Sentinel 411CV

12" screen, 1949
click on image to enlarge

Sentinel is probably best known to TV collectors for its trapezoidal 7" leatherette.  If you're familiar with that set, then you'll recognize this one's layout of four narrowly-spaced knobs below the screen...though the knobs on this model look much more like ordinary radio knobs.  The signal chassis in this set is very similar to the one in the model 400TV portable, but it is not identical.  In fact...

it's upside down!   It is mounted underneath the large deflection chassis (obviously not electrostatic) to a sheet of wood which slides into grooves in either side of the cabinet interior. 

Here's a photo and portion of text from the original eBay listing:  "...the line on the tube is after being turned on for a minute.  A line of white appears.  The last time I had an antenna hooked up was 1985 and it had a picture but the picture kept rolling."  Looks like a winner!  Nothing mentioned about all the holes the kids had poked in the speaker...but let's not get ahead of ourselves.
Tube Complement

Signal chassis:

  • RF amplifier                  1    6BH6
  • oscillator                      1    6C4
  • mixer                          1    6AG5
  • video IF                       3    6AG5
  • video detector               1    6AL5
  • video amplifier              1    6AU6
  • audio IF                       1    6AU6
  • audio detector               1    6AL5
  • audio amplifier              1    6SQ7
  • audio output                 1    6AR5
  • sync seperator              1    6AU6

Deflection chassis:

  • sync amp/phase splitter  1    6SN7GT
  • phase detector             1    6AL5
  • horizontal oscillator       1    6SN7GT
  • horizontal output          1    6BG6G
  • damper                      1    5V4G
  • vertical oscillator          1    6SN7GT
  • vertical output             1    6SN7GT
  • B+ rectifier                 1    5U4G
  • HV rectifier                 1    1B3GT
Restoration notes:

This one didn't take long at all.  Unlike my first adventure (see:  Emerson 699) wherein I progressed in stages, I finished this set all at once and really without difficulty, despite the lower chassis' small dimensions which make it somewhat cramped. 

Fixing this set was a valuable learning experience in a number of ways.  It has no external fine tuning knob, so tuning must be precisely set (for each channel that will be used) before buttoning everything back up.  But since even imperfect integrity of an IF tube's contact with its socket will affect the tuning, that precise setting can be an elusive mark.  Ultimately several tubes became finicky about contact with their sockets (including CRT at the filament!), so in future, cleaning of tube pins will be a matter of course.

The CRT mask is metal.  The lip was covered with some kind of gasket material that had mostly rotted away.  To replace it, I cut a length of telephone cable to size, removed the wires and cut a slit lengthwise into the jacket.  It took some patience to make it conform to the lip of the mask and stay put, but the result looks made to order.  Of note is the fact that the CRT mask is really too small.  It's too big to be the wrong mask (i.e. for a 10" tube), but it conceals the better part of an inch of useable, viewable surface around the left and right perimeter of the tube's face.  Oh well.

There were several punctures in the speaker.  None of the cone was actually missing, so I mended the tears with clear nail polish.  You'd never know there were holes in it now, it sounds fine.

©2006 Phoenix Enterprises