CTC-7: I am NOT smarter than the manual!

[miniman82]

K, after all the troubles I've been having, I decided I needed to break trouble spots down to their respective areas and start over. I was having simultaneous issues with the tuner and color demod, and was unable to figure out which circuit was causing what issue. Here's what I did.

I injected a composite signal into the set at the first video amp grid using my B&K NTSC gen, to bypass the tuner completely. I then ignored all other issues, and concentrated my efforts on the 3.58 Mhz local oscillator. The manual for the 7 does not have a very good proceedure for color AFC alignment, so I used the one from the CTC-9 Sams folder since it's easier to follow. The circuits are similar enough, just the voltages are different (for example, phase detactor voltages are + and - 13 volts for the 7, vice 30-ish for the 9).

Turns out the oscillator had been running way off (like 3 harmonics away from where it should have been), which became apparent when I did not have bars but a strange looking pattern like Phil had on his CT-100. First Sams has me peak the driver trans for maximum signal. I then grounded the junction of R727A/B on the phase detector, and adjusted the osc coil till I had bars that 'slowly float by' as per the manual. I then verified correct waveform on the R-Y amp. After checking the other amps for correct waveform, I went back and connected the sig gen to the tuner.

I had nothing. The slug for channel 3 was way off, and it didn't seem like I would be able to get anything at all no matter how far I went with it. It ended up being the AGC pot that was throwing off the tuner, and after adjusting that I was able to get a luma ladder on the o-scope through the IF strip to the video amps. Now I had color on the screen, though the tuner was very sensitive to fine adjustments. The noise gate was also set incorrectly, and after adjusting that sync got much more stable as well. Now I had a good signal, but bad colors. On to CRT grid and screen adjustments, and now I had something resembling a decent picture!

Only thing I have left to do now is getting the horizontal drive under 200ma and a full on purity, convergence, and grey scale attack. After that, I think this set will display a very nice picture. Too bad the Colorama 21CYP22A tube needed a brightener to get any normal brightness out of it- I picked up a NOS 70 degree one off Ebay for $20.

Then, It's on to a whole new can of worms: what to do with a beat up photo finish cabinet! Here's what I have on the screen right now.

[old_tv_nut]

congrats on wading through multiple problems!

[Phil Nelson]

That looks very promising. Patience pays off!

Photofinish with significant damage will not be easy to restore. Some people claim success with paints and artist brushes. Stewart Schooley has developed a DIY process for making new paper that may be worth trying:

http://www.radioatticarchives.com/fe...oto-finish.htm

If that set's a keeper, I'd be tempted to remove the photofinish and put on real veneer (easier said than done, I know).

Phil Nelson

[sampson159]

depending on the type of wood in the "photofinish",it can be replicated with minimal supplies.i ve just finished a zenith radio that had a severly damaged cabinet.couple different colors of stain,an artist brush,a sea sponge and some flat brown paint.my finish product has fooled some friends.although not perfect,i am pleased with the results.using a small roller,apply flat paint to surface.tear off a piece of sea sponge and dip into lighter of the stains.dab onto painted surface lightly.when dry,do same with darker stain.take an artist brush and pull stain to grain like pattern.pull in wavy like pattern.let this dry after finished for several days.take very fine,(00) steel wool and lightly rub surface.after rubbing and tack rag,apply gloss finish.i use tung oil of the wipe on variety.teak oil,danish oil,wipe on poly,etc.it will produce a pleasing,woodlike finish.it is time consuming but the finish result will be worth it.i ll post pics later.i have also done some paper woodgrains on an inkjet printer.these look good also.there is a really nice but expensive product out there call dy-noc.i have done a radio in this and the results are very good.personally,i like my paint and stain finish best

[miniman82]

Originally Posted by Phil Nelson

If that set's a keeper, I'd be tempted to remove the photofinish and put on real veneer.

That was my first reaction. This set would actually be easy to do, considering it has mostly flat edges on the cabinet. Any suggestions on what I should go with? I was thinking mahogany.