CTC-7 metal table top
 

figured I should start a thread with a good title

some action started, trying a few things on rust removal, followed with some shots of the fly cage and finally the chassis

the chassis only has a little bit of surface rust on the back corner near the HOT.

All the tube shields were badly rusted, and the shield on the tuner was also badly rusted. Lastly the fly cage was a mess. Very few papers, so should be an easy recap to get to a test run stage. I will replace the top hat that had a rusted off lead, check the B+ for shorts and if ok will try a slow start with the HOT and VOT pulled.

the horz centering pot was a little bit stiff, some lube spray helped but I will test to be sure its not open. I have had problems with those before.

Let's see some pics of the cabinet! Is it a Blonde by chance?

http://videokarma.org/attachment.php...0&d=1361386075

its in really rough shape, lots of rust on the inside and surface rust ruining the blonde faux wood finish.

did a little more cleaning, replaced the broken power diode, checked the plug resistance 150 ohms? oh yea the thermal switch. The B+ was about 10k thats good and it started out at about 3K so the filter caps don't seem to be shorted.

So next up will be the jump the thermal B+ AND jump the heater since I will be using a variac. Monitor the B+ and see how she goes.

Almost all of the tubes were heavy with corrosion on the pins, I used a wire brush and contact cleaner. I will prob have to work over the tube sockets as well with the dental brushes and cleaner.

The vert out looks like it was chewed on by something at one point, but I have a NOS one of those, same with the horz eff coil, but also have a backup.

The G1 and G2 pots are hidden behind a bolted on cover (nice) and were mostly frozen. again cleaner and lube seems to have gotten them going, but I may replace them all, I hate crappy pots, and I dont think they are anything special.

that was so odd, the B+ was coming up but not like it should. So I check the B+ at the cathode of each doubler diode, hmmm the one on the ground side was neg voltage compared to ground, thats not right. I had replaced the top hat with out even looking at the printing, duh the cathode was reversed from the other top hat. Geezz I never thought they were different (top hats), but this one was. so I reversed the new one and bingo all good. But very odd looking seeing those two diode connect back to back that way. This is why I like the variac, you can catch odd stuff at 10vac line that would blow a cap if you just plugged it in at full line voltage.

anyway letting it reform some watching current and voltage and temps of the caps.

the can caps were doing fine up to about 250v, up to 375v and one of the cans started getting real hot (triple section). letting it cool down will try again and will leave at 250v over nite and try again.

up to 300v staying cool so far.

Meanwhile I am electrocuting the fly cage, boil boil toil and trouble....

washing soda,H2O,rebar and 12v car battery.... vs fly cage... oh the humanity.

the fly cage looks much better, all the rust is gone, there are some pits where it was but not bad. I will soak in some more tomorrow and see if there is any more improvement. After that a shot of primer to keep it from rusting and then some black. Cranked down the variac for over nite to about 150vdc, will continue the reform in the AM.

well the fly cage is pretty much ready for paint, maybe this weekend. The B+ is at 375+ and the can caps are barely warm after a couple hours. I cranked it down and will let it cook overnite at 200v, I figure in another 24-48 hrs it will be good enough for a full power try.

You like to live life on the edge, huh? I personally won't give an old cap a chance if it gets slightly warm, that just means it's past its prime and likely won't smooth out the voltage well at all. It will act like it has reduced capacity, so ripple will be higher as will leakage. Why not just put new ones in? It seems such a small price to pay for transformer protection.

I will prob do just that, BUT I like to base line a set and I know the caps will last long enough to test the HV and basic function of the set. That being said I have many sets built a little later than this (mid 60's) that have been running fine on the orig caps for a couple years now. I will generally test a can cap and IF it test well after all this process then I will leave it be. I don't really think I am taking any big chances since I will be putting a very conservative B+ fuse and ad a thermistor to absorb the inrush. Besides sometimes I wonder if new caps are really all that great, I use the best I can (nichicons 105c rated) but still wonder if they will last, esp since I have 40 year old caps that work just fine.

My main concern is to not introduce any possible errors and then replace one can at a time (if the fail to come around). I do replace all paper based caps (wax cover, Bumble bees, etc...) as I know they always leak, prior to any full power test.

I after the GE detour, I finally got back on this set. Replaced the 2 .47's in the fly and put the cage back on (to avoid any oops's with the fly out in the open).

Mostly has brown drops which often are ok, so I went about replacing some the ceramic tube elmenco caps (some were replacements done in the past).

there was a bumble bee on the primary of the audio out, and there is one in the IF that looks to be a pita to do as its got the solder on bottom shield. I am tempted to just do a j hook from the top replacement, I dont like unsoldering those covers, alway worry about a slip of the iron then melting down some insulation. there are a couple single electro as well, one on the video bd and one in the chroma section. those will get replaced as well before the initial power up. Nice to see the use of better caps on this vs the CTC-5 which had ALL papers.

If you wanna take care of the rust business PERMANENTLY, on the inside of the cabinet, there's this stuff called Duro-Extend that I can HEARTILY recommend. You brush it on, it looks like watery milk, smells worse than Sh!t, & dries to a purplish tone, over which you can then paint. It bonds to/with the rust, & then the metal's protected for good. I would imagine any good industrial paint store would have it. I would imagine the salty air in Orlando wreaks havoc on things that were haphazardly painted, like the inside of TV cabinets...

I could not bring myself to doing a 1/2a$$ job on that cap in the IF board, so managed to remove the shield and replace it. That should do it so I hope to try it out soon. I know one of the filter caps have to be replaced as it still runs warm after my extended reform process.

whoo hoo whe got a raster!!

time to leave it alone for the night.

todays project will be to check all the tubes (yea I only did some subs on the HV tubes to get it working thus far), see about installing a cathode fuse on the HOtube (or at least a test point that is easy to get at).

there was some issues with the 1st start up, the drive to the HO tube was not right, very small PP and way to fast (like 8x fast) It seems to start out this way and then pops in as the H tube warms up. Not sure if its just a tube issue or one of the feed back caps in the H board may be an issue. I will check out some of those mica caps as well if a tube swap does not settle it down.

I need to get some correct fuses (the kind with the ears on one side) but at least I know the fly is ok, so I am willing to spend some more time on it.

the vert sweep was not full, about 4" short. I dont know if it was a mis adjusted pot (as I had cleaned them) but if not then I will need to check the electro in the cathode circuit, pretty sure its in a can as I could not see a single anywhere on the board.

My shop is in a bit of a state of flux, so I am having to work on the floor, in the garage, on top of boxes etc... not the best situation.

ah ha, a 1.8 meg plate load resistor in the H osc tube is reading 12+ meg. bet that has something to do with it. Turns out the is no cathode bypass electro cap in the vert out anyway. Since its a plate load resistor just another reason to get out the tube tester and check for shorts.

it was not that resistor, not sure what I was reading BUT there was a .01 brown drop that was very leaky. So I started checking... yep almost EVERY brown drop was badly leaky, and the one that was not was very lossy,

So I have completely recapped the vert board now, and I suspect I will end up dong a full recap of this one just like the 5.

Going to give it a rest for a while. Not looking forward to that point to point chroma section, plus I need to take stock of the caps I may end up needing.

Congrats on getting a raster. It's good to know the fly is good.

I had to replace all the brown drops on both the horizontal and vertical boards to get mine to sync. Here's the thread on mine:
I went ahead and replaced all the other brown drops except the ones on the convergence board (I'll probably do those soon).

You're getting there :thmbsp:

-Clark

yea I bitch and moan about replacing caps, but its therapy really for doing the books all day long...

Did you ever come up with a back for yours? I think I will see if I can find a source of the perf metal (I am missing one to), I would like it to be heavy gauge AND reinforced around the neck area with a metal cover for the neck as protection for the CRT.

it just keeps on going, leaky caps EVERYWHERE. so far I have about a 90% leak ratio. working the chroma section now. what a PITA. just replaced the .22 that couple the blanker tube plate (385vdc) to the cathodes of the -y amps, it leaked at 150v (would not open the eye at all). I have yet to look a the video board, I know there are some coupling caps there that if leaked would really upset the CRT bias thru the video out tube.

No, I never found a back. I'm thinking about going the perf metal route, too. I thought I read somewhere on VK that Home Depot may have something suitable. I probably won't have time to mess with it until the summer.

Recapping the color section was the biggest PITA but not too bad. Does yours have the metal shield over the color demod section? Mine is missing but it doesn't seem to cause any problems. Maybe it's more to keep the 3.58 MHz oscillator from radiating.

I had problems with intermittents on the video output board. The 12BY7 really cooks it. I reflowed all connections and that seems to have fixed things. But the tube socket for the 12BY7 has seen better days.

I look forward to seeing your progress.

-Clark

no metal shield over the chroma on this one. I just found another shorted cap across the shunt tube (.0033), that will booger up the HV regulation some.

its coming along, I will prob try it again after I replace that .1 in the grid of the video out. I just don't want to smoke any plate load resistors due to tubes cooking off with bad coupling caps. I got a couple more easy ones out of the way on the chassis bottom, some more .1's

You can see the fine cracks in the epoxy dip of a lot of the brown drops.

finished up the recap. put in the correct fuses, got a pic, but no color lock (rolling color bars). I never did check any of the tubes (just subbed in new HV tubes). So I will start there by subbing in a new chroma osc tube. if that does not do it I will try a new Xtal.

intermittent color lock after adj the fine tuning some (new color osc).

Has very weak sync lock (horz) but will lock just need to adj each time I start up.

Focus does not seem to change, I am getting focus voltage but was not able to check to see if the pot adjusted it or not. perhaps a new 1V2 is in order.

HOT current seems too high, but I need to check that again, I just realized I think I had the meter laying down, the needle may not have started at zero.

The HO tube seem s to have an intermittent filament so will need to deal with that. the HV reg pot seems to be working.

3 more things, I had replaced a power resistor (4.7k that was about 8.5k) and had failed to solder it (but it was neatly thru the term stip hole and wrapped completely around, it was part of the color osc circuit IIRC), 2 I noticed that one of the demodulator plate load resistors had been replaced in the past (poorly I might add), it was a 6.8k. I noticed the other demodulator plate load resistor was a 5.6k, I double checked the schematic and it was a 5.6k there as well. IF it had been a better installation I would have maybe chalked it up to a factory mod, but since it was poorly j hooked in I will replace it with the correct part (this is from a factory service manual not a sams). 3 I replaced the .15 cap that is connected across the eff coil. it tested very leaky but still was able to open the eye tube about 1/2 way when checking for value, but it was about .25 uf tested vs .15 marked. The initial test run I did not attempt to set the dip of that coil since it was inside the HV cage and I had no access to it. Now with that cap replaced (the 2 .1s on either side of it test like new) I will attempt another start up. this time with the set on its side so I can get easy access to that coil.

could not wait, 1st had to un stuck the eff coil slug, then turned it on, got tweaked it some and voila 185ma with a solid 24kv (adj pot working well as well on both the drive and HV) nice...

still a bit flakey on the color bars, but very happy with the HV now. Still got tubes to test, and a new Xtal to install but its getting late so will quit while I am ahead.

oh and the AGC pots is very crappy, that will have to get replaced. just touch it and it goes nutz.

I picked up a new 1 meg from rat shack, but before I installed it I tried cleaning the old one, that made a HUGE improvement (I must have missed that one in the 1st pass). I used the opportunity to demo the pot function both before and after the cleaning to my teen daughter, She enjoys watching dad work on stuff and we use it as a learning lab (both using digital and analog meters) on what a variable resistor is (in this case its configured that way) and the advantages of a analog device in some settings. working on the color code with her as well.

I think tv's make great labs, for troubleshooting, and general maintenance (like cleaning pots and switches etc....) of vintage electronics. I know its dead end tech but I still think there is an opportunity to learn some of the basics.

hope to get to the xtal later and the tube checks on all the rest (not much to be gained there as a working set is a better test, and other than the soft focus and the color lock being intermittent, its a working set.

new xtal made a little difference, I think its more a poor horz sync than anything else. both the vert and horz are pretty weak locks, so I think I will need to look into the sync sep circuits.

anyone have the setup procedure for the sine wave coil on a CTC-7?

never mind, found it, short the sine wave coil, gound pin 2 of the horz osc tube, adj the horz hold for somewhat sync pic, remove coil ground, adj sine wave coil to bring back in sync, jump the coil again to check.

did all that but I still have maybe 1/4 turn at most to flop the osc (using the hold adj), and since it does indeed flop my guess is its a weak sync pulse. I subbed in new sync tubes (sep and amp) but no real change, still very narrow sync range. I am going to have to scope the output from the separator and see whats coming out. My guess is some voltage issue from a drifted resistor. will check the video out as well, maybe something getting clipped before in the IF?

may have a break thru on the horz instability. while wiggling tubes (1st thing to do) I notice when I pushed the horz osc way over it went out of sync, by adj the hold while holding it over I was able to sync it back AND it had a lot more range once I got there. I will have to go over all the solder joints and tube pin connections, but at least I have something to shoot for now.

you guys that have predictas know the drill, broken tube socket right where there is a bridge between the pin socket and the pin insert to the pcb.

checking for continuity with the tube out (touch the probe to where the pin goes in and then the other side to the pcb shows good continuity. insert a tube socket extender with test points and try it again, now no continuity, moral of the story is if you see a predicta like tube socket, and something is not right, better check it with a tube socket extender to simulate an actual tube pin inserted. I have the correct tube socket so will replace it soon. :yes:

that was it. I put a new socket in (better q than the old predicta style). Reset the sine wave coil, Now has very good sync. I guess there was just a hint of sync getting thru the tiny gap (like a small cap) that made it work at all before.

The contrast is not that great, and of course the focus is a bit weak (but that may just be the test jig, its got a very dirty safety glass AND a bad cat, so not sure about a focus issue. the contrast is ok, I tried jumping the cathode bypass cap just in case it was weak, not much improvement. there is some video smear but again its hard to say with the lousy test jig. the color demodulation is good, and the tint range is perfect. I will need I will check out all the peaking coils later. I need to see if the filter caps are getting warm. I will prob go ahead and re stuff them since its coming along pretty well. I don't know the condition of the convergence assy, I just have the plug in the socket but not on the CRT.

Its full of those brown drops so I am sure they need to be replaced as well. I wonder if leaky brown drops on that board will be putting an undue load on the fly?

finally some working pics...

had to load again, goofed it as I ran out of space.
anyway the old angle of the screen shot is due to my test jig location, not the best, so I had to rig up a mirror just to see it.

there are a few brown drops left in, they checked fine, and I was out of new. I will have to order some more from mouser.

the filter caps seem to be doing just fine, not getting hot, but will keep any eye on them until I get around (if) to restuffing them.

pics

some pic of the boards

Congrats, Dave it's really coming along. The tube sockets really are crappy. I'm hesitant to replace the video output socket since the board is probably quite brittle from years of heat. Since it's working OK now, I'm going to leave well enough alone.

As I mentioned before, I haven't replaced the maroon drops on the convergence board. It never occurred to me that they could be increasing the load on the fly. I'll get them in the next round :yes:

I'm surprised to see the cat on your CRT. You must have a sub and not a CYP (maybe you mentioned that and I missed it).

-Clark

what you see is a test jig, the set had a dead CYP (red filament out) but I have a 21FBP to replace it with.

I will do a quick test on the effect of the board soon. Right now I am running it with a jig plug in the convergence socket (no load, just a 150 resistor), I also have the correct convergence board, its just not installed anywhere.

So the plan is to leave the digital meter hooked up, and do a test run with the board plugged in and then a quick comparison with just the 150 ohm jig plug. should be interesting. IF there is a difference (which I presume there must be) then of course the next logical thing to do would be to recap the convergence board (assuming the caps are all bad which is likely), and do another run.

I have other roundie convergence boards that are newer and have better caps. I assume they are wired the same (at least the ones with the octal plugs). would be nice to just try one and see as well (effect on current).