Solving a Common Problem on the Eton/Grundig Satellit 750 - Reverse Polarity Damage.

The Eton Satellit 750, which is practically identical to the Grundig Satellit 750 and the Tucson s2000, seems to suffer from a common problem that can cause damage to the radio. This occurs when a center positive DC jack is accidentally plugged into the external power socket, which is wired for center negative. This socket is used to allow for battery or external power.
Finding a solution to this problem can be difficult, especially since there is no service manual available on the web. However, in this video, I'll be showing you how to solve this common problem and get your Eton/Grundig Satellit 750 back up and running.
I'll also be discussing the voltage regulator, which can be hard to find, but I was able to find an alternative component. This video is perfect for anyone who has the same issue with their Eton/Grundig Satellit 750 and wants to learn how to solve it.
So if you're looking for a solution to this common problem, be sure to watch this video. We hope you find it helpful!
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[@624radicalham]

I had this radio in 2014 and one of the first warnings I found online was about the reverse polarity damage. I think it's needless to say, but what you've done here is pure gold. The amount of people you have helped with this is countless. I tip my hat to you Sir!

[@electronicsoldandnew]

It’s my pleasure

[@EsotericArctos]

I think if you have a working one, putting a protection diode in would be the way to go. Looking at the board that the power comes in on, it appears it could be easily modified to add a prtection diode that either shorts power if connected wrongly or, as noted in the video, runs in series with the power

[@mikes1798]

@@EsotericArctosAgreed. I had an old Passport radar detector that only accepted 9 volts when most brands were designed to accept 12 volts. Needless to say the protection diode in there did its job one day.

[@juanpascual5862]

Good morning. My friend Gustavo Ferrari, owner of a Grundig Saterellit 750 radio with the same problem, gave me the link to his magnificent video. Gustavo tells me, look at the video. I repaired it, something that wasn't easy. I decided to make a documented entry on my blog. Yes, I am Juan Pascual, the owner of the blog Electrónica Pascual and I have been excited to be able to help him a little in the repair of his equipment. I struggled quite a bit to be able to design the LDO voltage regulator so that it could run on batteries. I have to look in detail at the voltage regulator that you propose. For the issue of voltage inversion, use a polarized relay, I think, with a system so that when it is activated it consumes less rest current, since using a diode, even a Schottky one, produces a voltage drop, something that does not happen with the relay. Thanks again for your great video. A hug from Madrid, Spain 🇪🇸 Juan Pascual (Electronic Pascual)

[@electronicsoldandnew]

Thank you for your kind words, and thanks for your contribution. Abraço da Madeira, Manuel

[@poormanselectronicsbench2021]

Nice details on the repair, that looks like a nice little radio, and is worth saving for sure.

[@electronicsoldandnew]

👍

[@maartenschapendonk6345]

Always nice to see a repair like this. 👍

[@electronicsoldandnew]

👍

[@Leo6009]

Clever work! I kept a pair of 40 channel UHF transmitters this happened to 20 years ago. I will get them out of storage and take a look. Nothing much to loose. 😁 Cheers!

[@electronicsoldandnew]

👍

[@sw6188]

I had one of these in for repair last year. After a lot of diagnosing and measuring with the multimeter I was able to work out (as you did here) how the various voltages are switched and derrived. Only the 4VCW was faulty on this radio, and not wanting to wait around for replacement parts I went ahead and made a substitute regulator/switcher using a couple of bipolar transistors, a zener diode and some resistors. Worked perfectly and the owner has never come back so it must still be going!

[@electronicsoldandnew]

👍

[@radio-ged4626]

As stated by you and a lot of comments, why didn't they fit a reverse protection diode? Great video, good to know this problem. Very nice little radio.

[@electronicsoldandnew]

👍

[@sw6188]

Adding that diode would push up production cost of the radio. If the diode is 50 cents and they produce 100,000 radios, that's another $50,000 cost. They also work on the basis that if the owner uses the correct (supplied) adaptor, there is no possibility of reverse connection.

[@electronicsoldandnew]

True, but on the other hand, 100k diodes would probably cost them 1 cent each, and add significantly to the reputation of the product. It’s always a two-sided argument in these cases.

[@radio-ged4626]

@@sw6188 Two words: Bean counters. The designers' headache. Often times a good design is destroyed by penny pinching in the accounts department. This happened a lot in the 1960's. Yes, it's important to keep costs under control - but the very thing bean counters are trying to protect is the thing they end up destroying in the long run. Although there does need to be balance. SAAB refused to cut any corners for Vauxhall and ended up being shut down because they cost too much redesigning things Vauxhall had already supplied them with.

[@electronicsoldandnew]

👍

[@greengrayradio1394]

Nice "component detective work", Manuel! As many have commented, a diode in series or parallel with the input DC jack would keep accidents like this from happening. Have done the same with some Norwegian radios which had center negative jacks, but no uP's and elusive components in them..

[@electronicsoldandnew]

The series diode is in place. Wasn’t going to risk it.

[@VOO408]

Я положу это видео себе в плейлист! Благадарю❤❤❤❤

[@moshezaharia4666]

I have the Tecsun S-2000 version, they are all the same because they are made by Tecsun. One common problem is that the encoder becomes erratic, the best solution is to open the encoder and give it a proper clean. Great job and valuable info, thanks Manuel and all the best.

[@electronicsoldandnew]

Pleasure 👍

[@tiagomadeira838]

Uma versão chinesa de um clássico feito pela Tecsun. um excelente video como sempre. Obrigado

[@electronicsoldandnew]

Prazer 😊

[@heinz8770]

Thank You for the helpful and interesting video ! 👌

[@electronicsoldandnew]

Pleasure

[@randalltufts3321]

Was there any possibility of making the center positive to get it to industry standard? Or in lieu of that a full wave bridge so it doesn't matter. That would be easy to do . Even a reverse protection diode to prevent damage ever occurring again would be fantastic. A small 2.5a diode would be perfect for that job and save the radio from ever sustaining extensive damage like that again. Diodes are cheap and easy to install compared to having to shotgun the entire power supply. Great job on the rebuild, they really fried it good.

[@electronicsoldandnew]

I am afraid of changing the socket because someone may one day assume it is original, and then you have the same problem. I’m going to add a Schottky diode to protect it.

[@randalltufts3321]

@@electronicsoldandnew works for me! Anything to protect the ol girl brother! Too nice to get destroyed. Have a great week

[@electronicsoldandnew]

Thanks 👍

[@matambale]

Interesting to note: most of the radios, modems and random electronics I've encountered use center positive. So far, *nearly all* of the guitar effects pedals I've encountered are center negative.

[@electronicsoldandnew]

👍

[@mackfisher4487]

Nice job of finding parts replacements, I’m sure in the future when A web search pull up your repair another radio will be safe from the landfill. Thank goodness the Europeans were smart enough to mandate EV use the same charging connector.

[@electronicsoldandnew]

They still do this reverse polarity thing on guitar pedals 😊 European politicians don’t play guitar

[@matambale]

Wonderful job sleuthing the solution; have you considered, perhaps, a shorting, reverse-biased diode on the DC input? (edit: just saw your comment on that) I sympathize with you on the center-neg/center-pos issue; looks to be split right down the middle for the electronics in this lab. Must always check the diagram next to the socket.

[@electronicsoldandnew]

👍

[@jnbialik]

Hello, which of the two types of encapsulation is used pin by pin to replace the 4VCW: SOT 89-5 or SOT 23-5? Thank you so much

[@electronicsoldandnew]

I don’t remember, but should be visible in the video

[@piwex69]

Tecsun. Now I have desire to own it! It looks like the auxiliary power board, the one with barrel socket, is not equipped with a lot of components - maybe there was a factory option to have protection against mis-polarity.

[@electronicsoldandnew]

I believe there was an option for feeding in an AC supply, as there seem to be holes for diodes.

[@holgers5216]

would it not be easier to also fit a couple of reverse protection diodes, one for the +ve and one for the -ve rail, after the repair?

[@electronicsoldandnew]

Added a schottky in series

[@williammiller950]

i like your videos ,keep them comming

[@electronicsoldandnew]

😊

[@williammiller950]

i like your videos,keep them

[@electronicsoldandnew]

👍

[@herbertsax7169]

What about to put a Schottky diode in series to the power supply input to prevent the same problem again?

[@electronicsoldandnew]

That's exactly what I have done :)

[@wellenjaeger]

Well done! My Tecsun S2000 (which is equivalent to this etón) isn't working anymore on USB. And by the way, LSB is working properly. I don't know if this is a typical failure - have to figure it out ...

[@electronicsoldandnew]

Not sure what the issue could be. As I don’t have a schematic, I didn’t go too deeply into the radio section at all.

[@stevec5000]

What is that mini whip antenna that was mentioned several times?

[@electronicsoldandnew]

This is it: Build and test a PA0RDT MINI WHIP antenna. The tiny great solution for LW, MW and SW listening. kzbin.info/www/bejne/fmLTl4V5q85khpY

[@harryshector]

Perhaps there might be a way to use a mosfet as a switch for the external power. That could reduce the voltage drop to a negligible amount.

[@electronicsoldandnew]

👍

[@jimbrand6231]

Nice job troubleshooting! I have a problem with my Satellit 750 and am looking for help. Turned it on the other day and all I got was a motorboating sound from the speaker. All bands. Tried battery power and headphones, no change. My first guess was bad power supply but the LED display, tuning, etc work fine. I now suspect the audio amp is shot. I have no test equipment except a digital voltmeter so am wondering if the thing is worth fixing, or where to send it? The radio was a gift, infrequently used, but I really like it! Any suggestions would be welcome.

[@electronicsoldandnew]

It’s definitely worth fixing, but I don’t know where you are or who would do that in your area. I suggest you look at local social media and ask around for a repair guy.

[@NikiBretschneider]

There is another option with that diode protection. Put that diode in antiparalel and put some fuse right before this. If the PSU gives the right polarity, then this diode does virtually nothing, it is in reverse, so doesn't conduct. But if the polarity is wrong, then the diode starts conducting, puts the PSU into short circuit which blows that fuse. The advantage of this solution is that there is no voltage drop on it. The odd side is that if it reacts to a wrong polarity, it blows fuse, that needs to be replaced. And you can also use the zener diode instead with zener voltage slightly higher than the output voltage of that PSU should be, which behaves like a diode, so if the polarity is wrong, it starts to conduct the current, which puts the PSU into short circuit and blows the fuse, but it does the same also with the right polarity when the voltage is higher that it should be, which adds another protection to that whole thing.

[@electronicsoldandnew]

👍 that works too. Thanks

[@bobbader4789]

Mine stopped working with batteries only, any ideas?

[@jnbialik]

Hello, it usually happens to me that when I use the radio (it works fine) and I turn it off, then it doesn't turn on, that is, it only has no audio but the rest seems to work fine. Then I leave it unplugged for a reasonable amount of time, maybe a few hours or a day and it works fine again. I mean, I can't leave it plugged in. Do you have an idea what this could be? I leave you a cordial greeting and I look forward to any help or ideas you can give me. Thank you very much (from Rosario, Argentina)

[@electronicsoldandnew]

Check the power supply circuit. You may have something heating in there that needs changing

[@dirkboon3296]

i use batteries only on mine.. mains power introduces too much noise especially used with an external antenna

[@electronicsoldandnew]

Batteries will normally make it quieter, especially if you use a switched mode supply instead of a linear one.

[@Dorpmuller]

Same here. Oh, and whoever invented center negative needs a' whipping.

[@electronicsoldandnew]

😊 wazzantme

[@j3157]

Thanks, I just bought a Grundig 750 from HRO and the signal strength meter doesn’t work. The wall wort that came with it doesn’t confirm the center pin to be negative. I’m a little disappointed. I bought a Zenith 7000 Oceania for $35 that works as good as the Grundig.

[@electronicsoldandnew]

Some of those supplies don’t indicate clearly what their polarity is. It’s a trap if you don’t know what to look for.

[@DavidTipton101]

Well done Manuel, impressive. How many times have I got the camera out of sync and recorded what I don't want and missing the bits I do or, as in your case, not recording at all 😄

[@electronicsoldandnew]

As I said, I need a production team 😊

[@colinreece3452]

I was looking to possibly buy one of these but after watching this I will look for something else.

[@j7ndominica051]

I have one Panasonic radio with this kind of opposite plug. I didn't pay any attention to it, because usually nothing bad happens if you plug a 9V battery backwards in a transistor radio. Just a quiet hiss. The Chinese have designed a €300 brick. I might want to use a different power supply if the DC smoothing fails over time.

[@electronicsoldandnew]

👍

[@EsotericArctos]

What's your favourite model out of the Satellit series? I know you like them all, just curious on your absolute favourite one.

[@electronicsoldandnew]

I think the 3400 takes the prize 🏆 but don’t tell the others I said that 😊

[@anthonycosta1776]

I plugged in a 6 volt wall wart with the positive center and I heard a hum and it didn’t power up. I quick unplugged the wall wart and switched the wires. All was good nothing blown. I guess I got lucky or they installed a protection circuit. I do have a 2023 model.

[@electronicsoldandnew]

👍

[@mohinderkaur6671]

pchannel mosfet can be used as protection diode zero voltage drop.

[@electronicsoldandnew]

👍

[@brunobarbosa6519]

Can you please help me, im trung to fix a pilliphs radio b4x36a/35 cant find annything about that, cumps from Portugal

[@electronicsoldandnew]

Found this on doctsf.com archives.doctsf.com/documents/afficher_document.php?num_doc=33409&num_fic=1&PHPSESSID=b9a0b6925035c938fbbfb6ec3bc8ace6

[@electronicsoldandnew]

Está tudo la 😊

[@brunobarbosa6519]

Thank you so much my friend, your the best, i will let tou know if i sucess

[@brunobarbosa6519]

Tentar encontrar algum vídeo sobre reparação do rádio, não encontro nada :(

[@danielsaturnino5715]

Noob question! I've looked for it before on google but couldnt get to a conclusion. N-channel means NPN right? :) nice job on the puzzle.

[@electronicsoldandnew]

Not quite the same. N-channel mosfet starts conducting by applying a voltage to the gate which is positive relative to the source. For P-channel, that voltages is negative relative to the source. That’s why it works here: the source has the 6V supply, and when you apply a voltage lower than the source to the gate, it switches on.

[@danielsaturnino5715]

Thank you Manuel

[@rhrh9128]

Oh No!!! Lol. Hey, I just bought one of these and am in the USA. Do I need to get an electric adaptor?

[@electronicsoldandnew]

You need a supply suited to your mains voltage and the proper voltage and polarity output.

[@VOO408]

Я подписался!

[@accountant1653]

👍👍👍

[@williamcaspers4990]

Reverse polarity protection requires very little, unless you're an accountant.

[@electronicsoldandnew]

True 😊

[@davidcmather]

Just happened to me today. So I guess I fried it. Too bad becuase radio was a thrift store find for $150. :(

[@electronicsoldandnew]

Well, at least the repair seems quite straightforward

[@wowyummyyy]

LIKE 👍👍👍👍👍 🤩🤩 🤩🤩 🤩💖💖💖💖💖💖

[@electronicsoldandnew]

😊

[@bofor3948]

I know you lose upto 0.6V but an idiot diode in line with the power supply jack would stop all this damage at plug in. Shame the manufacturer didn't design the supply board and the voltages to allow one to be included. "Hapeth of tar"

[@electronicsoldandnew]

There is space on the little DC socket board, and I have added one - a schotky

[@dl7majstefan753]

Obviously this unit has no reverse voltage protection! So it´s NOT a Grundig! ... smile ... You could add an anti parallel diode, which shorts the DC-input.

[@electronicsoldandnew]

True. It’s just asking to be fried 😊 I’m going to add a series diode to protect it, even though it will cause a small voltage drop.

[@LionRoars918]

If someone reverses the polarity and fries their radio, it is on them. You cannot fix the stupidity that people create for themselves.

[@electronicsoldandnew]

That may be true, but a brand that makes an “unconventional polarity” device of this standard could at least have added some protection. The opposite polarity is unquestionably the “standard”, so errors in connecting the wrong supply are sure to happen.

[@darkMoon202]

Is there an automatic channel search on this radio or are we going to search with our hands all the time? Also, when comparing tecsun s2000 with this radio, which one do you recommend?

[@electronicsoldandnew]

Manual search, but lots of programmable channels. I’d choose this one over the tecsun, and the Grundig over this one.

[@darkMoon202]

@@electronicsoldandnew thanx for answer... I like the automatic channel badge more, it is easy and fast, manual is tiring and requires effort, you have to make sensitive touches like an amateur radio operator to fix a frequency, but as a result, I will try to get a very nice radio

[@RiverPlate-zy8fn]

ALGUIEN ME PUEDE DECIR CÓMO EVITAR EL RUIDO USANDO UN TRANSFORMADOR DE 6V? LA SW Y AM ES IMPOSIBLE ESCUCHAR DEBIDO A LA INTERFERENCIA PERO SI USO PILAS EL RUIDO DESAPARECE. EXISTE ALGUN TRANSFORMADOR QUE NO HAGA INTERFERENCIA? GRACIAS

[@electronicsoldandnew]

Make sure it’s not a switched mode supply.

[@RiverPlate-zy8fn]

@@electronicsoldandnew Gracias amigo

[@paul.alarner6410]

bit like the yaesu ft-290 crapbox!.

[@paul.alarner6410]

30ma when off seems a good way to eat batterys!WTF!!.