squelling and motor boating

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squelling and motor boating

Post by Sinatra1982 on Mon Oct 31, 2016 3:51 am

I have a Crosley 10-135 am tube radio that squeals very loud and motor boats. Can not pick up any stations. Noise is deafening. Any help appreciate. Has been recapped.

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Re: squelling and motor boating

Post by Wildcat445 on Tue Nov 01, 2016 10:53 pm

Tube shields, tube socket connections or output filter capacitor come to mind. The squeal is oscillation. The motorboating is another form of oscillation. An output filter cap leaky or under capacity can cause this due to its being the cathode bypass for the audio output stage in most small radios. This is a WAG, and your results may vary.

As a first step, I would get a schematic for the radio and make sure everything is wired correctly. Then wiggle the tubes to make sure of good contact. Then replace or bypass the filter capacitors to see if that makes any difference. After that, you should go stage by stage, starting nearest the speaker to see which stage the squealing starts in. It may not have been recapped correctly, or some components may have failed since the work was done.

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Re: squelling and motor boating

Post by Sinatra1982 on Wed Nov 02, 2016 2:26 am

I am very new at this and although I have a couple radio how to books they don't explain very clearly to me how to how to go stage by stage, starting nearest the speaker to see which stage the squealing starts in. Could you explain this to me and do I need any special equipment to do this? I am 68 and getting into this late and things are sinking in slow.

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Re: squelling and motor boating

Post by Wildcat445 on Wed Nov 02, 2016 1:19 pm

Do you know how recently the recap was done? If it was 30 years ago, the filter caps may well be leaky. They do not cost much, nor are they hard to replace. That might be a good place to start and is fairly simple. You can wiggle the tubes to make sure they are making good contact just to cover that. Since you say there is lots of noise with no stations being received, I believe I would change the filter caps at least and see if that makes any difference. Referring to the schematic will tell you what values should be there so you can compare. You should get into the habit of printing the schematic for any radio you are working on as a first step. Then learn to read a schematic. You will save yourself lots of grief if you establish this as part of your troubleshooting procedure. Good luck.

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Re: squelling and motor boating

Post by Sinatra1982 on Wed Nov 02, 2016 2:22 pm

All caps have been replaced a couple of months ago. I have the schematic but am having trouble reading it and figuring out exactly is and where it goes. I'm gonna keep trying. I just thought of something, when I got it the antenna was disconnected and there were 3 wires going to it from the chassis. Would that cause the problem if hooked up wrong? Even with the schematic I am not sure it is correct. Thanks

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Re: squelling and motor boating

Post by Wildcat445 on Wed Nov 02, 2016 4:55 pm

A suggestion I might offer on reading a schematic is this. It was how I was taught.

Consider a schematic as a road map of how electricity flows thru the radio. Look at the lower part of the schematic and find the power plug. The plug you put into the wall. This is where the power comes into the radio. The first element you will see is the power switch. Typically in an AA5 like this, the power switch is in one side of the power line. The other side of the power line typically goes to the plate of the rectifier. The rectifier tube has a number like a 35W4, 35Z5 or something similar. The rectifier will be the first tube following the switch. The input filter capacitor is connected to the cathode of the rectifier, the output of the rectifier. Next is typically a resistor, field coil or other choke to help smooth B+ to the radio. The positive of the input filter cap goes to the output stage typically. This positive of the output cap goes to the rest of the radio and typically serves as cathode bypass for the output stage. This can vary somewhat depending on receiver design, but it will get you looking in the right direction.

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Re: squelling and motor boating

Post by Bill Cahill on Wed Nov 02, 2016 4:57 pm

I would not recommend bypassing original electrolytics because the leakage would still be there.

My next question is I assume you know how to read schematics??
And, a gassy tube can also make it squeal. Do you have a tube tester? Are the tubes miniatures, or, eight pin octals?
You might need a volt ohm meter, but, there are a number of things to try first.

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Re: squelling and motor boating

Post by Wildcat445 on Wed Nov 02, 2016 5:14 pm

Learning to read a schematic is basic to troubleshooting.

I don't typically bridge caps. I usually just replace them. I'm not sure how disposed the OP is to doing this, so I was offering an alternative to try and help him. I'm sure he would welcome a better suggestion than mine.

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Re: squelling and motor boating

Post by Bill Cahill on Wed Nov 02, 2016 5:46 pm

Well, you gave mostly good information. It's a matter of elimination. Even sloppy wiring in the oscillator circuit could make it go into run away oscilation.
But, there are a number of things to check on first. We both agree on that.
Hmm. If set has miniature IF transformers, at times the first one could cause the run away oscilation if capacitors inside are bad. You know the type of troubles we have with the caps built into the base held together with a pop rivet. Rivet lleaks, eventually, shorts primary winding to secondary winding by shorting the built in capacitors out through leakage from the rivet.

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Re: squelling and motor boating

Post by Sinatra1982 on Thu Nov 03, 2016 4:04 am

This is all very good information, thank you. I am in the process of learning to read schematics. The tubes are miniature and I have tube tester Superior Instruments TV-11. But I am not sure it checks for gassy tubes. This might help, the volume of the sound of the squealing does not change when turning the volume knob up or down, no change, it is consistent up or down. Thanks everyone.

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Re: squelling and motor boating

Post by Bill Cahill on Thu Nov 03, 2016 5:12 pm

Is it the same volume in audio no matter where you set the volume control. ? If the answer is yes, that will give a better hint to what's going on.....

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Re: squelling and motor boating

Post by Wildcat445 on Fri Nov 04, 2016 2:04 am

If it is not controlled by the volume control, the oscillation may be starting after the volume control. This fact puts additional suspicion on the output filter capacitor. Good luck.

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Re: squelling and motor boating

Post by Sinatra1982 on Sat Nov 05, 2016 1:35 am

It's the same value in audio no matter where I set the volume control.

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Re: squelling and motor boating

Post by Bill Cahill on Sat Nov 05, 2016 1:10 pm

Wildcat445 wrote:If it is not controlled by the volume control, the oscillation may be starting after the volume control. This fact puts additional suspicion on the output filter capacitor. Good luck.

Have you replaced the power supply filters? What did you use, if you have. How old, what brand, what value?

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Re: squelling and motor boating

Post by Sinatra1982 on Sat Nov 05, 2016 10:48 pm

The filters were new, not sure the make, the logo on them is a u inside an oval circle. One is a 100 micro farad, one is a 33 micro farad and the other is a 10 micro farad. All are 160 volts rating. I have a question about installing new filter caps in one that had a can on top of chassis. Not this radio but another. The can is grounded to the chassis and there are three prongs coming through the can on the bottom. The three prongs are positive. How do I ground the new caps? Can I solder all three grounds to the chassis?

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Re: squelling and motor boating

Post by Wildcat445 on Sat Nov 05, 2016 11:19 pm

We need a make and model of the second radio so we can see how the filter can is connected. The way the can is connected really depends on the circuit it is used in. Some circuits use the can for negative, some use a seperate negative wire.

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Re: squelling and motor boating

Post by Sinatra1982 on Sun Nov 06, 2016 1:12 am

The second radio is a Continental Radio Model K6, 5 tube, AM and one SW band. If I reading the schematic correctly, it shows a chassis ground on all three cap prongs. I don't see any fourth prong or wire that might be a ground. I have replaced all the paper caps on this radio and am picking up stations on both am and sw bands, however am also getting a lot of static when tuning and some on the stations also. Thanks...

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Re: squelling and motor boating

Post by Sinatra1982 on Sun Nov 06, 2016 3:10 am

One question on this Continental radio. It has to antenna wires about a foot lone each coming out of the back, one I touch it and it picks up stations and the other when I touch it, nothing changes. How would I hook this up to an external antenna? I am not sure what to do with the wire that doesn't change when I touch it.

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Re: squelling and motor boating

Post by Bill Cahill on Sun Nov 06, 2016 8:40 am

On this type of radio, if it uses an external antenna, do not ground it. That puts you in danger from one side of line being on the chassis.
On that type of radio just put in a long wire for antenna.
It looks like it may be that type, or, it had an insulated antenna by means of an isolated ground with a third short turn of coil for ground.
But, it seems more likely that you don't use the ground. Only a long lead of wire.

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Re: squelling and motor boating

Post by Bill Cahill on Sun Nov 06, 2016 8:45 am

Sinatra1982 wrote:One question on this Continental radio. It has to antenna wires about a foot lone each coming out of the back, one I touch it and it picks up stations and the other when I touch it, nothing changes. How would I hook this up to an external antenna? I am not sure what to do with the wire that doesn't change when I touch it.

Do not ground this wire. Only use wire with a long lead on wire that brings in stations. Another thing you could do.
Does the radio have an antenna coil with hot wire going to ground, other wire non connection to that.

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Re: squelling and motor boating

Post by Sinatra1982 on Tue Nov 15, 2016 1:06 am

I don't know how to check the coil for that.

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Re: squelling and motor boating

Post by Sinatra1982 on Wed Nov 23, 2016 12:04 am

Still can't find cause for the squelling. Squelling is very loud and does not change whether volume to turned down all the way or up as high as it can go. I have checked all I know to do. If anyone has another idea please let me know.

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Re: squelling and motor boating

Post by Bill Cahill on Wed Nov 23, 2016 5:09 pm

Yes, I do. have you checked for dirty sockets, tube pins, and, bad tubes??
Do you have a tube tester???? You'll need one to check all tubes.
Do you have another set that uses The same types of tubes? If so, try those.
It's also important that you try to dress the wiring the same way it was wired by the builder.
Did you try tunning the radio with the station selector knob? Does the squelling vary while tuning radio??

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Re: squelling and motor boating

Post by Bill Cahill on Wed Nov 23, 2016 5:13 pm

Bill Cahill wrote:
Sinatra1982 wrote:One question on this Continental radio. It has to antenna wires about a foot lone each coming out of the back, one I touch it and it picks up stations and the other when I touch it, nothing changes. How would I hook this up to an external antenna? I am not sure what to do with the wire that doesn't change when I touch it.

Do not ground this wire. Only use wire with a long lead on wire that brings in stations. Another thing you could do.
Does the radio have an antenna coil with hot wire going to ground, other wire non connection to that.
Just don't ground radio to anything. Chassis has one side of the line. do not use a ground lead on these sets...
That, at the least, would damage set, blow a ciruit breaker, damage set, and, at the least, you could get a nasty shock that could kill you. Don't want anything bad to haggen to you. Also, if you have any test equipment, don't connect it directly to radio. You need a capacitor on each lead of tester to set. That would include ground. You'll need two capaiters for that. .1 mf 600 volts should do. One for each lead to be used..
Bill Cahill

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