Sentinel 430 restoration

[bandersen]

1000th post

What better way to celebrate than another restoration project ? This one's a real doozey!

Here are a bunch of videos if you'd rather watch than read
Sentinel 430 restoration - part 1 (Overview)
Sentinel 430 restoration - part 2 (Time to start recapping!)
Sentinel 430 restoration - part 3 (Finally, some real progress)
Sentinel 430 restoration - part 4 (More steady progress and a few surprises)
Sentinel 430 restoration - part 5 (Time to finally test the full size CRT!)
Sentinel 430 restoration - part 6 (A final twist and putting it all back together)


I received a tip on a picture tube that's compatible with this set. I'd never really checked it out other than determining that the CRT is weak. So before dropping some money on a replacement I figured I'd do a quick recap and slowly power it up. What I thought would take a few hours turned into four long, late night sessions

Here's the set. I got it a while back in Skokie, IL from the nephew of a woman that had worked in the Sentinel plant in nearby Evanston during the war. It had been in the same house all this time and it's in great condition. The only minor flaws being the 'piece sign' stained speaker cloth and a break in the CRT gasket.


Weak CRT


Here's the chassis. Copper plated so no rust to remove for a change!





I had to use a heat gun and some vaseline to get the CRT out. There's probably a joke or two in there somewhere
Then I dug right in and tacked in new electrolytics beneath the two cans. I also replaced all the big yellow ones below. I slowly powered it up slowly and all the tubes lit up nicely


My excitment was short lived though: no sound - not even a hum, no video, no HV. What could the problem be

I measured B++ it was about 75v too high. I remembered leadlike had a similar problem and I checked the filter choke. No voltage drop across it. I tested the choke and it's around 100 ohms.

I started tracing the path after the choke and discovered that it runs through two low valued wire-wound pots for vertical and horizontal centering. I checked the vertical pot - bingo it's open!

I didn't have any replacements on hand so I built a little substitute using 10 ohm resistors.