Late 1940s Air King Project

[jr_tech]

The Sams (121-3) shows the adjuster slug on the back by the focus control as "b-1, horizontal afc"... The schematic shows b-1 as being the horizontal frequency coil L-23 which is in the plate circuit of the horizontal osc (v-14). The coil Eric circled is shown as "b-4 horizontal lin". The other adjustment above b-4 appears to be in the sound circuit (L-22).

jr

[tvcollector]

Originally Posted by Eric H

I just noticed another adjuster near the one I circled, it could also be one of the above mentioned (drive, freq, width) adjustments.

The one you circled in the picture is one of the adjusters next to the flyback cage that adjusts from the top of chassis.. It's most likely L24.. It shows up as being the Horiz Lin control according to the sams.. The other smaller coil next to the HV cage, closer the the back side of chassis is Sound IF...

[tvcollector]

JR Tech that's what has been throwing me off, is L-23 because that coil is not in the same place, or not even sure it exists in this chassis... For some reason it comes in on channel 9 better as my modulators are set to 10... There's also a wave effect that's noticeable on still images, as if the set has bad filter caps, and they all have been replaced.. Putting the back cover on also throws off the ion trap.. Not sure why and how, it's not even touching the ion trap.. I did try and demagnetize the metal back cover with a degassing coil...

[dieseljeep]

Originally Posted by tvcollector

JR Tech that's what has been throwing me off, is L-23 because that coil is not in the same place, or not even sure it exists in this chassis... For some reason it comes in on channel 9 better as my modulators are set to 10... There's also a wave effect that's noticeable on still images, as if the set has bad filter caps, and they all have been replaced.. Putting the back cover on also throws off the ion trap.. Not sure why and how, it's not even touching the ion trap.. I did try and demagnetize the metal back cover with a degassing coil...

It would appear that the CRT was replaced at one time.
Air King products was owned by Hytron, the tube manufacturer. They all had Hytron CRT's in them. Maybe the original CRT had a single magnet ion trap, where the one that's in there now, might require a double ion trap. It's worth a try. I acquired a 12LP4 from a Philco, that only had a single ion trap. I left the ion trap on the tube as a reminder.

[jr_tech]

Originally Posted by tvcollector

JR Tech that's what has been throwing me off, is L-23 because that coil is not in the same place, or not even sure it exists in this chassis...

To clarify, the way I read the schematic (page 2) in the Sams folder, L-23 *is* adjustment B-1 which *is* the Horiz Freq. control, which is the brass screw adjustment on the back of your chassis marked "AFC" and shown as "B-1, Horizontal AFC" on page 10 of the Sams.
Page 11 of the Sams clearly shows L-23 mounted on the back of the chassis near the focus pot, the location of adjustment "B-1".

jr

[tvcollector]

Does any have an extra ion trap? should I worry about the weak 12BH7 tubes and the weak 5U4? perhaps would these tubes be causing the excessive buzzing and hum bars? Can see the hum bars on a blank screen, which has to do with wave effect...

[Username1]

Hum bars, and hum in speakers can be power supply, 5U4 is power supply part,
You should really get the PS under control first, as everything else depends on it.

.

[tvcollector]

I've never worked on a set with a 5U4, but according to the seller, 5U4 tubes are either good or bad, no in between, and they don't test, or can't go by what the tester says.. It's not like I have the extra room and have these tubes lying around somewhere.. If that was the case I would have tried other tubes.. If it's a questionable tube, it would be something I would have to find on eBay or order from Orlando.. I don't want to order tubes that are already good... To be honest, I don't know where to start.. I thought of ordering 12BH7 and 5U4 tubes.. But I don't know..

[Electronic M]

Unless the 5U4 is the damper it should be easy to test. If it is the main B+ rectifier just check the B+ voltage....if it is within 30% of spec assume it is good.

[Username1]

Well, people say you can't go by the tester on those tubes because you
would have to know the unit's current draw, and be able to tell the tester to
show "good" at or above the current the tube is expected to pass......
So to best test the tube in your set, you should check the voltage at the first
filter cap, and see if it matches the sams....
You could cut the line off the cathode and check the current, is it within spec of what
the tube should be able to pass...? Use a scope, is there ripple...? Too much ?

You could cut the circuit out, put a resistive load cathode to ground ans see what the
voltage is with say a 5ma load on it, then put on the rest of the tv, and see if
there is too much drop driving the set.... It would be good to have a known good
5u4 to compare to, but you should be able to get a feeling for what's going on.....

Hum bars, open caps in PS, too much load on ps.

.

[dieseljeep]

Originally Posted by Username1

Well, people say you can't go by the tester on those tubes because you
would have to know the unit's current draw, and be able to tell the tester to
show "good" at or above the current the tube is expected to pass......
So to best test the tube in your set, you should check the voltage at the first
filter cap, and see if it matches the sams....
You could cut the line off the cathode and check the current, is it within spec of what
the tube should be able to pass...? Use a scope, is there ripple...? Too much ?

You could cut the circuit out, put a resistive load cathode to ground ans see what the
voltage is with say a 5ma load on it, then put on the rest of the tv, and see if
there is too much drop driving the set.... It would be good to have a known good
5u4 to compare to, but you should be able to get a feeling for what's going on.....

Hum bars, open caps in PS, too much load on ps.

.

Hum bars, could be caused by a cathode-heater short in one of the tubes used in the IF, video and tuner.
The so-called restoration, seemed to be done rather well and neatly.
My opinion would be, that the restorer wanted to bail out, as they couldn't get it working, just right.
The set, shouldn't have been that far out of whack, just by shipping it.

[Eric H]

Hum bars and buzzing can be causes by your video source as well, older sets sometimes can't handle the strength of the signal from a RF modulator or VCR, try backing off the Contrast control a bit and see if that reduces the buzz in the sound.

[tvcollector]

I used a Blonder Tongue modulator wireless, and directly from cable box to channel 3.. No difference... At first it was channel 9 that was coming in better, now the tuner seems to give a better range on 10, where it's suppose to be with the modulator.. Adjusting contrast does help, but it's still very loud, sometimes even louder than the program.. It should be at minimal... The voltage checks I'll probably do sometime the end of the weekend, early next week..