My Brand New CTC-7! - Page 31 - Videokarma.org TV - Video

roundscreen · #**451** 08-20-2015, 07:48 PM

Quote:

Originally Posted by SwizzyMan

What would be considered minimum dangerous to the set? 119v? or not any higher than 115?

Start with 115 and see how the picture is. I run my color set's at 117 volts and have not any problems with them. Even the newer color roundies like 117v, And they are rated at 120v. Your 7 is 57 years old. You have to look at her as a fussy old lady. What is going to be the next set you restore?

SwizzyMan · #**452** 08-20-2015, 07:50 PM

I think I'd like either a DuMont B&W roundie or an RCA ctc-5 Blonde Whitby. Back to my previous question. Are there any temporary solutions to reducing the ac line output?

roundscreen · #**453** 08-20-2015, 08:00 PM

Quote:

Originally Posted by SwizzyMan

I really dont have the money for a variac. Is there any other possible alternatives?

A thermistor surge resistor on one side of the ac line would help. but you really need a variac. It is as important as a volt meter when working on vintage tv.

SwizzyMan · #**454** 08-20-2015, 08:03 PM

Hmmm, OK I will try to find a cheap variac. Does anyone here have a variac I could take off their hands?

Electronic M · #**455** 08-20-2015, 08:47 PM

I've been running a CTC-15 clone as a daily driver straight from the line for about 5 years. The first two were in an area where the line voltage ran high probably 120-125, since then it is usually 117 give or take 6 volts. I've never had a problem with the fly going into over-current....Granted I did monitor and dip the cathode current by adjusting the linearity coil (which is probably a better way to control it than a variac).

If you are worried about overheating the fly adjust the lin. coil for min H out Tube cathode current and leave the HV cage door open for ventilation.

SwizzyMan · #**456** 08-20-2015, 09:20 PM

I dont see a linearity coil but I do see a horizontal efficiency coil that looks like it is connected to pin 3 which is the cathode on the H out tube. Should I adjust that one?

ChrisW6ATV · #**457** 08-21-2015, 01:26 AM

Swizzy-

Look up "line bucking transformer" or similar. If I remember right, it is a setup where you use something like a 6-volt, 4-amp output (in this case) transformer in a wiring setup where the six volts gets subtracted from the input (122 volts in your case). Such a transformer should cost a lot less than a Variac, for ongoing use of your set.

SwizzyMan · #**458** 08-21-2015, 05:44 AM

Hmm a bucking transformer seems like a handful but I might give it a shot. But it says that it will lower the voltage from 120 to 110v isn't that too low?

roundscreen · #**459** 08-21-2015, 07:08 AM

Quote:

Originally Posted by Electronic M

I've been running a CTC-15 clone as a daily driver straight from the line for about 5 years. The first two were in an area where the line voltage ran high probably 120-125, since then it is usually 117 give or take 6 volts. I've never had a problem with the fly going into over-current....Granted I did monitor and dip the cathode current by adjusting the linearity coil (which is probably a better way to control it than a variac).

If you are worried about overheating the fly adjust the lin. coil for min H out Tube cathode current and leave the HV cage door open for ventilation.

You are right. The cathode current must be adjusted for proper dip. If this is not done, The current will run high no matter what the line voltage is. Still, Why beat on the set if you don't have too. He want's to use the set as a daily driver and the variac will give him some added protection. Running the set at the line voltage it is rated at.

MRX37 · #**460** 08-21-2015, 09:14 AM

You could also add a PC cooling fan, maybe attach it to a part of the chassis that outputs ~6 volts DC. that would run the fan at half speed and keep it nice and quiet, and keep the TV running nice and cool.

Electronic M · #**461** 08-21-2015, 01:25 PM

It is labeled Horizontal efficiency in some sets, H linearity in others. Sams horizontal adjustment procedure and schematic should list max safe current and how to adjust....Skip the osc. adjustment and the more complex HV reg adjustments unless the current can't be reduced, or those stages show signs of misadjustment.

Quote:

Originally Posted by roundscreen

You are right. The cathode current must be adjusted for proper dip. If this is not done, The current will run high no matter what the line voltage is. Still, Why beat on the set if you don't have too. He want's to use the set as a daily driver and the variac will give him some added protection. Running the set at the line voltage it is rated at.

I'm not telling him to beat up his set, just noting my observation that MY set that has been in regular often heavy use since I restored it has done fine without any line input voltage control....Heck the cathode current was running WELL below the max safe value when adjusted running on high line voltage.

In many places the line voltage fluctuates so if you truly want to get OCD on line voltage get a VRT/saturable reactor/(insert other aliases for it here) isolation transformer that puts out a constant 120V, and buck that down......
I've been approaching that setup recently. The place I've lived in for the last few years has intermittent sudden brief and rapidly reoccurring voltage dips that cause highly annoying blooming. I've been using a 120V out VRT to regulate out these dips, and on the '71 Zenith I've been using it on I've been contemplating using a variac or bucking transformer with it so I can dial in the vertical over scan to minimum.

IMHO the best way to power a low voltage DC fan in a TV set is to connect a bridge rectifier to the heaters and a filter cap to the bridge. Then depending on the DC voltage it puts out how quiet the fan needs to be and the air flow desired select either a 5 or 12V fan.

SwizzyMan · #**462** 08-21-2015, 03:39 PM

Going to just try a bucking transformer. My AC is stable at 120.6v and rarely moves down a volt. What exact transformer should I get for the bucking transformer? I thought I heard a 2.2kva one was right? Also planning on refinishing the cabinet on Sunday after I build the bucking transformer Saturday.

SwizzyMan · #**463** 08-21-2015, 04:27 PM

Would this one work? Secondary out is 10v so If I buck it the output will be 110v right? Or is that too low or am I wrong about my theory? http://www.skycraftsurplus.com/f6-10...vct120pri.aspx

roundscreen · #**464** 08-21-2015, 07:27 PM

Electronic m I am sorry for the poor choice of words to get my point across.

SwizzyMan · #**465** 08-21-2015, 07:32 PM

Hey Roundscreen would it be OK if I ran the set just for about an hour right now?