My Christmas day 9T246 restoration! Almost..... - Page 6 - Videokarma.org TV - Video

*Bill Cahill* · #76 02-02-2013, 12:01 AM

You're welcome, Tim. Always glad to help.
Bill Cahill

***Kamakiri*** · #77 02-12-2013, 07:24 PM

Since last post, I replaced the incorrect valued cap I'd installed on the horizontal linearity coil.

Since it seems I was using the wrong Sams, I had originally put in a .01 @ 600V cap. Solid lock on horizontal. Now, I replaced the cap (C85) with a .039 @ 1 kV, and I'm back to square one with the horizontal, and being out of lock every time I change the channel.

Also replaced the .018 @ 1 kV damper filter with .02 at same rating. The bumblebee had a huge crack across the back side, which I couldn't see until removed.

Next, replaced the line filter caps (C93 & C94) with the correct stated value of .01, but upped working voltage to 630.

That said, here's my question:

Would changing the horizontal linearity coil BACK to the .01 uF from .039 cause any harm? It had solid sync lock with that cap in it, but it was wrong according to the Sams, so I switched it back in fear of causing damage.

wa2ise · #78 02-12-2013, 08:11 PM

Quote:

Originally Posted by Kamakiri

That said, here's my question:

Would changing the horizontal linearity coil BACK to the .01 uF from .039 cause any harm? It had solid sync lock with that cap in it, but it was wrong according to the Sams, so I switched it back in fear of causing damage.

I'd switch back to the 0.01 cap. It worked for you before, and the other caps you replaced should have no effect on the horizontal hold circuit.

*Bill Cahill* · #79 02-13-2013, 12:28 AM

No. I know what's wrong.
You were loading down the poser supply before, so, horiz. osc. was right on. You changed it to correct values, taking some of the over load off, so, now, horiz. osc. needs re adjusting.
On the damper caps. not high enough voltage. They MUST be 1KV.
Tim, you are closer than you thought. The lin. coil doesn't adjust the oscilatr. Power supply was being overloaded before. Remember? Low hv?
Set was drawing more current.
Leave the correct caps in, and, re align the horiz. osc. according to instruction.
Bill Cahill

***Kamakiri*** · #80 02-13-2013, 05:12 AM

I re-read what I wrote, and went back and corrected it. I meant to say "line filter" caps, not damper filter.

***Kamakiri*** · #81 02-13-2013, 06:04 AM

Quote:

Originally Posted by Bill Cahill

No. I know what's wrong.
You were loading down the poser supply before, so, horiz. osc. was right on. You changed it to correct values, taking some of the over load off, so, now, horiz. osc. needs re adjusting.
On the damper caps. not high enough voltage. They MUST be 1KV.
Tim, you are closer than you thought. The lin. coil doesn't adjust the oscilatr. Power supply was being overloaded before. Remember? Low hv?
Set was drawing more current.
Leave the correct caps in, and, re align the horiz. osc. according to instruction.
Bill Cahill

Okay, review this with me for a sec

Since last update, I replaced the one .018 damper filter, which was basically split open on the back. I assume that's where I repaired the low HV issue.

I may be wrong, but I don't see how the cap on the linearity coil can affect HV. If anything, won't it affect the time base of the horizontal oscillator? In fact, when I first powered the set up, I was able to crank the control to the left and lock the picture in with multiple images.

*Bill Cahill* · #82 02-13-2013, 06:36 AM

NO. that coil isn't for adjusting the horizontal osc. frequency at all.
It makes the picture more linear. In other words, If you look at a circle on your screen, and, picture is non linear, the circle may be egg shaped, or, jagged, instead of completely round. Now, this is only a simple example, but, I hope it works.
Now, the horizontal drive will adjust the amount of voltage the control grid on the horizontal output receives. That will also affect your hv, but, not the oscilator frequency. But, if voltage is pulled down too much it can also, now, mind you, I'm not saying will, but, can affect the horizontal osc. frequency because it's loading down the horizontal output, which in turn pulls more current, which in turn pulls down power supply voltage, which will affect the frequency....

You neded to go back to the horizontal osc. coil, and, follow the directions on proper adjustment of the horizontal oscilator.
Bill Cahill

***Kamakiri*** · #83 02-13-2013, 08:26 PM

Well, for the heck of it, I tried it anyway. I took out the .018 cap and put the .01 back in. BAM! PERFECT FLAWLESS sync lock!

Picture looks great, everything is stable, sound is loud and clear, and the majority of the components in the set are new. Time to slam the hood and drive her off the lift.

Stick a fork in my 9T246, it is DONE!!!!

*Bill Cahill* · #84 02-13-2013, 08:49 PM

Congradulations, Tim!
Like I said, the circuit was drawing more current, loading things down. You put the correct part back in, and, poof.! Problem solved..........
Bill Cahill

***Kamakiri*** · #85 02-14-2013, 05:12 AM

Actually, no, I put the wrong part back in

*Bill Cahill* · #86 02-14-2013, 05:33 AM

OH, boy.......... I give up........

Bill Cahill

***Kamakiri*** · #87 02-14-2013, 06:21 AM

If an .008 uF capacitance difference locks in the circuit, I'm somehow good with that. Probably even less, considering a normal 20% tolerance.

DavGoodlin · #88 02-14-2013, 12:19 PM

This is like prof. Whopee and the 3-dimensional blackboard.

I think we all learned something here. Got 2 RCAs with this chassis but have not started yet.

Tim is the student with a good question and Bill is the professor.

Thanks Bill and Tim!

init4fun · #89 02-14-2013, 12:20 PM

Quote:

Originally Posted by Kamakiri

If an .008 uF capacitance difference locks in the circuit, I'm somehow good with that. Probably even less, considering a normal 20% tolerance.

While I fully understand the desire to follow the schematic "to the letter" , I understand there ARE times when this just isn't possible . Several times I have run into resonant circuits that work better with more (or less) capacitance than the circuit calls for . I had always attributed this to slight differences in components like the coils , which may themselves be slightly off of their designed tolerances .

Say for instance , your peaking coil that was supposed to be wound with 1000 turns accidentally left the factory with 950 turns instead . The capacitance required to get this particular coil to resonate at the desired frequency would certainly be different than that needed for the proper 1000 turn coil , and thus will never perfectly coincide with what the schematic calls for . It's instances like these where ya gotta give the circuit what it wants , rather than rigidly adhering to a schematic value that produces un acceptable results .

This is where a capacitor substitution box that has like 10 switchable values can aid greatly in the experimentation of finding the best fit for that particular circuit .

ChrisW6ATV · #90 02-14-2013, 08:28 PM

Quote:

Originally Posted by Kamakiri

If an .008 uF capacitance difference locks in the circuit, I'm somehow good with that. Probably even less, considering a normal 20% tolerance.

Tim, I got lost somewhere. It first appeared that you "re-replaced" a .01 capacitor with a "correct" .039, and also replaced a .018 with a .02. Now, you have put the "incorrect" .01 back instead of the .039, nearly a 4-to-1 difference in capacitance. Are you confident that the original part you took out was a .039? Photofact schematics are not infallible, as I am sure you know. Were other adjustments or replacements made in the horizontal oscillator or output circuits, while the .01 was in place? The bottom line of it all is, if it works well now, put the cover on and enjoy it as you said.