View Full Version : OSD shows before the picture fades in


lnx64
07-15-2017, 12:58 PM
Has anyone seen anything quite like this?

https://www.youtube.com/watch?v=4nLCLiLmsTc

If I turn the set off and immediately back on, the OSD comes up instantly as expected, but once again, the picture itself remains black for a few seconds before slowly fading in.

I'm assuming the OSD is just sent to the picture tube as instant as the TV starts up, and something is slowly ramping up the brightness to the picture perhaps, in the jungle IC?

Eric H
07-15-2017, 01:10 PM
Maybe the green gun warms up a little faster than the others?

lnx64
07-15-2017, 01:20 PM
Maybe the green gun warms up a little faster than the others?

Hmm, not entirely sure.. Just tried this, forcing the OSD to show red, and both the red and green OSD comes up well before the picture comes in, and the picture is showing a very vibrant Match Game floor.

https://www.youtube.com/watch?v=GxlgPUtjjGg

lnx64
07-15-2017, 01:26 PM
Update: I clipped on an oscilloscope to the green signal going to the tube, and sure enough, the OSD is there the moment the TV is turned on, but nothing else until after a few seconds then slowly rises.

I've never seen anything quite like that.

zeno
07-15-2017, 02:07 PM
My guess is..........
The set uses AKB or Auto Kine Bias. First used in RCA's IIRC.
The jungle IC has the circuit in it. It measures beam current
by firing each gun during blanking then adjusts the grey scale.
The OSD probably takes a different rout.
Some sets like Sony will not display a raster until its warmed
up & grey scale is good. Bad news is if the jug starts getting
weak the raster will blink on & off.

BTW if a set has AKB you can usually collapse the vert a little & see
3 color stripes at the top. Thats the guns getting fired.

73 Zeno:smoke:
LFOD !

lnx64
07-15-2017, 02:49 PM
That might be what it is, certainly sounds plausible..

old_tv_nut
07-15-2017, 03:47 PM
Sometimes on a set with AKB, it will do the opposite, and you will see the guns come on with too much drive (because the emission is low until the cathodes warm up and also because the filter capacitors in the AKB circuit need to charge up), and then get turned down (although the fact that the cathodes are warming up at the same time keeps it from being too bright). I had a Zenith in which the three guns reached equilibrium with slightly different delays, so the gray scale had three noticeable adjustments occur, one after another.

Maybe this could also be a channel change / source change blanking of some kind that happens to operate when first turned on? Would be interesting to see what it does when switching between sources or changing RF channels.

lnx64
07-15-2017, 04:20 PM
Sometimes on a set with AKB, it will do the opposite, and you will see the guns come on with too much drive (because the emission is low until the cathodes warm up and also because the filter capacitors in the AKB circuit need to charge up), and then get turned down (although the fact that the cathodes are warming up at the same time keeps it from being too bright). I had a Zenith in which the three guns reached equilibrium with slightly different delays, so the gray scale had three noticeable adjustments occur, one after another.

Maybe this could also be a channel change / source change blanking of some kind that happens to operate when first turned on? Would be interesting to see what it does when switching between sources or changing RF channels.

Hmm, changing sources causes a "fade in" for each input..

Also I have noticed a quirk, if the picture is bright, like a daytime scene in a movie, then goes to a night scene with a fast cut, the picture looks for a split second like the brightness is up too high, and then fades down to a proper looking picture.

I'll see if I can capture that.

lnx64
07-15-2017, 04:29 PM
Here's the fading, at least from bright to dark scenes: https://www.youtube.com/watch?v=2Si6LAZJ36Y

EDIT: Huh, apparently in slow motion, you can hear that the microphone on my phone picked up the horizontal sweeping noise from the TV. Never knew the mic on it was that sensitive. lol

old_tv_nut
07-15-2017, 05:43 PM
Looks like a long DC restoration time constant.

Edit: Does it happen the other way when going from a dim scene to a bright one? Simple diode DC restorers will be asymmetrical, gated clamps will not.

lnx64
07-15-2017, 06:26 PM
Looks like a long DC restoration time constant.

Edit: Does it happen the other way when going from a dim scene to a bright one? Simple diode DC restorers will be asymmetrical, gated clamps will not.

It does, when it goes from dark to bright, you can see for a split second the brightness ramping up.

lnx64
07-18-2017, 10:47 AM
And a second weird effect, though not as weird as I have certainly seen this before. The OSD is not affected by the brightness or contrast settings in the menu. I can turn then both down to zero, and have no TV picture, but the OSD is still there bright as it ever was.

Findm-Keepm
07-18-2017, 08:19 PM
Once again, those Apex TVs were never star performers.....what's the jungle chip part numbrt? With no schematic or chassis info, it's all just guessing.

Post a chip complement and I can dig through some notes, but without some meat, it's all just guesses....

Eric H
07-18-2017, 10:30 PM
I can turn then both down to zero, and have no TV picture, but the OSD is still there bright as it ever was.

If you could turn the OSD down how would you find the menu to turn the brightness back up?

Every set I've ever seen with an OSD worked this way.

lnx64
07-19-2017, 12:54 PM
If you could turn the OSD down how would you find the menu to turn the brightness back up?

Every set I've ever seen with an OSD worked this way.

Then I have a Philips Magnavox for you. ;) It goes down with the picture, but zero brightness and contrast doesn't make the entire picture disappear, just dark.

lnx64
07-19-2017, 12:57 PM
Once again, those Apex TVs were never star performers.....what's the jungle chip part numbrt? With no schematic or chassis info, it's all just guessing.

Post a chip complement and I can dig through some notes, but without some meat, it's all just guesses....

I'll do you one better, the schematic to the TV. I can't read the part number on it though in the schematic, and I already put the TV in my office, I don't want to pull it out as I hurt my back putting it in, heavier than I judged.

https://drive.google.com/open?id=0Bx7jBhvozV0HVEpHdlh2LTFBOWs

tom.j.fla
07-19-2017, 06:26 PM
Jungle chip on this one is a LA76514 if i read it right. Found no data on said chip though. All the best,Tom.J

lnx64
07-19-2017, 07:01 PM
Yea I couldn't make heads or tails on the chip. Next time I have the TV apart, if I ever do, I'll check it out. Until then, it's not so important as it's just a weird quirk, not a defect.

Findm-Keepm
07-19-2017, 09:42 PM
Jungle chip on this one is a LA76514 if i read it right. Found no data on said chip though. All the best,Tom.J

Probably a LA7651P or LA7651K - the datasheet is buried in the LA7655 data.

The LA7651P was two sets in one - ground a pin and you "lost" features. Wildly popular in many low-cost brands - my notes show a Citizen, Sansui and Curtis Mathes chassis all using the chip. The Curtis Mathes chassis is the first after they jumped ship from Mitsubishi/NEC.

Consolidated Electronics in OH sold the chip for $2.88 in 10 qty....in 1998. I can say we never replaced one, nor a flyback in those Apex sets. Most junkers were dropped sets or lightning strikes, else the repair was a cap, a SMPS quick-fix, or a LA7835/36 Vertical output chip and cap swap. 88 dollar sets don't get a lot of investment in them. You can find used remotes on fleabay, but anything else, and you are looking for a donor set. Even when they were new, Apex skirted the FTC support rules by keeping production numbers low. When they hit the threshold, they changed models or model numbers, just to avoid having to support the chassis. They weren't unique - AOC, Bohsei and Tatung all did the same. The only Apex manual I've ever seen was the one for their earliest DVD player, the one with player-side indexing and region swap, and the "manual" is only three pages, mostly in Chinese, with only the part numbers and encoding systems being in English.

Findm-Keepm
07-19-2017, 09:49 PM
BTW, the UL code resolves to Apex/Changhong Electric.....(edit) formerly the makers of some Haier, Hisense, and other low-cost brands of consumer goods.

http://www.cccme.org.cn/shop/cccme2342/index.aspx

Still a $12 Billion company....