Zenith - One color on startup?

[bogart219]

Yellow all,
Found this site researching all the havoc bad caps can cause. I seen the TV repair section and it appears there are many Knowledgeable folks on here. Maybe someone can point me in the right direction. I have a Zenith 32" crt set,
model# SL3285BG. When you first turn it on the picture is blue. After a while (and this time varies from 30 to 60 minutes), the picture will then be fine. So it seems that once the set warms up for a while the offending component starts working ok. This is the opposite of what I assume should happen (component heating up then failing). Any thoughts? Thanks!

[i4004]

Re: Zenith - One color on startup?

if it's older set that could even be crt, i'm afraid.

you should check rgb voltages on crt board (pcb attached to crt). but that can be dangerous if it's the first time you're tinkering with tv-sets.

perhaps wizard knows more about that model.

[Wizard]

Re: Zenith - One color on startup?

bogart219,

what's the manufacture date on this unit?

And Zenith is notorious for bad CRT from 1993 onwards. These zenith chassis is what I hate as I can't get them properly fixed and long term reliablity is doubtful, callbacks frequent.

Cheers, Wizard

[Krankshaft]

Re: Zenith - One color on startup?

What gets me is both the red and green dying at the same time?

One color ok but two?

Is this a common occurrence?

Don't rule out a cracked solder joint somewhere no drive = no color.

[i4004]

Re: Zenith - One color on startup?

when crt goes to hell you essentially have no control over particular gun...it disrupts other 2 guns.
i had a case of red(actually purple) screen becoming good after 20-30min or so...

common? when crt is nearing its death it can happen but it doesn't always happen...other times it just fades away (constrast is gradually decreased untill you no longer see anything)

>These zenith chassis is what I hate as I can't get them properly fixed and long term reliablity is doubtful

what's making them "special"?
crappy components overall?

[kc8adu]

Re: Zenith - One color on startup?

cracked solder joints or dried out caps.
the 32" and larger have toshiba crt.
likely to outlast the rest of the set.

[bogart219]

Re: Zenith - One color on startup?

bogart219,

what's the manufacture date on this unit?

And Zenith is notorious for bad CRT from 1993 onwards. These zenith chassis is what I hate as I can't get them properly fixed and long term reliablity is doubtful, callbacks frequent.

Cheers, Wizard

manufacture date on unit April, 1994

[Wizard]

Re: Zenith - One color on startup?

Have opened up the tv yet and looked for CRT label sticker?

Cheers, Wizard

[bogart219]

Re: Zenith - One color on startup?

Have opened up the tv yet and looked for CRT label sticker?

Cheers, Wizard

Not yet Wiz. Have been fighting the flu the last week. Hopefully today.

[bogart219]

Re: Zenith - One color on startup?

Yellow my fellow Americans,
The sticker on the tube had these numbers: A80JZH50X 9422 VX
The board on the back of the tube. Where it got hot. 3 big resistors, bad solder joints, loose.


Seen this also. Leaking cap? Isn't this next to the audio amp?


Plan on taking unit outside, blowing it out real good. Then go over all solder joints and replace that cap. I have a ESR meter and will check all caps. You think I'm on the right trail? Thanks!

[Wizard]

Re: Zenith - One color on startup?

You will find these big resistor leads had corroded and refuse to take solder, the fix is desolder them out and and take a razor knife and scrape these ends clean.

This circuit design is automatic kine adjustment/tracking.

Cheers, Wizard

[Krankshaft]

Re: Zenith - One color on startup?

Wow I wish I had easy fixes like this I guess it's never mean't to be .

Have opened up the tv yet and looked for CRT label sticker?

Cheers, Wizard

According to the tube number provided it's either manufactured by LG Electronics or Empire Video.

[Krankshaft]

Re: Zenith - One color on startup?

Damn edit time limit.

A cracked joint around the color output transistors (or resistors supplying them) would cause the color problem you experienced.

As for if that cap is part of the audio amp just lookup the ICs part number here:

http://www.alldatasheet.com

I can't see the numbers clearly.

[Wizard]

Re: Zenith - One color on startup?

This number is a model number of a CRT and it does uniquely ID a manufacturer of the CRT. This one is LG CRT. It should say Goldstar or LG logo on part of the sticker where the model number is on this CRT itself.

I'm not too sure about how good these LG CRTs were but I did have bad time with Goldstar CRTs back then. Because Goldstar was original brand name company before they renamed themselves to LG but quality helped as well.

Currently LG/Philips partnership for LCD and plamsa panels for awhile. Good so far.

Cheers, Wizard

[MegaOne302]

Re: Zenith - One color on startup?

Goldstar = Junk

[PCBONEZ]

Re: Zenith - One color on startup?

Goldstar = LG

[MegaOne302]

Re: Zenith - One color on startup?

Renamed junk... yayyyyyyyyyyy

[PCBONEZ]

Re: Zenith - One color on startup?

http://www.lge.com/us/about-lg/corpo...ew/history.jsp

[kc8adu]

Re: Zenith - One color on startup?

replace any caps with wet spots under them.look at traces under caps looking for darkened traces.these were eaten by electrolyte.
resolder that whole dark area scraping leads if the solder balls up.
any lytics in that area are cooked too.
as for the crt if the pic is good when the missing colors come back it is ok.
forgot to ask if the missing colors come back gradually or suddenly.

[bogart219]

Re: Zenith - One color on startup?

replace any caps with wet spots under them.look at traces under caps looking for darkened traces.these were eaten by electrolyte.
resolder that whole dark area scraping leads if the solder balls up.
any lytics in that area are cooked too.
as for the crt if the pic is good when the missing colors come back it is ok.
forgot to ask if the missing colors come back gradually or suddenly.

Thanks everyone for the tips, especially the one about scrapping the leads.
The missing colors come back suddenly. Will report back and let you know how I made out!