bgadow
01-16-2008, 12:28 PM
This is a 16" console that I've owned for about 10 years now. I've posted a picture long ago but will have to get another one sometime. It was a handsome piece when new, with full doors and a nicely built cabinet. The guy who sold it to me, a friend I know from work, had it stored for many years in an open shed. Luckily only the finish was ruined-the interior survived fine. I decided a couple years ago to tackle it. First issue was that part of the tuning knob could not be removed, so I couldn't pull the chassis. I tried everything: solvents, oils, intense heat. Nothing would work. Eventually brute force did it, but in the process it destroyed the internal workings of the Mallory inductuner. I had been blaming it on a glued-on knob but it now looks like corrosion between brass and aluminum. I did proceed to recap the set...this holds the record among tube sets I've worked on for the number of electroytic caps. Very well built, with leads nicely dressed and tied with string. Like some other "overbuilt" sets it uses twin HV rectifiers.
After recapping and some tube swapping I got a raster (and some video, despite the ruined tuner) but while bench testing one of the new caps started to smoke. At the time I didn't have the Sams so I put it aside until I had both schematic and tuner. Well, now I have both. The tuner arrived last week thanks to Bill Cahill, and was easier to swap than I expected. I then went after the cap problem. I don't know if I had installed it backwards or what, since when last working on it I cut the part out and didn't leave myself any notes-thanks a lot, Bryan! After carefully replacing it per the schematic I fired it up-and not much happened. I've been tinkering with the set for days but I've reached the (low) limits of my "expertise". The main issues are that all voltages are too high and there is not HV. (cathode current almost zero on the 6CD6, nothing at the anode at all) I took various voltage and current measurements but I can't figure it out. The other thing that seems strange is that a resistor in the video output circuit runs hot-I narrowed it down to the plate circuit. I can't figure out a reason for it.
Finally, last night I dug into the HV cage. There are 3 caps in there, all rated at 10KV. One is a typical doorknob (voltage doubler cap., per sams) while the other 2 are tubular (they are inside shields so I can't tell if they are some sort of black beauty or just what) and they are the HV filters. I don't trust them, but I'm not sure if that is the problem. I wonder where I will find .00047/10KV caps? I wonder what I will learn from this latest challenge? :)
After recapping and some tube swapping I got a raster (and some video, despite the ruined tuner) but while bench testing one of the new caps started to smoke. At the time I didn't have the Sams so I put it aside until I had both schematic and tuner. Well, now I have both. The tuner arrived last week thanks to Bill Cahill, and was easier to swap than I expected. I then went after the cap problem. I don't know if I had installed it backwards or what, since when last working on it I cut the part out and didn't leave myself any notes-thanks a lot, Bryan! After carefully replacing it per the schematic I fired it up-and not much happened. I've been tinkering with the set for days but I've reached the (low) limits of my "expertise". The main issues are that all voltages are too high and there is not HV. (cathode current almost zero on the 6CD6, nothing at the anode at all) I took various voltage and current measurements but I can't figure it out. The other thing that seems strange is that a resistor in the video output circuit runs hot-I narrowed it down to the plate circuit. I can't figure out a reason for it.
Finally, last night I dug into the HV cage. There are 3 caps in there, all rated at 10KV. One is a typical doorknob (voltage doubler cap., per sams) while the other 2 are tubular (they are inside shields so I can't tell if they are some sort of black beauty or just what) and they are the HV filters. I don't trust them, but I'm not sure if that is the problem. I wonder where I will find .00047/10KV caps? I wonder what I will learn from this latest challenge? :)