Snow.

[jpdylon]

And not the stuff you can pack and throw at people.

I'm nearly done with the capehart, but it has snow troubles. THe sound is crisp and clear and stays that way through the entire fie tuning adjustment.

There appears to be no lack of RF sensitivity, as the set will pick up off air stations 30 miles away (with no antenna connected) with about the same amount of snow as if I hook up the VCR to the antenna terminals.

I've torn down the tuner. The 300 ohm lead has no breaks. All the resistors are within respectable limits of tolerance, not one is more than 10% off. Tuner supply voltages are excellent, about on par with the schematic, B+ slightly higher. This is the later capehart tuner using the 6j6 oscillator and 6BK7 RF amp, a 13 position turret type.

All tuner and IF tubes have been replaced with NOS that all test like new on my heath and SiCo testers. THe set has been re-capped and alot of out of tolerance resistors on the power supply and sweep sections. THe power supply voltages are very good.

I've troubleshooted and determined that the AGC section is not at fault. Voltages on the AGC bus are well within spec and its adjusting properly when varying signal input.

At this point I'm somewhat stumped. I'm wondering if the video carrier is weak due to a failure in the iF strip. Perhaps a misalignment? THis set has been tinkered with alot by its previous owner, so there's no telling what else may pop up.

I'm close to being done with this set, just need to get this picture problem out of the way.

[Adam]

You've probably already thought of this, but once I had the exact same problem, and there wasn't anything wrong with the set at all but the little 300 ohm transformer I had hooked to the antenna terminals on back of the set was bad.

[Don Lindsly]

Make sure the B+ voltages get to the 6BK7. Measure the tuner AGC voltage; minus two or 3 volts maximum. If it is more, the problem is AGC, not the tuner.
Turret tuners can be serviced by removing all but one or two coils to keep the circuits functioning and get at the components.
I would suspect alignment last.

[jpdylon]

I've already swapped the 300 ohm transformer --first thing I thought of.

I will double check B+ at the RF amp. Thanks for the suggestion Don.

[andy]

...

[Boobtubeman]

Speaking of snow.... anyone know if a packard bell (my avatar) is supposed to have snow and white noise from the speaker?

Mine recieves well on cable and DVD, but the screen is blank and no audio when nothing is hooked up. Just wondering if this is normal for a 53 to act this way.

Steve

[compucat]

Originally Posted by Boobtubeman

Speaking of snow.... anyone know if a packard bell (my avatar) is supposed to have snow and white noise from the speaker?

Mine recieves well on cable and DVD, but the screen is blank and no audio when nothing is hooked up. Just wondering if this is normal for a 53 to act this way.

Steve

My 57 8" RCA metal portable is the same way. No signal gives you no sound and a blank raster. I have seen many sets like this from the 50s and earlier. It is probably normal.

[kbmuri]

Hmm... familiar. I haven't had time to look at my Capehart 504P (the one from Eric H) in the last couple of weeks due to job stress. But you're describing the problem I left it at last, to a T. It picks up local UHF channel 15 for some reason, around channel 12 or 11 on the dial, with no antenna at all, watchably but snowy. Maybe it's a harmonic, or maybe my local oscillator's just that far out of whack. Direct VCR output on Ch3 shows up on the TV at Ch3 on the dial, but it's just as snowy. I checked all the tubes and swapped a few anyway, but to no avail. Caps and resistors as Eric left them. Need to have another go-round with it at Christmas break, but 'til then I'm interested to see how it goes with you, and if you have any luck.

[Tubejunke]

My Tv's have snow and "snow sound" when no signal is present. In other words no blank raster and nothing coming from the speaker when I dont have something hooked up or an over the air signal.

[wa2ise]

Originally Posted by kbmuri

But you're describing the problem I left it at last, to a T. It picks up local UHF channel 15 for some reason, around channel 12 or 11 on the dial, with no antenna at all, watchably but snowy. Maybe it's a harmonic, or maybe my local oscillator's just that far out of whack.

That oscillator would have to be way off, as channel 11 is at around 206MHz, and channel 15 s at about 480MHz. But the oscillator's 2nd harmonic could find itself at 520 or so MHz, as well as 260Mhz, if your IF is at 40MHz.

[jpdylon]

The problem was in between the last IF stage and the video detector. THe 26mhz video carrier was very weak, which explained the crummy picture but good sound. I replaced some out of value resistors on the last IF stage and touched up the 26mhz coil for greatest carrier signal without overloading.

The picture is smooth as glass. Problem solved. Pics can be seen on the updated thread:
http://www.audiokarma.org/forums/sho...d.php?t=135772