
5 - 540V
13 - 640V
4 - 540V
9 - 3.5kV

If those voltages are correct, I can do all but the last 4 as my meter only goes as high as 500V. Oh, and are those AC or DC volts?

Originally Posted by zeno (Post 3074774)

Without going into much detail.........
I always pulled the IF jack when doing a grey scale if it was easy.
This gives a totaly dead raster or line.
Pin 9 is focus so not to worry for now. Pins 5-6-13 are G-2 and
may concern you. Measure at the chassis unless you have a test socket.
The only thing in the socket is spark gaps & 1 K resistors.
they do go bad but usually the focus pin from too much focus voltage
or constant high humditity.....
I highly recomend a rebuilt Fluke meter
off e-by. Got them for both sons & do more then the cheapo
meters. Also can drop them, hit people with it etc & will keep
running. Just be sure it goes to 1 KV DC. They run abt $75
but will last your life. Beond 1 KV you need an HV probe..........

73 Zeno:smoke:

Originally Posted by andy (Post 3074803)

4, 5, and 13 are the G2s. You won't be able to fit a meter probe in the socket (don't force it, or you'll ruin the socket). The exact voltage isn't important, but they should all cover roughly the same range when adjusting the corresponding G2 control. They should max out around 900v or so. You'll probably have to measure it from under the chassis.

Originally Posted by TinCanAlley (Post 3074818)

Thanks. I see they run under the chassis to the G2 pots. I will have to put the set on its side, take the base off, take the underside chassis cover off and leave it like that so I can measure the voltage. Since each one of those leads has more than 500V, I'll have to get my hands on a DMM that can do more than mine.

Is there any danger of a short if I accidentally touch any other lead on the G2 pot or the body of it?

Thanks

Originally Posted by zeno (Post 3075163)

Maybe I missed it but whats the chassis ## ?

IIRC the vert controls are on the module with little extention
shafts. If there is a large adjustment needed UNLESS the pot has
a bad spot or someone messed with it it HAS a problem.
You should do the vert next, it may cause more damage.
BTW your voltages are OK, its not unusual to tweek the
grey scale a little especialy an old set.
Be sure when doing your doing the final set-up the set has
run a few hours & is nice & warm.

73 Zeno:smoke:

Originally Posted by andy (Post 3075150)

You will probably need to readjust the G2s after changing the drive taps since they interact. Always finish with by adjusting the G2s for a dim white service line.

There is definitely a vertical size adjustment, but there might not be a width adjustment. It's not unusual (and considered normal) for there to be up to 20% horizontal over scan. Be sure to adjust the size before the convergence since they do interact.

Originally Posted by Jeffhs (Post 3074468)

I just watched an episode of Kojak (on MeTV) in which a Zenith Avanti color TV like yours was featured in an apartment. However, your Avanti is in excellent shape for being well over 35 years old. The white pedestal base on these sets often turns yellow with age, but yours seems to have escaped that, at least for now. Congratulations on finding one of these in nearly pristine condition.

I agree that the 4-lead safety capacitors should be tested and replaced if necessary, before the TV is used any length of time. I don't know how much you know about color-TV high-voltage systems, but one serious problem that can occur with them if the safety capacitor(s) should short or open is that the CRT second-anode voltage will go sky-high, often causing the neck to shear off the tube. I don't know what type of CRT the Avantis used, but if they are rare (or at least difficult to find), it is best to correct any HV problems before the original tube is damaged or destroyed.

Good luck. Your Avanti should give you many years of good service, once the HV safety capacitor(s) are replaced and the area around the second-anode connector is cleaned well. Dirt, dust or other foreign matter in that area of the CRT, especially under the rubber 2nd-anode cap, can and often does cause HV arcing, which in solid-state TVs can destroy parts such as the HV tripler. These may well be NLA (no longer available) for this set at this late date, so anything you can do to keep the original in good shape will be worth the effort.

Originally Posted by TinCanAlley (Post 3074974)

I got my hands on a Minwax mahogany stain scratch cover up stick. As long as you don't get too close or shine a light directly on the surface, you'll hardly notice if at all. My next step is to get all the off white color cards from Lowes and see if I can find a white the matches close enough. Can't exactly take the set to them for color matching.

Originally Posted by Findm-Keepm (Post 3075786)

Before you paint, look at the retrobrite project - they use chemicals to brighten yellowed plastics:

http://retr0bright.wikispaces.com/
I'm happy with the results on an old RCA plastic radio from the 70's. Best use of peroxide since gold recovery.....

Cheers,