Sylvania 1-076 arrived!

[John Folsom]

John,

Nice job on the IF transformer. Here is a link to capacitor color codes, hope it will help:
http://www.tpub.com/neets/book2/3g.htm

[jeyurkon]

Originally Posted by John Folsom

John,

Nice job on the IF transformer. Here is a link to capacitor color codes, hope it will help:
http://www.tpub.com/neets/book2/3g.htm

Thanks for the compliment and the link. The axial ceramic cap color code table is close. But, like all of the others I've looked at they don't include silver in the multiplier. I guess I should just assume it follows form since that gives the schematic value.

John

[jeyurkon]

I think I've found the problem with the horizontal circuit. The symptom is that it's only stable with the blanking bar down the center of the screen.

I don't fully understand the circuit. It's a sine wave type horizontal AFC.

But suffice it to say that the output of the sync clipper is fed to the horizontal discriminator through a 100pF capacitor. It was supposed to be an axial ceramic. It's actually a Micamold.

All the bad things I've heard about micamolds are justified. If a capacitor can be evil, this one is. The discriminator circuit requires it to not have any leakage. It has about 16 uA at rated voltage. But it gets weirder. The capacitor testing gives up trying to measure the value if the cap's been resting for a long time. After measuring the leakage, the capacitance tests out at 300 pF. It then gradually ramps up to 3,000 pF after a few minutes of testing.

At least this one is easy to get to. The other one that I'll replace is used to turn the line cord into an FM antenna. Given that it would probably burn my house down I'm inclined to replace it.

I wish the 13 others weren't so difficult to get to; I'd love to replace them but since they seem to be working I guess I'll replace them when their time comes.

John

[jeyurkon]

Finally!

I changed the micamold and found two caps I had switched. A 0.005 and a 0.010 uF. There's one micamold left that is for the horizontal ringing coil. It's hard to get to, but I should change it.

Here are some photos. Is this the typical linearity that you should expect for a set of this vintage?

John