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Unknown Tube Radio Part

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Menticol

Active Member
Hello!

This is my Grandfather's Mercury Stereophonic Tube Radio, circa 1960.

I don't know if that brand existed in other countries, I can't see any information on the net about it. The mode switch is labeled "Torotor", a Denmark brand, but nothing else.

Ok, let's proceed with the real question. I'm replacing the old, dry components with new ones. What are the blue discs, in series with the potenciometer?

PS: Sorry, left knob is lost
PS: I stripped it from it's original huge wooden box (2 meters). Very sad, but I had no option
PS: Look those funny tubular 10 nF caps on the last picture!
 

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Boncuk

New Member
Looks like NTCs or PTCs.

For final clarification remove one and measure its resistance applying heat.
 

whiz115

Member
if you tell us to where they are connected with might be able to help
one end is on the pontensiometer...the other is where?
 

Boncuk

New Member
I think your guess wasn't as ridiculous as you assume. As the valves build up heat in the radio the pots (mostly carbon) might increase their resistance and using NTCs they compensate for resistance changes.

Boncuk
 
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Dean Huster

Well-Known Member
I wouldn't replace any of the capacitors unless they're electrolytics or paper dielectric types. Replacing the little ceramic caps in RF circuitry could set you up for a lot of alignment headaches -- or a non-working radio.

Replace resistors only if they're significantly out of tolerance or appear to be over-dissipated (over heated). Make sure the primary of the output transformer is good as a common problem in old tube radios was a leaky or shorted coupling capacitor that caused maximum plate current in the output tube(s) to burn out the primary.
 

giftiger_wunsch

New Member
Ouch... just looking at that thing gives me a headache. I'm happy that most of the stuff I work with is of modern design. And there are so many places where it seems a short could easily occur between exposed component leads in that mess...

Enjoy! :D
 
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Sceadwian

Banned
Haven't they ever heard of perf board? =O That really is a rats nest.
 

Menticol

Active Member
I wouldn't replace any of the capacitors unless they're electrolytics or paper dielectric types. Replacing the little ceramic caps in RF circuitry could set you up for a lot of alignment headaches -- or a non-working radio.

Replace resistors only if they're significantly out of tolerance or appear to be over-dissipated (over heated). Make sure the primary of the output transformer is good as a common problem in old tube radios was a leaky or shorted coupling capacitor that caused maximum plate current in the output tube(s) to burn out the primary.

Thank you very much Dean! Just in time :)

Ouch... just looking at that thing gives me a headache. I'm happy that most of the stuff I work with is of modern design. And there are so many places where it seems a short could easily occur between exposed component leads in that mess...

Enjoy! :D

Haha Yeah! do you see the ugly silicon patch? It's mains! just centimeters (<1 inch) next to audio lines :eek: Extreme anti-engineering

I love this radio, but it gave me a very sad experience. Something fell from nowhere just over the radio, and shorted the transformer pins. It blew a beautiful equalizer connected to the phono lines, but at least didn't broke any tubes or burnt my PC too. That was the last time I operated it without a protective cover.

Haven't they ever heard of perf board? =O That really is a rats nest.

Did Perforated board exist at that time? Just kidding
 
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mneary

New Member
But why are they installed at the volume potentiometers?
Many radios of the era had their power switch mounted on the back of the volume control, making it an ideal place to mount an NTC..
 

greggles

New Member
Old caps

Hi, These are caps do not replace them unless faulty, they will last longer than you and I. Not like todays components they were build to last in them there days.
 

greggles

New Member
A new age

Testament is in the hands of all servicemen and women around the world who will gladly rise to the podium and hail vintage radio for its longevity. "No" today’s parts do not last and many will debate designed obsolescence to make sure sales continue.
Buy a part today and no longer available tomorrow is another one of today’s dilemmas.
 

ericgibbs

Well-Known Member
Most Helpful Member
Testament is in the hands of all servicemen and women around the world who will gladly rise to the podium and hail vintage radio for its longevity. "No" today’s parts do not last and many will debate designed obsolescence to make sure sales continue.
Buy a part today and no longer available tomorrow is another one of today’s dilemmas.

hi,
I'll go with that 'greggles', younger inexperienced people may criticise the older gear as being poorly built etc, but back in those days we didnt have the luxury of semi's and online forums.:rolleyes:
 

greggles

New Member
Good old days

hi,
I'll go with that 'greggles', younger inexperienced people may criticise the older gear as being poorly built etc, but back in those days we didnt have the luxury of semi's and online forums.:rolleyes:

Thanks for the vote, I am of the oppinion the old stuff was built well, open an old tube radio and try and find a dry joint on a tag strip, electrolytic caps have air around them and not mounted next to heat sinks at only 85 degree rating doomed for failure. Or stuck to a PCB with glue that fails and conducts. the Russians kept building with tubes while the rest of the world went semi and developed some of the worlds greatest devices impervous to EMP, Great for the war effort on their part.
I am a lecturer in electronics and still to this day bring old relics in for their eductation and spend a little time explaining valve theory just to keep my brain afloat i guess. But today its all about the micro and FPGA and its good i must confess. Its a very exciting time and getting better, wish i could be around 100 years from now to see what unfolds.
Cheers
 

flat5

Member
Quality really depends on the manufacturer and it's intention. GE (garbage electronics) used to make a very successful (marketing wise) color TV in the early 1970s that used it's own multifunction tubes. The set was made to last no longer than it's warranty. The tubes got so hot and the plastic case was so small that it warped. The yoke was a coil wound on cardboard. It did work when you bought it and was comparatively very low priced for a USA color tv.
 

greggles

New Member
Get out

Are you serious that is just criminal never heard that story. Thanks for the data
What a laugh.
Did it kick up a storm?
Seems GE may have been the pioneers of designed obsolescence. Look at the following they are getting now lol.
 

Sceadwian

Banned
This is common engineering practice now days, shouldn't be a surprise to anyone.While flat5's example isn't exactly what you'll find as far as cheap manufacturing and engineering goes today it's roughly the same, shoddy work designed to last no longer than the warranty.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
This is common engineering practice now days, shouldn't be a surprise to anyone.While flat5's example isn't exactly what you'll find as far as cheap manufacturing and engineering goes today it's roughly the same, shoddy work designed to last no longer than the warranty.

Legislation in the UK prevents such tactics, as you have six years to claim over any manufacturing defects.
 

giftiger_wunsch

New Member
Legislation in the UK prevents such tactics, as you have six years to claim over any manufacturing defects.

I had heard that, though I had also heard that there needs to be sufficient evidence that the problem existed from the start and wasn't caused by wear and tear. That usually involves hiring an impartial technician at enormous cost to produce the required evidence. My dad recently tried to claim on a plasma TV which has an intermittent fault, quoting the Trade of Goods Act without actually reading it first. Needless to say he was told where to shove it. Looks like a lovely new 52" LCD HDTV is in order! :D

Do you know what document actually contains that legislation? I read the Trade of Goods Act top to bottom and there's no mention of six years in that document, despite what my dad claimed.
 
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