1993 Magnavox issue

[jstout66]

Well…. Looks like the 1993 Magnavox decided to fail after 20 years of use.
Interesting back story on this one…. I found it at an estate sale almost 10 years ago, and bought it for my parents. My mom has ALWAYS had a console TV, and their 1979 26” Sony had developed high-voltage issues. Mom is quite picky concerning the cabinet style and it was hard finding just the right set, even then. It had to be oak…solid wood.. remote..stereo..AND 1 st of RCA inputs, and this fit the bill.
My parents retired around that time, so it’s seen almost 10 years of HARD use, but still had an outstanding picture. I’m debating whether to throw it out, or see if one of our 2 repair places will even bother working on a CRT set at this point.
Here’s the ODD symptoms, so am posting this to see if one of you might have an idea of what I’m in store for. “radiotvnut” had a youtube video on the same chassis, and it kind of points to something similar.
When powered on, it works briefly, but then looses horizontal sync . Here’s where it gets really odd. When turned on, it won’t turn off. ( power switch/or remote) If you hold the power button, the picture gets super bright, with a slight wave in the picture, but.. it won’t turn off. You have to unplug it.
Anybody see this, on this chassis before? I kind of picked up from “radiotvnut” this wasn’t the best NAP chassis.

[zeno]

If you post some chassis photos it can help us relate to the
chassis.
BUT the symptoms are strange. Sounds like its micro related.
About this time NAP 13" sets had a rash of micro failures.
IIRC they used toshiba micros. Toshiba also had quite a few go.
They seemed to be over sensitive to static. Micros came as a
kit with shielding to add.
What ever it is I doubt its an easy one. Getting it fixed at a
shop may not be possible due age & most parts being NLA.
If we were to take it in it would be with a BIG deposit & go
ahead first. sets like this tend to not get picked up.......

One thing, do you hear a relay click when you turn it off.
& when you hold the remote button does it do the same
thing bright pix etc ?

[jstout66]

Thanks Zeno, it's kind of what I thought concerning a shop taking it in. My repair skills arent the best. Older stuff I'm not bad, but this is too "new" for me.
And yes... the symptoms are odd. It does lose sync. I thought it might be a tunar issue, but it does it on the DVD player which is hooked up via RCA input jacks.
I forgot to say, when you do hold in the button, the sync also comes back, but with that super odd washed out picture. And no.. no relay click anymore when you hold the power button, or try the remote. It simply won't turn off.
Whatever happened, happened fast. I was up there Friday and it was fine, when I went back up Sunday, it was doing it.
I only pondered on getting it fixed, because the cabinet is nice and ALL wood. No plastic anything on it.

[zeno]

OOPS Something bothered me about this set ! IIRC they had
a problem with the regulator IC's or something in the reg that
caused it. Had a strange on/off set-up. Problem is age. MY AGE !
Cant remember the details but if I do I will post it.
An easy fix so dont junk it yet ! I am sure a NAP expert knows the
answer if I dont remember.CHASSIS PIXS WOULD HELP
It kinda sucks getting old..........


73 Zeno

[jstout66]

HA! Thanks Zeno,
I will try to get a chassis pix posted in the next few days.
However.. if you watch any youtubes, type "1993 Magnavox tv" in google, and there will be radiotvphononuts video of what I assume is the same chassis. The one he's working on is a 25" tabletop, but I bet the console used the same.
I did call one of our remaining repair places and they said the still repair a few CRT sets. The guy was nice, but go figure... it's the one wayyyyyyy across town. The other place is right up the street from me, but they are jerks, and make up EVERY stupid excuse in the world to NOT have you bring anything over 5 years old in.

[radiotvnut]

I'd change the 100uf200V cap behind the flyback for the sync problem. If this cap is bad, it will eventually take out the horizontal output transistor, the B+ fuse; and, quite possibly, the voltage regulator IC and TIP47 transistor in the power supply. I think there was a resistor in the power supply that would open and cause the set to not turn off.

[jstout66]

Thanks! I saw your youtube video, (i love your videos btw...) and kinda thought that was the problem. The not turning off thing threw me off tho.
The set just started acting up Sunday morning, so it hasn't been on much after that. ( just long enough for me to figure out the set was broken and it wasn't a cable issue)

[radiotvnut]

Don't even turn it on again until you at least pull and check that 100uf cap behind the flyback. I can almost assure you that it's bad. I was replacing them when those TV's were much younger.

[zeno]

Originally Posted by radiotvnut

Don't even turn it on again until you at least pull and check that 100uf cap behind the flyback. I can almost assure you that it's bad. I was replacing them when those TV's were much younger.

Watched the video & it almost all came back to me. Nice job RTVNUT,
I just dont remember the value of that resistor. Dont remember the
schematic either, Does the STR output go to the transistor base ?
whatever the case the resistor, cap, str, & transistor should do it.
Wont need the HOT & fuse.

73 Zeno