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 Post subject: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Sun 06, 2014 2:22 am 
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Location: Indianapolis, IN
Hello All,

I'd been looking for a couple sets of battery contacts for my "good" X31 as well as another cheap one to "play" with---and recently bought one & received it today...

Was listed for $9.99 opening bid with free, expedited shipping---so kept an eye on it... Was pretty "rough" with major battery leakage and corrosion, so guessing that is reason there was no other interest. Noticed that two of the spring (-) battery contacts looked salvageable, so at last minute put in a bid and won it. And then the "fun" began ! The seller evidently wasn't happy with what they got, so sent me an invoice for shipping (after I'd already paid for item through PayPal) even though listing clearly stated it was FREE ! After a couple exchanges about my leaving negative feedback and then being accused of "blackmail", they decided to send it---and then contacted me once again telling me that it cost them to "give" it to me !

Well---looks like another headache/challenge ! First of all, it's very dirty---when I wiped off some of the dirt & nicotine residue, it removed some of the dye from leather leaving it faded/chalky looking. Of course I knew it was already torn and scuffed in areas anyway. The major issue, though, was that someone had pried out the retainer and removed magnet from speaker !!! I'd wondered what hardware was jammed between magnet housing and battery compartment and now I knew---the retainer pieces ! And the compartment was broken where they had evidently inserted a tool to do their "dirty work"... Battery leakage residue had corroded one corner of speaker as you can see in pics below, and a little had "spilled" over onto cone causing a small stain.

Was able, though, to "harvest" two sets of battery contacts for my "nice" set and they cleaned up fairly well though plating was corroded off both positive ones (last pic)...

PCB thankfully looks good (topside) and hope it will be okay. Since battery compartment itself is cracked & broken (and now "contact-less"), going to leave it out and simply use a 4-"AA" holder for power. Wonder if one of the old speaker magnets I salvaged many years ago will be the right size ??? But haven't even tested voicecoil, yet...

Here are a few pics, the first three being from the Ebay listing:


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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Sun 06, 2014 3:02 pm 
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Joined: Oct Mon 26, 2009 10:02 pm
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Location: Indianapolis, IN
Well Guys---just couldn't wait to report some good news !

First of all, the speaker voice-coil is okay and the pieces were actually the voice-coil "core ?" and its support. Looks like the magnet was simply pressed in on top of these, so may be able to fabricate something using a small chunk of an old HDD magnet which I have several of...

But the best news is that the PCB is okay ! Attached test leads to a 6V battery pack and external test speaker---when I first turned on, nothing other than a "pop"... But within a couple minutes, noticed some crackling while tuning which got progressively clearer until radio began working---caps reforming ??? And it now performs as great as it's "better looking" sibling with low "noise-floor" and same outstanding sound bringing in stations clearly all across dial during daylight ! Motorola got the "inverse feedback formula" just right in this design as it is the closest thing to Hi-Fi sound I've ever heard in this size/age of radio ! Of course all electrolytics will still be replaced...

Stay tuned !

John


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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Sun 06, 2014 11:06 pm 
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... caps reforming ? "It's life, John, but not as we know it."

So much fun for under ten dollars... Great stuff.

Greg.


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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Mon 07, 2014 12:30 am 
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Old electrolytic capacitors can "reform" or recover over the course of a couple minutes with voltage applied to them (specifically the leakage current across the capacitor goes down), but they will never be trustworthy again. I have had some successes like John is describing in the past, but often the electrolytic capacitors in transistor radios (especially the American made "iei" and "Nashville" brand capacitors) are completely dried out and thus beyond saving. Plus the capacitors in transistor radios are so inexpensive, it's just not worth the trouble to remove them and reform them like some people do with tube radio capacitors.


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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Mon 07, 2014 12:34 am 
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egg. wrote:
... caps reforming ? "It's life, John, but not as we know it."

So much fun for under ten dollars... Great stuff.

Greg.


LOL How true! It's comparable to reanimated zombies. The up side of zombie caps is that less diagnosis makes repair simpler than on a completely dead patient. Frankly, John, from the pics it appears the patient should have been more of a challenge than humanly possible. Good going, as usual!

Bruce

P.S. Louis called...he want's his Motorola back.

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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Mon 07, 2014 2:27 am 
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Hey Guys---Even though radio did "come to life", I did replace all of the electrolytics today as planned...

But the speaker is basically trash---after wirebrushing what seemed like 1/8" of "rust crust" off of corner, discovered that more leakage than I realized had spilled over and settled around speaker cone outer edge and when I carefully blew off "rust dust" with compressed air, fragments of cone went with it ! Arghhh !!! I went ahead and straightened voicecoil core support screwdriver "bite" the best I could and installed parts on speaker and placed a small HDD magnet on core---did get sound, but at low level due to voicecoil "rub". Very carefully tried to center the support and did get brief moments of louder audio, but could tell that there was little hope of getting it right...

So now have to try to find another speaker or still another parts radio ! This speaker appears to have been of very good quality and is actually rated at 1.5 watts ! Another reason for this model's excellent sound quality (when all is good...).

Did get a lot of cosmetic cleaning done while disassembled and reglued tuning "window" and knob trimplate which were loose with Permatex Ultra-black non-acidic RTV.

And Bruce, I looked up Mr. Monken and he passed away in 1993 just a few months shy of his 80th birthday. The radio did look like it sat in an old garage or barn for 20+ years... Am guessing it "left home" when his widow either passed away or sold off estate. I'm going to leave his name & info on inside back cover...

John


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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Mon 07, 2014 3:31 am 
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Nice work, John. Yeah, that speaker looked to be too weakened to be salvageable. I also noticed that it only has three mounting tabs for screws. Whatever replacement you get -if it has 4 corners- you'll need to trim one off.

Judging by the owners serial number (he was an enlistee), he was about 2 million 200,000 ahead of me... :wink:

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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Tue 08, 2014 2:31 am 
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Well Fifties, imagine Mr. Monken was either in the Service before or during WWII going by his 1913 birth year---old enough to be your grandpappy (I think) !

That corner cut-off was used to give room for battery-check switch which I plan to remove since it's retaining nut is missing and it's really not necessary for occasional use. And I'm not going to reinstall the stock battery chamber, either, so a full-size 4" speaker will fit fine---but want to find one of at least the same quality as original.

Do wonder, though, if there is a SAMS for this later model as I found a couple circuit differences between this and the "early" X31A without -1 suffix. One is an additional .01 disk-ceramic cap on back of PCB which one lead had come loose or had never been properly soldered at factory as I can't see where it originally attached. One side goes to junction of series audio preamp emitter resistors and other is just lying next to PCB pad which is connected to same point of audio output transformer that the "inverse feedback" 180K resistor is... Don't remember this cap being in my other set.

John


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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Tue 08, 2014 3:19 am 
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G0d John :shock: if i put a radio in a big blender ... would you still fix it :P


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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Tue 08, 2014 4:57 am 
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John,

Your thread made me dig up and fix my XR31N-1 and it turns out it was not as bad as I remembered it being, it was just missing a couple screws and playing with distortion (and excess current draw). I replaced all of the capacitors, only one of which turned out to be faulty (although the rest were way out of tolerance) and now the set works great (perhaps a little too base heavy for my tastes, but it was probably built that way). My set does have that extra capacitor on the back of the circuit board, and luckily one of the pictures I took while recapping it showed that. Speaking of bad solder joints, one of the speaker connections was a cold solder joint and it looks like it came that way from the factory (the tab was clean underneath).

I would have considered the set you got off of eBay a parts set (although the dial plate is somehow in better shape than mine, despite mine coming with the lid attached), but I look forward to seeing how you restore it.

Matt


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front lid small.jpg
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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Tue 08, 2014 9:18 am 
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xrhonda91 wrote:
Well Fifties, imagine Mr. Monken was either in the Service before or during WWII going by his 1913 birth year---old enough to be your grandpappy (I think) !

My dad was born in 1914 and served during WW2, so our subject was just one generation ahead of me.

xrhonda91 wrote:
a full-size 4" speaker will fit fine---but want to find one of at least the same quality as original.

With the newer speakers having much larger magnets than were available back in the day, shouldn't be too much of a problem.

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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Wed 09, 2014 1:22 am 
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Ken---I'm worried about you ! Awhile back you talked of soaking some radios in a bucket of water for five years and now you speak of putting one in a blender... Oh man !

Matt---Many thanks for that pic, sure appreciate it !!! It is exactly what I needed and proves that the lead was indeed over the correct PCB land---am sure curious what difference it will make in the sound quality once connected ! And that is a really nice, clean X31 you have ! Glad you got it working... It is the first one I've seen with a battery tube for the two lower cells !

Fifties---your Dad was the same age as my Dad's Mom... And she had grandchildren your age (maybe older), I believe... Aren't you in your early 60's ? And you're right about the speakers---without the switch and battery tray, the only limit is the depth of cabinet for a standard 4" unit...

John


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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Wed 09, 2014 1:53 am 
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Another fascinating thread, John.

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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Wed 09, 2014 7:28 am 
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xrhonda91 wrote:

Fifties---your Dad was the same age as my Dad's Mom... And she had grandchildren your age (maybe older), I believe... Aren't you in your early 60's ?

69 here, John. I've got two kids, 4 grands, and one great grand... :wink:

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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Thu 10, 2014 12:58 am 
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Unfortunately my last post got deleted for some reason (is there any way to bring it back?)

I agree with John about this model, it's an excellent performer when it's working as it should. After replacing all of the electrolytic capacitors (and fixing a cold solder joint on one of the speaker tabs), I was able to pick up about 40 stations with this set at night (of which maybe 30 came in well enough to really listen to).

The battery tube in the picture is homemade, I added it because the bottom two cells kept buckling out contact with each other (there is too much space between the battery compartment and the back cover).


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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Thu 10, 2014 1:43 am 
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Location: Indianapolis, IN
Thanks Ed !

Richard---you're closer to the 7-0 than I thought ! Any of your descendants interested in radio ?

Matt---that explains why I've never seen another with a battery tube ! Can wait to get the battery contacts in "pretty" set and get this "user" set "usable"... Think I get around 15-20 stations clearly during daytime all across dial with mine---Chicago, Cincinnati, Indy locals, Lafayette, Ft. Wayne, and a couple other "small towner's"... It is another "top of list" performer in collection... And think the audio is the best, but should compare it more closely to a couple other "good sounders" one day to be sure...

And today found something very interesting (at least to me !)---was cleaning the tuning pointer with alcohol to prepare it for painting when I thought the "texture" of factory paint looked familiar. Just for curiousity, I cupped my hand around it and saw that it glowed purple---was phosphorescent as suspected ! Pretty neat bit of trivia about these sets ! Guess I shouldn't have painted the other one... Oh well...

Hope to get it together this weekend...

John


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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Thu 10, 2014 3:19 am 
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xrhonda91 wrote:

Richard---you're closer to the 7-0 than I thought !

You know John, you could have gone all day W/O reminding me of that! :wink:

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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Thu 10, 2014 4:49 am 
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Wow! John, I never noticed that the pointer was phosphorescent. It glows a purple color after exposed to strong light. I noticed the CD antenna connection. My X31A does not have this.

Also, is the push button supposed to test the batteries? I believe I read somewhere that if the batteries are weak you may hear a noticeable difference with weak signals when the button is pushed.

Really like the pictures. Mine is a gray colored leather case. Reception is excellent with the tuned RF stage and the sound quality is actually pretty good. It is one of my favorites when listening to my AM stereo CQUAM transmitter on 1580kc.

Jack


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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Thu 10, 2014 12:53 pm 
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John,

I nearly bid on this set myself as, like you, I saw it as the source of a particular part. Specifically the battery test push button which I need for my X-41. After reading about the hassle you had with the seller I'm glad I didn't bid. I've had nothing but trouble with eBay recently (but that's another story).

I'm glad to hear that it works, and look forward to the end result, as always.

Colin


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 Post subject: Re: 2nd Motorola X31A-1 another "challenge"...
PostPosted: Apr Thu 10, 2014 12:57 pm 
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Beefus wrote:
Also, is the push button supposed to test the batteries? I believe I read somewhere that if the batteries are weak you may hear a noticeable difference with weak signals when the button is pushed.
Jack

Jack,

On my X-41, when the batteries reach a certain level, and you push the button, it kills the output completely. I don't know if it's the same on the X-31.

Colin


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