Admiral Telebar help
 

I'm restoring an Admiral Telebar set for a fellow collector. The set has a high pitched ringing noise from what seems to be the flyback area. The original flyback had a cracked phelonic board, so I replaced it with an nos flyback. The noise is still there with no hv. Is this a horizontal oscillator issue causing this? I have recapped this chassis too.

The H Oscillator's probably running way off frequency causing the noise, it'll also kill the HV if it's too far out.

Does adjusting the H Hold control change the pitch of the noise?

Yes, adjusting horizontal changes the pitch of the noise, but it does not go away. I guess I'll start checking resistors around this tube?

Yup. Check the resistors in the Horizontal Oscillator. They're frequently way out of spec. Caps, too.:smoke:

If the usual caps, resistors, tubes bit don't get it working then the horizontal section may need adjusting. IIRC admiral subscribed to the same synchroguide H osc system RCA did, so it should require the same kind of setup....Get the waveform peak just a bit higher than the hump and make sure peaks are as far apart as the H sync pulses.

I tested all resistors around the horizontal oscillator and didn't find any resistors way out of tolerance. There are three mica caps on this 6SN7 tube, could one of these being leaky kill the circuit? What else could cause this noise and kill hv?

Have you gotten the scope out yet?

Check the value of the cap across the Oscillator coil, make sure you used the correct value.

I have mistakenly put in a .00* instead of a .0* on several occasions, that will throw the frequency so far off you can;t adjust it out.

Another possibility is someone in the past adjusted the Horiz coil to compensate for a bad cap and when you replaced it it's now way off.

I don't know this chassis or have a schematic so I'm guessing that in addition to the regular Horiz Hold control on the front , it has an adjustable Horiz coil somewhere in the Oscillator circuit, a coil with a slug most often, find that and give it a tweak and see what happens.

And yes, a bad Mica could be throwing it off, there have been more and more reports of failed Micas recently, even they don't last forever I guess.

When you say horizontal coil, do you mean the horizontal frequency, drive or linearity controls?

Frequency of course.

What's the model number of the set?

321k47

Here's an example, it's an Admiral but probably older than yours and a different model, same idea though.

Coil L20, B1 would be the adjustment I would look for, and make sure the capacitor C61 across the coil is the correct value for your set.

The squealing noise is sometimes of mechanical origin. If it's still there, try tightening the flyback clamp nuts and mounting hardware.

Ooooh, yeah. Micas in the Horizontal circuits are prime suspects now. They take a beating there.:smoke:

I replaced a few micas around the horizontal output tube and a couple resistors, but no improvement. Pin two on the horz output tube is supposed to be 305v, and I measure 250v. The mica cap on the horizontal lock coil is a 3900pf mica, which I don't have. Any more ideas?

It could be an IF stage. When the noise starts try tapping each if tube.

I had a 721 TCS that had these symptoms and it wasn't a horizontal sweep or synch problem. Swapped out a video if tube and it was fine.

I'm reaching here, but, there it is.:smoke:

3900pF = .0039uF...Get a film cap...If you don't have one that is close tack 4 .001 caps in parallel for temp.

Ok, thanks Tom. I'll try that!

I found that if I worked the horizontal lock coil in and out, at certain points the noise would stop. I still have little to no hv though. Thanks for the help guys!

Couple of questions. If you disconnect the plate connector from the HV rectifier, can you draw an 'air arc' from the connector (using a well-insulated screwdriver)? It should draw a nice quarter-inch to half-inch blue arc off the screwdriver. With the connector re-connected, can you draw the same arc?
Is the tube running hot?

I cannot draw an arc from the hv rectifier with it connected or not.

I replaced the 3900pf with a .0039uf film cap, but still no hv. I'm starting to run out of ideas on what is going on?

Sounds like a short somewhere, is there a doorknob cap in that set ?

There is a doorknob cap in this set. How do you test them, a continuity check?

Since you weren't getting any arc off the HV rectifier plate connector (even with the connector lifted and floating), what does that tell you?

Ok I missed that...

I'm not sure old coot-what does it tell me?

If you can't draw an arc from the fly lead that normally connects to the HV rect. top connection, when that lead is disconnected from the HV rect then it means the fly is not generating any HV.

Timmy was suggesting that you test to see if the doorknob was loading down the HV...Which is irrelevant at this point because if there is no HV to load down.

With power applied, what color is the 6BQ6 plate, black or red...?

I guess I need to test my nos flyback or what is causing no hv?

You said it did the same thing with the old fly then you changed it so there is no sense in checking the new fly.

The plates on the 6BQ6 are black. What's going on here?

How is the damper doing?

The plate in the tube can glow red if the Oscillator isn't running.

The squealing noise would seem to indicate that it is though, if it's loud then it's probably not at the right frequency.

If you pull the connector off the top of the 6BQ6 tube does the noise stop?

http://videokarma.org/attachment.php...1&d=1495079739

Which Sams are you using?

More specifically which chassis number do you have? The Sams website lists two different folders for that model number and the Horz circuits are not the same.

That chassis doesn't use syncroguide! Many models did, but not that one.
I don't remember what they called that circuit. I always seemed to have grief with that circuit. Synchroguide seemed to be a little easier to troubleshoot.

Sams lists Admiral model 321k47 in both 117-2 and 135-2. The circuit in 117-2 really does look like RCA's Syncroguide, no?

http://i452.photobucket.com/albums/q...pspeoodrf9.jpg