Are These Circuit Traces Bad

[zeno]

Originally Posted by DaveWM

so you still did not look into the horz blanking? that would have been the 1st place I would have checked.

Yes lets get back to the jail bars ! The filter can was a good learning
experience but as I suspected unneeded..............
The Sams is in front of me & I am redy to rock & roll !

73 Zeno

[DaveWM]

is this the 25dc56? I assume so,

I would look at the diode and blanking transistor, as well as the voltage divider in front of that.

Scope the fly pulse all the way thru the two blanking transistors.

[TinCanAlley]

I'm doing the best I can. I'm new to this and am doing the things I can do/know how to do. If those don't work, then I can start to tackle the harder things. I don't own a scope, so I'll have to borrow one. I've read through the SM and don't fully understand how to test the blanking circuit, etc.

I'm willing to go all the way in testing an fixing you you're willing to help and understand I'm pretty new to all this.

My first fix is to undo something I just did. If this problem sounds familiar, yell. After changing the horizontal board and caps, I now have a strange effect on the screen. It's hard to explain, but I think if you've seen it before, you'll understand. There are invisible waves rolling diagonally across the screen towards the upper left corner for a moment. They then stop and reverse direction rolling down towards the lower left. They stop again and reverse. The closest I can give an example of is when you're adjusting the APC to get the movement out of the color bars, except these aren't colors rolling, just invisible waves. I'm not sure if it's the what I did, or some other interference that's being introduced.

The chassis is the 25EC58 and if you want to point to things to test/replace, please fire away!

Thanks!

[DaveWM]

you need to deal with one problem at a time.

sounds like some kind of interference, make sure you are not setting a RF source near the set (like a DVD player on top of the tv) try a different signal source, double check that you have everything hooked up right (300ohm to 75 ohm balun) make sure you have not messed up lead dress inside the tv (crt wires, HV wires,tuner IF link). All grounds are in place.

Shot gun repairs often introduce new problems making diagnosis a more difficult problem. don't take it personally, a lot of peeps seem to think replacing every cap in sight will fix everything. It has been my exp that most sets from the mid sixties on do NOT require a lot of cap replacement, and doing so just introduces possible new problems.

So on to the existing problem without a scope its just a guess that the horz blanking is a problem causing the jail bars. if you have the schematic you should be able to find the diode that feeds the pulse to the blanking transistor. I do not know if its on a modual or chassis mounted. On the 25DC56 its NOT on the modual.

[TinCanAlley]

Originally Posted by DaveWM

you need to deal with one problem at a time.

sounds like some kind of interference, make sure you are not setting a RF source near the set (like a DVD player on top of the tv) try a different signal source, double check that you have everything hooked up right (300ohm to 75 ohm balun) make sure you have not messed up lead dress inside the tv (crt wires, HV wires,tuner IF link). All grounds are in place.

Shot gun repairs often introduce new problems making diagnosis a more difficult problem. don't take it personally, a lot of peeps seem to think replacing every cap in sight will fix everything. It has been my exp that most sets from the mid sixties on do NOT require a lot of cap replacement, and doing so just introduces possible new problems.

So on to the existing problem without a scope its just a guess that the horz blanking is a problem causing the jail bars. if you have the schematic you should be able to find the diode that feeds the pulse to the blanking transistor. I do not know if its on a modual or chassis mounted. On the 25DC56 its NOT on the modual.

I see a few things marked with "blanking." I'm attaching some pics of a basic circuit layout that might be what you're referring to. If it's there, point it out and I should then know where to look on the schematic. Also attaching a pic of a pin with a label regarding raster blanking. Not sure what that is, but the lead is headed over towards the tuner wiring.

[DaveWM]

Q202 is the one, you could try checking it, but I doubt its the problem. under the chassis you should see diode that goes to the base of that, then a couple resistors 33k then a couple 100k (5%). from there it goes to the flyback thru a cap.

I would check the transistor, diode,and resistors. Pretty sure you will need to take them out of the circuit to check, which will be a PITA and of course they may be ok. With out a scope you are handicapped into doing work to check things rather than just looking at the signal.

Again this is only a guess, so don't expect it to fix things its just an educated guess.

If I were you I would start looking into buying a scope, I know there will be some that say its a waste of money, true you can fix a lot of stuff without one, but when you run into tough dogs, it will save time, "don't be a dope, use that scope"

[DaveWM]

oh in case you do not know, its always wise to use heat sinks when soldering semiconductors, esp old ones that may be germainium. I use hemostats. clamp near the body of the part to sink out heat from the leads when soldering our un soldering.

[TinCanAlley]

Originally Posted by DaveWM

Q202 is the one, you could try checking it, but I doubt its the problem. under the chassis you should see diode that goes to the base of that, then a couple resistors 33k then a couple 100k (5%). from there it goes to the flyback thru a cap.

I would check the transistor, diode,and resistors. Pretty sure you will need to take them out of the circuit to check, which will be a PITA and of course they may be ok. With out a scope you are handicapped into doing work to check things rather than just looking at the signal.

Again this is only a guess, so don't expect it to fix things its just an educated guess.

If I were you I would start looking into buying a scope, I know there will be some that say its a waste of money, true you can fix a lot of stuff without one, but when you run into tough dogs, it will save time, "don't be a dope, use that scope"

My brother has a scope I could borrow on Sunday. If I got that, could testing be something I could be stepped though (where to hook up, what to set it for and what to expect)?

[DaveWM]

CR 201 on the schematic

[TinCanAlley]

Originally Posted by DaveWM

CR 201 on the schematic

I wish the Photfacts scans were clearer. If I'm counting correctly, I believe CR201 is across pins 11 and 12. I'm attaching a pic of what I think it is. I can also post a pic of the entire section of the underside if you like.

Does anyone else think it looks like it was either replaced before, or someone already cut one lead, tested it and then soldered it back together?

[zeno]

Looks like it was snipped but not changed.

73 Zeno

[DaveWM]

I am looking at the zenith factory schematic, so the numbers could be different from the sams, but that looks right. you can check that diode, the 33k and if you look further back there should be a couple 100k 5% resistors. Interesting that its already been snipped and soldered back.