|
|
|
#1
10-08-2011, 12:29 PM
|
|||
|
|||
|
25DC56 width
will checking out a few things I see a coil L219 mounted on the flyback mount. no mention of adj anywhere I can see in the sams. pn says (5th harmonic). It in p with a .03 5% cap. anyone know what the 5th harmonic is all about?
|
|
#2
10-08-2011, 03:02 PM
|
||||
|
||||
|
Isn't that the flat all solid state chassis? If so and if you're having width problems, check those white safety caps that are in the collector circuit of the horizontal output transistor. I think two or three of them are mounted on the flyback and the others are mounted under the chassis. In fact, it would probably be a good idea to change them, anyway. These are the ceramic cased HV caps that can blow up. If too many of them fail, the HV will skyrocket and burn off the neck of the CRT.
|
|
#3
10-08-2011, 05:30 PM
|
|||
|
|||
|
yes that is the chassis, and yes they have been replaced with the 'special' branded zenith caps (two on the top, one on the bottom).
I did some reading on the horz deflection, the tuned to the 5th harmonic has something to do with HV regulation. the purity was a tad off, so I reset it, wow, now the color really pops, its amazing how just a bit off can really effect the color performance overall. checked a diode that is in series with the blue wire (there is a diode and resistor) both checked fine. there is a .68 and a .47 caps that are around the output, and there is a big disk across the damper diode, but I dont really want to go messing with those unless some one else has found these to cause the excess width. I even tried it on the variac, it still has a problem even with the AC down under 100vac (has one of those loosely coupled power transformers that allow operation from 95-130vac).
|
|
#4
10-09-2011, 11:54 AM
|
||||
|
||||
|
So just to be clear, your set has all five of the white ceramic "crt-neck-snapoff" caps replaced with the orange 22-5001 special caps? If not, you're in jeopardy of hearing "ZZZZZZZZZZZZZZ-pffffffsssshhhhhhhhhhhhhhhhT!!!!" followed by the smell of ozone and the sound of glass powder tinkling down onto the chassis...
As far as the width goes, I can't remember how it's adjusted on that set. I do have all the manuals and supplements on it, but I'm in Dallas this week and they're in California, so I'll look it up next week if you need. Charles
__________________
Collecting & restoring TVs in Los Angeles since age 10
|
|
#5
10-09-2011, 01:26 PM
|
|||
|
|||
|
Charles, I only recall seeing three replaced, two were on the Flyback topside, and one was one was on the bottom, all the 22-5001 orange drops. I did not see any white caps remaining.
I hope you can find something to adj either the centering or the width, its shifted way off the right, although I think its more centering than width since round objects to not seem like they are overly wide.
|
| Audiokarma |
|
#6
10-09-2011, 02:52 PM
|
|||
|
|||
|
just sitting here watching football, those CC2 zeniths just make a GREAT pic, the color really is stunning. all I can say if everybody needs to save one for their daily driver. When I had the back off the other day I check the PT caps and the fly, all stone cold after extended running.
|
|
#8
10-10-2011, 05:35 PM
|
|||
|
|||
|
the horz hold control does move it some, but not enough, and it never breaks sync even at the extreme end of the control. odd, its a coil but seem to have very limited travel. I cant see an external limit stop like on older zeniths where its built into the knob. Of course there is prob something inside the chassis. I only get about 180 degrees of adjustment so there has to be something.
Last edited by DaveWM; 10-10-2011 at 07:04 PM.
|
|
#10
10-13-2011, 10:45 PM
|
|||
|
|||
|
thought I was on to something, a 3uf cap that connects to the base of the horz afc transistor thru a 1.5k resistor was open. Replaced it. I think its function was to smooth the voltage from the horz phase detector diodes, but not sure about that.
Next up will be to replace both horz phase diodes AND both 100k resistors that are connected in P with them. The sync is solid, I am only checking replacing these as I have read up on horz pos problems associated with the AFC diodes. Charles, I hope you can find something in your documentation, I have both the sams and goodman service manuals, could not find any reference to how to adj the horz posistion.
|
| Audiokarma |
|
#12
10-14-2011, 11:47 PM
|
|||
|
|||
|
could not wait of course, found a generic NPN silicon in my junt box motorola 306, popped it in (thank you zenith for the plug in transistors) bingo horz centered.
This shaper transistor was a grounded base transistor that took the horz pulse from a winding on the FLY and used coupled it to the AFC diodes.
|
|
#13
10-15-2011, 01:00 AM
|
|||
|
|||
|
What is the zenith part number and the actual numbers on the transistor?? I have lots of that stuff and should be able to find one.
Good job on that one, usually when transistors it results in smoke and or multiple other parts destroyed.
|
|
#14
10-15-2011, 09:20 AM
|
|||
|
|||
|
its an ECG123a. I am going to stop by the local surplus store, they have lots of old transistors.
Yea what threw me was the lack of other problems, just a little bit of horz postion (about 2" to the right), everything else worked perfect so like you I assumed the transistors were ok. was getting ready to replace the AFC diodes, checking them in circuit they looked ok. As long as I had the diode tester I did a quick sweep of the 4 transistors in circuit. When that one did not check I figured it was just a part shunting the BC, pulled it and tested again. I suppose if I had checked the voltages or waveform on that with the set running I would have seen it. anyway its all back together now. 121-447 GE-20 motorola HEP736 SK3124 ECG123a
|
|
#15
10-15-2011, 11:17 AM
|
||||
|
||||
|
Quote:
Mine has also survived a house fire, two severe earthquakes throwing it on the floor, and being moved countless times. Charles
__________________
Collecting & restoring TVs in Los Angeles since age 10
|
| Audiokarma |
 |
|
|
Linear Mode
