AirKing 4602

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Re: AirKing 4602

Post by frank1956 on Sun Feb 07, 2016 6:07 pm

Wildcat445 wrote:This schematic is not the best I have ever worked with. †There are no resistance to ground reading for the various test spots in the radio listed on the diagram. †I wonder if the tuning cap or antenna is shorted to ground. †One would think that such a short would have killed the signal from the signal generator. †We got IF thru the set to the speaker. †We should be able to get RF. †Try this. †Make sure the radio is off for this test. Check resistance from where the antenna connects to the tuning cap to chassis. †Do it both with the antenna connected and with the antenna disconnected. †See if there is a difference. Then check it to B- wit the radio turned OFF. †Something may be shorting out the RF.


I guess it's time for that dumb question lol! , but how to you disconnect the antenna?? Un solder the connection between the tuning cap and the antenna??
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Re: AirKing 4602

Post by Wildcat445 on Sun Feb 07, 2016 7:59 pm

The schematic just shows it connected. If there is a wire, unsolder the wire from wherever you feel most comfortable. This is one of those places where you are on your own. There has got to be a wire between the antenna and the tuner. Go easy with the heat unsoldering from the tuner. It might be safer to cut the wire between the antenna and tuner, then re-connecting that wire after the test. I can't see exactly what you have, so just use your best judgment.

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Re: AirKing 4602

Post by 75X11 on Sun Feb 07, 2016 9:00 pm

It may just be me, but it appears from what has been found with the unit so far, it should be working. It looks like the components on the schematic that are illegible may have a resolution to the problem. My copy of the schematic is poor as well. It looks like someone hand wrote the notations on the page. Maybe if someone had a different or better 1st generation print of it. There isn't even a parts list.WC, I can't think of anything more than what you have advised Frank to do to locate the problem.
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Re: AirKing 4602

Post by frank1956 on Mon Feb 08, 2016 9:28 am

Here are some pic's of what we are dealing with in regards to the antenna.



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Re: AirKing 4602

Post by willy3486 on Mon Feb 08, 2016 10:52 am

Excellent post here. I have looked at it from time to time †and wildcat and 75x11 have been great on suggestions so I haven't posted much. I am a little stumped as well but I have a couple of suggestions. I have run into similar issues. One time I couldn't figure out what was going on but it should have been going. One issue I had in the past I misread and put the wrong cap in. I worked on a radio years ago. It should have sent a signal to the speaker but nothing was coming out. This one radio I have I put it on the shelf over 30 years ago but never got rid of it. I came back to it and what I found out I had put say a .00047 cap where a .047 should have went.

The other issue I am running into more and more these days with the radio not playing after a rebuild is this. I can recap it and it should be working. I can inject a signal into the transformers and it works fine. But no tuning or anything. It seems like no antenna or no tuning cap. What I have found out is that many times they have these coils in the circuit close to the tuning area. They will two,three, or more leads. They usually are wound around a cardboard tube and may have wax on them.When I get to a point where it should play but doesn't up to the ifs I look for these coils. I will look at the diagram and find them. I figure out which connections are which. IIRC many times these coils are a couple of hundred of ohms at the most.

If I find one that doesn't get a reading I will look at it closely. Many times under a magnifying glass I will see it have a broke wire. I then will get a piece of wire like the power cord and strip about 3 inches of the covering off. I will then clip one strand off and wrap one end on the lug it is suppose to connect to. Then I will pull the broke wire up as carefull as I can and wrap it to the new wire lead. Then I take a soldering iron and heat the two to put solder on it. I then check the resistance again and see if I have a connection. I think I may have saw this only a time or two before I quit working on them back around 92. Since I got back into them in the last few years I have seen a few do this.

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Re: AirKing 4602

Post by Wildcat445 on Mon Feb 08, 2016 11:36 am

I was not expecting to see an antenna like that. You need to check the schematic and follow the wire from the antenna to tuner then disconnect it. Willy, I had the antenna coil in mind as well. I appreciate your input on this thing. I was trying to eliminate everything from the tuner on to the speaker. It is possible for the antenna to be shorting out somewhere. Or for the tuner to be shorting out somewhere, though that should have killed the IF from the signal generator. Talking Frank thru the antenna coil may take somebody above my pay grade. It will be easy for me to get him into a mess. I want to eliminate a short of some kind and to check the resistors in the AVC line before we get into the coil. I appreciate you and 75 jumping in here.

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Re: AirKing 4602

Post by frank1956 on Mon Feb 08, 2016 12:27 pm

I have attached the two of the same pictures as from my previous post with a question for each. I have circles the one I have a question or comment.

The first one is the 2 resistors that where in question. The one in the lower bottom has not been changed out, and as you see is pretty faded the value reads 109 K. The one circled in blue is there something that should go there ??

On the second picture just the top view of the tuning cap, should there be something there.

Just a question as I am still new to this. Thanks



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Re: AirKing 4602

Post by frank1956 on Mon Feb 08, 2016 12:36 pm

Wildcat445 wrote:This schematic is not the best I have ever worked with. †There are no resistance to ground reading for the various test spots in the radio listed on the diagram. †I wonder if the tuning cap or antenna is shorted to ground. †One would think that such a short would have killed the signal from the signal generator. †We got IF thru the set to the speaker. †We should be able to get RF. †Try this. †Make sure the radio is off for this test. Check resistance from where the antenna connects to the tuning cap to chassis. †Do it both with the antenna connected and with the antenna disconnected. †See if there is a difference. Then check it to B- wit the radio turned OFF. †Something may be shorting out the RF.

WC,
When you said check the resistance you are referring to the ohms correct? If this is the case then what should my meter be set to? If I am totally way off then please advise Question
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Re: AirKing 4602

Post by 75X11 on Mon Feb 08, 2016 1:04 pm

The lower resistor Brown black yellow should be 100k. The yellow violet red should be 4.7k.
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Re: AirKing 4602

Post by willy3486 on Mon Feb 08, 2016 1:05 pm

As far as that hole on the chassis I wouldn't worry too much about it. I have seen all kinds of holes in a chassis with no parts. I have worked in factories as maintainence, press setup,etc. It could be this actual metal frame/chassis was used on a couple or more models. It could have went through a production change, for example a model 123 may have a chassis for the year 1937 then they revamp it, put it in a new case and make a few design changes and give it a new number. Punch press dies are expensive to make so I can see extra holes if the die is reused.

Same thing with the tuning cap. That tuning cap may have been a standard model cap used on everything. It may have only used part of it while another radio could have used both sections. I have seen many radios where the lug had never been soldered. If you need 50,000 tuners for one radio and 50,000 for a different model if the tuner you need are close to design it most likely will be cheaper to make one that fits both.

One suggestion I have I see from your photo. The first photo has a coil on a cardboard round tube with a terminal on it on the lower right. . Does it go to the 12sa7 tube? If so does it have 3 terminals on it? If so take your meter and see if you get a resistance reading across the three terminals. I don't know what it should be, maybe amywhere from 0 to say 2000 ohms. If I am not mistaken all three should read. In other words terminal 1 to 2, 1 to 3 and 2 to 3 should all read. If you check the ohms and its like 100k to infinity that will be the issue. These are the coils I am seeing issues. If so let us know an I will go more in detail on fixing it.

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Re: AirKing 4602

Post by Wildcat445 on Mon Feb 08, 2016 1:08 pm

I'm just going out the door, so I'll take up you last post when I get back.

Try the suggestions that Willy offered. †Go back over every capacitor you changed to be sure they are all the right value. †This is not a criticism of your work, it is just possible that mistakes happen. †Then check the resistance to chassis for the antenna coil and tuning cap with the antenna disconnected. †You are indeed measuring ohms, and the meter should be set to a low scale. †We are not interested in exact here. †We want to see high resistance where the antenna connects to the tuner and low resistance across the antenna coil. †We do not want to see that antenna shorted to chassis, as is possible the way that antenna is mounted. †My feeling at this point is that everything is probably okay after the tuning cap to speaker. †I still believe our problem is in the antenna somewhere. †This radio should be working. †If Willy or 75 or someone else wants to jump in and help here, that would be great as well.

I see we were all posting at once. Sorry if I stepped on anyone's post. You are in good hands, Frank.

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Re: AirKing 4602

Post by frank1956 on Mon Feb 08, 2016 1:40 pm

I was checking the resistance of the antenna connected and dis-connected.

Connected to the tuning cap/chassis 4.4 †to the B- 4.1. The antenna dis-connected from the tuning cap no reading.

Not sure if this amounts to a hill of beans or not. In the attached picture I notice on the circle resistor (1 K) where the arrow points there is some old wire residue, why it there I have no idea. It should not be there correct??




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Re: AirKing 4602

Post by 75X11 on Mon Feb 08, 2016 2:19 pm

That was where the wire for an external antenna (the triangle in the upper left of the schematic) would have been. it would also be a place to clip a signal generator input. Some of these tabletop radios would have just a wire to connect to an outdoor antenna.
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Re: AirKing 4602

Post by 75X11 on Mon Feb 08, 2016 2:27 pm

Frank, could you also take a good clear picture of the pin sides of your 12SA7 and 12SK7 tubes, showing their wiring so we can get a good look at them too?
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Re: AirKing 4602

Post by 75X11 on Mon Feb 08, 2016 2:32 pm

For the future, when you start on a recap of a radio, †take good pictures of each of the areas where you will have to do any work. †It will save you a lot of aggravation and give you an easy way to check for any mistakes. †You can check back on any of the values of components you have replaced.
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Re: AirKing 4602

Post by willy3486 on Mon Feb 08, 2016 2:46 pm

Good suggestion on taking the photos 75, I did that a while back with my phltain that there is no diagrams anywhere on it. That wire on the resistor is probably just from production or someone resoldering it. One thing I noticed if that is the resistor is the one from the outside antenna connection you could check the ohms from there to what appears to be the chassis ground. It should read 1000 ohms plus a few other ohms from the antenna coil one way and on the other side of the resistor to the ground †it should read only the antenna coil. †I fixed my philtain radio a few weeks ago and it was doing the same thing. It seemed like it should work IFs seemed to work,then you would not hear anything. I got to looking around and one of the turns on the ferrite rod was cut. I soldered the two pieces back and it worked. Look at the connections of where the wires attach to the terminals. If the wire going to the terminal of the coil is bad it will do as you have posted.

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Re: AirKing 4602

Post by 75X11 on Mon Feb 08, 2016 2:49 pm

I had the same problem on a Motorola console. It was a failed mica in the IF amp section.
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Re: AirKing 4602

Post by frank1956 on Mon Feb 08, 2016 3:33 pm

75X11 wrote:Frank, could you also take a good clear picture of the pin sides of your 12SA7 and 12SK7 tubes, showing their wiring so we can get a good look at them too?





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Re: AirKing 4602

Post by frank1956 on Mon Feb 08, 2016 3:51 pm

willy3486 wrote:As far as that hole on the chassis I wouldn't worry too much about it. I have seen all kinds of holes in a chassis with no parts. I have worked in factories as maintainence, press setup,etc. It could be this actual metal frame/chassis was used on a couple or more models. It could have went through a production change, for example a model 123 may have a chassis for the year 1937 then they revamp it, put it in a new case and make a few design changes and give it a new number. Punch press dies are expensive to make so I can see extra holes if the die is reused.

Same thing with the tuning cap. That tuning cap may have been a standard model cap used on everything. It may have only used part of it while another radio could have used both sections. I have seen many radios where the lug had never been soldered. If you need 50,000 tuners for one radio and 50,000 for a different model if the tuner you need are close to design it most likely will be cheaper to make one that fits both.

One suggestion I have I see from your photo. The first photo has a coil on a cardboard round tube with a terminal on it on the lower right. . Does it go to the 12sa7 tube? If so does it have 3 terminals on it? If so take your meter and see if you get a resistance reading across the three terminals. I don't know what it should be, maybe amywhere from 0 to say 2000 ohms. If I am not mistaken all three should read. In other words terminal 1 to 2, 1 to 3 and 2 to 3 should all read. If you check the ohms and its like 100k to infinity that will be the issue. These are the coils I am seeing issues. If so let us know an I will go more in detail on fixing it.

Willy,
To answer your question you will see a red wire it runs to tube 12SA7 via a resistor attached to a 2 terminal lug then to pin 8, you will also see a plain wire that runs to tube 12SK7 pin 4. When you say terminal I assume you mean a lug ( I think that is the correct terminology). I measured between the two and got 1.62K
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Re: AirKing 4602

Post by 75X11 on Mon Feb 08, 2016 4:21 pm

I see a wire going from 12SK7 pin 2 to 12SA7 pin 7. †I see no such wire in the schematic.
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Re: AirKing 4602

Post by willy3486 on Mon Feb 08, 2016 4:53 pm

OK, here is something to try. Looking at your photo and the diagram the resistor is on the 4th lug of the second tube down that I think is the 12sa7. Looking at the diagram the other end to the red wire if you follow the diagram it goes down on the diagram ,to the left then up to the bottom of the antenna coil. By looking at the diagram the other end if the coil looks to make direct connection to the 4th lug on the 12sk7 tube on the end. If I am looking at it correct then if you check the resistance from lug from where the resistor and red wire join you should get a low resistance. Like less than 100 ohms or so. If it shows no resistance and I am seeing the diagram correct then that is the issue.

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Re: AirKing 4602

Post by willy3486 on Mon Feb 08, 2016 4:55 pm

75X11 wrote:I see a wire going from 12SK7 pin 2 to 12SA7 pin 7. †I see no such wire in the schematic.

Is that the filiment wire? Sometimes I see diagrams without that wire,

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Re: AirKing 4602

Post by 75X11 on Mon Feb 08, 2016 4:59 pm

Yes That's it.
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Re: AirKing 4602

Post by frank1956 on Mon Feb 08, 2016 5:16 pm

willy3486 wrote:OK, here is something to try. Looking at your photo and the diagram the resistor is on the 4th lug of the second tube down that I think is the 12sa7. Looking at the diagram the other end to the red wire if you follow the diagram it goes down on the diagram ,to the left then up to the bottom of the antenna coil. By looking at the diagram the other end if the coil looks to make direct connection to the 4th lug on the 12sk7 tube on the end. If I am looking at it correct then if you check the resistance from lug from where the resistor and red wire join you should get a low resistance. Like less than 100 ohms or so. If it shows no resistance and I am seeing the diagram correct then that is the issue.

Willy,
I checked the resistance as suggested from lug where resistor and red wire join and got no reading using a digital meter set at 200 ohms. Reading was taken from B- to lug? You are correct that is the 12SA7 tube.
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Re: AirKing 4602

Post by willy3486 on Mon Feb 08, 2016 9:49 pm

I am not sure if what I said was clear. Look at the diagram below. On the 12sk7 †I have marked the 4th pin on the left. It probably †has a wire going to what looks to be †tuning cap then the Antenna. Find this on your radio. Follow this wire on the radio to where it connects to a lug on the antenna form. Check the ohms from the antenna and the point, it should be a direct connection.

Then look at the connection where the resistor is and the wire I have pointed out. I think this is the red wire you pointed to. Check from the wire to the antenna lug it connects to. This also should be a direct connection.

If you check the ohm from the wire and resistor connection with one lead and the other lead to the tube connection I marked you should get a reading. If you donít get a reading on 200 go higher. I think it should be 1000 or less but it should read. If you donít get a reading or it is high that is your issue. If no reading look at the lugs on the antenna good to see if you see one of the hair thin wires loose. Also look the coil over for nicks. If you have a ferrite antenna coil on the junkbox with a resistance you might can sub this in with jumpers that have clips on each end. † Let us know if this helps.



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Re: AirKing 4602

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