View Full Version : Late 90s zenith television keeps turning off.


ELzekio
10-19-2016, 09:45 AM
Hello, i have a late 90s zenith television that keeps turning off when i tiurn it on.

If i shut off the television for the night, or for an extended peroid of time then when i turn the televisiom back on, it will turn on for an average of 1-6 seconds and then turn itself off. If i keep turning it on after turning it off it will eventually stay on for good until its turned off for a few hours.

Doing a bit of research, it seems like it is some protection circut that is triggering the television to turn off due to a bad connection.

Does anyone have an idea of exactly why this would be happening. Would it be an easy fix? The one thing i have always been nervous about working on is CRT televisions becasue if you do something worng you could send thousands of volts threw your body.

Here is a link to what the television looks like.
http://www.governmentauctions.org/uploaded_images/znith-700381.JPG

Electronic M
10-19-2016, 10:36 AM
Voltage don't kill, Current kills....Voltage merely wakes you up and or triggers reflexes. A mean static jolt from walking across carpet can have as much voltage as a CRT set. It takes 30mA (0.03 Amps) to kill a healthy person the HV supply in a TV is designed to supply about 2mA max. Your more likely to harm your self from a jolt from the line cord than the HV. I've personally got bit by HV a few times and am still here to tell about it...Worst it's done to me is make my arm reflexively smash stuff pulling away from point of electrical contact, and some foul language slip.

As for the set, that may or may not be the shorting CRT era of Zenith if it is dump it when it quits....Hell most working CRT sets of the era can be had for under $5 at a thrift shop (granted some places *cough goodwill cough* don't take or sell them anymore) or free at the curb or craigslist, and unless the set has sentimental value, you know electronics repair well, or enjoy tinkering it literally is not worth your time to repair instead of replace.

RCAZenith
10-19-2016, 02:43 PM
Hello, i have a late 90s zenith television that keeps turning off when i tiurn it on.

If i shut off the television for the night, or for an extended peroid of time then when i turn the televisiom back on, it will turn on for an average of 1-6 seconds and then turn itself off. If i keep turning it on after turning it off it will eventually stay on for good until its turned off for a few hours.

Doing a bit of research, it seems like it is some protection circut that is triggering the television to turn off due to a bad connection.

Does anyone have an idea of exactly why this would be happening. Would it be an easy fix? The one thing i have always been nervous about working on is CRT televisions becasue if you do something worng you could send thousands of volts threw your body.

Here is a link to what the television looks like.
http://www.governmentauctions.org/uploaded_images/znith-700381.JPG



Could be a bad jungle IC caused by a shorted CRT. The last time it ran did it have a purple or green hue to all of the colors?


Sent from my iPhone using Tapatalk

zeno
10-19-2016, 06:32 PM
First post the model number & a good pix of the
chassis. This will give us much more to go on.

If the set runs normal for a while this does point to a
HV shut down (HVSD) problem often. Cold solder joints or a
bad electrolytic cap are most likely. You can usually
give the set a good slap while running normal & if
it goes dead its a cold PC con........

Not to worry about the HV. Most sets after the mid 70's
will bleed off in seconds. Even if it gets you its no big deal.
Used to be a weekly event in the olden days. The only
bad place is the AC where the cord comes in. So unplug !!!

73 Zeno:smoke:
LFOD !

Findm-Keepm
10-19-2016, 08:22 PM
First post the model number & a good pix of the
chassis. This will give us much more to go on.



Amen, You want answers, help us first:

http://www.videokarma.org/showthread.php?t=265964

WISCOJIM
10-19-2016, 08:39 PM
Does this same behavior happen any time of day?

Does it coincide with the use of other equipment nearby?

Some posts I've seen on other forums indicate that some equipment can have handshake issues with HDMI products that cause this, other remote controls interfering, whether other components are in the on or off status, and even can be blamed on things like LED bulbs turned on in the room. Perhaps try moving the set to another location and see if it still occurs.

.

Findm-Keepm
10-19-2016, 08:57 PM
Does this same behavior happen any time of day?

Does it coincide with the use of other equipment nearby?

Some posts I've seen on other forums indicate that some equipment can have handshake issues with HDMI products that cause this, other remote controls interfering, whether other components are in the on or off status, and even can be blamed on things like LED bulbs turned on in the room. Perhaps try moving the set to another location and see if it still occurs.

.

That's either a Z, A or B-line set, and no HDMI - schools and motels were full of them - but we won't know until the OP pipes in with the model number. Hell, I probably have the service lit in PDF, thanks to LG University...

I also have 22,000 repair tips, but not one listed under "late 90's Zenith TV..."

Sams for this set? Try " Late 90s zenith television" at the sams website or in a paper index. Find anything?

</RANT>

Jon A.
10-19-2016, 09:26 PM
I've tested for HV seconds after turning the set off. I'm sure some was there but it wasn't enough to show on the meter. Just unplug and you're good.

The model and chassis numbers may be on the back. If the chassis number isn't there it's probably on a sticker inside.

Try to get multiple chassis pics from different angles, that's what I often do.

Cheers

ELzekio
10-19-2016, 09:56 PM
Yea, sorry i was not at home so i couldn't get the model off hand. i knew that issue would come up haha.

Anyway the model number is: B27A24Z

it is 26" and it was manufactured November 1999.

Here is a link to the service manual: https://www.manualslib.com/manual/1020452/Zenith-B25a10z.html#product-B27A24Z

it dosen't really have any sentimental value and im sure i can find some cheep televisions at the local thrift stores, but if it is somthing like an electrolytic im sure i can fix it. i just don't have much of any experience working on crt televisions and wondering if i can get some pointers.

i do know it needs a good cleaning so hopefully i can get to it this weekend.

Findm-Keepm
10-20-2016, 12:22 PM
Most of the problems with those regarding shutdown is centered around the 5V Standby to the micro. There are several caps off the 5V SB/SBF line that go bad. Most are small value - 1, 2.2 or 4.7uf - the one closest to the EEPROM went bad often.

Most of these sets had the dreaded weak CRTs - I'd make sure the CRT was good before pouring any effort into it.

radiotvnut
10-20-2016, 10:27 PM
There is also a capacitor in the power supply (close to the regulator IC) that was very high failure and will cause start-up problems. I think it's a 47uf.

zeno
10-21-2016, 06:53 PM
There is also a capacitor in the power supply (close to the regulator IC) that was very high failure and will cause start-up problems. I think it's a 47uf.

IIRC there were 2 little lytics on the primary side of the power supply.
Bad PC on the vert out IC were common for years as with most
other brands. BUT I dont remember if these had a vert detect for
the HVSD.
Did quite a few FBT's also. This is where a power rite or equivalent
would tell a story..........

73 Zeno
LFOD !