1981 Magnavox with a problem.
 

I have a 1981 Magnavox tv. Model number RA5054. It has a t815-09 chassis. It has not worked for a while but somehow i have convinced my mother not to throw it away. I was there when she bought it in january 1981. It has stereo speakers and separate 10watt amps to simulate stereo. It gave a little trouble when it was new, the crt module was replaced and an ic was replaced on the power module. When you turn it on the channel number displays, no picture, no sound, The picture tube gun lights but after 20 or so seconds the reset button kicks out. After reading some of your post i ordered a horizontal output transistor, installed and resoldered pins on the retrace module. It still does the same thing. I have had some repair training but would like the advice of an expert.

Check the 4-lead safety cap on the retrace module. They were known to short. If it's bad, you'll probably have to replace it with a current production "orange drop" cap because I don't think anyone makes the original 4-lead cap. Those 4-lead capacitors were not reliable, anyway. They would either short or blow open. If they open and the internal interlocking feature of the cap does not open, the HV will skyrocket and blow the neck off the CRT.

I am a little new to this, What is a orange drop cap?

I checked the safety cap and it is leaking so it is bad. The part number is 250663-18, also it says 648 at the top of the label. What rating cap do i replace it with. Also what is the best way to connect since there are four wires and only two on the cap?

Hi Firebird, welcome to VK.

I moved your posts to it own thread here in the Rectangular & SS Forum, it'll have a better chance of being seen and getting help than if it's attached to another unrelated thread.

I agree on that safety cap.. Replace first, and then if the set still kicks the circuit breaker out, you may have a bad HV tripler (the gray box with the anode lead from it, up to the top of the CRT). Those leaked a lot, and caused a heavy load on the power supply. Easy to verify; carefully unsolder and secure AWAY from any metal, the black wire from the tripler going to the flyback. Turn the set on, and see if it still shuts off. If not, the tripler is bad. But again, watch out for that black wire while you have it off the terminal. The RF can arc an inch or more, and will cause damage to other parts, or of course cauterize a hole in your finger ;-). Also, when you resolder that wire, use black silicone RTV sealant to cover it with a blob, so as to protect it from arcing later.

Charles

I also have the same question as Firebird with my 1977 T-995 chassis regarding replacing the 4 lead safety cap with a 2 lead orange drop cap on the retrace module. Do I just bridge the solder pads, or re-route the 2 leads a certain way? Schematic shows each lead goes to separate pins on one module socket. Pins 8,9,11,12 with a silicon diode across pins 8, and 12. I'm wanting to replace the 4 lead cap on my set for increased reliability after reading how they can fail, and destroy the crt. As far as I know it is the original one, and being 35 years old it could go bad any minute. Mine shows part 250563-11 which cross references to a .0086 mfd @1600 volts. The 250563-18 cross references to a .0135 mfd @1600 volts.

Yes, bridge the end terminals together. I had a T809 19" with a shorted 4-lead safety cap and I had to connect two HV orange drop caps in parallel to get the correct value. I removed the old cap from the chassis, bridged both sets of end terminals together on the chassis, installed the orange drop cap, and the set worked great.

When checking these caps, you will read a short circuit between each set of end terminals. There should be no short when measured from end to end. If it reads shorted or shows any resistance from end to end, it's bad and should be replaced.

Put in the capacitor. Set came on and stayed on. Still no picture. Where do i find a tripler? I have not been able to find one so far.

Are you looking for the tripler in the set...or are you looking to buy one? :) One of us might have a spare; I have a box of assorted triplers.

I am looking to buy one.

Do you have one for the T815-09 chassis?

Does anybody know where i can get one?

Do you know for sure that the tripler is bad? If you feel static on the screen when you turn on the set; then, you are getting HV and the tripler is likely OK. If no HV is at the CRT; then, unsolder the input lead to the tripler and if there is HV coming out of the flyback, the tripler is bad. If you have no HV coming out of the flyback, you have a problem in either the horizontal output, horizontal driver, or horizontal oscillator stages.

I have HV. Put in new horizontal output transistor. What do i look at next?

I would appreciate any help i could get.

What is the set currently doing when you try and run it?

Tuner lights no picture no sound

I recall an issue with solder joints on these sets. If you have HV, but no sound, that points to a "power supply" voltage common to both audio and video.

The key thing to remember is that not all power supply voltages come from a resistor (or voltage ladder) off the main power supply from the power transformer.

Many of these lower voltages are derived from a winding tap on the flyback, that feed a rectifier diode and finally a smaller value electrolytic cap. See if you have DC on the cathodes of any rectifier diodes fed from the flyback. Often, there is a low value or "fuse" resistor in series there.

I do not have the schematic on a set this new, but I could point it right out if someone could post it.

Have you resoldered the pins on the modules yet? That used to be the first thing I did to these sets years ago. I sure hope I'm thinking of the right chassis about now...

Soldered all the connections on the chassis till i got to the left under the picture tube. Did not have time to get to the video or audio boards on the left or the tuner. The picture came on in black and white, still no sound. Picture stretches a little to the right. Color sometimes appears when scene changes. Do i need to solder the rest or does it have a defective video or audio board?

Finished resolder, now when it comes on picture is red, no sound and the suction cup wire is arcing off bad at top of tube. If it is not the tripler then what would cause this?

Have you cleaned the bell of the CRT? Have you cleaned the suction cup?

You've probably bridged a solder connection. Check your work.

Did you solder the modules themselves, too?

Have you got a good magnafying (?) glass and a bright light source?

I am a little confused. Last week i resoldered the half of the chassis that has the flyback and it came on. Displayed a black and white picture with no sound. This week i resoldered all the modules on the sound and color half of the chassis and the flyback starts arcing. Still no color except for red and no sound. Why the arcing when i did not work on the flyback. I did solder the connection pins on the color and sound side of the main board. I double checked my work, no cross solder. Could the flyback or tripler be getting too much voltage?

How about the ground stakes that hold the circuit board to the chassis frame?

I wish I could see an image of what you are doing.

Whats the flyback arcing to?

I resoldered the ground stakes. The arcing is coming out from under the suction cup. I will try to post pictures.

Definitely clean the bell of the CRT around the HV connection. Be sure to discharge the CRT before you do anything having to do with this connection. Also, If you can find some silicone grease, clean the suction cup and put just a dab of the grease around the edge that touches the tube.

Is the ground connection from the CRT still connected to the chassis properly? This can cause wild problems, too.

Like Holmesuser01 said, clean the bell and cup first. Check your HV. If it's too high, it can arc even if it's clean.

Flyback
 

Pictures of my Magnavox. Blue arc can be seen at top on right in picture three. Picture is faded.

Flyback
 

Pictures

Arcing
 

Better Picture.

All pictures are mirrored, taken with an apple macbook pro, so ask them why.

Grease fixed flyback. Still no color no sound.

Did you physically remove each module when you soldered the mother board? And, you did resolder the connections on the modules?

You shouldn't have to redo everything on the boards. It's just the high-current connections that flex and break

Sometimes, you can take some fine sandpaper and clean up the stakes on the mother board to get a better connection to the module.

When you turn on the set, do you get a thump sound in the speaker? That would tell you if the amplifier module is at least working. Examined the module for discolored parts?

You dont have a schematic, do you? The FBT also supplies power to some of the modules. Your no sound problem could be something as easy as a fusable resistor that is open.

Best of luck. I never really had alot of issues with these Maggie chassis, other than the module and mother board soldering problems, and the occasional tripler, and/or horizontal output transistor.

Does not make any sound. Does anyone have a sound or chroma module for the t815-09? I also need the remote receiver module. I soldered every pin on the main board and all the modules. Picture also pulls a little to the right, with cut off graphics.

Which resistors and transistors near the flyback should i replace?

Does anyone have parts for the T815 chassis? Help would be most appreciated.

I need the verticle oscillator module. I believe the part number is 704200-3.

Replaced all the capacitors on the verticle oscillator module now only have two thirds of a picture and its snowy.

Removed and reconnected some parts. Picture is back like it was, no color, no sound. I believe the tripler is weak. Could this be the problem?