Embedded Files
Restored TV February 22, 2015
1950 Audrian Appliance CO. Advertisement showing the TC-125 (upper right) selling for $279.95
RESTORATION PERIOD: start October 2014 end February 2015
I always wanted to have a vintage TV console, especially the round tube or "roundie" as the collectors call them. Found this one for $45 on Craigslist in the Orange County, CA area. The TV had a lot of cabinet wear but the chassis looks great so I took it home. The model TC-124, 125 and 127 were 12" consoles sold around 1950. They were the last of the round tube consoles, and in the 1950 store ads, the TC-125 sold for an attractive price of $279.95 which was at least $100 less than the new larger rectangular tube TVs. The cool thing about this one is the big solid wood cabinet and big 12 inch speaker built around the small 12LP4 picture tube.
The chassis is the KSC34B which was used in many models. There were chassis variations but they were based on this one. If you look at RCA service manuals from 1949 through 1952 you may see a similarity in schematics with the noticeable changes in the introduction of new tubes.
This TV has 23 tubes plus the picture tube. If you own a RCA 630TS TV the chassis has some similarities as this one. A lot of 6SN7 octal tubes were used as well as 6AG5 remote cutoff pentodes in the video amp section.
Tubes used in this set: 4- 6AG5, 6J6, 2- 6BA6, 2- 6AL5, 12AU7, 4- 6SN7GT, 2- 6K6GT, 6BG6G, 1B3GT/8016. 6W4GT, 5U4G, 2-6AU6, and 6AV6
The Picture Tube or Kinescope is 12LP4. TV consumes 230 Watts.
Table of Contents
Set Evaluation Part 1: SEE BELOW
RCA TC-125 Electronic Restoration Part 2: RESTORE RCA TC-125 PART 2
RCA TC-125 Cabinet Restoration Part 3: RESTORE RCA TC-125 PART 3
Ideas for Restoration HOME Page: HOME
BEFORE RESTORATION
Mahogany finish. The front panel around the picture tube may be a laminate finish so I better be careful. The tuner knob and fine tuning knob are missing.
Complete rear view. The back cover is missing so good chance the TV has been serviced. I am now very sure because the picture has been replaced with a non RCA brand tube. Hope the picture tube is good.
I cleaned up the tubes and chassis of dust. Inside high voltage cage looks great, no signs of overheating.
RESULT:Tube is good, reading taken with CRT heater voltage at 5.8-6 V (should be 6.3v). CRT is a replacement and has been used a fair amount but still useable. Keep thegorrilla off my back for now!
3. View of Chassis on top. Need to check the flyback and power transformers, tubes and remove rust and repaint where possible. Look for missing hardware and replace if possible.
4. View of the chassis underneath before restoration. Lots of paper capacitors, 4 multiple can type capacitors and resistors. All the paper capacitors will have to be replaced and the can type capacitors will be opened, insides removed and new ones inserted and sealed (very tedious). All resistors will be checked for value in stated tolerance and replaced as needed.
Before I start working underneath, the picture tube needs to be removed carefully. Loosen the Yoke screws, remove the ion trap and loosen the securing strap on the front face will be done. I will mark the original position of the tube for reference.
Notice the long bracket above the Model #- Serial # Tag. That is a multiple tap wire wound power resistor called a CANOHM. Popular from 1940-1955. The chassis serves as a heat sink or dissapating device. their main problem is that over time the heat and cooling can separate the wire from the contact or snap the wire in between. Only simple solution is replace with individual power resistors or design a reactance load with capacitors which is more effiecient.
RESTORATION BEGINS-
2. Resistance Check on Power and Flyback Transformers-
The SAMS Photofact for the KCS-34B chassis gives the resistance values for these two difficult to replace parts. Result they both check good (a big sigh of relief). Some restorers like to turn the set on before any major restoration begins and check these parts, thay way they can get a quick diagnosis before putting too much time and money on it. With a lot of 60+ year parts and primitive components, it gives me a scary feeling of disaster if I did that. I'll play it safe and make the changes before turning it on.
The SAMS Photofact for the KCS-34B chassis gives the resistance values for these two difficult to replace parts. Result they both check good (a big sigh of relief). Some restorers like to turn the set on before any major restoration begins and check these parts, thay way they can get a quick diagnosis before putting too much time and money on it. With a lot of 60+ year parts and primitive components, it gives me a scary feeling of disaster if I did that. I'll play it safe and make the changes before turning it on.
Left and Middle- Check the Primary and high voltage secondary windings of the power transformer- Good
If these are bad I am in trouble because these are nearly impossible to replace, unless someone is trashing a vintage RCA TV.
Right- Checking the total flyback / horizontal output transformer resistance. This is an auto transformer so it has a single winding. In specification.
3. Remove, open and rebuild FP or can type electrolytic capacitors
1. As you remove the wires from the capacitor terminals, it is a good thing to ID the wires telling you where they go.
2. Taking the can out is always time consuming because the mounting tabs are twisted to lock them in. Often these tabs are the negative connection so they have a lot od residual solder on them. You wind up with TWO challenges, remove as much solder from the tabs and make sure the straight as possible so it can be pulled out. 3. Take the can out and saw off the base as shown, then heat the top of the can with a heat gun to soften the adhesive to pull the can off.
2. Taking the can out is always time consuming because the mounting tabs are twisted to lock them in. Often these tabs are the negative connection so they have a lot od residual solder on them. You wind up with TWO challenges, remove as much solder from the tabs and make sure the straight as possible so it can be pulled out. 3. Take the can out and saw off the base as shown, then heat the top of the can with a heat gun to soften the adhesive to pull the can off.
These parts are wonderful for new construction but are a potential nightmare when they need to be replaced. These FP type often have two to four capacitors built in. If one fails in time they all will so either you fined a direct replacement OR open it up and physically replace them- vert time consuming and this TV uses FOUR of them for a total of 13 capacitors!
4. Remove the old "guts" from base and drill new holes that will serve as feeder holes for installing new capacitors
5. Install new capacitor and mount leads into proper feeder hole and solder the leads.
6. Test the new capacitor assembly and install base onto chassis and reconnect wires.Make sure that no negative capacitor leads touch the chassis for this TV. Do not install cover until TV has been checked out.
4. Remove all paper capacitors and check resistor values to verify value
Paper capacitors are the most unreliable part in vintage electronic restoration. The wax coating used to prevent moisture from entering will shrink and crack over time and stress ruining the part. Vintage resistors were a carbon plug covered in a resin coating, Over time moisture will enter many of these and increase the value.
Bench setup for this process. I need only a soldering station, solder sucker, pliers and cutters, a digital multimeter and a capacitor tester. In this setup I used a vintage Superior Instruments model 76 Capacitor Tester & Signal Tracer from the mid 1950's.
All these capacitors and resistors tested bad or are out of tolerance
View of chassis after replacement and reinstallation of capacitors and resistors:
The tuner selects the stations and sends the signal to the rest of the TV set. Unlike modern television with digital tuners, vintage TVs used mechanical switches that over time had dirty contacts. The switches need to be lubricated to make turning easier.
5. Cleaning contacts and replacement of parts on the station tuner
Removal required tagging wires, unsoldering and unscrewing the mounting screws. The fine tuning control uses a speed reduction belt and gear system. The leather belt was replaced with a 4.2" DIA flat rubber belt.
The contacts over the years are tarnished and a film of grime has built up. First contact cleaner or alcohol is used to remove most of the grime. Then where possible a pencil eraser is used to polish the contacts. Contacts that were not acessible a cotton swab is used with alcohol and the contact was rubbed. Contact cleaner is sprayed again and wiped dry. Resistors and other parts were inspected to determine if replacement is required.
Replace normally reliable mica capacitors (left) with silver mica capacitors (small dark red parts) on the right. I guess the large pulses of the horizontal sweep and vertical sweep may acts as surges and damage the part. I had a problem like that on a 1947 Motorola VT-71 TV, where a bad mica capacitor would cause a 47K ohm 2 watt resistor to overheat.
6. Last minute mica capacitor replacements
Did some reasearch from other restorers and they agree that very reliable mica capacitors will fail in the large pulse vertical and horizontal sweep circuits. Decided to use reliable silver mica capacitors.
When I was doing a wiring check to make sure I put the new components and the wires I took off back to the right place, I found a resistor that I missed and found it to be a possible incorrect part installed by RCA.
6a More Discoveries
This resistor was used as a cathode bias resistor for a 6K6GT video sweep amplifier. The marked value appears to be 270 ohms. It measured over 1720 ohms as shown on the Fluke 8000A Lab DMM. The schematic and parts list from two sources, SAM's Photofact and 1950 RCA Service Manual say 2700 ohms. I unsoldered it and it appears to be factory installed. Maybe RCA installed the wrong part.
7. Speaker Check
Use a battery and connect the leads to speaker voice coil terminals. Hear a pop=goodSpray cone on both sides of speaker cone with preservative like Armour-All to prevent drying and cracking
8. CRT Aquadag Replacement
Early CRT's used a water based graphite coarting on the bell of the CRT to provide a uniform electric field, reducing picture distortion. Over time the coating flakes off and must be replaced.
Left- 12LP4 CRT before old aquadag coarting removed
Middle- Use denature alcohol, steel wool and a cloth to remove coating and clean the surface
12LP4 CRT is masked at anode plug,edge of the CRT bell at the front and neck. Ready for new graphite coating
Use industrial dry graphite lube that adheres to surface to form a capacitor around the CRT bell
9. Final assembly and view of the completed chassis restore:
Left to Right: Carry the Picture Tube by supporting the bottom of the bell and grasp the neck. Slowly fit the neck through the yoke assy making sure the path is a smooth one. Finally make sure the spring sliders touch the black coating.
10. The Big Moment
On these older tv's, don't forget to install the ion trap in the correct direction (usually an arrow is engraved). If there is no ion trap damage to the picture tube screen can result, as the electron beam will concentrate in one spot.
Carefully tighten the bell strap to secure the picture tube in place. Time to turn it on and see what happens.
Return to RESTORATION HOME: HOME
GO TO RCA TC-125 Console TV Restoration Part 2: RESTORE RCA TC-125 PART 2
GO TO RCA TC-125 Cabinet Restoration Part 3: RESTORE RCA TC-125 PART 3
Google Sites
Report abuse