Entertainment Center: TVs, Stereos, VCRs and DVDs - toshiba TV, only 1/2 picture till warmup?

my tv picture is squished in the upper half of the screen until it warms up then, then it is o.k. all other operations are o.k.

Check for cracked solder joints on the pins of the vertical output I.C. and leaky electrolytic capacitors in the vertical circuit.



Fred:)

thnx i'll give those a look

FreddieG,
reflowed solder joints (3x) and still no luck. also saw no leakage. the condition is present on start up and goes away gradually during warmup. (takes around 10-15 min) could something be shot or out of adjustment???:(

Whats the model number and date of manufacture of that television?



Fred:)

toshiba model CF1910K
june of 1990

Fred,

I'll take my multimeter and start checking.

Thanks

fatkid66, These are the typical capacitors by location that need to be checked: C301, C305, C306, and C308.


Fred:)

i'll check those and get back to you. btw thanks for all the help!!!!

Freddy,
reflowed solder at those points, checked for leakage. still no change. playing with the height adj. pot in the rear of the set makes a small difference, but not enough to restore the screen to full height until it warms up. any other advice b4 i trash the set???:(

Before you trash it lets do a few more checks. Lets check the voltages at the vertical ouput i.c.

pin#1=ground

pin#2=16.5volts

pin#3=28.9volts

pin#4=.7volts

pin#5=-.3volts

pin#6=2.3volts

pin#7=27.9volts

When it comes to electrolytic capacitors your checker can fool you somtimes. The best thing to do is replace them with new ones.


Fred
:)

FreddyG
Measured betweem pin#1 (ground) and the other pins with my Fluke 87 DMM. Got some disturbing readings. way off what you said i should find.

#2=7.3v

#3=3.9v

#4=231mV

#5=6.5mV

#6=4.1v

#7=.36v

Although i am an electrician, i am not so comfortable with electronics. i'm picking my way thru as well as i can. do these readings spell doom for my set. btw i also piggy backed with another poster on another tv problem. (mitsu proj. tv) please give that post a look if you can.
Thanks:(

From one electrican to another your doing just fine.


#2 is vertical output to vertical yoke windings

#3 is B+ for vertical output

#4 is vertical drive voltage

#5 is trigger input

#7 is B+ for vertical output i.c.

with all those reads being low, looks like the i.c. is the culprit here. What's the part on the i.c.? Its on the face of the i.c..


Fred
:)

thanks for the vote of confidence!

the numbers are:
.050
AN5515

Fatkid:D

You can find the original replacement at www.mcmelectronics.com
1-800-543-4330
#AN5515(panasonic i.c.)
Cost $3.20each
$20.00 minimum

If you live near a rca/ge parts supplier they usually carry panasonic replacement parts.



Fred:)

what a nightmare!!! had a hard time finding a place on the net that didnt have a $15-$20 min for ordering, then called a local tv repair in town. he was real standoffish, didnt want to help at all, and gave me the name of his supplier knowing full well that they couldn't sell to me. they only deal wholesale. they said to have him call back and order the part and he could sell it to me. i did just that and he told me he didnt want to get involved!!! he told me he didnt have any in the shop even though the supplier told me that is one of the most common parts they sell!!!
well it all comes down to i found the part at another place in town, and will probably put it in over the weekend. ill get back to you on the outcome:D

The little red cap near the IF chip 2.2 uf
I have seen these create all kinds of problems.
THis particular model may not use it but it is a common Toshiba problem

hey, ill check that too thanks for the input!:D

fred,

replaced the part, didnot change anything. i will now check the voltages on the new i.c. and see what i have. any other thoughts???:confused:

fred,
i feel like such an idiot. checked those caps (red ones) again, actually removed them and they were cooked!!!
had an old moniter laying around, so i took a coupla caps out of that and replaced both red ones c301 and c305 i believe. (ones you had me check b4) guess what??? the picture is back, but not full screen seens like about an inch on top and bottom. checked the screen adj pot in the back, but it is maxxed out. any suggestions?? btw thanks again for all of your help. seems like we're getting there!!:D

There is a 2.2uf cap near the Jungle IC (IC301 i think, not sure) that will cause this problem.
Is there any vertical distortion is is it just not tall enough ?

replaced that one i think. got rid of all the red ones, (only 2), and there seems to be a small amount of distortion, but there is only a little bit of the top and bottom missing.

Its better to change all electrolytics in the vertical circuit regardless to how they check. You still have leakage in one or all if the vertical size trim pot is at max. This is just a minor troubleshoot now, the hard parts done. Good Show!



Fred:)

latest news from the front:
replaced 3 of the 4 caps you had me look at originally. c301, c305, c306. still havent replaced c308. this one (35V 2200uF) i cant find laying around here in the shop. ill have to stop at the shack or somewhere else on the way home. btw, checked the voltages on the new ic after replacing those three caps. they are as follows:
pin2=11v
pin3=25v
pin4=1v
pin5=0v
pin6=1v
pin7=26v
im hoping replacing the last cap will fix the problem, but im not feeling too sure. its a big one and appears to be in good shape. as ive said before the picture on the screen is beautiful!! just short still on top and bottom.:(

When you check the caps, you're doing it outside the circuit, right. Checking them while still being in the unit is a big no-no as you're reading that cap in line with whatever else is in the chassis.

Do yourself a favor. Replace all the caps with NEW ones. Try to find an electronics store that has 105 degree versions for any that say they're 85 degrees C. This makes them last longer. Also, the voltage rating is only important on the upper scale. Meaning that if you're taking out a 25Mf 15V capacitor, replacing it with a 25Mf 50Volt capacitor is fine. I'd suspect that you've got an electrolytic that shows up fine with a multimeter, but at full load is just shy of it's tolerance.

The other way to diagnose is to hit some caps with freeze spray until the problem is repeated, then replace the last component checked.

Hope this helps. Deflection is a pain.

Taz:D

took me a while, but i replaced the last cap and still have the same problem. any ideas???? i feel im gaining on with your help, i know ots probably something minor.:confused:

The pot you adjusted that "almost fixed" the problem. Run that puppy back and forth a few times and see if the picture jumps rather than ramps up and down. If it jumps, the pot is dirty. If you can replace it with another, do that. Otherwise hit it with some contact cleaner and excercise it. That may do it. Some resistive part of the circuit has got a bad connection and after it warms up that part makes a good connection, so as I may have mentioned, get the freeze spray (if you can't get that, get the can duster stuff and turn upside down). After the set warms up and you get a full picture hit one component at a time until the problem reappears. That component or area may have a cold solder joint or a bad component that's out of tolerance.

Hope this helps.

Taz:D

havent tried the freeze spray deal, but no change after cleaning the size adj pot. no jumping when adjusted it just wont cover the whole screen. can i just jump the pot out??? will that help to diagnose wether or not the pot is the problem??? i let the tv run for an hour, and even after warm up, the screen didnt come in full so solder connections are probably not the problem. i also did the plastic poke rod deal, and none of the components when poked made the screen change. ?!?!?!?!?!?!?!?!?!!?:confused:

Replace R352 vertical height trimpot. Value 2000ohms listed on the schematic I have, should have value on part. Check on some of your old circuit boards for one. Like we were saying the two red capacitors when replaced correct 90% of the vertical problems on this chassis. Post back with the board locations of all the capacitors you have changed. Radio also carries trimpots.



Fred:)

fred,
o k so far ive changed c301, c305, c306, c308, c448, c807.
they are the ones associated with the vert circuit that you told me about, and a couple that had a dubious appearance. i also changed the ic. im in the process of changing the pot, but i jumped it out, and it didnt correct the problem, so im feeling that that isnt the problem. if there are any other associated caps or other items associated with the vert ill change those too.
thanks
FATKID:D

If you have any componet freeze spray ic501 first and see what happens, if no change spray other parts of the vertical board section.


Fred:)

changed the pot, and still same same. will try the freeze spray and see whats what.

btw, i know that the voltage on the cap is ok if its larger, what about the uF value. is it ok to use a higher value. and if so how much higher.:confused:

what a dope!!!!!!!
well i guess this is one of those live and learn deals. freddy g you are the man !!!!!!!!!!!!!!!!!!!!!!!!!!!1
i cant believe that the problem the whole time was the nut loose behind the soldering iron!!!!
when i swapped out the caps in the vert. circ i used a higher voltage AND a higher uF rating. (typical electrician!) when i swapped back to 2.2uf from the 3.3s i put in there the pic came back full screen!!! boy do i feel dumb. well im just posting to update and finalize this thread, and to thank all of you for your time and assistance especially Freddy G!!:o
btw stay tuned, ive got a 17" moniter that needs fixin!!!

We all have are days. No matter how many years you work on this stuff your bound to make mistakes. As long as you can reason it out and find the problem thats all that matters.



Fred:)