CTC-7 metal table top - Videokarma.org TV - Video

DaveWM · #1 02-28-2013, 08:56 PM

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

DaveWM · #2 02-28-2013, 09:00 PM

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.

DaveWM · #3 02-28-2013, 09:04 PM

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.

***Eric H*** · #4 02-28-2013, 09:38 PM

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

DaveWM · #5 02-28-2013, 09:49 PM

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.

DaveWM · #6 03-01-2013, 05:20 PM

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.

DaveWM · #7 03-01-2013, 07:43 PM

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.

DaveWM · #8 03-02-2013, 02:16 PM

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.

DaveWM · #9 03-03-2013, 04:36 PM

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.

DaveWM · #10 03-03-2013, 10:44 PM

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.

DaveWM · #11 03-04-2013, 05:58 PM

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.

miniman82 · #12 03-04-2013, 10:39 PM

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.

DaveWM · #13 03-04-2013, 10:49 PM

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.

DaveWM · #14 03-10-2013, 05:38 PM

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.

Sandy G · #15 03-10-2013, 06:32 PM

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...