Sentinel 400 Width

[Doug66]

I'm restoring a Sentinel 400. After recapping and replacing out of tolerance resistors, it was playing rather well except the picture had a horizontal jitter. I posted about that on Antique Radio Forum, and was told the jitter was probably because I hand not put the HV cage back on yet.

Upon reinstalling that, something inside the cage started arching. I turned the set off, removed the cage and couldn't see anything that was near the cage that would cause an arch. I put the cage back on, powered it up, and it arched again, but stopped after about 15 seconds. Then the horizontal width had shrunk.

I have checked, rechecked, and replaced every resistor and capacitor in the HV cage. All voltages on both the Horiz Osc and Horiz output tubes are ok.
I've subbed new 6SN7 tubes for the horiz osc and output, a new 6Y6 for the HV oscillator, and tried another 6X5 in the LV rectifier. I've also replaced all the dropping resistors in the string too. I'm out of ideas. Any help is greatly appreciated.
Thanks
Doug