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-   Solid State CRT Televisions (http://www.videokarma.org/forumdisplay.php?f=184)
-   -   1981 Magnavox with a problem. (http://www.videokarma.org/showthread.php?t=254034)

holmesuser01 06-14-2012 02:59 PM

Triplers dont get weak.

Firebird 06-14-2012 03:40 PM

Why still no color no sound?

holmesuser01 06-14-2012 03:50 PM

Look for a common voltage source between the sound module and the color module. Most voltages on that set (I think) come from the running flyback windings, thru a diode, and a low ohms resistor before being fed to the circuits.

If you found bad capacitors on the VERTICAL module, Don't you think other modules need capacitors, too?

You're having problems that I rarely saw when I was working on these sets, unless something odd had happened, like a lightning strike....

TV Engineer 06-16-2012 06:05 PM

Those 4 lead caps are available from a seller on eBay. Do a search with "safety capacitor" and it'll come up. I've bought many from him over the last few years.

Firebird 06-16-2012 07:04 PM

Radiotvnut says they can damage your picture tube. That is not the problem, i replaced it with a two lead capacitor. I can not find the reason for no color no sound.

radiotvnut 06-16-2012 07:09 PM

If the 4-lead safety cap opens and the internal interlock does not break, the HV will skyrocket and literally blow the neck off the CRT.

holmesuser01 06-16-2012 08:07 PM

I lost a beautiful Zenith console this way once. I turned it on to see what was up, and heard this SNAP and a rush of air. The neck snapped at the bell, and the yoke and convergence parts all let go and fell.

Your no color and no sound issues could be what I said before. Have you got a meter? Schematic? Schematic will help you.

Firebird 06-16-2012 10:40 PM

I have a meter. No schematic. I have not been able to find any bad resistors. Have replaced most capacitors. I have not replaced the ones on the main board.

Firebird 06-28-2012 06:11 AM

Any ideas will be appreciated.

holmesuser01 06-28-2012 06:46 AM

Get a schematic and use that meter that you have.

Firebird 08-15-2012 06:37 PM

I think it is a .68 resistor on the retrace board or a .69. Hard to find. It is one watt, brown, bands are blue, white, silver and silver.

Firebird 09-13-2012 03:45 PM

Was not resistor and since i have no sound i think it could be the flyback. Does anyone have a flyback for the T815?

holmesuser01 09-13-2012 05:04 PM

I've never replaced a flyback on the T815.

Firebird 09-14-2012 12:25 AM

How do you fix no sound? Also has no color but sometimes flashes in for a second.

holmesuser01 09-14-2012 08:05 AM

GET THE SCHEMATIC if you cant figure out whats what. The color is something else.

Didnt you have a picture at some point? Then you soldered up the grounds? Then no picture? Recheck your work!!!

Firebird 09-14-2012 08:55 AM

I still have a picture, once i got it never lost it. It is just black and white. Pulls a little to the right.

Firebird 10-01-2012 01:31 PM

Anyone have a flyback for the T815 chassis?

rpm1200 10-04-2012 11:37 PM

You should really get a schematic and measure the voltages around the sound and color sections before replacing the flyback. Have you tried SAMS 1860-1? It is available on samswebsite.com for $22, instant download (I have no affiliation with them).

https://www.samswebsite.com/en/photo.../samsid/1860_1

Firebird 10-05-2012 05:42 PM

Does anyone have experience working on these sets?

holmesuser01 10-09-2012 05:26 PM

I did authorized service on Magnavox TV's and worked on plenty of 815 chassis. It was a good design. Once I soldered most of them up, they rarely came back for service again. Get the schematic and take readings.

miniman82 10-09-2012 08:09 PM

There have been multiple suggestions that you obtain a schematic, i suggest you heed that advice before taking any more stabs in the dark. You're only likely to cause self-induced faults by shotgunning parts into it, and I doubt there's anything wrong with the flyback if you still have high voltage.

Firebird 10-10-2012 05:41 AM

No its the sound and color.

miniman82 10-10-2012 06:20 AM

Go to Sams website, order the schematic if they have it.

holmesuser01 10-10-2012 08:32 AM

See post #58.

My final reply on this.

Firebird 11-29-2012 09:35 PM

Can anyone tell me what component would cause this set to have a near perfect black and white picture. No color, no sound. Picture does streach about a half an inch to the right. Tuner seems to work perfect on basic cable and of course there is no analog broadcast tv anymore. If you can help you will be a hero. TV has not played regularly since 1986 when it died right in the middle of a Joan Rivers joke. Of course i knew nothing about tv repair back then.

mpatoray 11-30-2012 12:05 AM

No we can not GUESS at what component may have failed. You need a schematic to troubleshoot. I know you have been told that many times but for some reason you do not want to listen. Heck if you don't want to BUY a Sam's for the set some good public libraries have collections, find it and make a Xerox!

Firebird 12-01-2012 07:02 AM

Where i live in rural NC?

holmesuser01 12-01-2012 10:02 AM

I live in rural NC, and have no problems getting schematics for things I want. Dont blame NC for your problems.:nono:

sampson159 12-01-2012 04:03 PM

the techs here in this board will point you in the right direction but you have to perform the actual work.get a schematic and get busy.we will help you along the way but start with a schematic.ask for one here and you will get one.i wish you the best of luck on this set.pretty decent models with a fine picture when right.

Firebird 12-02-2012 08:13 AM

Does anyone have a T815 schematic?

dieseljeep 12-02-2012 11:26 AM

Quote:

Originally Posted by sampson159 (Post 3055530)
the techs here in this board will point you in the right direction but you have to perform the actual work.get a schematic and get busy.we will help you along the way but start with a schematic.ask for one here and you will get one.i wish you the best of luck on this set.pretty decent models with a fine picture when right.

I don't remember if that set is a modular set. The set came out around the time I quit repairing, on a regular basis.

Jeffhs 12-02-2012 12:09 PM

I agree with Sampson159 as to finding a schematic for anything you attempt to service or repair, be it a TV, radio or anything else electronic, before troubleshooting; "blind" attempts at finding trouble in a set often cause more problems than are solved.

My only other advice, however, is to be cautious around the CRT, as it has a very high voltage (in the double digit kilovolt range) -- the second anode voltage -- on it that can be lethal or can cause serious injury if you don't take the appropriate precautions. In color sets like your Maggie, the normal HV will be around 25kV or so; in a b&w set, it is a bit lower, around 18kV or thereabouts, but still, nothing to take lightly. And whatever you do, do not work on a TV or radio while the unit is still under power (plugged in to the AC line). Pull the plug and discharge the CRT in a TV before doing anything inside the cabinet. To discharge the tube, simply slide a metal screwdriver under the cap covering the high-voltage lead coming from the flyback. Remember that the HV charge on a CRT can remain on the tube for quite a while after the set is turned off, even if it has been unplugged and unused for years.

jr_tech 12-02-2012 01:29 PM

Quote:

Originally Posted by Jeffhs (Post 3055624)
To discharge the tube, simply slide a metal screwdriver under the cap covering the high-voltage lead coming from the flyback. Remember that the HV charge on a CRT can remain on the tube for quite a while after the set is turned off, even if it has been unplugged and unused for years.

Hopefully that is a GROUNDED screwdriver! :eek:

jr

holmesuser01 12-02-2012 04:30 PM

Quote:

Originally Posted by dieseljeep (Post 3055622)
I don't remember if that set is a modular set. The set came out around the time I quit repairing, on a regular basis.

Its got several modules. Other than the mentioned parts earlier, I rarely had one on my bench that had other problems. I worked on them from 1981-on.

I threw out a good T-815 chassis that had been sitting in my old shop for 10 years. Kept it because it worked, and the CRT went to air. Intended to use it, but never had another one to work on.

Bill R 12-02-2012 05:27 PM

I will look and see if I have a t815 manual.

Bill R 12-02-2012 06:44 PM

I looked and didn't find it. It may still be packed with some other stuff in th office. There is a folder of manuals missing.

Jeffhs 12-03-2012 01:50 PM

Quote:

Originally Posted by jr_tech (Post 3055630)
Hopefully that is a GROUNDED screwdriver! :eek:

jr

I stand corrected. Yes, a grounded screwdriver should be used to discharge the residual HV charge on a CRT; I've been in electronics (as a hobby) and in ham radio 40 years, and should know that.

This is a good warning for newcomers to tube TV repair, however, as folks who have only known solid-state and, particularly (since the mid-'80s) flat-screen TVs may not be aware of the dangers of the redsidual charge on the CRT bell on old analog NTSC TVs -- even after the set has been unused for some time. The aquadag coating on the CRT bell acts as a huge capacitor and can hold a charge for a very long time, so discharging the tube by using a grounded screwdriver slid under the second anode cap until it contacts the terminal which connects to the 2nd anode well on the side of the tube is a must, before any work is begun on the chassis. (I would discharge the CRT even before changing tubes, as some older TVs had some tubes located near or directly under the CRT bell; I've owned a few -- my Philco Microgrid 390 23" console, now long gone, of course, comes to mind.)

Again, the voltage coming from the flyback in all CRT televisions is extremely high (20kV+ in color sets) and can cause serious injury or even death, so be careful. The voltage on LCD or plasma panels in today's flat TVs is nowhere near that high (several hundred volts at most), but, nevertheless, caution should be used around them as the potential for serious injury still exists.

Firebird 12-13-2012 07:16 PM

Been away for a while, let me know if you find it.

Firebird 12-22-2012 04:14 AM

Anyone here ever work for Magnavox?

holmesuser01 12-23-2012 05:54 AM

I said before that I was finished with this topic. I cant help myself. It's like driving by an auto accident. I dont want to look, but I cant help it.

First, how old are you, Firebird?

Second, you've been given the SAMS PHOTOFACT number for your TV chassis. GET IT.

Third, BUY THE SCHEMATIC. You live in a rural area? So do I, and I dont have this problem. Didn't you get and replace a load of capacitors from somewhere? Those arent made in rural NC, either.

Fourth, Go back to posting #60, and comprehend it.

Fifth, I'm not being mean. You won't follow the suggestions that you have been given. Nobody here can fix your set for you if you just throw parts at it.

This said, I hope that you have a very Merry Christmas, and hope that Santa brings you a T815 chassis.


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