Hello fellow enthusiasts! I havent posted on here for quite along time, new job and no time for hobbies. All my vintage Tv's are working fine and haven't broke!

This past weekend we went into my parents storage unit and pulled out my Sentinel 400TV trapazoid suitcase. The cover on the case is shot and looks bad. Its missing knobs..... Ugh. . . .

I worked on this TV 10 years ago when I was in high school before I knew what the hell I was doing. So when I had it yesterday I removed the chassis to find out what I did as far as recapping. I expected some shoddy work... Yes it was pretty shoddy. An unsecured electrolytic(witha cold solder lead that just pulled out when I gave a tug!!) My silicon diode replacements were terrible, but wired correct. They just look bad. I don't even know if I was using a schematic(or even knew how to read one!) because the power supply had been hacked by a previous mechanic and instead me fixing it right I just did what he did. It was a large power resistor that had been bypassed and individual resistors used instead. I havent checked the values....... I found a big descrepensy(SP) on the deflection picture chassis with a large paper cap of 1 MFD and 200 volts. Never seen a paper cap that large. According to the schematic it was supposed to be a 20MFD 25 volt cap(electrolytic). Its C21 on the cathode of the vertical amp. It looks origional too. I reviewed the production notes on the Riders and see no notes on that. What should I do?

With things touched up and no shorts anywhere I decided to bring it up on my(very nice) fused variac. 50 volts. 75... Sound...... 90 volts.. Raster!! 115 volts... no smoke!! The 7JP4 works well, with plenty of brightness and the HV tranny works!
I know there is a big faul somewhere in the filtering of the sweep chassis's power supply(split chassis TV with there own rectifiers) The screen snakes, the whole screen is S shaped. I figure I've got a grounding issue on the caps, and with the previous tech messing up the resistor I will need to be taking voltage readings.. But the S shap if I am correct is a filtering issue in the horizontal section.

The audio works fine(minor 60 cycle hum) and the TV picked up a local non digital station. Its basically audio only because the picture was unwatchable, I couldn't get the horizontal to stabalize and its running off frequency as sometimes I could see multiples across. The picture had no detail and almost no contrast.

Tonigh I will check all the tubes on my tester. QUESTION--if the sound is clear that tells me the tuner/IF amps/video detector/and video amp are all working correct?

I'll try and take some pictures of the screen when I get home tonight. Don't laugh when you see the TV, the exterior looks bad!
I'll try and post every night I work on this, this TV will need some advice from all you pros to get it watchable again. I know Im 75% there!

Regarding C21, I'd install a 20mfd electrolytic as Riders indicates. Sams shows the same value for that cap and does not indicate any alternates.

If an S bend moves slowly up the screen, I'd suspect a 60hz filtering problem. If you have a stationary bend (which may move or get worse or better with horizontal adjustments), that may be a sweep issue.

You're correct, audio is picked off at the video amp, so sections upstream of that are working reasonably well (at least well enough to pass audio).

You may be closer than you think. Sometimes just one or two funky sweep components can mess up the picture a lot.

Phil Nelson

I used to have one of these. I thought it was an Airline when I bought it but I didn't keep it so I sold it on ebay years ago.