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New.....I need help on replacing a fuse, please.


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Hello all. First off let me applaud the creators and moderators of this site. Nice work!

I am an amature when it comes to fixing electronics, but i do have a little bit of experience with it.

I recently bought an old Valve\Tube Radio from and overseas vendor in Germany. It's a '59 Nordmende Elektra. I have replaced the plug on the end and have turned the voltage switch to accept 110V now.

However, I have a question on replacing the fuse. I need to know if i am reading the voltage from back of the radio the right way. Here is a picture of what I am refering to:


I am Having trouble understanding the comma in between the zero and six on this line - "Sicherung fur : 110/125 = 0,6A trage" . Does the comma act as a period like this " 0.6 Amp Slow " or does the comma just act and read like this "6 Amp Slow"?? I have some 6.3 amp 250V Slow-Blow fuses. Will those work or do i need 0.6 Amp Slow blow fuses?

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Well I know what the frequency can do to some devices when it is the other way around. A transformer built for 60Hz can sometimes be overheated when run at 50Hz. And I know about the relationship between inductance and frequency. Some radio armatures that imported their rigs from the US have found this out the hard way. However I have no experience the other way around so I assume it will work but I doubt that it will reach its original performance.

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It seems the radio was made to handle 5 diffrent voltage inputs. Would you still have that frequency rating to worry about if the radio was built to handle these voltage changes? Here's the switch witht he cover off:


And here's a pic with the cover on:


I would like to know if i can use a "T630mA/250V" fuse for 110V?? The 110V requires a 0,6A Slowblow. Can use the T630mA/250V fuse ?

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  • 2 months later...

The power input on a tube radio is usually a multi voltage input transformer. And a transformer is an inductor so yes the frequency matters. I am just not sure how much!

Take a LQQK at the general transformer equation: VN= 4fSB where:
VN: Volts/Turns ratio
f: Frequency (Hz)
S: Core X-section area (sq. m.)
B: Flux Density (Wb/m2)

Now: B= VN/(4fS) so:

B ~ VN/f

Since B is porportional to the reciprocal of frequency, you can go to a higher frequency while keeping the V/N ratio the same. This will mean that the xfmr is operating at a slightly lower flux density, which won't do any harm, other than to somewhat compromise the efficiency due to increased core losses.

Going lower in frequency is the killer. In most xfmr designs, the core's already operating close to its saturation flux density so as to make the core and the core losses as small as possible. Operating a 60Hz xfmr at 50Hz could very well lead to core saturation if the voltage isn't porportionally reduced.

I noticed an extra fuse included with this radio In a ziploc bag. On the head of the fuse it reads "T630mA/250V" Is this fuse just a replacement fuse for the 220V setting? Or did he include the 110V fuse i need in the ziploc bag?

The only thing a voltage rating means concerning fuses is that the fuse is guaranteed not to arc over once it blows if operated at or below the voltage rating. A 250V fuse on a 120V main will work just fine. A 110V fuse on a 240V main could possibly arc after it blows.

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  • 16 years later...

Hello Moderators, I realize this is 17 years old but very contemporary with all the resurging interest in Analog - I am trying to save a R2R BeoCord 2000, that does not power up. I am hoping it is just a fuse (labeled T630/250). I see quite a few potential replacement but none of the fuse listed have the T letter, for ex just, 630am/250V, what does the T mean and can use one of the replacements that do list T. 

BTW the unit is originally for 220v 50 CPS 15-90W. 

Appreciate any advice. 



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Pack of 5, T630mA250V, T630mA 250V, T630m 250V Cartridge Ceramic Fuses 5X20mm

see for example: https://www.ebay.com/itm/151136254075?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0

T for time delay? From Amazon.com:

Pack of 5, T630mAL250V, T630mA 250V, T630mL250V Cartridge Glass Fuses 5X20mm (3/16" X 3/4"), 630mA 250V, Slow-Blow (Time Delay)

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