Hawes Mechanical Television Archive by James T. Hawes, AA9DT
Col-R-Tel® Troubleshooting (Instructions, Part 8)

How Col-R-Tel logo might have looked in color

About the table, below. I base it on the small troubleshooting guide from Color Converter, Incorporated. This guide appears in the original, 1955 Col-R-Tel manual. I expand the guide with new illustrations and the action items. The table format is new. For clarity, some rewording becomes necessary. The document now provides vendor links for lubricants (and spells “Silicote” properly). If 1955 customers could have consulted the Web, would Col-R-Tel have sold better? Tell me what you think. You can contact me through the footer on this page.

Troubleshooting Table for Col-R-Tel

Symptom Cause Action to Take
Poor or no color
  1. Program isn't color telecast.

  2. Improper installation

  3. Shorts or poor connections in cable to scanning wheel

  4. Improperly aligned contacts on commutator

  5. Fine tuning on TV set out of adjustment
  1. Switch to a color show.

  2. Check all Col-R-Tel® tubes except motor-driver V6 (6BL7).

  3. Quick rotation of color control should produce temporary fluctuation of brightness. NO FLUCTUATION: Trouble is in V4 & V5A circuit. (Tube V4, 6BE6, is chroma detector. Tube V5A, 12BH7-triode, is color difference amp.) Repair circuit problem as follows...

    1. Either V4 or V5A might be missing or bad. Replace tube.

    2. Cable to picture tube might be loose. Repair or replace cable.

    3. If necessary, repair or replace scanning wheel cable.

  4. Align commutator contacts.

  5. Adjust fine tuning on TV set. This control must permit tuning to edge of sound bars.
Still have poor or no color Antenna or lead-in problem...
  1. Improper antenna

  2. Poor antenna location

  3. Problem with multiple set & antenna distribution system

  4. Impedance mismatch at lead-in
  1. Replace improper antenna with good antenna. (Yagi, log periodic, dipole, folded dipole, bow tie, etc. Use sufficient mast for your area & good ground system. If necessary, add antenna amplifier. Use short, coax lead-in wire with right matching baluns.)

  2. Relocate antenna as necessary. It must be free & clear. As compared with roof-mount antennas, attic antennas perform poorly.

  3. Multiple set & antenna distribution systems often degrade color. Perform one or more of these actions...

    1. Connect set directly.

    2. Add antenna amplifier.

    3. Replace cable & connectors with proper type.

  4. Fix impedance match by installing proper baluns on lead-in.
No scanning wheel sync
  1. Weak tube in motor control section: V5B & V6

  2. Extreme high or low line voltage

  3. No vertical sync pulse from set

  4. Poor connections in cable

  5. Improper contacting at commutator

  6. Slipping or worn belt
  1. Check or replace tubes as necessary...

    1. V5B (12BH7-triode).

    2. V6 (6BL7).

  2. Connect adapter circuit to proper line voltage.

  3. MISSING PULSE PROCEDURE

    1. Turn on TV & Col-R-Tel decoder box.

    2. Scope both sides of capacitor C26.

    3. NO PULSE AT OUTPUT, but pulse at input: Replace capacitor C26.

    4. NO PULSE AT C26 INPUT: Use scope to check for sync pulse at both sides of plugs P2 & P1.

    5. Repair plugs P2 & P1 (or cable) as necessary.

    6. STILL NO PULSE: Check continuity of cable between vertical output tube & plug P1.

    7. Repair plug P1 (or cable) as necessary.

    8. STILL NO PULSE: Check for pulse at vertical output tube on host TV.

    9. STILL NO PULSE: Replace vertical output tube & retest for pulse.

  4. Replace cable.

  5. Service commutator.

  6. Tighten or replace belt.
Color wheel is squeaking or grinding
  • Requires lubrication

 Lubricate with one of these products...
Lack of certain colors
  1. Bad phase-selector tube V3 (6BC7)

  2. Bad cable P3–P4–P5

  3. Dirty or bad commutator or contacts

  4. Incorrectly tuned, 3.58 MHz trap L7–C22
  1. Replace tube V3 (6BC7).

  2. Replace or service bad cable.

  3. Service bad commutator or contacts.

  4. Tune trap.
Incorrect colors
  1. Incorrect adjustment of "Color Lock" (hue) control

  2. Misalignment of tuned circuits (Burst transformer T2 is most critical.)

  3. Wrong polarity on secondary of phase-splitter coil L2
  1. Adjust "Color Lock" for best flesh tones.

  2. Align tuned circuits, starting & ending with T2.

  3. At L2 secondary, flags mark outside transformer tabs.

    1. Find flagged contacts at L2 secondary.

    2. On flagged contacts, reverse wires. Leave center tap alone.
Streaks in Picture
  1. Dirty commutator

  2. Incorrect pressure on commutator contacts
  1. With alcohol or acetone, clean carbon off commutator.

  2. Adjust contacts for 1/16" compression.

How Col-R-Tel logo might have looked in color

Illustration, front of converter chassis with parts callouts (mechanisches Farbfernsehen)

Col-R-Tel chassis, back, top-left to right

Mechanisches Farbfernsehen: Col-R-Tel converter chassis. Parts on back of chassis, top row.


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All content, line drawings of Col-R-Tel adapter & logo typography by James T. Hawes.
Copyright © 2015 by James T. Hawes. All rights reserved.

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