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 Post subject: Crosley E-20 not receiving stations
PostPosted: Oct Sun 11, 2020 8:15 pm 
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Joined: Oct Sun 11, 2020 6:56 pm
Posts: 5
Hey all!
I have a barn find E20 crosley chassis: 15-20e. It was a bit rough: a mud dauber had made its home there :shock:, the dial plates were coated in rust, and its cord was cut. The board the loop antenna is attached to is 1/3 gone but everything is intact otherwise. A recap and it lit right up with no magic smoke. This is my first tube radio to play with on my own. I do own another aa5, but had someone do the dirty work for me as it's kind of an heirloom.

Now I'm a bit of a tinkerer and I've recapped a couple of vintage transistor radios quite successfully. This one I was hoping would be as easy, but it needs a bit of trouble shooting.
My first concern is silver mica disease may have taken it out since it's been outside in a shed for at least a decade, but I'm hoping not. It had no pops or clicks or thunderstorm sounds though. There's a small section of the tuning band that does get crackly when you run through it, but I'm going to assume dirty plates unless told otherwise. Volume pot makes a little whispery noise, but nothing terrible.

There's a little bit of that 60hz hum you get when something isn't quite grounded. Kind of like a turntable. The radio seems to respond when you touch the antenna wires. There's a phono/aux jack that, when used, works perfectly. No 60hz hum or anything. So that eliminates, if I'm understanding this correctly, the 12av6 and 50c5 tubes and their sections from being the problem. I swapped the 12be6 tube, no difference.

I poked around with a pen to see if I could illicit a response. Nothing. I've gone through and reflowed all of the old solder joints to be safe. No dice. I gave the IF pots on top of the cans a couple of wiggles. No response. There's continuity between all pairs of IF's pins.

I'm still a bit new to figuring schematics but I think I have the basics. But from what I have managed to trace there are things that are and aren't on the schematic I found, but it's mostly there. Missing some of the capacitor values on the diagram (IF cans for example)

I hope you have a lot of patience for a newbie! I don't quite understand what feeds what. Someone is gonna have to explain like I'm five to point me around to diagnose further. I only have a digital multimeter and a capacitance meter to guide me around. Not the best but better than nothing I guess. I have yet to decide if I want this to be a hobby.

Thanks much! :D


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 Post subject: Re: Crosley E-20 not receiving stations
PostPosted: Oct Sun 11, 2020 11:03 pm 
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Joined: Dec Wed 25, 2013 6:57 am
Posts: 5420
NeWave017 wrote:
Hey all!
I have a barn find E20 crosley chassis: 15-20e....The board the loop antenna is attached to is 1/3 gone but everything is intact otherwise...
Assuming you've made no mistakes and the rest of the radio is "working," this is where the problem might be. This is the equivalent of a newer radio with broken ferrite rod antenna.

The loop antenna doubles as the inductor for the tuning circuit. This antenna needs to be the exact length of wire shaped into same size/number of turns. Essentially, you need to rebuild this back to the way it was. This inductor works with the tuning capacitor/trimmer ("LC circuit"); after rebuild, the antenna section would need alignment by adjusting the trimmer at C1a.

https://en.wikipedia.org/wiki/LC_circuit

Can't tell from your description if that hum indicates trouble or a mistake. It could be that you turned up the volume trying to receive a station.

http://www.nostalgiaair.org/resources/762/M0003762.htm


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 Post subject: Re: Crosley E-20 not receiving stations
PostPosted: Oct Mon 12, 2020 4:46 am 
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Joined: Oct Sun 11, 2020 6:56 pm
Posts: 5
Thanks for the response!
There's continuity in the antenna loop, just the press fiber board it's attached to has seen better days. everything it's connected as it should be. There's also that open loop that looks like is what's left attachment to external. One bit was snapped off at a lug where it soldered, but was easily reattached. I can't locate a trim cap. Nothing obvious above or below at least and nothing that looks to be in parallel with it. I interpreted c1a as the 2 sections of the tuning cap in parallel. Did I read that incorrectly?

I found the schematic you were going off of. The radiomuseum copy is.. hard to read. The one I could read was a little Different than the one you have shown a snippet of. (r1 on yours is r14 on the one I found)

Maybe this wax covered bit on bottom with two leads out of each end? I initially started scraping at it thinking it was a cap to replace, until I shed a very fine copper wire on that band looking thing on the upper middle of it and I halted messing with it. It had two layers of wax, the typical stuff covering caps and that red stuff. I hope I didn't mess that up and that be the problem. That .08 (c5,c 10) in the pic has one directly behind it as well. and a ceramic tube resistor (c2) hiding behind that glob of solder. And that resistor sort of parallel is r16 with r1 hiding behind the bottom there. I guess what I'm yammering on about is I think that bit is L2. I have no idea if that pertinent.

The only caps I initially replaced were the the big electrolytics and two smaller caps tucked underneath them which were the .05 off of pin 7 of the rectifier (c15), the .01 off of pin 7 (c17) of the audio output, and one of the .08's (c14?) in line with the switch ground. The .01 had a broken solder joint, so I also swapped that one after testing it.

Hopefully the pics translate well.


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 Post subject: Re: Crosley E-20 not receiving stations
PostPosted: Oct Mon 12, 2020 5:30 am 
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Joined: Dec Wed 25, 2013 6:57 am
Posts: 5420
In your version of the schematic, M1 is the dual section tuning capacitor. The dotted lines mean they turn at the same time. Alignment trimmers (A5, A6) are the screws on the tuning capacitor. The screw adjusts the gap between two metal tabs.

Leave that coil alone. The wax is to protect it.

Do this in order:
- Replace all remaining paper capacitors; don't troubleshoot or expect a fully functional radio before that. I counted six paper capacitors on the parts list
- Double check the IF alignment is correct where signal strength is peaked
- Adjust A5 (oscillator) so the dial is correct. It's most accurate if you use a known station on the upper end of the dial
- Then adjust A6 (antenna) for maximum sensitivity

Here: http://www.nostalgiaair.org/resources/762/M0003762.htm

At 0.08mfd, that capacitor would pass enough AC current to make the chassis somewhat hot. Some of us would change to a lower value like 0.01-0.015, not a big deal either way, but treat the chassis as live.


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 Post subject: Re: Crosley E-20 not receiving stations
PostPosted: Oct Mon 12, 2020 7:12 am 
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Joined: Oct Sun 11, 2020 6:56 pm
Posts: 5
Oh! I'll get right on that. I thought with that metal band that those screws were holding down a jumper. I didn't even see that picture diagram. I was looking for a cute little mini version of an air cap! My mistake :oops: . Hooray for learning. And that link, thank you! Looks like the electrolytics were changed at some point or the factory just put in what would work. a two section 50/30 and a separate 100 where schematics call for 30 10 and 100. Fun.

I simply withheld replacing the caps at once due to the adage of catching a mistake sooner than just tackle it all at once and figure out where you messed up. But I guess that's pointless when you can't get a signal in the first place.
I'll get right on the remaining caps. Just the two .08s pictured and a single .002 and I'll give it further tinkering. we agree on the cap count and I didn't miss anything, good!
I have .1uf's replacing the 08's. Going by the +/-20% tolerance thing, I didn't know you could go down to .015 like that. Hopefully that .1 should be fine. I've checked the chassis with the multi and got nothing. I still try not to touch it though. And I've also tapped the thing with my arm mindlessly and didn't get zapped. So there's that I guess.
I don't own a signal generator, so tinkering with the IFs will be fun unless I can pull in a station to focus on. The good news is 1120 KMOX is local and easy to find blindly. I will update soon!


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 Post subject: Re: Crosley E-20 not receiving stations
PostPosted: Oct Mon 12, 2020 10:14 am 
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Joined: Dec Wed 25, 2013 6:57 am
Posts: 5420
NeWave017 wrote:
....I have .1uf's replacing the 08's. Going by the +/-20% tolerance thing, I didn't know you could go down to .015 like that...
Most other capacitors need to be close to the original value or exact. But this one is not that critical.

It's a good idea to take "before" photos of each capacitor; and turn on the radio briefly after replacing each to make sure you did it right, before moving on to the next one.

For the alignment adjustments, assume it was previously aligned correctly, so that you only need to make very small tweaks (like 1/16, 1/8 turn). It's easy to turn the screw too much and get lost, so go slow.


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 Post subject: Re: Crosley E-20 not receiving stations
PostPosted: Oct Mon 12, 2020 2:39 pm 
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Joined: Jan Tue 16, 2007 6:02 am
Posts: 5523
Location: Lexington, KY USA
... wax covered bit on bottom with two leads out of each end? I initially started scraping at it thinking it was a cap to replace, until I shed a very fine copper wire on that band looking thing on the upper middle of it ...

This was probably the oscillator coil. A broken wire will keep it from working. Check the two windings for continuity. Sometimes these can be repaired.

If you have not already done this, it is a good idea to check each coil and winding in the chassis for continuity. This is a good first step before doing other work on a radio.

All three of the 0.08uF capacitors in the chassis connect the circuit to the chassis, or the circuit to external connections. One is also the AVC time constant capacitor. Changing the values may affect operation. It might be best to start with the 0.08 or 0.1uF value and later see if lower values are satisfactory. In any case, a safety agency approved part would be a good idea to use. For troubleshooting to get the set operational, regular film caps will be OK.

I expect that there is no way to make this set meet present day safety standards while remaining functional. You want to do the best you can about the original safety arrangements, then exercise some caution when using it.

If the set is not receiving any stations, some of the above suggestions won't work. Particularly, there is no way to align the radio when it is not working.

You might tell us what test equipment you can use to work on this.

Ted


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 Post subject: Re: Crosley E-20 not receiving stations
PostPosted: Oct Mon 12, 2020 7:52 pm 
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Joined: Oct Sun 11, 2020 6:56 pm
Posts: 5
Usually Lurking wrote:
This was probably the oscillator coil. A broken wire will keep it from working. Check the two windings for continuity. Sometimes these can be repaired.

I wasn't quite sure how to measure, so I did the left branch on each end and the right branch on each end. Continuity on one, but not the other. I'll assume that's the smaller coil I busted. How would I even go about fixing it, if it even is repairable? I have 30 gauge magnet wire, but this seems way thinner than that. If I can't save the current coil, I can turn it into some Bluetooth powered thing since that aux circuit works just fine. Lesson learned.

The good news is I have a parts radio I nabbed cheaply off that one auction site that "was receiving stations years ago, now is not" that I thought would come in handy. Looks like I was right, in the wrong order. It may be easier to just start over and make this one my parts piece and start the diagnosis process anew.
Quote:
You might tell us what test equipment you can use to work on this.

My only experience is recapping a couple of already working vintage transistor radios. The only equipment I have is a multimeter and a capacitance tester. The Multimeter has a fixed square wave generator. While that may be good to check paths, I can imagine that it is useless for an alignment.


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 Post subject: Re: Crosley E-20 not receiving stations
PostPosted: Oct Mon 12, 2020 8:47 pm 
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Joined: Mar Fri 06, 2020 2:48 am
Posts: 257
Location: Bangor, Maine
As a word of warning, be very careful about what you plug into that AUX jack. Whatever you connect to it becomes as live as the chassis as far as I can see. I wouldn't plug in anything line powered, and even so be very careful.


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 Post subject: Re: Crosley E-20 not receiving stations
PostPosted: Oct Tue 13, 2020 8:58 pm 
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Joined: Oct Sun 11, 2020 6:56 pm
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IlikeTech wrote:
As a word of warning, be very careful about what you plug into that AUX jack. Whatever you connect to it becomes as live as the chassis as far as I can see. I wouldn't plug in anything line powered, and even so be very careful.


I used an old MP3 player to test it out initially, which would be isolated. I was thinking a plugged in sort of Bluetooth thing. Thanks for the warning.


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