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  #1  
Old 07-15-2014, 08:39 PM
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dtvmcdonald dtvmcdonald is offline
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My "New" CT-100 restoration

I got my CT-100 from the ETF home safely. Thanks to Steve
for getting it all safely in the van.

It appears mostly unmolested. I have tested all the tubes.
A few were missing. One had a bad filament. Four tested weak,
including the focus rectifier and the shunt HV regulator,
but I have my doubts as to how well the Hickok transconductance
checker did on them.

The bottom of the chassis in very nice clean shape. The top has been
partially cleaned and the rest is not bad. The HV cage is incredibly
dirty. It took a huge quantity of alcohol to clean the tubes in it.
What do people do to the parts inside? They clearly MUST be cleaned,
but should I take it all apart or try to clean them in place.
What cleaning agent do people use? Alcohol works, and
won't hurt the ceramic caps, but what about resistors, especially the
spiral high-ohmage ones?

About half the white peaking coils are clearly bad, half appear
to least to have the right resistance.

More, including pictures, later.
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Old 07-16-2014, 10:24 AM
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dtvmcdonald dtvmcdonald is offline
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Some questions.

After careful examination, restuffing the chassis mounted electrolytic cans will
be a nightmare if done as described in the article mentioned in the sticky
thread at the top of this forum (remove can from chassis, uncrimp buttom) because
they are all soldered in, most at two or three places. Some are riveted in.

I'm not intending to leave the chassis bottom original looking, but I am the top,
more or less. I could do a "cut off at the base and cover the gap with
silver color tape" bit on them, but that would not look original even at a glance.

What I'm thinking of doing is just leaving them in as is, removing them
electrically, and adding terminal strips to hold the small new caps.
For the ones in the power supply, I would remove the seleniums, which are
huge, and mount the new caps, 1N4007s, and their associated dropping
resistors, on a circuit board mounted inside their cage. The rest should
easily fit under the chassis. What do people think of this ... it would be
easily cosmetically reversible if a future owner wanted to, as I'm saving all the
old parts.

Where is the Candohm resistor on the schematic?
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Old 07-16-2014, 03:02 PM
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init4fun init4fun is offline
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I say this with all due respect and no malice whatsoever ;

Some sets , sure , I'd go the terminal strip route in a heartbeat rather than dive into the mess of wires required to do a "pretty" restuff . But a CT-100 , THE holy grail of tube color TV to most collectors , deserves , no , , really outright demands ! , that a proper cosmetic restoration accompanies the electronic restoration . In my view , historical value dictates the extremes one should go to in preserving the original looks , and what color TV would be more deserving of proper cosmetic restoration than your history making CT-100 ?

Your set will only be virgin once ........
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Old 07-16-2014, 05:58 PM
DaveWM DaveWM is offline
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normally I don't worry about making it look completely original, I do cut off the cans and mount the alum tape back on , but that is for the sake of keeping lead dress the same. I never use term strips, just cut drill insert and solder. Sometimes I do not even bother with putting the cans back over the caps. Its just a TV and my only goal is to get it functional.

IF I had a CT-100 (which I prob would avoid since I would constantly worry about the CRT) I am sure I would go the extra mile to restuff by uncrimping and would also prob restuff the wax caps as well. It goes against my nature but due to the historical value of the set I think it deserves it. I think for me I would just look at it like this, its a one time deal, so take what ever amount of time is needed to do it right. Once its done its unlikely that that I would ever do again.
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Old 07-17-2014, 08:20 PM
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dtvmcdonald dtvmcdonald is offline
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Here are some pictures.

Edit: I should add that the original of the chassis bottom is about
10,000 x 10,000 pixels, as mentioned below.
Attached Images
File Type: jpg Dirt_in_HV_Supply.jpg (107.1 KB, 100 views)
File Type: jpg Uncleaned_Chassis_Area.jpg (93.2 KB, 72 views)
File Type: jpg The_Chassis.jpg (104.6 KB, 75 views)
File Type: jpg WhitePeakingCoil.jpg (50.9 KB, 99 views)
File Type: jpg ChassisBottom.jpg (136.3 KB, 110 views)

Last edited by dtvmcdonald; 07-18-2014 at 07:36 AM.
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Old 07-17-2014, 08:22 PM
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dtvmcdonald dtvmcdonald is offline
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And here are more.
Attached Images
File Type: jpg Are_These_Things_Resistors.jpg (99.5 KB, 62 views)
File Type: jpg Dirt_in_LV_Supply.jpg (132.2 KB, 66 views)
File Type: jpg LVPowerSupply.jpg (117.5 KB, 71 views)
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  #7  
Old 07-17-2014, 09:20 PM
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dtvmcdonald dtvmcdonald is offline
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My goals may be different from some. Here they are,
in order of higher to lower importance:

1) Make the set work as originally intended, receiving signals
at RF with full exact NTSC specs: including correct Q signal
with 0.5 MHz double sideband and I with 0.5 and lower with 1.5
MHz bandwidth, even if
I have to create these myself from RGB output of a DVD player.

2) Leave the top view of the chassis unchanged as far as
possible. If there are bad controls I will try to find proper looking ones.
There is a white peaking coil there, which I will replace,
and a paper cap. The cap will be restuffed and I will make a little
paper cap to cover the new coil, not perfect but will do.

3)Save all removed or replaced parts. I have made a 100 megapixel
image of the chassis bottom so that a future owner could
do a full restuff with proper placement. I'm not going to restuff
anything under the chassis.

4) Leave the horribly dirty areas as clean as reasonable. This
is not a 60's Tektronix scope, where the factory manual
says to start a calibration with a good hosing down and sun dry!
Water or even gallons of alcohol would damage coils. The cleaning
has to be done with paper towels and Q-tips. Wires on the
chassis top and insides the cages are filthy and slimy. Goop followed
by alcohol seems to be the cure.

That said, I have decided to not restuff the can electrolytics ..
doing it without damage while unsoldering them from
the chassis would be a nightmare and possibly beyond my skill.

I'm going to compromise on point 1 above and remove the seleniums
and install silicon diodes, their series resistors, and the new
electrolytic caps for the power supply in the cage
mounted on a fiberglass perf board. The board and caps
will be painted bright orange. That will have to do for "the look"
inside the cage.

Doug McDonald

Last edited by dtvmcdonald; 07-17-2014 at 09:25 PM.
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  #8  
Old 07-17-2014, 10:09 PM
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Username1 Username1 is offline
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Hey those orange things with the fins are pretty neat looking.....

You gunna keep them the original color.....?
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Yes you can call me "Squirrel boy"
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  #9  
Old 07-18-2014, 07:59 AM
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dtvmcdonald dtvmcdonald is offline
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Quote:
Originally Posted by Username1 View Post
Hey those orange things with the fins are pretty neat looking.....

You gunna keep them the original color.....?
As I said, they are going into the "removed innards bag" that
some day sells along with the TV. They will be replaced with
modern parts, completely different looking, painted that color.
If you are unfamiliar with these sets, they are inside the perforated
metal cage at left in the chassis top photo, and are essentially invisible
if you look inside the set with the back removed. The top lifts off this
set and they are visible, inside the cage, with the top off.

Oh! I have another idea: series dropping power resistors have to be added
in series with silicon rectifiers. I could use resistors intended to be
mounted on heat sinks, and paint the heat sinks that color.
The originals are 3 inches square. These could be as
wide but only 3/4 inch or so high, leaving room for the caps I will put there.
I'm feeling much better now about the original look!

Ideas like that last one are why I am seriously over-planning this project.
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  #10  
Old 07-19-2014, 02:56 PM
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dtvmcdonald dtvmcdonald is offline
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I have completed cleaning and recapping the HV cage.
This was a nightmare because it was so dirty and cramped.
The 2.7 Meg 1/4 watt resistor was at 3.3Meg, and was
replaced with an identical but in-spec part.
The two 25 meg
HV ones were right on the button.

"After" photos are attached.
Attached Images
File Type: jpg HV_Cage_Front_after.jpg (127.2 KB, 93 views)
File Type: jpg HV_Cage_Back_after.jpg (111.0 KB, 81 views)
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  #11  
Old 07-20-2014, 12:27 AM
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Phil Nelson Phil Nelson is offline
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Looks like a good start. There's no such thing as too clean, when it comes to the HV cage.

Take your time and enjoy. My theory with a project like this is that I may never get another chance to do another one of these. It's not a race, I sometimes have to remind myself. It's better to do a job right the first time than to beat some imaginary clock. And while the rest of us may offer advice or cheer from the sidelines, you are the ultimate arbiter of what is "the right way."

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html
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  #12  
Old 07-20-2014, 10:20 AM
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dtvmcdonald dtvmcdonald is offline
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Quote:
Originally Posted by Phil Nelson View Post
Looks like a good start. There's no such thing as too clean, when it comes to the HV cage.

Take your time and enjoy. My theory with a project like this is that I may never get another chance to do another one of these. It's not a race, I sometimes have to remind myself. It's better to do a job right the first time than to beat some imaginary clock. And while the rest of us may offer advice or cheer from the sidelines, you are the ultimate arbiter of what is "the right way."

Phil Nelson
I agree. I'm working on it about an hour or at most two a day.
More and I get eyestrain and overexcited.

This morning I went though the Sam's resistance to ground
chart. The vast majority of the numbers are well within tolerance,
most well within 10%, including most > 1Meg resistors.

This is good news.

This evening I will do the resistance to B+ part.

I noticed that Sam's has a 12AT7 on their topside tube chart in
a 7 pin socket! (Its really a 6AU6).

I still have not got a reply to where the Candohm is in the circuit,
and the nature of the 100 ohm resistors inside the chassis connected
directly across its parts. Are these R286 and R287 in Sam's?
The ".100" resistor in Sam's surely must be 100 ohms, otherwise there
would be nowhere near -30v on the bias supply, as there can't
possibly be 1.7A B+ current.
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  #13  
Old 07-20-2014, 11:18 AM
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Looking Good!

Quote:
Originally Posted by dtvmcdonald View Post
I still have not got a reply to where the Candohm is in the circuit,
and the nature of the 100 ohm resistors inside the chassis connected
directly across its parts. Are these R286 and R287 in Sam's?
I believe that the Candohm on the back of the chassis is R-285 (see arrow on page 20 of Sams), a 33 ohm resistor shown in the power supply. it is in parallel with a 100 ohm resistor, R-286.
The two U-shaped loops that you pictured earlier are "fuses" M-6 and M-7 in the heater supply... they are just short lengths of #26 wire enclosed in sheathing.

jr
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Old 07-20-2014, 11:23 AM
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jr_tech jr_tech is offline
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OOPS! double post!

jr
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Old 07-21-2014, 09:31 PM
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dtvmcdonald dtvmcdonald is offline
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"All" I did today was disconnect the vertical convergence transformer from the
focus pot and its 0.01 uF cap and apply an external 5.2 kV through a 750 Meg resistor and a microammerter in series, for an hour (at room temp of course) to test
the transformer "safely". (Safely for the transformer with the 750 Megs and
safely for me with everything except the 5kV supply sitting on my 1/2 inch glass
dining table.)

It passed. Of course this is not forever at higher temps, but its better than fail.

Doug McDonald
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