Alternative Way to replace a Selenium Rectifier

[@daleburrell6273]

You are a lot braver than I am- I would have installed a resistor in series between the rectifier and the filter capacitors and left it at that! Tearing into that power transformer was a formidable undertaking!!!

[@AstraWerke]

Thanks :D

[@daleburrell6273]

Adrian Straub ...you realize that it will very difficult to return the radio to its "original" condition(?)

[@AstraWerke]

​@@daleburrell6273 It would most certainly be quite a task. HOWEVER: 1. It would be hard enough to obtain a working selenium rectifier of this type to replace the worn-out original 2. I don't think anybody would bother putting in a selenium rectifier that required the higher voltage 3. This radio will most certainly remain in my posession until my death. In that timespan, I can assure you, no one apart from myself will fix this radio - and I will most certainly not put a selenium rectifier into it. To sum things up, I don't think returning this radio to original will be considered by anyone in the coming decades, so there's no need to worry about it. All the Best Adrian Ps.: I JUST noticed your comment - sorry it took me over a year to answer ;-)

[@daleburrell6273]

@@AstraWerke...time flies(!)

[@vtjmproductionsusa2390]

WOW, talk about having big balls, your a genius!!!! Your my HERO!! This has to be the coolest video ever! Your incredible. Fantastic repair. If my Grundy ever needs the same repair I'm going to go for it and do this. Thank you so much, absolutely amazing you are. Great work 👍👍 This is a TEN STAR ⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐ ViDEO 😺

[@nor4277]

This the second time I have watch this video this young man ,is very skilled at what he is doing and what he no,s about electronics,that radio is in very good shape,and it's a very nice looking radio.👍👍nice job .I hope to find more of your videos

[@nor4277]

Thanks for getting back to me ,your info is helpful ,I do worry about running to a hot chassis radio,why they ever made those, is be yound me ,makes radios dangerous, I am mostly a kit builder,but I have been tinkering with electronic over fifty years ,I just started with tube radios ,I watch a lot of videos on repair of them and with what I no ,together I will do repairs on stuff that I no how to do,anything else I won't do ,changing cap,testing tubes ,checking resistor ,I do like your videos a lot hope you make more your fan

[@gladstonefuller953]

Hi, I just subscribed. I am in Canada. Thanks for an interesting video. I have. several tube radios including a Grundig and two other German made ones. Altogether I have more than a dozen tube radio. The last time I tried the Grundig, it played nicely for less than a minute then the sound gradually became distorted and the volume dropped. It might be the rectifier. At some point in the future I will attend to it. By the way, your English is perfect! Cheers! Oops, another thing to mention, I have collected a number of old typewriters. I like the one on you table. Awesome!

[@DennisMurphey]

Amazing Project you are indeed very brave i hope my Grundig Majestic will not require such a repair but if it does i will be back. Great Job Young Man.

[@oppiz0]

kudos to you Adrian, A brilliant workaround.

[@ianbutler1983]

Very interesting. Thanks for making this video, your effort is appreciated. Ian

[@MINUX75]

You should clean the contacts of the DMM multimeter.... maybe another KZbin episode.

[@StefanSR6346]

Hi Adrian, great video, thanks for sharing! I see that the voltage selector is put on 240 V AC. Did you check the filament voltage at any time? Usually when I do this with tube radios, the filament voltage gets a little low. That kind of makes me hesitant to do so because I heard that the tubes hate it to be “underheated” it.

[@AstraWerke]

Thanks, line voltage at our house usually is around 235-237V, so all my radios are on the 240V setting. I never measured tube voltages, but the radio shown in this video runs about 10 hours daily (except weekends) and has never had any problems regarding underheated tubes.

[@JohnCox-oz5km]

You are constantly amazing. 31 45B

[@nicolaeolar7596]

You got the math right, except the last step, so you should remove 280 windings instead of 300.. I guess the low voltage result comes from that. 180 V tested was without load.

[@AstraWerke]

You won't believe it, but I actually took the thing back apart a couple of months after this video and put some windings back onto the transformer. It did actually put out around 175 Volts AC the way it was, but I accuse the Variac's Volt Meter of not being accurate - it required about 210 Volts AC from the Transformer in order to produce the 260 Volts DC specified in the schematic. All the Best Adrian

[@StefanSR6346]

Great discussion!

[@arthurserino2254]

Very nice video!

[@danmcbmusic]

On the one hand this is a pretty accomplished hack - I never thought of stripping a mains TX and changing the ratio, and if I did, i'd have hesitated to try it! On the other - are you sure you are fixing a problem that actually exists? If the anode voltage on the tubes is 10% high while they warm up, does it even matter, as long as it is less than the maximum rated for that tube type (and the working voltage of the caps of course)? If there is no current there is no power dissipated in the anode anyway, so how will it do any damage?

[@AstraWerke]

To be honest, I simply didnt like the idea of a big, chunky resistor burning all the excess voltage. I did try running the tubes straight from the rectifier before I dug into the transformer and had a quite disturbing amount of static hum - so something had to be done to reduce voltage. Without a doubt though, the radio would have run just fine without this complicated procedure! This was just a brainchild of a late night that would not leave me until I had tried it ;-) It certainly puts less strain on the transformer though - this thing runs on my desk pretty much all day long and the transformer barely gets warm to the touch. All the Best Adrian

[@danmcbmusic]

@@AstraWerke fair enough! very best to you too.

[@cpayne6084]

Great video! I sent a message regarding a project I'm working on, I hope you might have some insight for me! Thanks again this was very informative!

[@larryshaver3568]

a thermistor would slow the voltage down so the tubes wouldn't get zapped too hard

[@electronicsoldandnew]

Very brave to go into the transformer. Great job. By the way, where do you get those black film caps? I use the yellows, but the black ones give it a more authentic look.

[@AstraWerke]

I got them at a website called "Antikradio Restored" - here's their website if you want to take a look: shop.antikradio-restored.de/

[@electronicsoldandnew]

+Adrian Straub : thanks.

[@rubenproost2552]

In my philips (with tube rectifier) the transformer is soaked in tar. Can't even get a single plate off to fix a short.

[@1badpete999]

Very knowledgeable young man what is your school formation on electronics ??

[@AstraWerke]

Well, we had capacitors, resistors, Ohm's law and other basics, but all I know about tube radios comes from the Internet and is pretty much self taught :D

[@nor4277]

You could all so use locktite on the transformer bolts.good video

[@AstraWerke]

Sure enough - just didnt have anything handy that moment. Glad you enjoyed :D

[@christiandietachmair334]

very good video indeed, what is your Citizenship ?

[@AstraWerke]

Glad you appreciated, I come from Germany.

[@pibbles-a-plenty1105]

Paralleling rectifier diodes with small values of capacitance (~ 1 nF) slows the reverse recovery transient which reduces radio frequence interference production. Paralleling the silicon rectifier with large values of capacitance (> 47 nF) is nuts. Transformer winding current is increased which causes resistive loss and increased heating of the transformer winding, i.e., less efficiency. The resistor solution is to be preferred because electrolytic capacitors are designed to withstand a surge voltage. If a capacitor fails (shorts or opens) on start-up it was ready to die anyway. Install new capacitors - less work, simpler!!!

[@larryshaver3568]

Is that a telefunken or Grundig radio? I have always wanted a Grundig tape recorder

[@AstraWerke]

Its made by Grundig. Grundig produced very sophisticated tape machines - I have two of them and even the cheaper one didnt fail to impress me on how much forethought they put into maintenance and repair! All the best Adrian

[@nor4277]

Me personally I would have removed the selium, it serve no purpose anymore and it may confuse the next owner,I rather see the new parts ,but that's just me ,I bought a restored radio ,the guy left the filter cap in ,and right up again it was the new replacement caps and it look very ugly and confusing ,may be I will pull the old cap.can you tell me is a variact a good investment ,I only have two tube radios I am recapping ,what else can a variact be used for anyone ?

[@AstraWerke]

Well, first of all this Radio is a family heritage so I dont plan on ever selling it. Leaving old capacitors in is indeed confusing - if I'd absolutely want to keep the tin cans, I'd open them up, remove its guts and stuff a new capacitor into there. That could also be done with the rectifier but that was too much effort in my opinion as opposed to just leaving the old one in there. I'm pretty sure a person working on the radio would quickly figure out the Selenium Rectifier isn't hooked up to anything. Considering the variac: Its not worth it. I have borrowed this one for that single purpose and never needed one ever since. If you just have two radios, I'd rather use the lightbulb trick to do the initial power-up. Basically all you do is hook a 40-60W light bulb in series with the radio. Worst case: A dead short in the radio. Instead of letting the smoke out, the light bulb will simply light up brightly and limit the current to prevent any further damage. It's also a good way to monitor how much current is going into the radio - simply judging by the bulb's brightness. I show a device I made myself for that in some other video - I think its about a Nordmende. All the Best Adrian

[@christiandietachmair334]

I guess you are German or Austrian - I think you are Austrian - Btw . excellent video !!

[@dejan.b17]

He's German

[@YeeThirty]

Nice choice of caps, however you hit one with the iron...

[@AstraWerke]

Yeah I know... It was my first radio XD

[@daleburrell6273]

That is not really "hum"...what is happening is that the silicon diodes produce very high frequency noise when they conduct. This noise can show up as interference when the radio is playing. The capacitors across the diodes serve to short out this noise.

[@AstraWerke]

Should have called it "hiss", you are absolutely right.

[@josetavares7789]

very bad way to reduce the voltage to a silicon diode, just put a resistor i series and you are don, this is just a radio , ,,not a precision machine boy ,,,,,, a lot work for nothing, or maybe you want showof, my finger go down on this video

[@AstraWerke]

For a "very bad way" it's held up surprisingly well during the last 6 years. What you do to your radios is your choice.

[@agarso]

Dude, if you don't like it don't watch. For Christ's sake, why do people always feel the need to chime in with negativity. He said he was trying something different. Why squash experimentation? Let the grown-ups speak ;-)