Sentinel 400 No High Voltage
 

Greetings,

Hoping to find individuals that have worked on the Sentinel 400 before to help with this issue.

I recently acquired a rough, but untouched original, Sentinel 400. First time I have worked on this deflection type TV. Long story short, I have replaced all capacitors and checked all resistors for tolerance, (including HV side). Verified all tubes and after slowly bringing up on an isolation transformer and variac, I have good filament voltages to all tubes on both chassis, expected AC/DC voltages on tuner chassis, but no B+ or HV on the picture chassis. The schematic shows basically a voltage doubling setup with two selenium rectifiers in the video chassis with the center tap of the two rectifiers is where the 115 VAC is injected via a 100 uf electrolytic capacitor. The 115 VAC shows coming from connection 12 of the chassis connector. Am I reading all of that correctly?? I just can't find where I am losing the AC coming from the tuner chassis to the video chassis. Seems like it should be easy to find but I can't and without it I obviously will have no B+. I do get 115 coming from the secondary of the transformer meant for supplying AC to the Video Chassis but once it enters the Video Chassis, I lose it. What am I missing?

Ideas or suggestions on where to look?

Thanks in advance,
Rudy

Double check your work on the capacitors and the power supply caps and get rid of the selenium rectifiers and replace with good 1n4007 diodes. Start there. And be sure of the position you put them in.

Im assuming you checked the fuse? AC as in no tubes light in the horizontal section? My fuse in my admiral checked good, the fuse holder itself for both fuses had failed and wasnt making contact with the fuse.

Thanks Timmy. I already double checked the work I did on the capacitors, I will check again though. I was planning on dropping in the 1n4007 diodes to replace the selenium rectifiers once I was sure the unit worked, and the CRT was good. I have a universal CRT tester but not one for the 14 pin 7JP4.

@fumplet, the 400 I have has no fuse in line. I did see in the documentation it suggests that as an upgrade for the earlier models like this one.

Question, since the tuner chassis has AC and B+, could I not just inject 115v into the center tap of the voltage doubler in the video chassis to test the rest of the unit and see if HV even comes up?

Thanks,
Rudy

I've seen the Jones plug/socket that links the chassis go flakey on these.

Thanks to all that replied. High Voltage issue is resolved.

As Timmy eluded to in his message, it was user error. I guess I am so used to newer electrolytic cans' mounting tabs being to ground through the chassis, that when I replaced C26 100uf Electrolytic, I didn't notice that the mounting tab only connected to the phenolic and not to metal, so it was essentially connected to the pos 100 uf so when I clipped the positive lead off the capacitor and relocated to the new 100 uf, I just left it soldered to the tab thinking that was something that needed to go to a ground. That was the 115 vac I needed. Slow down! Pay attention. :dammit: