Author Topic: Becker Mexico TR repair/restore  (Read 12056 times)

Aaron h

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Becker Mexico TR repair/restore
« on: April 03, 2020, 05:21:32 »
Our lovely friend, "Kampala", or Oz, sent me one of his radios to repair.  Being trapped inside during isolation I wanted/needed something to do, so he really caught me at a good time, as I normally don't do this for others, but what the hell, right? 

So, upon first inspection, I noticed a wire going to the return solenoid burned in two, along with some scorch marks.....it looked to have been a pretty dramatic event.  haha   The self seeking mechanicals were very stiff from old grease, the dial pointer was catching on a rivet underneath, and one of the iron ferrite cores for one of the tuning capacitors was broken causing the tuner to bind.  Both the head in unit and power supply/amplifier are full of burst/leaking/open/shorted electrolytic capacitors.  All of which will be replaced. 

Upon arrival I tested the radio, and it worked, but the volume had to be turned all the way up to get any audible sound out of it.  I kind of suspect that one of the output transistors is giving some trouble.  This particular set uses a pair of PNP AD150 Germanium transistors....of which I have a healthy stock of.  You wouldn't believe the prices people ask for Germanium transistors these days.  If not a transistor I'll turn to resistors, diodes, and check for open/shorted windings in the output transformer. I'll have to disconnect all of the leads and see how well it rings out.  I like to use an old Flyback/yoke tester for televisions for this purpose.  Though, the first thing that'll have to be done is to renew all of the electrolytic capacitors.  They, too, can cause this symptom. 

A word of advice.....if your radio is still working ok and it's all original, I can promise renewing the electrolytic capacitors will be money well spent.  These capacitors are 50+ years old.....50+ year old electrolyte isn't kind to paper and foil.  It becomes acidic and deteriorates the paper between the pieces of foil causing severe electrical leakage, external leakage due to corrosion from within, and in some cases a dead short that can damage other unobtanium components within the radio itself. The point here is that the electrolytic capacitors are far beyond their life expectancy, and it shocks me that "certain" Becker repair facilities don't replace them unless one specifically asks for that service.  This should be a mandatory preventative maintenance item!  So if any of you send your radios off to other places make certain that you request all electrolytic capacitors be replaced. 

I'm making a youtube video of this repair in my make shift work station for entertainment purposes. (the top of a 1955 Philco stove haha)  I'll post it when it's all said and done.  All this to say that your radio arrived safely, Oz.  It's being taken care of!  I just thought everyone would like to see what was going on, how I went about making the various repairs, etc.  What else have we to do when in quarantine?  :)  I'm going to make the best of it all that I can. 

« Last Edit: April 04, 2020, 04:41:32 by Aaron h »

kampala

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Re: Becker TR repair/restore
« Reply #1 on: April 03, 2020, 05:31:15 »
Aaron,

Great that you are sharing the Becker Experience!  Really appreciate your diagnosis and surgical treatment of the unit and look forward to the youtube and more details as you progress.

best,
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Peter van Es

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Re: Becker TR repair/restore
« Reply #2 on: April 03, 2020, 10:02:28 »
Excellent... excellent advice on the capacitors too. Love to see your video.
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Pawel66

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Re: Becker TR repair/restore
« Reply #3 on: April 03, 2020, 10:25:15 »
Also waiting for the video!

This lockdown may take a while... have you thought of doing more of these? I have Europa to be refurbished.... ;)
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Garry

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Re: Becker TR repair/restore
« Reply #4 on: April 03, 2020, 11:26:43 »
Video would be great.  I actually need a Becker Europa for my 230sl to replace the current Becker with cassette that
needs  refurbishing but belongs in a ‘71 or later Merc. May be I should put a wanted  to buy in.
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Aaron h

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Re: Becker TR repair/restore
« Reply #5 on: April 03, 2020, 13:05:08 »
Well, we've hit that moment when you simultaneously say "Oh S*%t" and "well, we tried".  haha  In the picture below you'll see a multi function point type relay that controls the self seeking starting and stopping, as well as the way to supply a linear amount of power to the return relay.  The black plastic stand offs on the right side have been melted when whatever it was got so hot, and also probably when the one wire going to the return solenoid burned in two.  So at this point the self seeking will still work, but it won't return to the beginning when it reaches the end.  Oz will have to turn the radio off, and then back on, and then manually turn the tuner knob all the way back to where he wants.  So unless one of you have a spare relay or whole Mexico TR lying around this is something that I personally don't think I can repair. 

Pawel, yes, I've thought about doing this more often, but I just don't want the liability and extra responsibility.  I'm sure I could do it.  My other hobby is restoring pre 1955 televisions, and because of that I have pretty much everything I need along the lines of test equipment, parts, supplies, schematics, alignment procedures, and specifications.  Having said that, I'm happy to occasionally help a fellow car buddy out, but it's just not something I want to do often.  Repairing them would pay well, but often times repairing one particular radio can also end up costing more than buying another one that is in good shape....story of our lives, right?  ;) 

Garry, I'm assuming that since you have a cassette model in your 230SL that someone has hacked out the radio opening.  A 230SL would have originally had a narrow face radio, and there weren't ever any narrow faced cassette models made.  Regardless, I'm sure that either myself or someone on here would have a more appropriate radio for your 230. :)

Peter and Kampala, thank you for the kind words.  The video(s) will be amateur, I go off on a few rants, I make mistakes that I catch mid shooting, and I repeat myself a few times, but it should be informative nonetheless.  You might even laugh a little.  If so, then go for it.  haha

Oz, send me a message and tell me how you'd like to proceed given the aforementioned.  Again, it should work fine, but the self seeking won't work 100% with this half melted relay. 

scoot

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Re: Becker TR repair/restore
« Reply #6 on: April 03, 2020, 14:11:53 »
Aaron, this is a great thread.  Looking forward to the video.
Scott Allen
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Altadena, California

kampala

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Re: Becker TR repair/restore
« Reply #7 on: April 03, 2020, 14:13:47 »
Aaron

Let’s fix what you can - maybe you will find an alternate relay  ;D. It will be great to just having working as much as possible. No issue if tracking bar does not return.

Scoot may have the parts? 

Appreciate your diligence.

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280sl - 1971 - Auto - LSD

scoot

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Re: Becker TR repair/restore
« Reply #8 on: April 03, 2020, 14:24:02 »
Scoot may have the parts? 
I have lots of working Beckers and some partially working or dead ones.  I sold most of my dead radios a couple years ago to a guy in Spain.  So right now, I don't have anything with parts available such as that relay.  I would disable the auto search feature (remove little wire that grounds from search bar) and enjoy the radio without auto search...  That's a really nice radio.  I might have the parts to turn it into a small-face radio, but probably don't have the correct dial scale for an LMKU.

Aaron, is it trivial (or doable) to turn the L and K buttons into FM (U) tuner buttons?

cheers
Scott
Scott Allen
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kampala

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Re: Becker TR repair/restore
« Reply #9 on: April 03, 2020, 14:27:12 »
Scot

Thanks for the reply. Appreciated.  Ignore my PM. 

Best

250sl - later - manual
280sl - 1971 - Auto - LSD

Aaron h

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Re: Becker TR repair/restore
« Reply #10 on: April 04, 2020, 00:04:21 »
Oz, I'll reply to your messages shortly. 

Scott, on this particular early Mexico the buttons aren't pre-set buttons.  They are not connected to the tuning capacitors in any mechanical way like a Europa TR or others would be.  The buttons on this radio are all electric in that they're all connected to 5 separate switches on a common printed circuit board.  Electrically, one could make all of those buttons FM, but it would be redundant since you'd still have to manually tune the radio.  Again, no presets. 

In a Europa or any other later radio in which the buttons serve both as a band selector and tuner preset one could potentially make all or part of the buttons FM only.  I imagine all that would have to be done would be to modify the cam on the respective buttons that moves the sliding band switch.  A very interesting thought for 4 band radios that are used here in the U.S.  :) 
« Last Edit: April 04, 2020, 00:27:09 by Aaron h »

Peter van Es

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Re: Becker Mexico TR repair/restore
« Reply #11 on: April 04, 2020, 10:55:47 »
Aaron,

I frequently sit musing about finding ways of replacing electronic circuits in more modern "youngtimer" cars with functionally equivalent, programmed microcontroller circuits when they break. Might be a fun hobby when (if) I retire...

Could you not replace the relay with an assortment of more modern electronics to replicate its function. Something like the ATmega328P with a few driver transistors. Sure it would look different but how often do people open up their radios?

Another forum I frequent is about people restoring 1980's computers. They tend to like originality too -- but they do open up their housing to show off the printed circuit boards. One guy describes how he disassembles old electrolytic capacitors and mounts a new (often smaller) capacitor in the old housing. Bit obsessive.

Peter
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mbzse

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Re: Becker TR repair/restore
« Reply #12 on: April 04, 2020, 13:13:48 »
Quote from: Aaron h
.../...A very interesting thought for 4 band radios that are used here in the U.S
I have heard before that bringing a car radio over the pond is not optimal. Aaron (or anyone :) ), would be interesting if you could comment on this.

Found this statement (among other texts): "Will a US car radio work in Europe?
No, a radio purchased here in the US can not be taken to another country. The frequencies used in some other countries,
like Europe, are even (102.8 ) The frequencies used here in the US are odd numbers (102.7) and can not be changed"
« Last Edit: April 04, 2020, 14:46:25 by mbzse »
/Hans S

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Re: Becker Mexico TR repair/restore
« Reply #13 on: April 04, 2020, 15:13:30 »
Just a tip, the web site https://www.radiomuseum.org/ is a useful resource for our old SL car radios.
For instance, has circuit diagrams and detailed spec.
/Hans S

Aaron h

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Re: Becker Mexico TR repair/restore
« Reply #14 on: April 04, 2020, 22:50:53 »
Peter, most definitely.  I, too, know a lot of people that do just that.  I'd equate that to someone installing a 1N007 diode in place of a cooked selenium rectifier.  You'd never know it was there unless you removed the chassis, and it does the intended job of rectification.  Though, there always seems to be a catch.  You have to check and adjust your B+ when replacing a selenium rectifier with a diode.  It's not hard, just time consuming at times.  And yes, I suppose I could install a more modern solution in Oz's radio, but between what I found here at home and the spare Mexico Oz found for next to nothing online Oz would likely end up spending much more money.  Not necessarily for parts, but the time involved in creating that make shift solution would likely prove to be cost prohibitive.  Not to mention the amount of room inside of Oz's radio is next to nothing. 

Regarding the obsessive aspect of restoration....I'm one of those crazy people that will gut an old original paper/wax capacitor and put a newer, smaller one inside, fill it with wax, and then reinstall it.  However, I'll only do that with really special Tv's or radios that are unusual or extremely original and nice cosmetically. 

MBZE.....That quotation isn't true at all.  That has to be one of the more far out, bombastic, and humorous comments I believe I've ever read.  That makes about as much sense as an 8 amp fuse working in the U.S. but not in Europe because they're on different lines of latitude and longitude. haha If that were the case, then Oz's radio I'm working on wouldn't work because his is a European model.  Think about it this way.... consider the two radio stations 105.4 and 106.1.  In order to get to 106.1 you have to pass 105.4.  If there is anything being received at that 105.4 frequency the radio is going to pick it up.  The radio doesn't know the difference.  It merely does its job of receiving, amplification, demodulating, multiplexing (for stereo), oscillating, and sending an output to the speaker(s).  The radio does't care on the 88.1 to 108 scale where the signal is coming in.  The part about Europe using even numbers on the right side of the decimal used to be true, but I don't know if they still do that or not.  I would imagine they do since we still use odd numbers.

Though, do bear in mind that the early European radios would often have an FM scale that would only go up to the 102-103 frequency range. Have a look at Oz's radio in the first picture on this post.  You'll notice that the FM band only goes up to 103.  Naturally, we wouldn't be able to pick up any radio stations above 103, but I can promise you these radios will work here or anywhere else in the world as long as a signal is being transmitted. 

I only mentioned about Scott's comment being an interesting thought because we don't have Longwave here, and Shortwave is rarely used here.  My thought process was that if someone had a 3 or 4 band radio with pre-sets here in the U.S. then converting the LW and SW to additional FM or AM buttons would be useful.  Though, there are some radios that couldn't as easily be done to, such as a Monte Carlo TR (LW/SW/BC only) a Le Mans TR (SW/BC only), or a California (BC only).  But it's not common to come across those anyway. 

I'm a member of Radio Museum, and I've thoroughly enjoyed the website over the years.  The vetting process used to be pretty invasive, but I don't think it's too bad anymore.  Though, you still have to contribute as often as you can.  They're on a point type ratio system.  If your ratio of downloading schematics to contributing schematics/sales figures falls more in favor of downloading schematics then they'll ban you until you repair the ratio.  It's definitely a haven for fellas like me.  Though, I wish I had known about it before I bought so many Riders and Sam's volumes.  They are absolutely massive books.  The Riders books are around 2 feet by 1 foot, and 4-6 inches thick!  I don't mind though.  About 99% of the time I prefer an actual book anyway. 
« Last Edit: April 04, 2020, 22:55:17 by Aaron h »

Aaron h

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Re: Becker Mexico TR repair/restore
« Reply #15 on: April 16, 2020, 14:14:33 »
I haven't done anything to Oz's Radio this week due to a fuel pump repair for a fellow member.  Hence, the stillness of the post.  However, up to this point there has been footage recorded.  My initial idea was to make one long video......an hour or so, but my dumb camera is so cheap that it doesn't have the ability to pause/resume.  So every time I stop the camera and then start it again it starts recording a separate video.  To make matters worse, it doesn't even have auto focus.  Some of the footage will be somewhat blurry, especially when I'm trying to show something up close or pointing things out on the schematic.  I bought/subscribed to a video editor to make all of these videos into one, but the learning curve takes some time.  So for now I think I'm just going to post the separate videos one at a time in the order in which I've progressed on the radio.  When you go to the youtube channel you'll just have to click on the individual videos.  They'll be labeled in such a fashion that one will be able to tell in which order they're to be viewed.  So onward I go......

kampala

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Re: Becker Mexico TR repair/restore
« Reply #16 on: April 17, 2020, 15:09:42 »
Aaron

No rush. 

Thanks. 
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lpeterssen

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Re: Becker Mexico TR repair/restore
« Reply #17 on: April 21, 2020, 10:48:06 »
Dear Aaron

Great post.  Thanks for sharing your knowledge on Becker radios repair.  Will see your YouTube video for sure.

Best regards
L.peterssen

Aaron h

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Re: Becker Mexico TR repair/restore
« Reply #18 on: May 13, 2020, 03:13:05 »
So, I FINALLY have an introductory video up and going.  It's 35 minutes long.  It's probably boring to most, but I felt it important to tell everything that I know up to this point.  So enjoy, and don't hesitate to correct any mistakes I say or make!  The link to the YouTbe video is below. 

https://youtu.be/iTl4BNeDmRA

Aaron h

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Re: Becker Mexico TR repair/restore
« Reply #19 on: May 13, 2020, 05:14:13 »
Here is the first inside repair/inspection video.  It has to do with the self seeking clockwork mechanism. 

https://youtu.be/vSgcAXC2LOg

Aaron h

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Re: Becker Mexico TR repair/restore
« Reply #20 on: May 13, 2020, 05:29:38 »
And here is part II, where I touch on the description of the governor of the self seeking movement. 

https://youtu.be/jo7uD4NuBYw

Aaron h

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Re: Becker Mexico TR repair/restore
« Reply #21 on: May 13, 2020, 05:40:28 »
Part III showing broken ferrite tuning slug.  (repaired before video) 

https://youtu.be/_a7duiacjUI

kampala

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Re: Becker Mexico TR repair/restore
« Reply #22 on: May 13, 2020, 16:21:10 »
Aaron

There’s a lot more going on inside that TR than I would have ever thought.  Great explanation on the sensitivity and such.  Now I know.  Appreciated. Keep the clips coming.
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Aaron h

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Re: Becker Mexico TR repair/restore
« Reply #23 on: May 16, 2020, 05:41:54 »
Part 4.  Repairing the multi function relay.  Thank goodness for parts radios! 

https://youtu.be/XH4e6Daltsk

DaveB

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Re: Becker Mexico TR repair/restore
« Reply #24 on: May 19, 2020, 02:36:02 »
Thanks Aaron!
DaveB
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