Vintage RCA 630TS TV Checkout Page
PART 3: Getting the TV ready to power up can be a little scary because one is dealing with high voltages. Highly recommend when dealing with the unknown work with one hand, always be wary of what is around you if you need to probe around with equipment and not a bad idea to have a pair of goggles on just in case a capacitor goes or something blows and things start flying out. If possible use a VARIAC or adjustable line voltage transformer to slowly bring up the line voltage to 120 VAC. Before turning on I did a static test to make sure the line had no shorts by checking the resistance across the power plug (power transformer primary) with switch on. I got close to the value specified in the service manual.
3- 6J6, 4- 6AG5, 3- 6AL5, 2- 6AU6, 3- 6K6GT, 2- 6BA6, 1- 6AT6, 1- 6SK7 1- 6SH7, 1- 6SN7GT, 1- 6AC7, 1- 6BG6G/GA, 1-5V4G/GA, 1- 6J5, 1- 1B3GT/8016 2- 5U4G/GB, 1- 10BP4 / 10FP4 CRT
4 years later the 1950 line of RCA televisions would significantly cut the number of tubes to 24 (KCS34B chassis) and the power consumption dropped to 225 Watts at 120 VAC.
1. INITIAL POWER UP:
a. Connected a test picture tube 8YP4. The 8YP4 is a 110 deg deflection tube so the neck is shorter, You'll need a socket adapter from 110 deg socket to 10BP4 socket.b. Turned on power and slowly brought up line transformer to 120 VAC. No picture, only sound. With HV probe measured anode voltage of CRT and got nothing. Checked HV components, all check to service manual values, problem could be Horizontal Oscillator and Sweep section. Remove the CRT, and removed the HV and Horizontal Tubes.
c. Checked some of the changes I made and I found that I forgot to connect the common negative lead of C222 to the rest of the tv. This would only improve the dc ripple and sag from the low voltage power supply. Turn the TV on and got a stronger sound level and heard the vertical oscillator transformer (60 Hz), but the horizontal oscillator was dead (no reading with the oscilloscope).
d. Wanted to find out if the front end was operating. Set the tuner to channel 3 and connected a signal source from a DTV decoder. Got a audio signal from a known TV station. Slightly adjusted the sound IF and descriminator transformers (I usually don't recommend but if you can remember that if you make an adjustment and no change, just remember to go back in the other direction the same amount) and got a strong clear audio signal.
The power supply voltages look good (at BLEEDER CKT BOX- R185 and R186)
+128 V (s/b +135 V), +300 V (s/b +275 V),
-3 V (s/b -2 V). -23 V (s/b -18 V), -97 V (s/b -100 V)
Checked the vertical oscillator V121 (6J5 plate). Not pretty but it is oscillating around 60 Hz.
The Horizontal sync pulse at C166 (82 pF) is there and at the correct level.
However the horizontal oscillator was dead at the output of the 6K6GT tube (V125). Could be a bad sync discharge transformer, bad mica caps or other things so I looked over the entire area. No horizontal oscillator means no horizontal output and no high voltage sweep or accelerating voltage for CRT (no picture).
e. everything checked correctly EXCEPT I installed a replacement coupling capacitor C172 (0.004 uF) to the wrong side of the transformer. Made the correction and turned the set on and the horizontal oscillator is humming along at 15.75 KHz, the sweep frequency.
Adjusted the horizontal hold control (R168) which will slightly shift the frequency. That work also! You can see the wave shift to the RIGHT. Looks just like the service manual example.
2. POWER UP AGAIN:
a. Put the test picture tube back in, slowly powered up and I get a raster with sound.
Too bad the picture tube is on sideways, but it was the only way to get the CRT far in enough to connect the socket. I made some rough adjustments with the vertical and horizontal controls and I can get a full raster. Decided to put the original 10FP4 (10BP4 equiv with built in ion trap) in.
One of the sore spots of this vintage tv is the installation of the CRT. Unlike later sets which have chassis clamps to secure the CRT, this model requires the cabinet to secure the CRT. I had to put padding and to secure it.
Notice the ion trap magnet and clamp on the work bench. Won't need it with the 10FP4 but when I am all done, will have to find a place to secure it in the set.
Much bigger picture. Can barely see the vertical bars and when I change station the picture flips. Got more work to do. At least now I have raster and sound.
3. TROUBLESHOOTING TIME WITH THE OSCILLOSCOPE- WAVEFORM CHECKS
Video to grid of CRT (10FP4) - Low level
Vert sync to T106 Vert Osc XFMR. Looks okay.
Horizontal Sync at 6AL5 (DC Restore Ckt) output to Descrim/Sync XFMR T108:
Seems to look okay but low level???
4. TIME TO BE A TV REPAIRMAN
a. Hooked up my CONAR TV Pattern Generator to the RF input (ANT). The generator puts out a constant signal for horizontal, vertical and composite making it easier to see the signal being processed along the TV. With the waveform photos from RCA Service Manual the Tektronix 453 oscilloscope and Triplett 9045 DMM went back and check the key points from each tube from grid of picture tube to vertical and horizontal oscillators.
Video Signal to CRT Grid
b. Found a trouble spot! At the DC Restore circuit V114 (6AL5 tube) the signal entering the tube and leaving was degraded and the sync signal was very low level. The peak to peak level was only about 200 mV and should be around 9 V. Suspect the tube, but the twin diode tube tested good on the Hickok 600 tube tester. Power off, pulled the two resistors at the grid bias network at final video amplifier V116 (6K6GT) before the DC Restoration, and found that both 5% tolerance resistor were out of tolerance. One was 18% off and the other was 33% off. Less important two Sprague "Orange Drop" 0.047 uF by pass and signal coupling capacitors that were installed by a past repair were 23% out of tolerance (stamped 10% on each part), For safe measure replace tube, resistors and capacitors. Here are some before and after waveform pictures.
BEFORE parts replacementVideo 100 mV P-P
AFTER parts replacement Video 10 V P-P
c. Connect converter box to TV, connected the test picture tube, turn set on and I got horizontal and vertical bars out of sync and looks like a picture. As I adjusted the vertical and horizontal hold the picture began to stabilize. I needed to adjust RCA's horizontal sync lock and as the horizontal started to lock and suddenly the TV went dead. Checked the +275 V at the bleeder resistor R186a and found that the +275 V dropped to +40 V. Something is loading down the power supply. Changed out the twin 5U4GB rectifier tubes and still no change.
Noticed that the 5V4G damper tube (which the +275 V goes to) filament was not glowing. Disconnected everything, took CRT off, flipped the chassis over and found a huge glob of solder at the 5V4G filament connection touching the chassis. I could tell this was originally there from day 1, but over time as the TV was serviced with me being the latest, the glob finally had a chance to touch the chassis and there goes the low voltage power supply. Cleaned that up and looked for other sloppy solder joints on the set and cleaned those up as well.Set must been assembled at the end of the week.
Noticed that the 5V4G damper tube (which the +275 V goes to) filament was not glowing. Disconnected everything, took CRT off, flipped the chassis over and found a huge glob of solder at the 5V4G filament connection touching the chassis. I could tell this was originally there from day 1, but over time as the TV was serviced with me being the latest, the glob finally had a chance to touch the chassis and there goes the low voltage power supply. Cleaned that up and looked for other sloppy solder joints on the set and cleaned those up as well.Set must been assembled at the end of the week.
PHOTO ABOVESmall burn mark on chassis next to pin 8 of 5V4G socket. High current track made by solder bridge pin 8 to chassis providing a +275 V sink.
d. EUREKA! PICTURE AT LAST! Reconnected everything and monitored the +275 V line at the bleeder. Got a recognizable picture on the test picture tube. The horizontal sync lock worked nicely. Only a portion of the video is shown because the 8YP4 test picture tube is a 110 deg deflection while the original 10BP4 or 10FP4 picture tube is 50 degree deflection. So we have a mismatch at the yoke. No big deal since this is for testing anyway.
ABOVE: Only have picture shown because the 8YP4 test picture tube is 110 deg deflection while the original yoke is 50 degree deflection.
ABOVE Monitor the +275 VDC source while TV is running. Definitely the solder bridge from 5V4G filament and Damper output to ground was a factor
5. Installation of 10FP4 CRT that came with the TV set. Picture adjusted before installation. Ran set for almost 2 hours.
Notice that the 10 inch CRT had to be propped so it would be level and secure. There is no chassis support except at the focus coil and yoke.
The Warm and Vintage Glow of Vacuum Tubes. Gobbling up 325 watts of power.
FYI: Comparison of a 10BP4 / 10FP4 50 deg deflection (LEFT) versus 8YP4 110 degree deflection CRT:
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