View Full Version : Admiral Telebar help


Radiotronman
05-16-2017, 01:55 PM
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.

Eric H
05-16-2017, 02:14 PM
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?

Radiotronman
05-16-2017, 02:41 PM
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?

M3-SRT8
05-16-2017, 09:41 PM
Yup. Check the resistors in the Horizontal Oscillator. They're frequently way out of spec. Caps, too.:smoke:

Electronic M
05-16-2017, 10:31 PM
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.

Radiotronman
05-17-2017, 03:05 PM
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?

David Roper
05-17-2017, 03:25 PM
Have you gotten the scope out yet?

Eric H
05-17-2017, 03:27 PM
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.

Eric H
05-17-2017, 03:29 PM
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.

Radiotronman
05-17-2017, 05:31 PM
When you say horizontal coil, do you mean the horizontal frequency, drive or linearity controls?

Electronic M
05-17-2017, 07:09 PM
Frequency of course.

Eric H
05-17-2017, 07:19 PM
What's the model number of the set?

Radiotronman
05-17-2017, 07:24 PM
321k47

Eric H
05-17-2017, 07:27 PM
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.

old_coot88
05-17-2017, 08:55 PM
The squealing noise is sometimes of mechanical origin. If it's still there, try tightening the flyback clamp nuts and mounting hardware.

M3-SRT8
05-17-2017, 09:27 PM
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?

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

Radiotronman
05-17-2017, 11:56 PM
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?

M3-SRT8
05-18-2017, 07:38 AM
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:

Electronic M
05-18-2017, 09:45 AM
The mica cap on the horizontal lock coil is a 3900pf mica, which I don't have. Any more ideas?
3900pF = .0039uF...Get a film cap...If you don't have one that is close tack 4 .001 caps in parallel for temp.

Radiotronman
05-18-2017, 10:25 AM
Ok, thanks Tom. I'll try that!

Radiotronman
05-18-2017, 10:27 AM
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!

old_coot88
05-18-2017, 01:39 PM
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?

Radiotronman
05-18-2017, 04:35 PM
I cannot draw an arc from the hv rectifier with it connected or not.

Radiotronman
05-18-2017, 06:00 PM
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?

timmy
05-18-2017, 06:26 PM
Sounds like a short somewhere, is there a doorknob cap in that set ?

Radiotronman
05-18-2017, 09:28 PM
There is a doorknob cap in this set. How do you test them, a continuity check?

old_coot88
05-18-2017, 10:34 PM
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?

timmy
05-19-2017, 06:06 AM
Ok I missed that...

Radiotronman
05-19-2017, 09:49 AM
I'm not sure old coot-what does it tell me?

Electronic M
05-19-2017, 09:57 AM
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.

David Roper
05-19-2017, 01:20 PM
With power applied, what color is the 6BQ6 plate, black or red...?

Radiotronman
05-19-2017, 06:06 PM
I guess I need to test my nos flyback or what is causing no hv?

timmy
05-19-2017, 07:08 PM
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.

Radiotronman
05-20-2017, 08:15 PM
The plates on the 6BQ6 are black. What's going on here?

Electronic M
05-20-2017, 11:53 PM
How is the damper doing?

Eric H
05-21-2017, 01:22 AM
The plates on the 6BQ6 are black. What's going on here?

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?

Kevin Kuehn
05-21-2017, 10:42 AM
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?

http://videokarma.org/attachment.php?attachmentid=194696&stc=1&thumb=1&d=1495079739

Which Sams are you using?

Kevin Kuehn
05-21-2017, 11:08 AM
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.

dieseljeep
05-21-2017, 02:04 PM
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.

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.

Kevin Kuehn
05-21-2017, 06:35 PM
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/qq245/Kuehn/VK%20Pictures/Admiral%20321k47%20002_zpspeoodrf9.jpg

Radiotronman
05-22-2017, 02:47 PM
So, any ideas on why there is no hv?

bandersen
05-22-2017, 03:38 PM
Sure looks like Syncroguide to me.

Here are a few possibilities.
Flyback is bad or hooked up wrong - Check your wring and check the resistance between flyback windings. Should be close to values shown on scheamtic

Horizontal oscillator running way off frequency. Check waveform on pin 5 if you have a scope.
Weak drive signal to 6BQ6 - Does adjusting the horizontal drive do anything ? Check DC voltages on 6BQ6 too.

Radiotronman
05-24-2017, 09:16 PM
Bob,

Adjusting the horizontal drive doesn't do anything.

dieseljeep
05-24-2017, 09:35 PM
Sure looks like Syncroguide to me.

Here are a few possibilities.
Flyback is bad or hooked up wrong - Check your wring and check the resistance between flyback windings. Should be close to values shown on scheamtic

Horizontal oscillator running way off frequency. Check waveform on pin 5 if you have a scope.
Weak drive signal to 6BQ6 - Does adjusting the horizontal drive do anything ? Check DC voltages on 6BQ6 too.

The schematic must be the Syncroguide version, not the set the OP is working on!
The OP is referring to the .0039 cap across the horizontal lock coil.
The chassis should have a horiz phase det tube like a 6AL5. :scratch2:

dieseljeep
05-24-2017, 10:01 PM
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.

Riders shows that model number to use a 21B1 or a 21L1 chassis.
The schematic shown is not the right one.
The OP should only use the chassis number. Model numbers mean very little.
Riders volume # 13, page 13-1. There was a multitude of changes made throughout the production run.

Kevin Kuehn
05-31-2017, 12:18 PM
Riders shows that model number to use a 21B1 or a 21L1 chassis.
The schematic shown is not the right one.
The OP should only use the chassis number. Model numbers mean very little.
Riders volume # 13, page 13-1. There was a multitude of changes made throughout the production run.

I suppose the .0039 cap was the clue to reading between the lines, but then again one never knows for sure what changes have been made to the set before someone comes on here asking for help. :dunno:

Radiotronman
05-31-2017, 10:15 PM
I've checked every resistor and cap around the horizontal oscillator and horizontal output tubes. Any out of tolerance resistors were replaced. I also tested the flyback and it tested good on my tester. I still get no hv. These Admirals are usually easy to restore. What am I missing and what's going on here?

EdKozk2
06-01-2017, 12:11 AM
Tom asked you to check the damper. You should be getting at least 250 vdc on pin 5 of the 6W4. Pin 3 of the 6W4 should be about 415 volts, this is your B+ boost voltage. Make sure there is continuity through all the terminals of your linearity coil. These voltages are the same as your boost voltage and they pass through pin 1 of the flyback to the plate of the 6BQ6.

Radiotronman
06-01-2017, 11:40 AM
Ok, thanks. I will take those readings and report back tonight. I used my BK Analyst and injected horizontal drive voltage to the cap of the 6BQ6. I now get an arc off the cap of the hv rectifier, but no arc at the second anode button on the crt. I still don't get a raster, but can hear the hv running with the analyst for the first time. I also checked and replaced any out of tolerance resistors in the base of the hv rectifier while I was at it.

bandersen
06-01-2017, 01:26 PM
OK, so if you've got an arc at the HV rectifier cap, either the rectifier isn't working or it's being loaded down by a short or there's a break in the HV lead. Easiest to try first is swap out the HV rectifier. Also check for continuity in the HV lead going to the CRT.

Kevin Kuehn
06-01-2017, 02:07 PM
Also check the resistor in series with HV lead. It's probably hiding under the HV Rectifier socket.

Radiotronman
06-01-2017, 05:21 PM
Kevin, I replaced the 470k resistor in the hv socket that runs to the hv lead to the crt second anode. I also tested the 2.7ohm resistor on the hv filament and it was right on.

EdKozk2
06-01-2017, 07:03 PM
When you say " injected a drive signal to the cap of the 6BQ6" ,did you mean plate cap ? I would think in order to properly test the circuit you would inject the signal to the junction of R85 and R83 which is connected to the grid pin 5 of the 6BQ6. Also if your 1B3 is OK, and all your voltage tests , along with continuity checks, the you may may have a bad 500mmf doorknob. I had to replace them in the two Admirals I fixed this spring.

Electronic M
06-01-2017, 07:23 PM
When you say " injected a drive signal to the cap of the 6BQ6" ,did you mean plate cap ? I would think in order to properly test the circuit you would inject the signal to the junction of R85 and R83 which is connected to the grid pin 5 of the 6BQ6. Also if your 1B3 is OK, and all your voltage tests , along with continuity checks, the you may may have a bad 500mmf doorknob. I had to replace them in the two Admirals I fixed this spring.
ED, the B&K analyst family can drive a set's flyback directly at the output tube plate lead...I've got a B&K 1077 analyst and have used it that way several times.

EdKozk2
06-01-2017, 08:09 PM
ED, the B&K analyst family can drive a set's flyback directly at the output tube plate lead...I've got a B&K 1077 analyst and have used it that way several times.

HiTom, I figured since he threw in a new flyback that it would be better to check the operation of the horizontal output tubes associated circuits.

old_coot88
06-01-2017, 08:24 PM
The Analyst will drive the grid too, right?

Radiotronman
06-01-2017, 09:19 PM
Ed,

How did you know those doorknob caps were bad? What symptoms did they cause and were they killing hv? Where did you get replacements?

EdKozk2
06-02-2017, 12:38 AM
Ed,

How did you know those doorknob caps were bad? What symptoms did they cause and were they killing hv? Where did you get replacements?

The second anode voltage was too low and causing the HV rectifier arc internally. Had close to no HV on the other set also, so I just changed it any way. I replaced the doorknobs with 15kv ceramic disk caps, .001mfd. I had to modify the mount and connections to use the cap on the underside of the chassis. Special attention to lead placement and spacing is required when modifying. You don't want intermittent arcing. Only make this change if your sure about the doorknob. Don't forget that troubles with vertical output transformer can load down the B+ boost voltage too.

Radiotronman
06-02-2017, 10:47 AM
I did a continuity check on the hv cable last night and could not get continuity from pin 7 on the hv rectifier socket to the hv button. I did get continuity from pin 4. The cable ties in with a 470k resistor off pin 7. They might have used pin 4, since it's an unused pin as a junction point for the cable and resistor, but shouldn't I have gotten continuity from pin 7, where the other leg of the 470k resistor should attach? I'll take apart again tonight and check this. There was some sloppy repair work on this set before I got it, maybe they hooked something up wrong while repairing. Instead of a 470k resistor in the hv socket, there was two 1meg resistors in parallel (making 500k). I can't imagine that was original from Admiral, but maybe.

Kevin Kuehn
06-02-2017, 02:03 PM
I think you're right about pin 4 being a tie point, because there's no pin 4 or 6 on a 1B3.

bandersen
06-02-2017, 03:24 PM
I would expect you'd measure 470K between the HV button and pin 4. That might be too high if you have your multimeter in continuity mode.

There were parts shortages in the early 50s due to high consumer demand and the Korean war. I've seen lots of crazy resistor combinations that were made at the factory.