Work begins on the Penncrest CTC-15

[RetroHacker]

As soon as I got home from work, I pulled the chassis out of the set, and started cleaning it. I pulled all the tubes, and noted them down. I have the schematic for the set (Sam's 810, folder 3), and compared the tubes to the tube layout on the schematic. There are some differences:

The first video IF tube was a 6BZ6. The schematic shows a 6JH6
Chroma Bandpass Amp/Color Killer is a 6EA8 (schematic: 6GH8A)
Z Demod is a 6HZ6 (schematic: 6GY6)

Chroma Sync Phase Det./Color Killer Det. is an a Rayetheon tube with the number rubbed off, schematic lists it as a 6JU8.

When I pulled out the 6BK4, it jingled. It jingles quite a bit when tilted back and forth, although I see nothing loose inside the glass. It still has vacuum and does not look very old. The set came with several used tubes - the previous owner got a whole bunch of tubes real cheap when a TV shop closed, and replaced all the tubes he could with new ones, just in case. So I have the used 6BK4.

The vertical output transformer is a Stancor. Likely a replacement.

Looking under the chassis, I looked closely under the flyback cage - the previous owner said that he saw smoke from under there when the set failed. R204 and R115 are large ceramic block resistors, and look to have run pretty hot, but that's normal. C99, a .01 @ 1400v ceramic disc cap is singed on the top. I don't know if it was due to the heat from the resistors, or it's own failure.

Electrolytics are all original, and I would like to replace them, although I don't think I have all of the proper values in my stock. How close do I have to be? For example, 80uf @ 450 is an odd value. Can I use 100uf? Or what about going from 160uf up to 220? I've done similar subs in other sets before, but not in a complicated color set. I know I can use 47uf in place of 50uf - since the difference of 3uf isn't enough to matter, especially with the tolerance of those old parts.

I don't have a ceramic cap to replace C99. But I do have some modern .01uf @ 1600v plastic block type capacitors. Are these suitable for this kind of circuit?

Any pointers about this chassis before I fire up the soldering iron?

Thanks!

-Ian