I've been blessed!

[old_tv_nut]

Have scrounged enough parts to replace the broken blue lateral magnet, and also the missing spring clip to hold the convergence coils together around the neck. Of course, when replacing the latter, it was so tight that I managed to bump everything while fighting it, so had to go through the complete purity and convergence procedure again.

Still want to try checking tuner and IF alignment, but that will have to wait a while as April is going to be very busy for me.

[old_tv_nut]

Well, getting to the alignment did take "a while." Got a 2500 ohm 100W resitor to load the B+ with the sweeps disabled, read the procedure in SAMs and RCA about 10 times each, then realized I had to make some cables that were missing from the B&K sweep gen I bought on the bay.

Finally fired up everything today and started the sound alignment and video sound trap. Discovered the B&K will produce modulated IF marker frequencies, but not the modulated 4.5 MHz called for in the old procedures. No problem aligning the sound IF and detector, as there is an alternate procedure for doing it with a sweep. However, the video sound trap (actually a 4.5 MHz trap in the chroma take-off coil) only has a procedure for using 400 Hz modulated 4.5 MHz. So, I tried it with the sweep instead, and I hope I got it right, because it looked like the trap frequency was off quite a bit low. It was hard to see, though, because the chroma board is crawling with 3.58 MHz CW. [doh - just had a thought - before I tear down, I should see if I can kill the color oscillator temporarily - will have to try that] A wrong trap frequency could have something to do with the color ringing I have seen on color bars, but I really want to make sure I haven't screwed it up.

Next after the audio is to get everything connected for aligning the IF, which the B&K is fully capable of, even the procedure that uses CW at various frequencies and then checks the overall result with the sweep.

[old_tv_nut]

Today I repeated the 4.5 MHz trap adjustment with the color oscillator killed (0.01 microfarad from grid to ground). I was reading the wrong point when the 3.58 MHz was running and obscuring the waveform. The trap was not tuned as low as I thought and may not have been wrong at all. Definitely have it tuned to 4.5 MHz now.

BTW, the Sams said the trap is the top core and RCA said bottom. Sams is correct.

On to the IF...

[old_tv_nut]

This weekend I tried the If alignment and screwed it up. The first step of tuning the coupling coil between the 1st and second IF required quite a large adjustment, it seemed, and I did get to the correct response, but then the end-to-end sweep came out far too narrow. Will have to go back to the beginning and make sure the loading circuit is correct and connected to the correct point, leads are extra short, etc. etc.

Are we having fun yet?

[old_tv_nut]

Got back on this this weekend, but not as much as I wanted because I was called on to photograph the kids at the neighborhood block/Halloween party. Anyway, I couldn't get the 1st-2nd IF coil tuned right this time until I discovered that somewhere along the way I had switched to an un-terminated input cable - duh!

Now have to find out what I have been doing wrong in the over-all IF alignment.

One more thing: terminal "C" on the video board is the first video grid and should be grounded during alignment. Terminal "C" on the IF is filament supply and should not be grounded unless you like the smell of burning jumper wire insulation.

[miniman82]

Have fun with the alignment! I've read in a supplement that IF alignment should not be attempted as a fix, only as a last resort if all other fixes fail. Guess that shows to go ya how much the techs liked doing alignments, huh?

[old_tv_nut]

Originally Posted by miniman82

Have fun with the alignment! I've read in a supplement that IF alignment should not be attempted as a fix, only as a last resort if all other fixes fail. Guess that shows to go ya how much the techs liked doing alignments, huh?

Less than 1/8 turn of one of the cores in that dual-core coil can throw it out of spec (45% +10/-5% lower marker, 55% +10/-5% on the upper, IIRC). I can see that if you had no idea of how a double-tuned circuit should behave, you could be in trouble.

This reminds me of a job I had one summer at a UHF tuner manufacturer doing final alignment. Those who had experience (mostly women who had no electronics knowledge, but lots of experience aligning tuners) could do it about three times as fast as I could at first - because they knew what to expect for that design and could quickly see which way to go from an initial out-of-tune state. That was much worse than doing an IF alignment, since it involved getting stages to track across the whole band - and the tuner had peculiarities where it would develop a suckout at certain channels that could be reduced by very slight compromise of the over-all tuning. So, my first output tended to be very good on the good channels, but to fail inspection at the bad frequencies.

[Phil Nelson]

Originally Posted by miniman82

I've read in a supplement that IF alignment should not be attempted as a fix, only as a last resort if all other fixes fail.

It makes sense to eliminate simpler causes first. No need to rebuild an engine if it just has a dirty carburetor.

Phil

[old_tv_nut]

Well, it appeared that several coils needed adjustment, inlcuding some of the traps. Here is the result as it sits on the bench now.

On the left is the sound trap marker at 41.25 MHz (4.5 in video, not really visible because it's at the baseline), then about 10% up the left skirt is 41.67 (4.08 at video), then at 50% is 42.17 (3.58), then approaching the top is 42.67(3.08); and right above that on the skirt is 42.75, whihc is supposed to be up on the top of curve, but I can't get it there without ruining the overall response (think it's OK as is). At top right is 45.0 (per spec), then 45.75 (video carrier) at 50%, and hard to see at bottom right is 47.25 adjacent sound trap.

[old_tv_nut]

Well, I disconnected all the test gear and put the chassis back in the cabinet. Picture looks OK, but the problem with the sound volume getting low when the fine tuning is correct is now worse. OOPS - forgot to turn the page in the instructions and do the last step where one sound trap is deliberately detuned to get the sound carrier 22 dB below the video.

Well, since I understand what they are shooting for, I am going to try detuning it "by ear" while listening to the sound on the test pattern disc. Strange thing to me is that they say to detune it, but they don't say which way. I would think it should go towards the upper adjacent channel, that is, lower in frequency at IF, so it is moved away from the edge of the chroma. So, since I can't tell which way is which without the sweep, I will try both ways and see if there is any bad effect in the picture one way or the other.

This brings up a question: should the sound volume be so sensitive to the sound carrier amplitude? Can someone with a similar set try the fine tuning and let me know if it affects the sound volume strongly? If it doesn't, I should be looking for some sound trouble. BTW, I did check alignment of the sound section, so I know that's not it.

[old_tv_nut]

Can someone with a "Super" CTC-5 try the fine tuning to see if it affects the sound volume?

I 've read up on the schematic of the sound section and operation of the ratio detector. This chassis (the Super) has only one sound IF stage instead of two (in the Deluxe), so it may be gain-challenged. The ratio detector has some built-in AM rejection capability, but my understanding is that its output level due to the FM deviation is also proportional to the intercarrier amplitude if there is no limiting preceding the detector.

I've also ordered a couple of replacement sound IF tubes to see if that offers any improvement.

[old_tv_nut]

I completely detuned the sound trap, and now have reasonable audio (and do not have sound beat in the picture). Sound volume still varies some when adjusting fine tuning (runnning up and down the slope), so this set is far from being in limiting. Waiting to get the replacment tube(s) and see if that does anything.

Picture was blurrier than ever after the alignment (don't know if its supposed to be that way, or my efforts narrowed the IF too much). So, I tweaked the interstage to bring up the high freq video and chroma a bit. I'd definitely rate the "super" chassis as a stumble along the path of cost reduction of color sets.

I've decided I'm going to button this up for a while and get my living room back, at least over the holidays. Got the bezel and pencil box back on and the back installed. Will use it to view some DVDs of old Christmas shows, just because.

[old_tv_nut]

Now that I have my living room back, I turned the set around to face the room for normal use. Of course, I then had to touch up purity and convergence.

Have just been watching some Bob Hope holiday excerpts, some pix of which I posted to another thread under general topics, titled "Hope for the Holidays."

[old_tv_nut]

drat - forgot that I need to replace the channel indicator lamp, now can't see what kind of base it has, or find it in Sams, and don't have a tool that can get in to unscrew it.

Before I pull the tuner again, anybody know what bulb this is and where to find one? (suspect it's a common bayonet base bulb)

[Steve D.]

My Sams is for the CTC-5 Deluxe models. It lists under misc. a #44 bulb. Not sure if it's different for a Super chassis set. The other option may be a #47 bulb. Surprised it isn't listed in the misc. section.

-Steve D.